Monitoring Insect Pest Populations Across Soil EC Based Management Zones in Midsouth Cotton With and Without Wheat Cover Crop

Cotton producers in NE Arkansas typically plant cereal winter cover crops to protect cotton seedlings from damage due to blowing sand. Additional benefits from use of cover crops can include improvements in weed suppression, run-off water quality and arthropod management. An objective of this 2012 field study was to contrast infestation levels of cotton insect pests across spatially variable fields of cotton grown with a winter weed fallow field and wheat winter cover crop. Paired commercial fields on three NE Arkansas farms were separated into four management zones based on soil electrical conductivity (EC) properties classified from measurements using a dual depth Veris 3150 Soil Surveyor.  In each management zone, thrips infestations were monitored by collecting 10 plants per site; there were three sites per zone. Plants were washed onto filter paper, and thrips counted under magnification. Weekly counts of tarnished plant bug (Lygus lineolaris Palisot de Beauvouis) were made with drop cloth. Crop maturity measures using the COTMAN crop monitoring system were used to document date of physiological cutout. Thrips infestations (tobacco thrips (Frankliniella fusca (Hinds)) and western flower thrips (Frankliniella occidentalis (Pergande)) were detected in the first three weeks following crop emergence. High thrips numbers  were observed on one of three farms, where significantly fewer thrips were associated with cotton grown with a wheat cover crop compared to cotton without wheat. There was no apparent spatial component associated with thrips distribution in the six fields with no differences in thrips numbers observed among soil EC based management zones. Plant bug numbers did not exceed the Arkansas action threshold prior to cutout. Late season numbers were higher in management zones where plants continued to produce squares in late season. Early maturing plants had fewest plant bugs. The late season plant bugs numbers had no significant impact on yield.