David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Sweet Corn by Bill Cissel and David Owens
Sweet corn trapping data is updated by Tuesday and Friday mornings and can be accessed here: http://agdev.anr.udel.edu/trap/trap.php. Spray guidelines for silk stage sweet corn can be found at: http://extension.udel.edu/ag/insect-management/insect-trapping-program/action-thresholds-for-silk-stage-sweet-corn/. When using these guidelines to adjust spray intervals, there are several things to keep in mind. Silks grow very rapidly when daily temperatures are greater than 80 degrees. Corn earworm eggs can also hatch in just a couple days when temperatures are warm. This should be taken into consideration when determining spray intervals. When using the guidelines, do not rely on a single trap site or trap date to make spray decisions; take a look at nearby traps and note general statewide trends. Corn earworm moths are very attracted to tassel-push/early silk sweet corn and the proximity of the trap to silking stage sweet corn also influences the trap catch, i.e. a trap placed close to silking sweet corn will typically catch more moths. We try to place our traps in locations that will provide reliable trap catch information. However, our traps are not always located next to silking sweet corn throughout the duration of the season. Trap catches can also vary within a relatively short distance. We have 4 traps setup at one of our farm locations, all adjacent to field corn planted around the same time. Two traps routinely catch moths and two others do not. Having said that, CEW numbers are beginning to pick up from last week and can change rapidly. Last week we caught very few moths. If interested, both Heliothis traps and Corn earworm pheromone lure for the traps can be purchased from greatlakesipm.com. Trap counts for Thursday are as follows (traps generally had similar numbers Monday):
| Trap Location | BLT – CEW (3 nights total catch) | Pheromone CEW (3 nights total catch) |
| Dover | 4 | 51 |
| Harrington | 1 | 0 |
| Milford | 1 | 1 |
| Rising Sun | 3 | 10 |
| Wyoming | 0 | 2 |
| Bridgeville | 1 | 7 |
| Concord | 1 | 0 |
| Georgetown | 0 | 0 |
| Greenwood | 0 | 0 |
| Laurel | 1 | 10 |
| Seaford | 0 | 3 |
Also of interest, Virginia has begun catching some fall armyworms in their pheromone traps.
Cucurbits by David Owens
Spider mites continue to move in and reproduce in cucurbit fields, we are seeing hot spots develop not just near field edges but also in field interiors. During hot dry spells, try to limit mowing as much as possible, spider mites feeding on the grasses will be forced to look elsewhere for food once the plant they are on has been cut. Also be on the lookout for cucumber beetles, activity is a little higher than last week.