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level: Level 2

Questions and Answers List

level questions: Level 2

Question	Answer
What trait is very effective against WBC?	Bt corn
What trait is very effective against WBC?	Bt corn
What trait is very effective against WBC?	Bt corn
Corn pest - How many generations do common stalk borers have per year?	One
Common stalk borer - start scouting at _ GDDs (base temp of _), or when _% of larvae move from grass to corn	1400, 41°F 10
Common stalk borers - check plants by _ areas, and look for larvae in the _ of the corn plants	grassy, whorl
Common stalk borer - EIL is based on crop height, crop value, and control costs. If corn is V2 and valued at $4 per bushel, EIL is _% infestation.	8
Common stalk borer - Insecticide is sometimes only needed on _ rows, applied before they burrow into _.	border, corn stalks
Common stalk borer - if the field is infested with _ and _ weeds, an insecticide may need to be applied across the entire field.	grass, giant ragweed
What corn trait does a good job controlling common stalk borers?	Bt corn
What is this corn pest?	Corn rootworm
Which rootworms are the most troublesome for corn production in Iowa?	Northern and Western rootworms
What kind of corn rootworm is this?	Northern corn rootworm
What kind of corn rootworm is this?	Western corn rootworm
What kind of rootworm is this?	Southern corn rootworm
Name these corn rootworms from left to right	Southern, Western, Northern
True or false: Southern corn rootworms cause corn damage in Iowa by themselves.	False
Corn rootworm - Larvae feed on roots for _ weeks between _ and _. Adults emerge throughout the summer, but peak emergence is in _.	5, June, July, August
Where and how do N and W rootworms overwinter?	Overwinter in Iowa as eggs in the soil
Often, corn rootworm beetles feeding on _ before pollination can reduce yields.	Corn silks
To scout corn rootworm, count a minimum of _ consecutive plants. Count the beetles. In continuous corn, the ET is _ beetles/plant, whereas in first-year corn it is _ beetles per plant.	20, 0.7, 0.4
Corn rootworm - Seed treatments are only recommended for _ to _ infestations	Low, medium
Corn rootworm - What corn trait protects the plants?	Bt corn and other biotechnology
What is another effective option to control corn rootworm, which are better than seed treatments?	In-furrow insecticides or at-plant insecticides. Provides a zone of protection until roots can replace themselves.
If corn rootworm insecticides are broadcast at-plant, how far should they be incorporated into the soil?	1"
When should you start scouting for corn rootworm?	In early July, when beetles first appear
What kind of corn pest is this?	European corn borer
What do European corn borer adults look like?	Moths
How many generations do European corn borers have in Iowa?	2
European corn borer - 1st gen lays eggs when?	Mid-June
European corn borer - 2nd gen lays eggs when?	Late July - early August
European corn borer - first gen feeds where?	Leaves, tunnels into midribs
European corn borer - second gen feeds where?	Stalks, tassels, ear shanks, leaf collars, and developing ears. Can crawl into ears and feed on corn kernels.
Where do European corn borers lay their eggs?	Underside of corn leaves, by the midribs.
Start scouting for first-gen European corn borers when?	About 8-10 days after moths begin to emerge. Look at earlier-planted fields first.
Start scouting for second-gen European corn borers when?	Late July
European corn borer foliar insecticides only have a _ to _% effectiveness because of the larvae that have tunneled into the stalks prior to application.	70, 80
To control second-gen European corn borers, what is a cultural approach?	Harvest early, but beware of energy costs when drying grain.
What corn trait does a good job controlling European corn borers?	Bt corn
What is this corn pest?	Western bean cutworm
Western bean cutworms emerge in late _ or early _	June, July
Where do western bean cutworms lay their eggs, and how many eggs can be on each mass?	Tops of leaves, 5-200
WBC - Corn ears that contain _ larvae can destroy _ to _% of the kernels.	10, 50, 60
How can you determine when to scout fields for WBC?	ISU has a moth-trapping program. Check the website.
WBC management relies on _ or _.	Insecticide applications, Bt corn hybrids
WBC management - Apply insecticides if _% of plants have an egg mass, or if _ are found in the tassel.	8, young larvae.
When should you apply insecticides to corn for WBC?	When 90-95% of tassels have emerged.
WBC management - After tassels have emerged, insecticide applications should be made when _ to _% of the eggs have hatched.	70, 90%
What trait is very effective against WBC?	Bt corn