Early-planted Small Grains Risk Insect Invasion

Armyworms and aphids already on the attack on DelMarva.

Substantial Mid-Atlantic acreage was planted to small grains before the recommended Hessian fly free dates. But this year, insects already on the attack aren't Hessian flies.

Joanne Whalen, Extension IPM specialist at University of Delaware, urges scouting of all small grain stands at emergence for aphids, true armyworm and fall armyworm feeding. "In past years, we have seen economic damage from all three insect pests," she reports, "especially in no-till situations."

"Although there's no threshold available, you'll need to watch for larvae feeding on small plants. Since there have been reports of grass hay fields being destroyed by armyworms in Delaware and Maryland, watch fields for both armyworm species since damage can occur very quickly."

Early fall infestations of the greenbug aphid, which causes direct damage to small grains, are favored by cool, late summer conditions. Since we have recently seen an increase in aphid activity and have had a few periods of cooler weather recently, all fields should be monitored for aphids.

When to treat wheat

Factors that increase the potential of a return from applying an insecticide to control aphids and to reduce barley yellow dwarf virus infection in wheat include:

  • Normal-cool summer temperatures with adequate rainfall
  • Intensive wheat management including high fertility
  • Use of BYDV susceptible varieties
  • Planting before the Hessian fly free date
  • A late, warm fall

Two seed-applied materials, Gaucho and Cruiser, are available as a preventative treatment for aphid control in wheat and barley. If you plan to scout for aphids, as a general guideline a foliar treatment should be considered if you find 10 aphids (especially winged forms) per linear foot of row.

But, if you have had BYDV in your area, lower this number based on information from the South where BYDV is more prevalent. Southern states are using thresholds as low as 1to 3 per foot of row.

Direct damage from greenbug aphid has also been an issue in recent years. Treatment thresholds from areas to the south suggest treatment will be needed in the fall if you find 10 aphids per foot of row.

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