David Owens, Extension Entomologist, owensd@udel.edu
Soybean
Right now, we are monitoring a dozen fields for slug pressure with the help of Drew Harris and Nick Adams. While it is still early and gray garden slug eggs have not hatched yet, we have seen unusually low marsh slug or gray garden adult slug activity (less than 1 per 6 shingles).
Alfalfa
If you have not scouted your alfalfa, the time is NOW. Alfalfa weevil activity appears to be both lower this year and delayed. However, there are still plenty of fields that are well over threshold. We updated our alfalfa weevil insect control factsheet with revised thresholds and control guidance: https://www.udel.edu/academics/colleges/canr/cooperative-extension/fact-sheets/alfalfa-weevil-control/ In fields that are well over threshold, Steward has been the most consistent, most efficacious insecticide for weevil control. In a trial a couple of years ago, Malathion and Imidan provided similar levels of control as pyrethroids. If your alfalfa is over threshold, do not spray next Monday, Tuesday or Wednesday, as temperatures are forecast to be cold; and the weevils will not actively come into contact with spray residue.
Note: We have seen a high numbers of alfalfa aphids in a couple of scattered fields, Steward will not control aphids nor will pyrethroids, use organophosphates, Sivanto, or Sefina. Please note neither Sivanto nor Sefina will control weevils.
Small Grain
I was sent a ‘what is it’ picture earlier this week of a syrphid maggot from small grain. Syrphids are voracious predators on aphids, but it got me to wonder if the aphid situation has changed since late Fall. We checked eight fields across Sussex and Kent Counties with no apparent increase in aphid counts. That’s good news. The other good news is aphid thresholds start increasing into the many dozes to 100 or more per row foot this time of year and without natural enemies. Generally, a natural enemy to aphid ratio of 1:100 should keep aphids in check.
Early Season Moth Activity
We have begun monitoring early season moth activity. Right now, counts are not concerning. Many thanks to Joanne Whalen (extension entomologist emeritus) and Haley Sater (Wicomico County Extension Agent) for checking traps.
| Location | # nights | True Armyworm | Black Cutworm |
| Salisbury, MD | 7 | 6 | 0 |
| Laurel, DE | 7 | 35 | 1 |
| Seaford, DE | 7 | 101 | 0 |
| Harrington, DE | 7 | 105 | 1 |
| Suddlersville, MD | 3 | 0 | 0 |
| Smyrna, DE | 7 | 88 | 1 |
| Middletown, DE | 7 | 0 | 0 |