|
|
|
Corn
Volume 57 Number 19 Date 08/23/2012 CORN ROOTWORM - Below is a map summarizing the results of the 2012 corn rootworm beetle survey conducted from July 20-August 17. Populations decreased as compared with the 2011 data in the southwest, south-central, west-central, central and east-central areas and increased in the southeastern and northern areas. The state average of 0.6 beetle per plant compares to 0.7 last season. District average populations are 0.8 per plant in the southwest, 0.9 per plant in the south-central, 0.9 per plant in the southeast, 0.5 per plant in the west-central, 0.5 per plant in the central, 0.4 per plant in the east-central, 0.5 per plant in the northwest, 0.3 per plant in the north-central and 0.6 per plant in the northeast. Economic counts of 0.75 or more per plant were found in 57 of 230 (25%) fields surveyed. The cause of the decline in rootworm numbers is uncertain and somewhat unexpected based on the abundance of beetles noted during surveys in alfalfa, soybeans and vegetable crops earlier in July. Nevertheless, average counts in all three southern districts are still considered high or economic and suggest a potential threat of root damage to non-Bt, continuous corn next season. CORN EARWORM - Migratory moths continue to arrive in the state. Counts at the Ripon locations in Fond du Lac Count increased to high levels of 202-229 moths, while numbers at other sites decreased or remained the same as the week before. As previously stated, all susceptible sweet corn fields will require monitoring until harvest. Moth counts during the last reporting period were: Bloomington 68, Chippewa Falls 2, Janesville 21, Manitowoc 3, Marshfield 0, Ripon a 202, Ripon b 229 and Wausau 0. EUROPEAN CORN BORER - Second generation larvae range from second- to fifth-instar in the southern and east-central counties. Larval infestations affecting 10-20% of the ears have been reported in a few later-planted sweet corn fields but most sites appear to have had adequate control. --Krista Hamilton, DATCP Entomologist 
|
|