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Corn
Volume 57 Number 17 Date 08/09/2012 CORN ROOTWORM - The annual survey of adult rootworms has been completed in five of the nine crop reporting districts. Examination of 161 fields during the period of July 20-August 8 found the district average count to be 0.9 per plant in the southeast, 0.9 per plant in the south-central, 0.5 per plant in the central, 0.3 in the north-central and 0.5 in the northwest. Economic populations of 0.75 or more beetle per plant have been noted in 41 of the 161 (25%) fields surveyed as of August 8. Currently the higher counts can be found in later planted corn fields in which the silks have just begun to turn brown. Final survey results will be provided in the August 23 issue of the bulletin. EUROPEAN CORN BORER - Damage to corn has been infrequent, usually with only 2-28% of plants showing midrib feeding, frass or other evidence of infestation. Treatment is no longer advised now that the degree day accumulation has surpassed 2,100 (base 50°F) in most areas and second generation larvae are boring into corn stalks. Larvae produced by the summer flight of moths are primarily in the third and fourth instars. PICNIC BEETLE - Low to moderate numbers of this group of insects were observed in field corn in the southern and west-central areas. These beetles are found late in the season feeding on ear tips that have been exposed by corn rootworm adult feeding or blackbird damage, and are associated with European corn borer tunnels. The adults observed in the past week had tunneled under the husks and were feeding on silks and kernels of corn. Picnic beetles can be damaging to sweet corn varieties with exposed tips but are usually considered secondary invaders or indirect pests. --Krista Hamilton, DATCP Entomologist 
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