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Title: Improved chemical control for the Mexican rice borer (Lepidoptera: Crambidae) in sugarcane: Larval exposure, a novel scouting method, and efficacy of a single aerial insecticide application

Author
item WILSON, BLAKE - Louisiana State University
item Showler, Allan
item REAGAN, THOMAS - Louisana State University
item BEUZELIN, JULEN - Louisiana State University

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2012
Publication Date: 12/10/2012
Citation: Wilson, B.E., Showler, A., Reagan, T.E., Beuzelin, J.M. 2012. Improved chemical control for the Mexican rice borer (Lepidoptera: Crambidae) in sugarcane: Larval exposure, a novel scouting method, and efficacy of a single aerial insecticide application. Journal of Economic Entomology. 105(6):1998-2006.

Interpretive Summary: The Mexican rice borer is a major pest of sugarcane in south Texas, but because of its cryptic habits, chemical and biological control tactics were discontinued. We found that a pheromone trap threshold for initiating monitoring of larval infestations, and a threshold of >5% of stalks with larvae present on plant surfaces to trigger insecticide applications were effective at timing insecticide applications for when early instar larvae were still exposed on the plant surfaces. Novaluron, an insect growth regulator that provided superior control compared to ß-cyfluthrin; was associated with a 14% increase in sugar production. A greenhouse experiment determined that >25% of larvae on the resistant variety HoCP 85-845 and half the larvae on the susceptible variety HoCP 00-950 tunneled inside leaf mid-ribs within 1 d of eclosion. Exposure time of all larvae was <1 wk, a short window of exposure of E. loftini larvae, but we demonstrated the potential utility of pheromone traps for improving insecticide intervention timing such that a single application might be all that is required.

Technical Abstract: A three-treatment aerial application insecticide experiment was conducted in five commercial sugarcane, Saccharum spp., fields in south Texas to evaluate the use of pheromone traps for improving chemical control of the Mexican rice borer, Eoreuma loftini (Dyar), in 2009 and 2010. A threshold of 20 moths/trap/wk was used to initiate monitoring for larval infestations. The percentage of stalks with larvae on plant surfaces was directly related to the number of moths trapped. Reductions in borer injury and adult emergence were detected when a threshold of >5% of stalks with larvae present on plant surfaces was used to trigger insecticide applications. Novaluron provided superior control compared to ß-cyfluthrin; novaluron treated plots were associated with a 14% increase in sugar production. A greenhouse experiment investigating establishment and behavior of E. loftini larvae on two phenological stages of stalkborer resistant, HoCP 85-845, and susceptible, HoCP 00-950, sugarcane cultivars determined that more than half of larvae on HoCP 00-950 and >25% on HoCP 85-845 tunneled inside leaf mid-ribs within 1 d of eclosion, protected, therein, from biological and chemical control tactics. Exposure time of all larvae averaged less than 1 wk for all treatments and was shortest on immature HoCP 00-950 and longest on mature HoCP 85-845. This study shows a short window of vulnerability of E. loftini larvae to insecticide applications, and demonstrates the potential utility of pheromone traps for improving insecticide intervention timing such that a single application may be all that is required.