2nd generation European corn borer and sunflower insects
Assefa Gebre-Amlak,
Extension Specialist, Colorado State University Extension
European corn borer moths continue to emerge in most of the pheromone trap locations in northeastern Colorado. Second generation flight can last for four weeks. Damage due to second brood in corn may contribute to lodging and ear drop losses.
2nd generation egg masses are generally found on the underside of the leaf usually within three leaves above or below the ear leaf. These egg masses appear flat and white with black spots appearing as the eggs mature.
Generally, late maturing cornfields are more attractive to 2nd generation egg laying moths than early maturing fields. The female summer moth prefers to lay eggs in corn that is tasseling and in the green silk stage.
The 2nd generation borer egg masses are used for scouting to determine economic threshold for this insect. The simple method used to determine economic threshold is based on accumulation of the percentage of plants with egg masses during two consecutive weeks of scouting following the early portion of the egg laying period.
Survival of second‐generation larvae is highest during pollination, so treatments should be considered when weekly scouting has an accumulated total of 25 percent of plants with egg masses. This percentage should be raised to at least 50 percent after pollination. If egg laying continues after the treatment, a second application may be justified under some circumstances.
Another more detailed method based on treatment cost, predicted yield, larval survival, and corn prices is found in the High Plains IPM Guide at: http://wiki.bugwood.org/HPIPM:Crops. All effective products for European corn borer control are also found in this guide.
Other insects to monitor include western bean cutworm (corn and dry beans), sunflower head moth, banded sunflower moth, sunflower seed weevils (red and gray weevils). For effective products and other pest management information on these insects and others, check the High Plains IPM Guide at: http://wiki.bugwood.org/HPIPM:Crops and or www.nocopestalert.org or call Colorado State University Extension Office in your county.
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