Pest & Crop

Purdue Cooperative Extension Service
June 30, 2006

Pest & Crop Newsletter, Entomology Extension, Purdue University

In This Issue Insects, Mites, and Nematodes

Western Corn Rootworm Beetles Emerging - (John Obermeyer, Christian Krupke, and Larry Bledsoe)

  • Western rootworm beetles can now be seen.
  • Beetles should not be a concern until fields are pollinating.
  • Late planted/replanted fields could be a "trap crop" for beetles and egg laying

Western corn rootworm beetles are beginning their annual emergence from the soil in northern Indiana. The male beetles are generally first to emerge and feed for several days until females begin emerging a few days later. Females mate, then feed and disperse, sometimes over long distances.

After emerging, beetles will begin to feed on corn leaves if pollen is not available. Leaf feeding damage is of no economic importance. However, pollinating plants with high beetle populations could suffer economic losses from the beetles clipping silks prior to the completion of pollination. Pest managers should closely watch their fields for this type of feeding activity when pollination begins.

Western corn rootworm male and female

Western corn rootworm;
male (left) and female (right).

Adult beetles survive for several weeks and are consistently attracted to pollen sources throughout their lifespan. Therefore, late-planted fields are particularly susceptible to silk-clipping in areas with large beetle populations. Because of this year’s staggered planting and replanting, beetles may flock “in droves” to fields that are pollinating later than surrounding areas. These delayed areas should be closely watched for silk clipping. For additional information on rootworm beetles and their control, see Extension Publication E-49-W, Managing Corn Rootworms - 2006 (Rev. 5/06), which can be viewed at

Rootworm beetle leaf feeding

Rootworm beetle leaf feeding.

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Corn Borer Populations Are Generally Low, Treatment Window Closing- (John Obermeyer, Christian Krupke, and Larry Bledsoe)

  • European corn borer infestation levels are low in most fields.
  • Some highly infested fields found too late.
  • Before applying a control, determine if control is possible and/or economical.

For most non-Bt corn at this time, first generation European corn borer appears to be causing only minor damage. However, calls this week from southern Indiana indicate that there are some highly infested fields. It is too late for control however, since the borers are burrowed into stalks and therefore are no longer treatable in this region.

Severe corn borer whorl damage

Severe (obvious) cornborer whorl damage.

Soon, borers will be entering corn stalks throughout the state. As noted above, cnce in the stalk or tassel, the borer is protected from insecticides and percent control drops dramatically. Therefore, pest managers should closely examine stalks for borer entry before making control decisions. If treatment is necessary, it is recommended that the control material be applied before 1/3 of the borers have entered the stalk. Midvein leaf feeding indicates that stalk tunneling is soon to begin; frass accumulation in a leaf axil signals that the stalk has been entered by a borer.

corn borer in midrib of leaf

Corn borer in midrib of leaf.





Corn borer is stalk is impervious to insecticides.

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Bug Scout

Happy 4th of July!

Bug Scout says "Have a Safe and Happy 4th of July!"

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Click for Table.
Black Light Catch Report.

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Weather Update

Temperatures as of June 28, 2006

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