Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Alfalfa
Be sure to check for alfalfa weevil adults and larvae within a week of cutting, especially if populations were above threshold before cutting. Feeding from both stages can hold back re-growth. After cutting, there needs to be enough “stubble” heat to control the weevils with a cutting. A stubble treatment will be needed if you find 2 or more weevils per stem and the population levels remain steady.
Field Corn
Be sure to watch for both cutworms and slugs feeding in newly emerged corn fields. As a general guideline, a treatment is recommended for cutworms if you find 10% leaf feeding or 3% cut plants. If cutworms are feeding below the soil surface, it will be important to treat as late in the day as possible, direct sprays to the base of the plants and use at least 30 gallons of water per acre. For cutworms, fields should be sampled through the 5-leaf stage for damage. If slugs are damaging plants, you will be able to see “slime trails” on the leaves.
Small Grains
We are just starting to find the first true armyworm moths in our light traps. As a reminder, both overwintering and migratory moth populations are responsible for our infestations. As indicated in previous newsletters, trap counts in Kentucky have been significantly greater than their rolling 5-year averages.
The first grass sawflies and true armyworm larvae have been detected and cereal leaf beetle populations have increased in isolated field throughout the state. Research from Virginia and North Carolina indicates that the greatest damage from cereal leaf beetle can occur between flowering and the soft dough stage. Although armyworm can attack both wheat and barley, they can quickly cause significant losses in barley.
The first native brown stink bugs (not brown marmorated stink bugs) have also been found in barley and wheat. Information from states to our south indicates that wheat may be susceptible to native stink bug feeding at the milk and soft dough stages. Thresholds in the south for native stink bugs in wheat range from one per head to one per 5 to 10 heads. Currently, these detections are being found along field edges.
I have had a number of questions about an adult fly that can be easily found in no-till fields again this season. The fly is the banded wing /picture-wing fly and is present in fields due to the heavy covers in many fields. (http://bugguide.net/node/view/564782). Adult flies are generally attracted to rotting plant material and larvae develop on decaying organic material.