Agronomy Pest and Weed Management 2 — Questions and Answers
Question 1: Which group of insects are important biological control agents for aphids in crops?
- Thrips and spider mites
- Ladybugs (lady beetles) and parasitic wasps (Correct answer)
- Cutworms and armyworms
- Wireworms and white grubs
Correct answer: Ladybugs (lady beetles) and parasitic wasps
Lady beetles and parasitic wasps are natural enemies of aphids, feeding on or parasitizing them and reducing aphid population growth.
Question 2: What is herbicide resistance in weeds?
- Temporary tolerance of weeds to low herbicide doses
- Inherited ability of a weed biotype to survive a herbicide dose that kills normal plants (Correct answer)
- Herbicide breakdown before it reaches target weeds
- Weed dormancy triggered by herbicide application
Correct answer: Inherited ability of a weed biotype to survive a herbicide dose that kills normal plants
Herbicide resistance is a heritable trait in weed populations that allows surviving plants to tolerate doses that would kill susceptible biotypes of the same species.
Question 3: Soybean cyst nematode (SCN) is best managed long-term using what strategy?
- Annual nematicide application
- Rotating SCN-susceptible and resistant soybean varieties combined with crop rotation (Correct answer)
- Deep tillage to bury cysts
- Flooding fields during fallow
Correct answer: Rotating SCN-susceptible and resistant soybean varieties combined with crop rotation
Combining SCN-resistant varieties with rotation to non-host crops (corn) reduces SCN population densities and extends the effectiveness of resistance genes.
Question 4: What is a pre-emergent herbicide?
- A herbicide applied after weeds have emerged and established
- A herbicide applied to soil before weed or crop emergence to prevent germination (Correct answer)
- A herbicide that kills only grass weeds
- A herbicide mixed into fertilizer only
Correct answer: A herbicide applied to soil before weed or crop emergence to prevent germination
Pre-emergent herbicides are applied to soil before weed seedlings emerge, forming a chemical barrier that prevents germination or kills seedlings as they emerge.
Question 5: The corn rootworm beetle's economic damage to corn is primarily caused by what?
- Adult beetles defoliating leaves
- Larval feeding on roots, reducing water and nutrient uptake and causing lodging (Correct answer)
- Beetle feeding on pollen and silks
- Adults boring into stalks
Correct answer: Larval feeding on roots, reducing water and nutrient uptake and causing lodging
Corn rootworm larvae feed on corn roots, reducing the plant's ability to uptake water and nutrients and causing yield loss and lodging.
Question 6: Which crop disease is caused by Fusarium graminearum and affects the heads of wheat and barley?
- Septoria leaf blotch
- Fusarium head blight (scab) (Correct answer)
- Powdery mildew
- Crown rust
Correct answer: Fusarium head blight (scab)
Fusarium head blight (scab), caused by Fusarium graminearum, infects wheat and barley heads, causing yield loss and contaminating grain with mycotoxins like DON.
Agronomy Pest and Weed Management 2
Which group of insects are important biological control agents for aphids in crops?