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level: Soybean pests

Questions and Answers List

level questions: Soybean pests

Question	Answer
Where are spider mite eggs laid?	Undersides of leaves
Which corn pest can also attack soybean seeds and seedlings?	Seedcorn maggot
What soybean pest is this?	Bean leaf beetle
Bean leaf beetles emerge in the _ when _ plants emerge.	spring, soybean
BLB - Larvae live in _ and feed on _	the soil, roots/root nodules
How many generations of BLB?	2
When is the 1st generation of BLB in Iowa?	Early July - mid August
When is the 2nd generation of BLB in Iowa?	Early Sept - crop maturity
True or false: The 2nd gen of BLB hibernates and feeds on next year's young soybean plants.	True
BLB scouting - Using a sweep net, scout _ feet from the field's edge and take _ sweeps.	100, 20
Biggest factor with BLB infestations?	Defoliation, pod destruction, can transmit soybean pod mottle virus.
BLB management	Seed treatments for early-season protection, foliar insecticides for early- and mid-season use (if thresholds are reached).
What is this soybean pest?	Green cloverworm
When are GCWs the most damaging?	July - August
When do adult GCW moths fly into Iowa?	In the spring
GCW moths lay eggs where in May?	Underside of alfalfa leaves
GCW moths lay eggs where in June?	Alfalfa and soybean plants.
How many generations of GCW each year?	2
Where do GCWs feed?	Leaf tissue, between veins
Best approach for GCW sampling?	Drop cloth
EIL for GCW?	If crop is $8/bushel, EIL is 14 larvae per RF
GCW treatment should occur if thresholds are reached, and at what percent defoliation?	20%
True or false: Low populations of GCW are kept in check by parasites, predators, and a fungal disease, but a large infestation needs insecticides.	True
What soybean pest is this?	Soybean aphid
What trees do aphids lay eggs on?	Buckthorn trees
True or false: Soybean aphid infestations can develop at any soybean stage.	True
What residue do aphids leave behind that can affect the plant?	Honeydew
What diseases can aphids transmit?	Alfalfa mosaic, bean yellow mosaic, and soybean mosaic viruses
When should you start scouting soybean fields for aphids?	Mid-June. Check uppermost trifoliate and stems.
How often should small aphid infestations be scouted?	Every 2-3 days
What is the threshold for soybean aphid treatment?	250 aphids per plant and increasing from R1-R4
Insecticide applications between _ and _ have shown consistent yield protections for soybean aphids.	R1, R4
The benefit of insecticide applications after _ is greatly reduced for aphid control.	R5.5
What kind of soybean pest is this?	Two-spotted spider mite
What weather conditions facilitate spider mite infestations?	Drought stress
Where do spider mites overwinter at?	Alfalfa fields or broadleaf plants on field borders
When is peak spider mite population time?	August-September
How long are spider mite life cycles?	19 days
Where do spider mite infestations start?	Edge of soybean fields
What are the thresholds for spider mite infestations?	No thresholds, but treatments are justified in hot and dry weather with damaged soybean leaves and spider mites are present.
True or false: Field borders may only need to be treated for spider mites, but it is possible to have to treat the whole field.	True