Term
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Definition
Lisa Simpson
An auxinic herbicide in the phenoxyacetic chemical family. Some people have strong opinions about it, believing it to be harmful to human and animal health. A component of Agent Orange. On the Simpsons, Lisa is Bart (IAA)'s little sister; she looks similar to him, but is different. Principal Skinner (GH3) does not put Lisa in detention, but she has the same effect on Herman (SCF). 2,4-D is not conjugated like IAA is, and it accumulates in the cell, activating genes. Weeds have developed resistance to this herbicide. |
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Term
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Definition
| A component of Agent Orange. It can be converted into TCDD if the synthesis reaction is not conducted perfectly. It is no longer commercially available. |
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Term
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Definition
| A plant hormone involved in cell senescence and death. |
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Term
| Acetolactate synthase (ALS) |
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Definition
Acetohydroxyacid synthase (AHAS)
A plastidic enzyme involved in amino acid synthesis. Inhibited by group 2 herbicides. Condenses two pyruvates to form 2-acetolactate, a precursor for valine and leucine synthesis. It also condenses pyruvate with 2-ketobutyrate to form 2-acetohydroxybutyrate, a precursor for isoleucine synthesis. Has a higher affinity towards making 2-acetohydroxybutyrate. The first enzyme in the branched amino acid biosynthesis pathway. Inhibition leads to depletion of amino acids and intermediates required for crucial processes. |
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Term
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Definition
| The weight of auxinic herbicide acid in a formulation. Indicative of the toxic action. Weight of salts and esters can vary, but acid weight is always the same. |
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Term
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Definition
Otto Mann
Carries IAA into the cell. On the Simpsons, Otto is the bus driver who drives Bart (IAA) to school. |
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Term
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Definition
| 2,4-D mixed with 2,4,5-T. Used during the Vietnam War. It had an orange stripe on the barrel. During its synthesis, 2,4,5-T can be converted into TCDD if the reaction is not conducted perfectly. |
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Term
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Definition
| Plant species which are mostly out-crossing. Shown to have a greater propensity to develop multiple resistance, since traits are easily transferable among individuals, resulting in accumulation of resistance mechanisms in progeny. Out-crossing allows weed populations to acquire a broader spectrum of resistance that spans multiple herbicide groups and modes of action. |
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Term
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Definition
Group 2 herbicides
Inhibit ALS, an enzyme in amino acid synthesis. Includes sulfonylureas, imidazolinones, triazolopyrimidines, pyrimidinyl-oxy-benzoates, and sulfonylamino-carbonyl-triazolinones. Became available in 1982 with introduction of chlorsulfuron. Extensively used because of several advantages: low use rates (g/ha), low toxicity to mammals, broad spectrum of control on a wide range of crops, active in soil and foliage, and safe environmental profile. Drawbacks include long-term soil persistence. Death is caused by shortage of branched chain amino acids (isoleucine, leucine, and valine). Symptoms include stunting, purpling, and chlorosis, seen first in young leaves. Eventually young leaves become necrotic. Mostly phloem-mobile. Purpling of the veins on the underside of the leaf is indicative of an ALS inhibitor. There is an ALS inhibitor safe for use in most crops. Resistance to ALS inhibitors has reduced since the release of Roundup Ready crops. |
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Term
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Definition
| An herbicide which can move in the xylem and the phloem. Includes glyphosate. Has symplastic and apoplastic movement. |
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Term
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Definition
| A type of formulation for auxinic herbicides. Less active, but less volatile. May need to be applied at higher rates. Often formulated as water based solutions (Sn). |
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Term
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Definition
| The building blocks of proteins. There are twenty different amino acids. Found in all organisms. Humans can synthesize some, but others we must eat. Includes a carboxyl group, an amino group, and an R group which determines the type of amino acid. Involved in enzymes, pigments, and secondary metabolism. |
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Term
| Aminomethylphosphonic acid (AMPA) |
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Definition
| About 100 related compounds had potential as water softening agents. Originally synthesized by Monsantos' Inorganic Division. Some were found to have herbicidal activity, and were used to develop glyphosate. |
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Term
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Definition
Loliu rigidum
Family Poaceae. Leaf blade is hairless, with a shiny look. Has long, clasping auricles. Seed head is a main axis with green or straw-coloured spikelets. Grows in problematic dense stands. It was one of the first glyphosate resistant weeds.
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Term
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Definition
| Pre-existing, DNA-binding auxin-response proteins that activate gene transcription in response to high auxin concentrations. |
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Term
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Definition
| A PSII inhibitor herbicide. Can cause injury to pumpkins and soybeans. |
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Term
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Definition
| An identifying feature of grasses. Projections of the ligule at its edges, clasping the stem. May be claw-like, short/stubby, or absent. |
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Term
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Definition
Indole acetic acid
Bart Simpson
A plant hormone. Produced in the growing point of the plant, and moves to the rest of the plant, controlling growth and development. It is involved with phototropism of shoots, accumulating on the shaded side of the shoot, promoting cell elongation so that the shoot will bend towards the light. It causes activation of repressed genes. On the Simpsons, Bart is driven to school by Otto (active carrier protein), put in detention by Principal Skinner (GH3), and gets Herman (SCF) to help him stop Nelson (repressor) bullying Milhouse (repressed genes). |
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Term
| Auxin-binding protein (ABP1) |
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Definition
Repressor
Nelson Muntz
A repressor of auxin-regulated gene expression. Induced by high auxin concentration, as a feedback mechanism. On the Simpsons, Nelson bullies Milhouse (repressed gene), and is stopped by Herman (SCF). |
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Term
| Auxin signalling F-box protein (AFB) |
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Definition
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Term
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Definition
Hormonal herbicides
Comprise different chemical families. Interfere with auxin. First created during WWII. Used mostly to control dicot weeds in grass crops such as corn, grains, turf, and forage. Used in some non-grass crops when dormant, such as strawberry. Most grasses can withstand its action due to enhanced rates of metabolic degradation. Mostly absorbed through foliage, but root entry is possible. Activity before absorption can be seen, though the residual period is short and activity varies. Phloem-mobile, accumulating in growing points. Control perennial dicots because they are systemic. Mode of action involves deregulation of gene expression, producing epinasty. Auxin systems which direct plant growth are disrupted. Death is caused by hyperaccumulation of ethylene, abscisic acid, and reactive oxygen species. All auxinic herbicides are acids, but with varying water solubility. Often formulated as esters or amine salts. In Ontario, seven active ingredients are available, and dozens of formulations. Many are generic. |
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Term
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Definition
Echinochloa crus-galli
Family Poaceae. Common in Canada. Easy to identify. Leaf sheath and leaf margin are hairless. Lacks auricles. Stem has a flattened cross-section. Seed head is a central axis with clusters of dense spikelets which are green at first but turn purple as they mature.
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Term
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Definition
| In baseball, pitchers can be over age 44 and still play in Major League. Their main style of pitching is kuckleballs, which are hard to throw, hard to hit, but easy on the arm, good over the long-run. However, successful pitchers use more than one type of throw. This is an analogy for using different weed management techniques. Some methods are great, work well, and should be used often, but for long-term success, a variety of methods is required. |
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Term
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Definition
| Herbicides which inhibit PSI. Includes paraquat and diquat. |
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Term
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Definition
| An herbicide injury symptom. Loss of chlorophyll and carotenoids. Tissue turns yellow and then white. Carotenoids are lost first, leading to death of chloroplasts. Usually followed by necrosis. |
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Term
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Definition
Poa sp.
Family Poaceae. May be annual or perennial. Lacks auricles. Ligule is membranous. Leaf blade is smooth and narrow, folded along the midrib. It can be hard to identify in a large stand of weeds.
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Term
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Definition
| An enzyme that degrades glyphosate in the soil, producing sarcosine and inorganic phosphate. |
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Term
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Definition
Conyza canadensis
Horseweed
Family Asteraceae. A widespread weed, focused in the southwest. Some strains are resistant to Roundup, and some are resistant to both glyphosate and ALS inhibitors. Glyphosate resistance is conferred by enhanced sequestration of the herbicide in the vacuole, away from chloroplasts. Populations in the USA have resistance to dicamba. Lends itself to mobility because it has small, windblown seeds with parachutes that can travel several kilometers, and cling to objects including vehicles. Can be killed only by two herbicides: Eragon and dicamba. Causes yield losses of 10 - 100%. Its seeds have little dormancy, germinating as soon as conditions are good. Once it sets seed in the field, new plants can germinate. Produces many seeds. Has two peak emergence periods: June and August. When first germinated, there are 4 million plants/acre. With so many plants, even a small percentage of survival translates into large yield losses. Control must occur in the fall but also in the spring. Just one tillage pass in the fall made them worse in the spring; plants branched and got bigger quicker. Some plants will die over the winter. Causes problems mostly in corn and soybeans.
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Term
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Definition
Brassica sp.
Family Brassicaceae. A crop which is closely related to many weeds. Has poor seed germination, and can be a bad volunteer. It is difficult to kill using herbicides, due to its thick cuticle.
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Term
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Definition
| A pigment essential for photosynthesis. Preventing its production causes plant death. Yellow in colour. Acts as an antioxidant, protecting chlorophyll from singlet oxygen which would otherwise inhibit photosynthesis. |
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Term
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Definition
| Unique to plants. Not found in animals. Found in some bacteria. |
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Term
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Definition
| Studied phototropism of plants in 1880. Found that when the shoot apex is excised, or shielded from light, phototropism is lost. |
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Term
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Definition
| When a molecule binds to a metal ion. Ethylenediaminetetraacetic acid (EDTA) chelates to metal ions. Glyphosate is a chelating agent, which is why it is deactivated by hard or dirty water. |
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Term
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Definition
Classic
A sulfonylurea ALS inhibitor. Registered for use in soybeans. |
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Term
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Definition
| A pigment essential for photosynthesis. Preventing its production causes plant death. Synthesis is inhibited by protox inhibitors. Requires protoporphyrin IX for its biosynthesis. |
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Term
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Definition
| A common herbicide injury symptom. Death of chloroplasts, and loss of chlorophyll. Green tissue becomes yellow. Nitrogen or iron deficiency can cause chlorosis. |
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Term
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Definition
Telar
A sulfonylurea ALS inhibitor. Used for broadleaf control in cereals. Registered for use on non-crop land. |
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Term
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Definition
| The main product of the shikimic acid pathway. The precursor for the aromatic amino acids tryptophan, phenylalanine, and tyrosine, required for protein biosynthesis. Converted into quinones and indoles, which are precursors of a host of secondary metabolites. |
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Term
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Definition
| An auxinic herbicide in the picolinic acid family. |
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Term
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Definition
Amaranthus tuberculatus
Family Amaranthaceae. An allogamous species with multiple resistance. Has resistance to 2,4-D in Nebraska.
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Term
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Definition
Firstrate
A triazolo-pyrimidine sulfoanilide ALS inhibitor. Registered for use in soybeans. |
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Term
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Definition
Zea mays
Family Poaceae. It can be treated with 70 different herbicides. Research consistently shows that dicamba is the most effective herbicide.
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Term
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Definition
| The student takes 6 classes at a time, for at least 3 semesters. Doesn't close the door to a PhD, but is more common when going into industry afterwards. |
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Term
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Definition
| Can be broadcast seeded into standing corn. Improves herbicide performance. Covers the ground with a wanted plant species, reducing weed recruitment. Not 100% effective. Reduces weeds considerably. |
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Term
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Definition
| Can occur if herbicide is applied at too high a rate, or during stages with reduced metabolism, such as booting in cereals. |
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Term
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Definition
| A method of reducing herbicide resistance. A diverse landscape reduces the ability of weeds, diseases, and insects to develop resistance to treatment. Facilitates rotation of herbicides. Only delays the onset of herbicide resistance. |
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Term
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Definition
| The former premier of Ontario. Wanted to ban 2,4-D because it was seen as bad for the environment and harmful to human health. Instead banned pesticides for cosmetic use. |
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Term
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Definition
Engenia
An auxinic herbicide in the benzoic acid family. Works on Canada fleabane. The most effective herbicide in corn, but can cause twisting and lodging if applied at too high a rate. Has an effective mode of action. Can have issues with drift. In Arkansas, there was a proposal to ban it. |
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Term
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Definition
| A class of protox inhibitor. Stops an enzyme in the porphyrin pathway. Includes oxyfluorfen. |
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Term
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Definition
Reglone
A bipyridillium. Can be used as a desiccant in potatoes or beans. |
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Term
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Definition
| Early work in the late 1950s helped to explain the mechanism of action of PSII-inhibiting herbicides. Shown to reversibly inhibit photosynthetic electron flow at micromolar concentrations. Additional work revealed that it was acting at the reducing site of PSII in the vicinity of bound acceptor plastoquinones, QA and QB. |
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Term
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Definition
| When water droplets are moved away by wind. To avoid, spray when there is minimal wind, use lower spray pressure or anti-drift nozzles, or lower the boom closer to the target. Can be a problem when the herbicide drifts into non-resistant crops, or wild plants. |
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Term
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Definition
| A herbicide which is chemically similar to Agent Orange. |
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Term
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Definition
| A factor which can affect yield loss caused by weeds. Cooler weather can lessen the impact of weeds. Nutrient availability and allelopathy can have an effect. Rain or irrigation can reduce the effect of weeds. |
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Term
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Definition
| An herbicide injury symptom. Leaf and shoot twisting. The main symptom of auxinic herbicides, seen within 24 hours of application. Shoots become narrow and spindly. Leaves can take on a cupped shape. Caused by disruption of hormones that direct plant growth. Cell divisions are dysregulated. |
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Term
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Definition
5-enolpyruvylshikimate-3-phosphate synthase
The enzyme inhibited by glyphosate. Catalyzes a key step in the shikimic acid pathway, condensing shikimate-3-phosphate (S3P) and phosphoenolpyruvate (PEP), producing 5-enolpyruvylshikimate-3-phosphate (EPSP) and inorganic phosphate. Plays a key role in the physiology of a a plant, making it an ideal herbicide target site. Found only in plants and microorganisms. |
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Term
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Definition
| An herbicide which worked well on Canada fleabane. Requires a high rate. Can injure soybeans. |
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Term
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Definition
| A type of formulation for auxinic herbicides. Have better entry in leaves. More active, but more volatile. Most often formulated as emulsifiable concentrates (EC). Lower volatility esters have been introduced, with longer alcohol chains. |
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Term
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Definition
Muster
A sulfonylurea ALS inhibitor. Registered for use in spring canola. |
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Term
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Definition
| A plant hormone involved in ripening of fruits. |
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Term
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Definition
Panicum dichotomiflorum
Family Poaceae. It is the last annual grass to appear in the spring. Lacks auricles. The seedling is very hairy, and the plant becomes less hairy as it matures. Ligule is short and hairy. Seed head resembles that of witchgrass, but with a narrower shape. Leaf blade has a prominent midrib, and is less hairy than that of witchgrass.
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Term
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Definition
Everest
A sulfonylamino-carbonyl-triazolinone ALS inhibitor. Registered in Western Canada as a post-emergence product for wheat. Prominently a grass herbicide, with some activity in dicot species. |
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Term
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Definition
Broadstrike
Dual
Magnum
A triazolo-pyrimidine sulfoanilide ALS inhibitor. Registered for use in soybeans. Has long-lasting soil persistence. You cannot grow cabbage or cauliflower up to three years after use. |
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Term
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Definition
Valtera
A dicarboximide protox inhibitor. |
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Term
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Definition
| A diphenyl ether protox inhibitor. |
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Term
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Definition
Option
A sulfonylurea ALS inhibitor. Registered for use in field corn. |
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Term
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Definition
| One grower had small, deformed corn cobs in his crop. Field records showed that he had sprayed a fungicide during V8 stage, when the number of ovules is determined. The fungicide was used at too high a rate for the surfactant with which it was mixed, causing the damage. |
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Term
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Definition
| An herbicide for which the patent has expired; older chemicals. Any company can create and sell a formulation. Often dozens of formulations are available. Many auxinic herbicides are generic. |
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Term
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Definition
Auxin conjugation protein
Principal Skinner
An enzyme that reversibly conjugates IAA with amino acids to form inactive conjugates. On the Simpsons, Principal Skinner puts Bart (IAA) in detention, but not his sister Lisa (2,4-D). |
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Term
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Definition
Heracleum mantegazzianum
Family Apiaceae. Originated in southern Russia, where it was used as an ornamental. Its sap causes photosensitivity; sun exposure leads to burns and blisters on the skin, and can cause permanent scarring. The rash starts off reddish pink, then blisters. The sap can be washed off with water. If you get sap on your skin, protect the spot from sunlight before you wash it, to prevent photosensitivity. It does not cause blindness. One unfortunate man weed-wacked giant hogweed in shorts, the blisters that formed on his legs became infected, and he had to have his legs amputated! May be found in parks and field edges. Has a 60 cm deep taproot from which it can regenerate; mowing is ineffective. When cut at the base, it almost always regenerates with small flowering shots. Must be controlled with a pray suit and gloves, which can be hot and inconvenient. May live for several years before flowering, after which it dies. Leaves are huge, up to a metre across. May be controlled with Truvist. Mortality is greatest during seed-set. Produces 20,000 seeds/plant, which dry up and fall off. The seeds may float in streams, but usually have vertical dispersal.
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Term
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Definition
Ambrosia trifida
Family Asteraceae. Normally found in ditches and field edges, until it suddenly jumped into fields. Single plants were seen at first, and then larger patches. Can grow to be over 6 feet tall, and may even tower over corn. Produces allergenic pollen.
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Term
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Definition
Basta
Ignite
Liberty
Glufosinate ammonium
An herbicide which inhibits glutamine synthetase. A fast acting, non-selective, contact herbicide. No soil activity, rapidly degraded by microorganisms. Ammonia accumulates, interfering with photorespiration and photosynthesis. Produces toxic radicals that are light-reactive, causing lipid peroxidation. Does not provide long-term control of perennial weeds or grasses. Death is caused by shortage of branched amino acids (valine, leucine, isoleucine); effect can be reversed by supplying these amino acids. Liberty is a less harsh formulation than Ignite. |
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Term
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Definition
| An amino acid which is essential for the metabolism of nitrogen. Produced from glutamate by glutamine synthetase (GS). |
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Term
| Glutamine synthetase (GS) |
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Definition
| An enzyme involved in amino acid synthesis. Inhibited by glufosinate. Converts glutamate into glutamine, with a γ-glutamyl phosphate intermediate, consuming ATP and ammonia (NH3), and producing inorganic phosphate. It functions in ammonia detoxification, which would otherwise be converted into glyoxylate. |
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Term
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Definition
| A photorespiration byproduct which inhibits Rubisco, causing death. A degradation product of glyphosate. Produced when ammonia accumulates in the cell, such as after glufosinate treatment. |
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Term
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Definition
Roundup
[N-phosphonomethyl]-glycine
The most widely used herbicide in the world, used more than the next 9 combined. A phosphonomethyl derivative of glycine. A white, odourless, crystalline solid. Comprised of one basic amino acid, and three ionisable acids. Can react as a base or an acid, and may dissolve in dilute aqueous bases and strong aqueous acids, producing anionic and cationic salts. Has strong intermolecular hydrogen bonding, making it unstable in non-aqueous solutions. More soluble in water when converted into monobasic salts. Generally formulated with a monobasic salt, such as isopropylamine, sodium, potassium, trimethyl-sulfonium, or ammonium. A dense molecule (1.75 g/cm3) with strong molecular bonding, not prone to evaporation from surfaces. Stable in sterile soil and water, but subject to microbial degradation under aerobic and anaerobic conditions. Degraded by the GOX pathway and C-P lyase enzyme. Can photodegrade in solutions containing calcium ions under artificial light; not significant in the environment. Binds to clay particles, but not sand or organic matter; little activity in most soils. A chelating agent; activity is reduced when mixed with hard or dirty water, or if there is dust on the leaves. Any ion with a charge of +2 will bind to it, inactivating it. Once all cations in the water are tied up, the remaining amount may have herbicidal action. Phloem-mobile because it is ionisable and polar; removal of one group reduces phloem transport. Has a favourable, relatively safe environmental profile. Low toxicity to animals, and low volatility. Low oral, dermal, and inhalation toxicity; no evidence of carcinogenicity, mutagenicity, neurotoxicity, reproductive toxicity, or teratogenicity. |
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Term
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Definition
| Inhibits the enzyme EPSPS. Disrupts the negative feedback loop produced by L-arogenate, causing buildup of shikimate, and carbon shortages for other pathways. Evidence shows that death is caused by increased carbon flow into the shikimate pathway, causing drain on the rest of the plant. Supplementing amino acids does not save the plant. Primary mode of action is inhibition of EPSPS. At high concentrations, taken into the cell with passive transport. At low concentrations, taken into the cell with energy-dependent active transport via a phosphate transporter. Alternation of uptake mechanism can have implications on plant response. An ambimobile herbicide. Moves through the apoplast until it enters the symplast, passively in the mesophyll, or actively in the phloem companion cell. Reduction in phloem loading could prevent it from reaching lethal concentration in growing points. Translocated to sink tissues where EPSPS is most highly expressed. Damage is seen first in new growth. Non-selective; kills most plants. Can knock down large weeds which are otherwise difficult to kill. Other herbicides usually work only on young plants. Works best when plants are actively growing. Stress conditions, or mixing with other herbicides may reduce efficacy. May reduce plant tolerance of pathogens. Has slow action; if you make a mistake during application, you won't know for a week. |
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Term
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Definition
| Glyphosate was not originally invented for herbicidal use; it was first invented by Henri Martin. Phil Hamm discovered the herbicidal action of related chemicals, and John Franz re-invented the chemical in 1970. It was commercialized as an herbicide in 1974. Use was limited before release of GR crops, because it could not be applied in-crop. Originally used in Malaysia for production of rubber, trees, vines, bananas, and coffee, with up to six applications annually. Used in cereals and for non-crop uses in the USA. It was expensive when it was first released. One farmer traded a few bottles of it in order to back out of a lease for rented land. It now costs around $6/L, and farmers are willing to use high rates of the herbicide. |
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Term
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Definition
| Weeds resistant to glyphosate. Have a variety of target site and non-target site mechanisms for resistance. Modified forms of EPSPS have been documented, with substitutions of proline 106 to threonine, alanine, or serine, or proline 182 to serine or threonine. It was originally speculated that weeds could not develop target site resistance to glyphosate. Resistance involves a non-target mechanism in most glyphosate resistant weeds. Some have reduced translocation of glyphosate to meristems; exact basis is unclear, but there is enhanced sequestration in the vauole. EPSPS gene may be amplified, causing large increases in amount of mature EPSPS enzyme, conferring a high level of resistance. Resistance to Roundup is a bad issue, worse than predicted in 1998. |
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Term
| Glyphosate resistant crops (GR) |
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Definition
| Crops which are genetically modified to be resistant to glyphosate. Prior to their commercialization, glyphosate was used in field crops, intercrop rows, and around perennial trees and vines. Allows for post-, in-crop application of glyphosate at high rates and at multiple times during the growing season, without injuring the crop. Use of glyphosate increased dramatically with introduction of GR soybeans and canola in 1996, followed by cotton in 1997, corn in 1999, and sugar beets in 2008. GR alfalfa was commercialized in 2005, but deregulated due to legal clearance, and resumed in 2008. |
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Term
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Definition
Eleusine indica
Family Poaceae. Glyphosate resistance is conferred by modified forms of EPSPS.
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Term
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Definition
| A pathway which degrades glyphosate into AMPA and glyoxylate in the soil. |
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Term
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Definition
| More focused than an udergraduate degree. Focuses on a specific topic, with some peripheral learning. Self-directed. Requires time management skills. You can make some money by being a TA. Includes course-based and thesis-based grad school. Only the last four semesters count towards the application process. |
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Term
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Definition
| Family Poaceae. Species may be hard to identify. Some identifying features include the ligule, auricles, and leaf sheath. |
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Term
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Definition
Setaria viridis
Family Poaceae. May be annual or perenial. Lacks auricles. Ligule is hairy. Leaf blade is hairless on both sides. Leaf sheath and leaf sheath margin are hairless. Seed head is a fluffy, bristle-like spike of yellow-green flowers. Produces small seeds. Stem has a round cross-section.
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Term
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Definition
| Water with divalent cations, such as iron. Mixing it with glyphosate reduces the herbicide's efficacy, because it binds to the cations, becoming deactivated. Well water is usually hard water. |
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Term
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Definition
| A Swiss scientist who worked for the pharmaceutical company Cilag, which was later acquired by Johnson and Johnson. The original inventor of glyphosate, but at the time it was determined to have no pharmaceutical applications, so it was sold to Aldrich Chemicals along with several other research samples. |
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Term
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Definition
| Chemical groups of herbicides were randomly assigned numbers. |
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Term
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Definition
| Depends on the mode of action and translocation of the herbicide, and the timing and dose of application. Symptoms can include chlorosis, necrosis, bleaching, epinasty, purpling, and stunting. |
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Term
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Definition
| In the USA, a system was proposed that would reduce development of pesticide resistance. An inspector would come to the farm every time a pest problem arises, and give a prescription to the farmer for what products they can use. Farmers dislike this idea, because they may be forced to buy expensive products, or accept yield losses. |
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Term
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Definition
| Increase in frequency of individuals with resistance alleles within a treated weed population. Scientists in the 1950s debated whether it would become an issue; some believed that plants lacked the genetic diversity to be able to evolve at such fast rates, but they were wrong. The first case was found in 1957 in Milton Ontario; wild carrot resistant to 2,4-D. Becoming worse in recent years. At the onset of selection, resistant individuals are at a low frequency, so overall efficiency of the herbicide is not compromised. Survivors of an herbicide application produce seed and enrich the seed bank with more resistant plants. Resistant lines may have some bleaching in response to the herbicide, but survive the treatment. Continued use of the herbicide leads to geometric increase in resistant plants, until the herbicide is useless. Reduced efficacy of the herbicide over time may be blamed on something else. Resistance may be manifested at any stage of herbicide action, from interception to target site. Mechanisms include target site and non-target site mechanisms. Prevention measures can include rotation of herbicides, rotation of crops, mixing herbicides, developing herbicides with new modes of action, mechanical control, and avoidance of herbicide use. Annual weeds with high seed output develop resistance faster. Some herbicides can have resistance in as little as 3 - 5 years. Factors which increase the speed of resistance development include: initial frequency of resistance allele in the population, population abundance, intensity of selection (herbicide dose and frequency of application), inheritance patterns of the trait, and mating systems of the weed. |
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Term
| Herbicide tolerant crops (HTC) |
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Definition
| Crops genetically engineered to have resistance to herbicides. Includes GT corn, Xtend soybeans, Enlist, and Roundup Ready. Can have issues with drift when non-resistant crops are growing nearby. |
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Term
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Definition
| Can be expensive. Sometimes do more harm than good, harming the crop. Risk development of herbicide resistance. Which herbicide can be used is limited: must be safe to the crop, and kill the weeds. Timing is limited; there are pre-emergence and post-emergence spray windows, you cannot enter the field during late stages of some crops, and there is a minimum period after spraying before you can harvest. Parts of the field can be accidentally missed or sprayed twice. In developing countries, herbicides and equipment may be inadequate, leading to improper usage/dosage, and unsafe application. |
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Term
|
Definition
| Produced from p-hydroxyphenylpyruvate by HPPD. Converted into plastoquinone. Its production stops with application of an HPPD inhibitor. |
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Term
|
Definition
Arsenal
An imidazolinone ALS inhibitor. Registered for non-crop and non-grazing areas. |
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Term
|
Definition
Cleansweep
Conquest B
Pursuit
Valor
An imidazolinone ALS inhibitor. Registered for soybeans, dry common beans, adzuki beans, snap beans, Clearfield corn, Clearfield canola, processing peas, and alfalfa for seed production. Has long-lasting soil persistence. You cannot grow tomatoes or potatoes the year after using it. |
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Term
|
Definition
| A class of ALS inhibitors used in agriculture. Developed recently. Includes five active ingredients. Used in soybeans, legumes, and cereals to control dicot and monocot weeds. Includes imazapyr and imazethapyr. |
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Term
|
Definition
| A branched chain amino acid. Produced from 2-acetohydroxybutyrate, the product of ALS when it condenses pyruvate and 2-ketobutyrate. Has a negative feedback lop; inhibits TD, the enzyme which synthesizes 2-ketobutyrate. |
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Term
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Definition
Balance
Converge
A diketone HPPD inhibitor. Weeds have developed some resistance to this herbicide. |
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Term
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Definition
| A Monsanto chemist who took the AMPAs with weak herbicidal action, tested by Phil Hamm, and developed them into more efficacious chemicals. He re-invented glyphosate in 1970. |
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Term
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Definition
| A post-chorismate intermediate for phenylalanine and tyrosine synthesis. Produces a negative feedback loop by inhibiting 3-deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase-Mn, which is used for the production of shikimate-3-phosphate (S3P), a substrate of EPSPS. Regulates carbon flow in the shikimate pathway. |
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Term
|
Definition
Chenopodium album
Family Amaranthaceae. Glufosinate is not an effective herbicide.
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Term
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Definition
Digitaria sanguinalis
Family Poaceae. An annual grass. Reproduces by seed only. Lacks auricles. Leaf sheath is hairy, with a hairless margin. Both sides of the leaf blade are hairy. Ligule is membranous. Seed head consists of slender, finger-like spikelets that branch out from one point.
[image] |
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Term
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Definition
| An identifying feature of grasses. The basal section of the leaf which wraps about the stem. Its surface may be hairy or smooth, and its margins may be hairy or paper-like. |
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Term
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Definition
| A branched chain amino acid. Produced from acetolactate, the product of ALS when it condenses two pyruvates. Has a negative feedback loop; inhibits ALS, as well as IPSM, an enzyme in its own synthesis. |
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Term
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Definition
| An identifying feature of grasses. The strap-shaped tissue which protrudes at the border of the leaf sheath and the leaf blade. May be membranous, hairy, or absent. |
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Term
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Definition
| An auxinic herbicide in the phenoxyacetic chemical family. |
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Term
|
Definition
| An auxinic herbicide in the phenoxyacetic chemical family. |
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Term
|
Definition
Callisto
A triketone HPPD inhibitor. Weeds have developed some resistance to this herbicides. |
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Term
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Definition
| Works with farmers and researchers in Ontario, solving weed management challenges. Formulates effective management plans for farmers. |
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Term
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Definition
| A method of reducing herbicide resistance. Favoured by farmers; not very complex, and cost-effective. There is reduced selection pressure on weeds, because the plant would need to develop resistance to every herbicide in the mixture in order to survive the treatment. It can be easy to make a mistake and mix herbicides which cancel each other's action, or react badly. If a precipitate forms, it can damage the sprayer. A nickname for farmers who overuse this method is "Captain Cocktail". Formulations are available that are mixtures with several modes of action. Can be expensive, and there is increased risk of crop injury. |
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Term
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Definition
Stacking
When a weed accumulates multiple resistance mechanisms to multiple herbicides. Shown mostly in allogamous species such as rigid ryegrass. Occasionally leads to enhanced resistance to more than one herbicide. |
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Term
|
Definition
| An herbicide injury symptom. Death of plant tissue. Tissue becomes a brown, grey, or black colour. Symptomology is not very specific. Leaf blade may be dead, but not the veins. With fast-acting contact herbicides, necrosis can be seen only on spots where droplets landed. |
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Term
|
Definition
Accent
Accent One-pass
Accent Total
Extra
Summit
Ultima
Ultim Total
A sulfonylurea ALS inhibitor. Registered for use in field corn, seed corn, and some varieties of sweet corn. |
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Term
|
Definition
Tolerance
A mechanism of herbicide resistance. Involves biochemical/physiological changes that prevent herbicide from reaching or accumulating at the target site in inhibitory quantities. Includes enhancement of metabolic degradation of the herbicide. |
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Term
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Definition
| Has sandy soil, which is relatively easier to till. |
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Term
|
Definition
| A diphenyl ether protox inhibitor. |
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Term
| P-hydroxyphenyl pyruvate dioxygenase (HPPD) inhibtors |
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Definition
| Has competitive inhibition of p-hydroxyphenypyruate. Inhibits carotenoid synthesis, leading to lack of protection from UV, and typically leaf bleaching. Stops production of homogentisate, a cofactor in carotenoid synthesis. Stops production of plastoquinone, preventing electron transport. Supplying homogentisate reverses the symptoms; the plant dies from starvation, not accumulation. Chlorophyll is unprotected from singlet oxygens created by UV radiation. Leads to lipid peroxidation, chlorophyll breakdown, and bleaching. Symptoms include chlorosis where applied, and necrosis near leaf margins. Xylem-mobile, affecting older leaves first. Includes diketons and triketones. |
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Term
|
Definition
Amaranthus palmeri
Family Amaranthaceae. Glyphosate resistance is conferred by amplification of EPSPS amounts.
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Term
|
Definition
Gramoxone
A bipyridillium. Used in industrial sites, for pre-seeding, pre-planting, or post-harvest. Can be used as a desiccant, or to kill all weeds, making harvest easier. Causes chlorotic spotting and rapid wilting.
1. The oxidized ion steals an electron from PSI, becoming a reduced paraquat radical.
2. Paraquat radical reacts with water (H2O) and oxygen (O2) to create superoxide (•O2-).
3. Superoxide reacts with an enzyme to form hydrogen peroxide (H2O2) and oxygen.
4. Hydrogen peroxide forms a hdyroxyl radical (•OH) which causes cell membrane damage. |
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Term
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Definition
| The patent for a chemical lasts for 18 - 20 years after its discovery. The company must conduct all testing and development for the product before it expires in order to turn profit, which can take 5 - 10 years. Use usually slows after the patent expires. |
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Term
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Definition
| A species of moth which changed colour in England and Ireland during the industrial revolution. The tree species which they live on had light-coloured bark that became black due to soot emitted by the coal-burning factories. White moths which used to blend in with the bark were now more visible to birds, and easy prey. Rare mutant black moths which were normally eaten by birds were able to escape and reproduce. Eventually the entire moth population consisted of black moths. |
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Term
|
Definition
| Long-term activity of an herbicide in the soil. Can be an issue on rented land. Depends on the soil chemistry. There may be increased persistence in low pH soil pockets. ALS inhibitors have long-term persistence. |
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Term
|
Definition
| An app which aids farmers with pest management. Field data is entered, including what types of weeds and pests, and timing constraints for field activities. the program gives the best spray program. It does not consider cost, but is more accessible to farmers than Publication 75. |
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Term
|
Definition
| Studied phototropism of plants in 1913. Found that a mica barrier inserted unilaterally into the shoot caused false phototropism, however a gelatin barrier did not. |
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Term
|
Definition
| Takes 4 - 5 years to complete. You can go directly from an undergrad into a PhD, though it is uncommon. |
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Term
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Definition
| Cause the browning seen in apples exposed to oxygen. |
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Term
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Definition
| A scientist who tested AMPAs synthesized by Monsanto. Found that two of the compounds showed herbicidal activity on perennial weeds, but the activity was too weak to be used as a commercial herbicide. |
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Term
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Definition
| The process in plants where solar energy is transformed into chemical energy within the chloroplasts. Water is oxidized within the thylakoids, producing protons, electrons, and oxygen. Electrons move through different intermediates, producing ATP and NADPH. The energy is used in the enzymatic reduction of CO2 into carbohydrates within the chloroplast stroma. An important process, providing the basis for life. Plants provide the initial source of energy for many food chains. Operates based on two photosystems: PSII and PSI, which move electrons from high to low energy, operating in a series. Herbicides which target either system are likely to be lethal. |
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Term
|
Definition
| Contain particular polypeptides, pigments, and electron acceptor/donors, and P700. Receives electrons from PSII. A second light reaction transfers the electrons to their final acceptor, NADP+, producing NADPH. ATP is produced during photosynthesis, and together they provide reducing power during carbon fixation. |
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Term
|
Definition
| Contains particular polypeptides, pigments, and electron acceptor/donors, and P680. The primary reductant is produced from photolysis of water. Transfers electrons through a sequence of carriers with descending reducing power, to PSI. There are many more inhibitors of PSII than of PSI. Reaction centre is comprised of two reaction subunit proteins: D1 and D2, encoded by psbA and psbD, respectively. There is only one binding site for each reaction centre, and binding-dissociation constants are similar to inhibition constants. |
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Term
| Photosystem II inhibitors |
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Definition
| Include many of the oldest and most widely used herbicides. Represent approximately half of all herbicides found in the Pesticide Manual. Includes many different compounds from numerous chemical groups, including phenyl ureas, triazines, triazinones, uracils, anilides, phenylcarbamates, and phenols. Diversity illustrates the importance of PSII as a target site. Reduce electron flow from water to NADP+ during photosynthesis by binding to the QB site on the D1 protein, and preventing plastoquinone from binding to this site. Inhibition results in lack of NADPH and ATP for carbon fixation, and prominent cell death. High effectiveness, imposing a strong selection pressure for developing resistance. Sometimes used repeatedly with limited rotation. When absorbed by the roots, there is chlorosis between leaf veins, followed by death of leaf tips and margins. When absorbed by leaves, there is chlorosis and necrosis where the spray lands, with little movement to other leaves. |
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Term
|
Definition
| An auxinic herbicide in the picolinic acid family. |
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Term
|
Definition
| A lipid-soluble electron carrier. Binds to the QB site of PSII; this binding is prevented by PSII inhibitors. Produced from homogentisate. Drives electron transport, and the enzyme that produces phytoene, a precursor of carotenoids. Its production stops with application of an HPPD inhibitor. |
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Term
|
Definition
Toxicodendron radicans
Family Anacardiaceae. Produces an oil which can cause an allergic reaction.
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Term
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Definition
| A factor which can affect yield loss caused by weeds. The more weeds there are, the more competition there is, and lower yield will be. |
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Term
|
Definition
Summit Extra
A suflonylurea ALS inhibitor. Registered for use in field corn. |
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Term
|
Definition
Accent One-pass
Peak Plus
A sulfonylurea ALS inhibitor. Registered for use in field corn. |
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Term
|
Definition
| Accumulates in the cytosol after application of protox inhibitors. Reacts with light and oxygen, generating reactive oxygen species which attack membrane lipids. Causes the rapid development of necrosis typical of protox inhibitors. |
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Term
|
Definition
Protoporphyrinogen IX oxidase
An enzyme which converts protoporphyrinogen IX into protoporphyrin IX in the chloroplast, as part of chlorophyll synthesis. Inhibited by protox inhibitors. |
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Term
|
Definition
| Herbicides which prevent synthesis of chlorophyll, leading to accumulation of an intermediate with toxic effects. Inhibits protox in the chloroplast, stopping production of protoporphyrin IX, and causing accumulation of protoporphyrinogen IX. Protoporphyrinogen IX leaks out of the chloroplast into the cytosol, where another enzyme converts it into protoporphyrin IX. Plant damage is characterized by rapid development of necrotic zones on the leaves. Tolerant plants survive by enhanced metabolism, but may show damage at high doses or in hot or humid weather. Includes diphenyl ethers and pyrimidinediones. |
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Term
|
Definition
Guide to Weed Control
An OMAFRA publication. can be a pain to work with. There is inconsistent listing of the names of herbicides, with trade names and chemical name used interchangeably; can be very confusing for users. |
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Term
|
Definition
| A symptom of ALS inhibitors and glyphosate. Prominent in some dicots, especially on leaf underside. The herbicide reacts with red pigments. |
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Term
| Pyrimidinyl-oxy-benzoate (POB) |
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Definition
| A class of ALS inhibitors used in agriculture. Developed recently. Includes two active ingredients. Includes pyrithiobac. |
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Term
|
Definition
Staple
A pyrimidinyl-oxy-benzoate ALS inhibitor. Used for broadleaf control in cotton. |
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Term
|
Definition
| An acceptor plastoquinone tightly bound to the D2 subunit of PSII. Transfers electrons to QB. |
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Term
|
Definition
| An acceptor plastoquinone loosely bound to the D1 subunit of PSII. Accepts electrons from QA. Can be displaced when an herbicide molecule attaches to the D1 binding site, preventing electron transfer. |
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Term
|
Definition
| Includes oxygen (O2), superoxide anion (•O2-), peroxide (•O2-2), hydrogen peroxide (H2O2), hydroxyl radical (•OH), and hydroxyl ion (OH-). Harmful to the cell, and lead to cell death. |
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Term
|
Definition
Milhouse Van Houten
Expression is repressed by gene repressors. On the Simpsons, Milhouse is bullied by Nelson (repressor). |
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Term
|
Definition
Lolium rigidum
Family Poaceae. Glyphosate resistance is conferred by amplification of EPSPS amounts. An allogamous species with multiple resistance. Populations have been found with two distinct glyphosate resistance mechanisms: target site modification and reduced translocation. These populations had much higher resistance than single mechanism plants.
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Term
|
Definition
Battalion
Prism
Ultim
Ultim Total
A sulfonylurea ALS inhibitor. Registered for use in field corn, potatoes, transplanted processing tomatoes, and rice. |
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Term
|
Definition
| A mixture of glyphosate and glufosinate. It was created because there was a demand for a faster-acting Roundup. However, glufosinate is a contact herbicide, killing phloem tissue, and preventing the translocation of glyphosate, reducing glyphosate's efficacy on perennials. |
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Term
|
Definition
Crocus sativus
Family Iridaceae. A crop which takes 2 - 3 years to develop.
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Term
|
Definition
| A pyrimidinedione protox inhibitor. |
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Term
|
Definition
Herman Hermann
A complex consisting of Skp1-cullin-F-box-proteins. Degrades repressors of gene expression, activated by IAA or 2,4-D, leading to increased gene expression. On the Simpsons, Herman owns a war memorabilia store. He shows Bart (IAA) some fighting tactics to help him stop Nelson (repressor) from bullying Milhouse (repressed genes). |
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Term
|
Definition
| SCF-ubiqutin ligase E3 complex, containing the TIR1 protein. Specificity is determined by TIR1. Targets IAA repressor proteins for polyubiquitination and degradation. |
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Term
|
Definition
Glycine max
Family Fabaceae. Planted at a density of 150 thousand plants/ac. Has few herbicide options. Pre-plant applications can be used. Sensitive to Dicamba, except Xtend varieties. Yield loss of 30% is equal to losing $150/ac; this is much greater than the cost of weed control in early stages ($7 - $20/ac), even if you control regularly.
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Term
|
Definition
| A concern of society. An herbicide should kill only the weeds, and not non-target organisms in the environment. |
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Term
|
Definition
| A difficult herbicide injury symptom to identify; you must compare the plants with an untreated check. May be noticeable when a strip of the field is missed by accident. |
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Term
| Sulfonylamino-carbonyl-triazolinone (SCT) |
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Definition
| A class of ALS inhibitors used in agriculture. The most recently developed ALS inhibitors. Includes two commercialized active ingredients, including flucarbazone-sodium. |
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Term
|
Definition
| A class of ALS inhibitors used in agriculture. The first ALS inhibitor to be marketed. Includes 22 commercialized active ingredients, including chlorsulfuron and thifensulfuron-methyl. Widely used in Canada and USA on soybeans, corn, and cereals. Controls dicot and monocot weeds. |
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Term
|
Definition
Touch Down
Glyphosate prepared with a sulphur-based salt. Patented by Syngenta. Has similar efficacy to glyphosate. |
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Term
|
Definition
| An enzyme in the plant which causes death when inhibited. The cell is destroyed, and the plant meristem is killed. As small a dose of the herbicide as possible is ideal. The ideal target site may be different for society, farmers, and companies. |
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Term
|
Definition
| A mechanism of herbicide resistance. Generally due to point mutations that code for single amino acid substitutions in the target enzyme. Mutations result in a target enzyme that is much more insensitive to the herbicide than the wildtype, due to lowered herbicide binding affinity. Level of resistance varies from low (less than 10-fold) to very high (greater than 1,000-fold) depending on the combination of herbicide, target site, and mutation. |
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Term
|
Definition
2,3,7,8-tetrachlorodibenzo-p-dioxin
Produced from 2,4,5-T during the production of Agent Orange, if the reaction is not conducted perfectly. Very persistent in the environment, and difficult to degrade. It has had negative effects on Vietnamese populations as well as Vietnam War veterans. |
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Term
|
Definition
| The permanent posting of a professor. Makes it difficult to be fired; you would have to do something really bad. Ensures scientific integrity; companies or superiors cannot pressure scientists into producing false results by threatening to fire them. They can only withdraw funding. |
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Term
|
Definition
| The student completes a project and writes and defends a thesis. Takes longer than course-based grad school. Usually the preface of a PhD. |
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Term
|
Definition
Pinnacle
Refine Extra
A sulfonylurea ALS inhibitor. Registered for use in soybeans, wheat, barley, tomatoes, and oats not underseeded in legumes or grasses. |
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Term
|
Definition
| A factor which can affect yield loss caused by weeds. When weeds emerge ahead of the crop, yield loss is greatest; the weeds can form a canopy over the crop. |
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Term
|
Definition
Armezon
Impact
A triketone HPPD inhibitor. |
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Term
| Transporter inhibitor response (TIR1) |
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Definition
| Homologous to AFB. Part of the ubiqutin-26S proteasome-mediated pathway for protein degradation and turnover. Determines the specificity of the SCFTIR1 complex. |
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Term
|
Definition
| The number of trials for a control measure is important. Environmental factors can change the outcome of a trial. |
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Term
|
Definition
| A class of ALS inhibitors used in agriculture. Developed recently. Includes four active ingredients. Two members are used mostly in soybeans. Includes flumetsulam. |
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Term
|
Definition
Upbeet
A sulfonylurea ALS inhibitor. Registered for use in sugar beets. |
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Term
|
Definition
| An herbicide registered for use on giant hogweed. Mostly effective on seedlings. |
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Term
|
Definition
| The bacteria which causes this disease has resistance to many antibiotics. It is always treated with a mixture of antibiotics, to prevent development of further resistance. |
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Term
|
Definition
| A branched chain amino acid. Produced from acetolactate, the product of ALS when it condenses two pyruvates. Has a negative feedback loop; it inhibits ALS. |
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Term
|
Definition
| When herbicide easily volatilizes. Avoid spraying auxinic herbicide when the weather is hot, and use amine formulations instead of ethers, to avoid this. |
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Term
|
Definition
Abutilon theophrasti
Family Malvales. Glufosinate is not an effective herbicide.
[image] |
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Term
|
Definition
| The USA opposed Chinese and Russian communists in Vietnam. Their enemies hid in the jungle, so the USA sprayed Agent Orange to defoliate the trees. |
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Term
|
Definition
| Sometimes growers delay weed control because there are only a few weeds in the field. It is better to control at this point, to prevent it from becoming a bigger problem later, costing less in the long term. |
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Term
|
Definition
| Have non-uniform germination, and good seed dormancy. |
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Term
|
Definition
| A method of applying herbicide. A long sponge is saturated with herbicide, and mounted on the tractor boom at a height so that it wipes herbicide onto tall weeds which tower over the crop. Must be careful that the herbicide doesn't drip onto the crop below. Can be challenging to use. |
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Term
|
Definition
Triticum sp.
Family Poaceae. Planted at a density of 1.4 million plants/ac. Harvested in July and August.
[image] |
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Term
|
Definition
Avena fatua
Family Poaceae. A problematic weed in the prairies, in cereals. Lacks auricles. Ligule is long and membranous. Leaf blade is hairless, but there are some short hairs on the leaf margin near the base. The leaves twist counter-clockwise. Seeds resemble those of oats, but are shed earlier. Has a large, relaxed panicle. Each spikelet has two papery glumes. An autogamous (self-pollinating) species which has multiple resistance.
[image] |
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Term
|
Definition
Oryza sp.
Family Poaceae. An aggressive weed in rice. Has shared characteristics with the crop, making it difficult to control. Looks similar to rice before flowering, making hand weeding difficult. In the 1930s, breeders created rice varieties with purple leaves, to make hand weeding easier; wild rice are the only green plants in the field. However, this was a strong selection pressure and in 4 - 5 years, the wild rice had evolved to be a similar colour to the crop.
[image] |
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Term
|
Definition
Panicum capillare
Family Poaceae. Seedlings look similar to those of large crabgrass. Lacks auricles. Ligule is hairy. Leaf sheath is hairy, with a hairy margin. Both sides of the leaf blade are hairy. Stem has a round cross-section. Seed head is a branched panicle.
[image] |
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Term
|
Definition
| American and British plant physiologists working on auxin regulation of plant growth used different chemical analogues of plant hormones which had effect on plants. When the potential of some of these molecules for inhibiting plant growth was recognized, the research became classified by the army for its potential as a chemical weapon. After the war, restrictions were released and 2,4-D and MCPA became commercially available. |
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Term
|
Definition
| Dicamba resistant soybeans. Allows for almost 100% control of Canada fleabane. |
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Term
|
Definition
Setaria pumila
Family Poaceae. Seedlings look similar to those of green foxtail. Ligule is hairy. Leaf blade has long, scraggly hairs at the base. Stem has a round cross-section as a seedling, but then becomes flattened as the plant matures. Seed head is similar to that of green foxtail, but with shorter, red/brown bristles. Seeds are larger than those of green foxtail.
[image] |
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Term
|
Definition
Cyperus esculentus
Family Cyperaceae. Stem has a triangular cross-section. Leaf blade is hairless. Seed head consists of branched yellow clusters. A perennial. Has vegetative propagation with tubers, which are edible. It is grown as a crop in some places, including Egypt and Spain. Tubers can be used as bait for carp or wild turkey.
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