Exam 2 herbicide questions

Preplant herbicide applications in ag refers to treatment _____________ the crop is planted

before

Preemergence herbicides in crops can be used ___________ and ____________ weeds emerge but ONLY __________ crop emerges

before after before

The inherent sensitivity to herbicide at cellular level refers to the ________________ basis of herbicide selectivity

biochemical

Herbicides are absorbed through the process of _____________

diffusion

2 forms of directed herbicide application

drop nozzle and ropewick

____________ herbicides are wax and oil soluble, fast moving, and less sensitive to water stress

non polar

2 reasons herbicide resistance occurs

1. A small portion of weeds within a population are naturally resistant. 2. Repeated use of herbicides that inhibit the same site of action select for the resistant plants.

4 Factors affecting cuticle thickness

1. Age 2. Species 3. Light exposure 4. Moisture status of the developing plant

4 mechanisms of herbicide resistance

1. Altered binding sites 2. Overproduction of binding sites 3. Metabolism 4. Compartmentalization this website helps http://pesticidestewardship.org/resistance/Herbicide/Pages/Mechanisms-of-Herbicide-Resistance.aspx

3 methods of herbicide placement

1. Broadcast 2. Banded 3. Directed

3 Pros and COns of PRE herbicides

1. Can be applied when planting 2. Less work required to apply than PPI 3. Great for Band apps Cons: 1. Needs rain 2. Envmt controls when app can be made 3. Used before the problem can be seen

2 forms of protectve barriers used during herbicide application

1. Charcoal barriers 2. Spray shields

3 ways roots absorb herbicide through DIFFUSION

1. Concentration gradient 2. in a soil solution 3. in vapor phase

Leaves are the most important site for herbicide absorption by plants. What 3 anatomical characteristics of a leaf impact it's ability to absorb? What characteristic has the biggest impact on absorption?

1. Cuticle 2. Cell wall 3. Plasmodesmata Cuticle

5 factors that affect foliar absorption

1. Cuticle thickness 2. Herbicide (and all factors considered with each) 3. Environment 4. Moisture status of the plant 5. The use of adjuvants

2 ways plants can metabolically alter herbicides to improve efficacy

1. Deactivation 2. Activation

3 morphological characteristics of herbicide selectivity

1. Differential Interception 2. Differential retention 3. Growing point location

3 factors that effect Rate of Spread of Resistance

1. Dominant vs. Recessive traits of the plant 2. Nuclear vs Non-nuclear plant genes 3. Weed biology (seed and pollen mvmt potential)

2 forms of non-selective herbicides

1. Foliar active 2. Soil active (Fumigants, sterilants)

3 areas of a leaf where cuticle is generally thinner

1. Guard cells of the stomata 2. Cells over vascular tissue 3. Cells of trichomes

2 morphological factors effecting herbicide RETENTION by a plant

1. Leaf surface 2. Orientation

3 ways herbicides can be absorbed through the roots

1. Mass Flow 2. Root interception 3. Diffusion

5 biological factors effecting herbicide selectivity

1. Morphological 2. Growth Habit 3. Physiological 4. metabolic 5. biochemical

3 Characteristics of PRE herbicides

1. Must have residual 2. Relatively non volatile 3. Requires rainfall

3 characteristics of PPI (Preplant incorporation) herbicides

1. Must have residual effect 2. May be volatile 3. Good crop tolerance

3 Pros and Cons of PPI herbicides

1. No interference at time of planting 2. Less dependent on rainfall than PRE 3. Less trips across field Cons: 1. Less flexibility to change 2. Not as effective in reduced till systems 3. Higher costs

4 characteristics of POST

1. Non volatile 2. May be soil active or foliar ative 3. May be selective or non selective 4. Systemic and non systemic

3 advantages of herbicides

1. Reduce labor costs 2. Reduce tillage 3. Reduce crop injury risk

5 practices to reduce risk of herbicide resistant weeds

1. Rotate chemistry with different site of action 2. Scout 3. Rotate crops with differing life cycles 4. Mechanically remove weeds 5. Avoid transport of resistant weed seeds

3 cons of POST herbicides

1. Timing 2. requires scouting 3. when applying very sensitive to envmt

3 ways plants biochemically affect a herbicides efficacy

1. altering binding site 2. plant has multiple forms of binding sites 3. Overproduction of binding sites

There are _____ Sites of Action, _______ modes of action, and _________ chemical herbicide families

12, 10, 24

When was the start of the "pesticide era"

1945

When was EPA invented?

1970

How long can soil sterilant persist in the soil? Fumigants?

2 years for sterilants >2 days for fumigants

2 ways PRE herbicides can be applied

Broadcast Banded

The formation of chemical complexes

Conjugation

Resistance to two or more herbicides with the same site of action.

Cross resistance

In 1972, what pesticide was banned?

DDT

For PPI herbicides, what piece of equipment is generally a poor choice

Disk machine

The inherent ability of a plant to survive and reproduce following exposure to a dose of herbicide normally lethal to the wild type refers to????

Herbicide resistance

4 PHYSICAL factors affecting herbicide selectivity

Herbicide; 1. Rate 2. Placement 3. Protective barriers 4. Formulations

In 1948 Mueller won the Nobel Peace Prize for....

His discovery of the high efficiency of DDT as a contact poison against several arthropods

Until the late 1940s, what was the most widely used pesticide?

Lead arsenic

3 morphological factors effecting herbicide interception by plant

Leaf 1. Size 2. Shape 3. Orientation

Resistance to two or more herbicides with different sites of action.

Multiple resistance

Preplant ____-____________ herbicides can be used days to months before planting of crops. Preplant ________________ herbicides can be used within a month of planting crops. ________ preplant herbicides can be used 10-45 days before planting/. Often this method is used in no till systems adnd utilizes rain for incorporation

Non-Selective Incorporated Early

Herbicides that work well on perennial weeds prior to planting

PPI

______ herbicides are water soluble, slow moving, and are very sensitive to water stress.

Polar

3 ways herbicides are classified

Selectivity, mode of Action, method of application

Who is Paul Mueller?

Synthesizer of DDT as an insecticide

Form or herbicide that disrupts physiological processes in the plants

Systemic

In 1995 "Our Stolen Future" discussed what?

The Endocrine Disrupter Hypothesis

The amount of pesticide residue permitted by federal law to remain in or on a crop"

Tolerance