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11 Cards in this Set

  • Front
  • Back
Why is weed control desirable in terms of increasing crop yield and minimizing costs?
reduce competition for light, water and minerals (more yield)

replace manual/mechanical labor

eliminate weeds which contain toxins

less cover for other pests including diseases and insects
What are some terms for herbicide use? (many types of uses)
contact- kill only plant parts to which herbicide was applied

systemic- absorbed by roots or above ground parts and moved to distant tissues

eradicant- completely eliminate vegetation

selective- kill or stunt weeds without harm to crop
What are the terms for timing of application of herbicides?
Preplant- before crop is planted for control of annual weeds

preemergence- before crop or weeds emerge

postemergence - self explanatory
What are the terms for how you apply the herbicides?
band- continuous over a restricted area

broadcast- uniformly over entire area

spot treatments- small areas

directed sprays- applied to selected weeds or to the soil to avoid contact with the crop
What are some factors which contribute to herbicide effectiveness?
1. weed type
2. soil condition- its type, moisture, and herbicide absorption
3. rainfall or irrigation- water usually required for activation
4. time of application- time of growth of weed/crop and when the herbicide is effective during which stage
What are the different types of herbicide placements and note any disadvantages?
Preplant incorporation- volatile and photolabile herbicides incorporated before planting
- most effective at dry weather, moisture insures activation-

Preemergence (PRE) applied to soil surface
- activated by rain

Postemergence (POST) applied to germinated weeds
What's the difference between a dessicant and defoliant?
Dessicant- accelerate leaf fall

Defoliant- cause foilage to lose water and leaves remain on plants
Which of the dessicant/defoliant must be applied early?
Defoliants must be applied early
What are the advantages between dessicants and defoliants?
Dessicants- can apply later, functions longer, contributes to cotton seed quality

Defoliant- earlier harvesting, higher grade of cotton because fewer leaves remain to clog the mechanical picker, increase exposure to sun and air
What are the benefits from using plant growth regulators?
Better quality foods, you get fruits and vegetables year round (despite "out of season"), and lower food cost (no need for manual labor)
What are the six types of PGRs and an example of each? (especially auxin and gibberellins)
auxins- indoleacetic acid, enhance elongation in shoot cells- loosening of cell walls

Gibberillins- stimulate cell division/elongation - GA3 most used

Cytokinins- prolong storage life- induce cell division- derivatives of adenine

Ethylene- induce ripening

Inhibitors- inhibit growth and germination- prevent sprouting of stored crops (potatoes)
- benzoic acid

Growth retardants