David Owens, Extension Entomologist; owensd@udel.edu
Sweet Corn
Continue scouting whorl stage sweet corn for fall armyworm and tassel push sweet corn for corn leaf aphid. Either of these may require additional insecticide applications.
Corn earworm populations are VERY HIGH across the state in the blacklight traps. With rain, it is possible that many of those moths were not corn earworm, but the scales get washed out and beaten up by other insects getting into the traps. With high temperatures less than 82, a tight schedule is warranted, but four blacklights are suggesting a 2-day spray schedule (Blacklight trap capture greater than 30/night) across the board. In areas with a moderate or moderately heavy flight, I think a 3-day spray schedule following a Besiege or Elevest should suffice, and a 2 to 3 day Lannate/Pyrethroid spray. I have tried the last two years to get data on a Radiant/Warrior spray or an Intrepid Edge/Baythroid spray at 2 days vs 3 days, but last year and this, when that sweet corn started silking, our temperatures dropped.
Trap captures for Thursday are as follows:
| Location | Blacklight trap capture | Pheromone Trap Capture |
| Dover | 88 | 48 |
| Wyoming | 131 | 61 |
| Magnolia | 146 | 37 |
| Milford | 323 | 87 |
| Harrington | 45 | 23 |
| Woodenhawk | 25 | 115 |
| Bridgeville | — | 104 |
| Concord | 31 | 51 |
| Georgetown | — | 40 |
| Laurel | 150 | 32 |
| Delmar | — | 54 |
| Lewes | — | 64 |
| Milton | — | — |
| Salisbury MD | — | 79 |
The UD Insect Trap webpage has been updated find trap counts here:
UD IPM Black Light and Pheromone Trap Counts
(European Corn Borer & Corn Earworm)
Stink Bug Black Light Trap Counts
Cole Crops
Fall seedling and recently transplanted cole crops use a low 10% infestation threshold for worms. The one exception to this is cross striped worm, where the threshold is 5% plants with cross striped worms. Remember to avoid using broad spectrum materials with high bee toxicity that will remove natural enemies (please note the neonics will not harm natural enemies even though they are bee toxic; they are good on harlequin bugs and aphids). From a soft, diversified IPM approach, I like using Bt early, then transitioning to other contact worm materials, and finishing a crop program up with materials that have translaminar activity like the diamides and spinosyns.
Tomatoes
Corn earworm activity has increased in late tomatoes at the Carvel REC. Consider treating tomatoes on a 7-10 day spray schedule with a good worm material.
Lima Bean
Scout flowering lima bean for podworm and soybean looper. Diamides are only partially effective on soybean looper.
Peppers
Beet armyworm continue to be extremely active in pigweeds and the potential for them to get into peppers is high. There have been a couple of complaints this season and one bioassay suggesting diamide resistance is present at some level. Other worm materials appear to remain effective.
Cucurbits
Various aphid species are very active this year, scout for melon aphids in the crop. Other threats include squash bugs on pumpkins, rindworm, and cucumber beetle. Our overwintering beetles are emerging and may feed on rinds. Striped cucumber beetle populations tend to decrease in September. Among the rindworms, corn earworm and beet armyworm (especially in fields with pigweed) are the most troublesome.