David Owens, Extension Entomologist, firstname.lastname@example.org
Continue scouting fields for slugs. With cold weather this past week, crops are just sitting in the ground and are prime fodder. Warmer weather this weekend will help, but beware rain and a few more cool days next week. If using shingles, I generally think of 3 slugs per foot as a population of concern, however, recent field visits combined with cold soil may make me revise that thinking. In sites that we are watching closely, slug egg counts increased last week which means that juveniles observed in the last couple of weeks are now maturing.
If you are seeing a large amount of stand loss in field corn, take a look at this 2016 article in the Weekly Crop Update for what to be considering: https://sites.udel.edu/weeklycropupdate/?p=9254. Dr. Bob Nielsen from Purdue also has an excellent article on yield, stand, stand loss and replanting: https://extension.purdue.edu/jasper/article/24979.
Early Season Moth Activity
Trap counts for the week (checked Tuesday and Wednesday) are as follows, with thanks from Cody Stubbs, Joanne Whalen, Emily Zobel, and Maegan Perdue. I expect counts will come up now that warmer night time temperatures are finally here.
We started tracking degree days for black cutworm on April 14 in Seaford. That trap captured an average of 9.6 moths/night. It generally takes about 300 DD (base 50) before any eggs laid become larvae large enough to cut plants. At the end of next week, we will be around 250 DD and will need to start scouting for cut plants. Willards had an average of 8/night the week of May 1, and Harrington last week had an average of 8.4. This does not mean that fields will have problems in these areas, nor does it mean that a prophylactic spray will be beneficial. Cutworms can be affected by seed treatment and by Bt trait, although both treatments are much less effective on cutworms than on other pests. Black cutworms will oviposit in weeds, including weeds not in ag fields. There are also species of cutworm that could impact crops, such as the dingy, bristled, and variegated cutworm. Soybeans are not immune either, in each of the last two years I had a call regarding cutworm damage to soybean stands in June.