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AgAlerts 2007 From Griggs County
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Issue # 5: July 11th, 2007
With the increase in corn acres the last three years, there is an increase in corn bore populations. If you are planting Bt corn, corn bore pose a less of a problem. Conventional and Roundup Ready corn are susceptible to corn bore. Adult corn borer moths are starting to emerge and lay eggs. Now is the time to start scouting for egg masses to determine possible thresholds that warrant control strategies. For more information, click on the following publication "European Corn Borer Management in North Dakota".
Now is the time to start scouting for soybean
aphids. Growth stage is important when determining whether treatment is
needed. If you are finding 250 aphids per plant when the soybeans are in
the R1 to R4 stage, treatment may is recommended. If the soybeans are past
the R4 growth stage, yield response is less predictable. The R4 stage is full
pod. The pod is 3/4 inch long at one of the four uppermost nodes on the
main stem with a fully developed leaf.
Last year during the dry conditions a question arosed,
"what effect does drought have on soybean aphid and does it pay to treat
under possible low yields?" High temperatures above 90 degrees will
slow and eventually stop reproduction of soybeans aphids and increase mortality
rates. Typically, soybean aphids have a 30-39 day life span. This
can be shortened to 11 days with 90 degree or above temperatures.
NDSU field scouts are finding potato leaf hoppers in soybean, dry beans and alfalfa in eastern North Dakota. The threshold for these crops are as follows.
Dry bean = 1 leafhopper per trifoliate leaf;
Alfalfa = 1-2 leafhopper per sweep when alfalfa is 8-14 inches high;
Soybeans = 5 leafhoppers per plant in vegetative stage and 9 leafhoppers
per plant in early bloom stages
Potatoes = 10-20 adults per 20 sweeps or 1 nymph per 10 leaves
Please Contact Our Office For Additional Information
E-mail: john.swenson@ndsu.edu
Go to the 2007 AgAlert Index Page