David Owens, Extension Entomologist, owensd@udel.edu
Small Grain
Small grain risk for barley yellow dwarf virus may be lower this year. Aphid populations in the fall were generally low. Cold winters with little snow cover and late, cool springs are generally associated with reduced risk for BYDV. How does this year look? We had a bitter January, extremely warm February, and below average March and April. So far, aphid populations are very low. Winged females started parachuting in with the warm weather last week. The most common species is English grain, although bird cherry oat started showing up in the last couple of weeks. A good key to species can be found here: http://ipm.ucanr.edu/TOOLS/KEYAPHIDGRAIN/. The only species we have are the bird cherry-oat, greenbug, corn leaf, and English grain. Beneficial insects and aphid-killing fungi are active in fields. One beneficial insect: 100 aphids should result in sufficient aphid control. Scout fields if a pyrethroid has been applied to make sure aphids don’t get ‘released’ from natural enemy pressure.
Winged English grain aphid and non-winged clones in barley last week
With last week’s warm weather, we have picked up a couple of cereal leaf beetle eggs in a single field near Milford, and have seen signs of adult feeding in a couple of wheat fields. Overall, numbers are extremely low.
Corn
Corn is starting to go in the ground. Between planting and V4 is a critical time to scout for slug presence and feeding damage. UD extension has a couple of videos on slug scouting which can be found here: https://youtu.be/yJAiut5IHqY, https://youtu.be/-5YD2BArGOg, https://youtu.be/JM2xTfw7z-M. Cool but not cold, cloudy, wet weather favors slug activity. Windy, dry, or sunny conditions will drive them deeper into the canopy or under residue. Corn is much more resilient than soybean to slug feeding, but may need rescue if half or more of the new leaf growth is destroyed and weather conditions favor slug activity. This is not a hard and fast rule, there is still a lot we don’t know about slugs and corn. Oregon has a slug activity predictor that might be interesting to look into: https://agsci.oregonstate.edu/slug-portal/life-slug/slug-activity-predictor.