VegNet Vol. 13, No. 18. August 29, 2006
Ohio State University Extension Vegetable Crops
On the WEB at:  http://vegnet.osu.edu
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In This Issue

1. Insect Report

Insect Report 8/29/06 by C. Welty

European corn borer: The activity of European corn borer moths increased sharply at the end of last week as indicated by the number of moths caught in both pheromone and blacklight traps. This sharp increase in trap catch usually indicates the start of a third generation, although our temperature accumulations predicted that a third generation should not start for another 10 days. Plantings of peppers and late sweet corn will be at high risk of infestation by third generation larvae in about 2 weeks. Trap catch data at several sites is posted on the internet at: http://bugs.osu.edu/welty/veg-traps06.html

Corn earworm: The trends in the corn earworm population reported in VegNet on 9 August have continued through August. Last week the catches of moths in the standard Scentry traps were 1 to 96 moths in one week, while the catch of moths in the large Hartstack traps was 184 to 439 moths in one week. Trap reports for Ohio are posted on the internet at: http://bugs.osu.edu/welty/veg-traps06.html . Trap data for Ohio and other Midwestern States is posted at:

http://www.ent.iastate.edu/trap/cornearworm/

Late sweet corn should be treated with insecticide to prevent infestation by corn earworm larvae. At most sites, where moth catch in the Scentry trap is 7 to 91 moths in one week, a 4-day schedule I needed if temperatures are below 80F or a 3-day schedule I needed if temperatures are above 80F. Corn earworm is also called the tomato fruitworm and can attack tomato and pepper fruit if its preferred food, fresh-silking corn, is not available. Until recently, pyrethroids such as Warrior, Mustang, Capture, or Baythroid were a popular choice for earworm control, but resistance to pyrethroids is now developing across the Midwestern USA. Where pyrethroids alone are not providing good control, other options for sweet corn are SpinTor, Larvin, or Lannate, or a tank mix of Lannate (3/4 rate) and pyrethroid (mid to full rate). Options for tomato are SpinTor, Proclaim, Avaunt, or Intrepid.

Fall armyworm: Fall armyworm moths were active for several weeks in late July and early August but their activity has fallen off in late August. If hurricane weather patterns develop in the southern USA, then we could see an increase in fall armyworm moths that blow northward in weather systems. Fall armyworm infestations are likely in sweet corn, peppers, and tomatoes. Fall armyworm is not very susceptible to pyrethroid insecticides, but can be controlled by Larvin or SpinTor.

Whitefly: Whitefly infestations have been reported from peppers and snap beans. We do not have guidelines for thresholds on these crops, but insecticide treatment is warranted If nymphs are found. Whitefly nymphs are white scale-like insects found on the undersides of leaves. The neonicotinoid insecticides (Provado, Assail, Actara, Venom) are effective for whitefly control.

Corn rootworm beetles: The western corn rootworm beetle has been found in exceedingly high numbers in sweet corn and pumpkin fields. This is the species that is sometimes confused with the striped cucumber beetle. The western corn rootworm beetle is somewhat larger, usually has thick stripes on its back and always has a yellow abdomen (belly), while the striped cucumber beetle is slightly smaller, has narrower stripes, and has a black abdomen. There are also some northern corn rootworm beetles active in sweet corn and pumpkins but in much lower numbers; this species is solid pale green. In sweet corn the rootworm beetles are clipping silks, which can prevent pollination, and in pumpkins they are feeding on pollen in flowers but starting to feed on rinds of fruit as flower production is tapering off. The beetles are readily killed by broad-spectrum insecticides but care must be taken to prevent kill of bees that are active in these crops.