David Owens, Extension Entomologist, owensd@udel.edu and Bill Cissel, Extension Agent – Integrated Pest Management; bcissel@udel.edu
Sweet Corn
Bill Cissel and David Owens
Corn earworm populations are higher than last week, and yesterday’s trap capture was higher in all but one location from Monday’s trap capture. At the research station, our trap captures increased significantly in the last two nights. Blacklight trap captures are also increasing. Focus more on the state-wide trends. Monday trap capture can be found at (http://agdev.anr.udel.edu/trap/trap.php). As a reminder, what is reported on the web is on a per night basis, the table below is cumulative over Monday, Tuesday, and Wednesday night. These trap captures correspond to a 3-day spray schedule, though some states recommend a 2-day schedule.
Joe Ingerson-Mahar at Rutgers in New Jersey recently wrote about the need for product rotation, citing pyrethroid resistance monitoring Virginia has been doing (https://plant-pest-advisory.rutgers.edu/corn-earworm-control-in-sweet-corn/). We have been using Virginia’s vial testing method and have seen similar results, near 30% of tested moths can fly after 24 hour exposure. Does this mean pyrethroids are ineffective? No, but it does highlight the need for chemistry rotation. We also do not know how vial tests translate to sweet corn efficacy where we apply products several times in a narrow time frame.
| Trap Location | BLT – CEW | Pheromone CEW |
| 3 nights total catch | ||
| Dover | 2 | 17 |
| Harrington | 1 | 28 |
| Milford | 2 | 41 |
| Rising Sun | 0 | 6 |
| Wyoming | 4 | 65 |
| Bridgeville | 3 | 63 |
| Concord | 3 | 56 |
| Georgetown | 4 | 32 |
| Greenwood | 2 | — |
| Laurel | 2 | 132 |
| Seaford | 5 | 52 |
Watermelon
David Owens
Spider mite populations have generally been decreasing, but can still be an issue with the warm weather. High humidity favors fungal pathogens of spider mites, but fungicide sprays can suppress them. Infected mites are going to look crumpled and may even be brown in color and a slightly fuzzy appearance as mite-killing fungi sporulate. Cucumber beetles are very active, as are various members of the rindworm complex. Yellow striped armyworms are present in fields.