Multistate Evaluation of Cotton Yield Loss Caused by Twospotted Spider Mite

The objective of this research was to determine how yield is affected when mite infestations are initiated at different times of the year.  Cotton yield losses due to mites have been reported to range from minimal to severe, depending on environmental conditions and when the damage occurred.   In general, the literature suggests that TSSM cause greater yield loss when infestations are initiated before or during flowering periods.  In this experiment cotton was artificially infested with high densities of mites at 3 true leaves then at 200 heat unit intervals from flowering to cutout + 650 heat units (HU), resulting in a total of ~6-7 infestation-timing treatments plus an uninfested check.  The study was conducted at eight locations across Mississippi, Arkansas, Louisiana, and Tennessee.  A preliminary run of the study was conducted in 2008.  Although daily thunderstorms caused mite populations to crash in late-July, yield was reduced by 9.4% or 100 lb lint per acre in cotton infested at first bloom.  Data from the 2009 trials is not yet available.