CSU Golden Plains Ext News: PEST ALERT – Early emergence of western bean cutworm moth in northeastern Colorado
Issued by Assefa Gebre-Amlak (PhD) Extension Specialist, Pest Management, CSU Extension
We are seeing early emergence of western bean cutworm moth in most parts of northeastern Colorado this year. According to the historic monitoring data, the moth population will peak between the third week of July and first week of August in Colorado (www.nocopestalert.com).
Eggs are deposited in clusters on the top surface of leaves. Following hatch, young western bean cutworm larvae move to one of the two places on corn plant, depending on the stage of development. If the has not tasseled, larvae will feed on pollen in the developing tassel. If the corn has tasseled, larvae will on silk in the ear. Once the ear is formed, the larvae will feed on developing kernels.
Control is expected with only those Bt corn hybrids containing the Herculex I or Herculex Xtra events. For corn hybrids that do not contains these events, fields should be scouted for this pest the next three weeks; good control will be difficult once the larvae move into ears.
Monitoring for this insect based on determining the per cent of corn plants with egg masses. Chemical control is justifiable if eight per cent or more of the plants have egg masses or small larvae in the tassels and the crop is at least 95 percent tasseled. If tasseling is much less than this, the economic threshold should be raised to as fewer larvae are likely to reach the ears.
Effective insecticide products are found in the High Plains IPM Guide: www.HighplainsIPM.org. Many of the insecticides registered for western bean cutworm have been associated with spider mite outbreaks, so fields should be monitored for mites after a treatment is made.
The other pest to pay attention at the moment will be the banks grass mite (BGM). It should be monitored especially if dry and hot conditions should prevail during the growing season. Webbing on leaves and discoloration are often the first signs of an infestation. BGM builds on the plant the bottom up, treat when there is visible damage in the lower third of the plant and small colonies are present in the middle third of the plant before hard dough stage. Effective products for BGM management can be found in the High Plains IPM Guide: www.HighplainsIPM.org.
Once again this was written and submitted by Assefa Gebre-Amlak (PhD) Extension Specialist, Pest Management, CSU Extension