Pheromone Trap Counts and Assays, July 22, 2016

Pheromone trap catches for tobacco budworm this week were at higher levels than normally seen during this time of year in all areas of the state. Bollworms were back down some this week after being quite high in some regions last week. Based on these trap catches, it is likely that a significant portion of Heliothine eggs observed at this time are tobacco budworm eggs. This means that the Bt technologies should provide excellent control, but foliar applications of pyrethroids will be largely ineffective. In fact, not only are pyrethroids ineffective against budworms, recent efficacy of pyrethroids on bollworm in laboratory assays has also been poor. Using a diagnostic concentration of a pyrethroid on moths in a lab assay this year, we had 90% mortality in May, 61% mortality in June, and only 53% mortality so far in July. Historically we have had 80-90% mortality throughout the year at this concentration. We saw reduced efficacy last year and now even worse efficacy this year, so there has clearly been a change in bollworm susceptibility to pyrethroids in Mississippi. Several other states in the southeastern US have observed similar losses of efficacy over the last several years.