Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Soybeans
We continue to hear reports of soybean loopers in full season and double crop fields. Defoliation can occur quickly so be sure to check all fields for this insect. Refer to last week’s WCU articles from Delaware and Virginia for information on this insect pest.
There are also a number of other insects still present in double crop fields including stink bugs, bean leaf beetles, grasshoppers, and green cloverworms. The threshold of all may need to be reduced if a mixed population is present. As a reminder, both bean leaf beetles and grasshoppers will also feed on pods.
Small Grains
As you make plans to plant small grains, you need to remember that Hessian fly can still be a problem. Since the fly survives as puparia (“flax seeds”) in wheat stubble through the summer, you should still consider this pest as you make plans to plant small grains. In our area, damage has been the result of spring infestations. Plants attacked in the spring have shortened and weakened stems that may eventually break just above the first or second node, causing plants to lodge near harvest. Warm fall weather conditions can extend fly emergence and egg-laying beyond the fly-free dates, but these dates should still be used as a guideline for planting. Since we rarely see plants stunted in the fall, we still feel that most of the damage we see is occurring from spring infestations. Plants attacked in the fall at the one-leaf stage may be killed outright. Wheat attacked later in the fall will be severely stunted, with the first tillers killed and plant growth delayed. Plants infested in the fall can easily be recognized by their darker than normal bluish coloration and leaves with unusually broad blades. Combinations of strategies are needed to reduce problems from Hessian fly:
● Be sure to completely plow under infested wheat stubble to prevent flies from emerging.
● Avoid planting wheat into last season’s wheat stubble, especially if it was infested with Hessian fly.
● Avoid planting wheat next to last season’s wheat fields – the most serious infestations can occur when wheat is early planted into wheat stubble or into fields next to wheat stubble.
● Eliminate volunteer wheat before planting to prevent early egg-laying.
● Do not use wheat as a fall cover crop near fields with infestations.
● When possible, plant after the fly-free date. (Oct 3 – New Castle County; Oct 8 – Kent County; Oct 10 – Sussex County).
● Plant resistant varieties. You should look for varieties that have resistance to Biotype L. You will need to check with your seed dealers to identify varieties that our adapted our area.