Joanne Whalen, Extension IPM Specialist; jwhalen@udel.edu
Field Corn
As the first plants emerge, be sure to watch for cutworm, slug and bird damage. You can distinguish bird damage from cutworm damage by the pattern in the field. With bird damage, you generally see longer strips of damaged plants, plants pulled out of the ground, and/or plants cut high that are compressed at the base of the stems. Although birds can cut plants off at the soil surface, they tend to pull plants out of the ground. In addition, if you look closely you should see “bird prints” near the missing plants or holes where birds have pulled plants out of the ground. In Delaware, the 24(c) Special Local Needs Registration for Avipel Hopper Box (dry) Corn Seed Treatment for bird management in field corn is still available. The 24 (c) label and use directions should be on the pesticide canister. Over the last week, we have started to see an increase in the number of slugs encountered under shingle traps. We can also find moderate levels of adult marsh slugs, slug eggs and the first grey garden slug juveniles under the soil surface trash. Marsh slugs can cause damage to newly emerging corn; however, the most damaging species is the grey garden slug. Although we generally see more damage on seedling corn when conditions remain cooler and soil remains wet, significant egg hatch of grey garden slugs generally occurs during warmer days in April and early May. Although no thresholds are available, in the past levels of five or more grey garden slugs per square foot have indicated the potential for a problem.
Small Grains
In general, insect activity continues to be low in barley and wheat. Cereal leaf beetle adults, eggs and small larvae can be found in a few fields. However, the recent cool weather has slowed egg laying and egg hatch. Cereal leaf beetle populations are often unevenly distributed within a field so it is important to carefully sample so that you do not over or under estimate a potential problem. Eggs and larvae may be also be found on leaves near the ground so careful examination of the entire plant is critical. The treatment threshold is 25 or more eggs and/or small larvae per 100 tillers. If you are using this threshold, it is important that you wait until at least 50% are in the larval stage (i.e. after 50% egg hatch).
As a result of the continued cool weather, we have received reports of an increase in winter grain mite activity. Adult and immature mites feed on the plant’s chlorophyll giving plants a silver or frosted appearance. Severe feeding may result in dead or stunted plants, and it has the potential to significantly reduce yield. Young plants are more susceptible to the feeding damage than older, more robust plants. Plants that are either drought stressed or nutrient deficient also exhibit more severe feeding damage than unstressed plants. More information on identification, sampling and management can be found at the following link: http://extension.udel.edu/factsheet/winter-grain-mite-management-in-small-grains/
Kudzu Bug
The first adult was found this past week on a trap in Sussex County near a kudzu patch. Although it was only one bug, it is an indication that this new insect of soybeans can overwinter, at least in southern Delaware. The following link provides more information on the trapping program and levels being found in Virginia. (http://www.sripmc.org/Virginia/archives.cfm).