Master of Science (MS)



Document Type



The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), is one of the most yield- limiting insect pests attacking cotton in the Mid-Southern region of the U.S. This pest is almost exclusively managed with chemical control strategies. The organophosphate insecticide, acephate, has been one of the most important insecticides recommended to control tarnished plant bugs. In recent years, reports of unsatisfactory acephate performance have become common and actual field rates have been increased to improve control. The objective of this study was to survey acephate susceptibility in Louisiana populations of tarnished plant bug using laboratory bioassays and evaluate acephate efficacy in field trials. Insecticide residual on glass (vial tests) bioassays were used to estimate acephate dose mortality responses (LC50’s) for five, nine, and six populations during 2007, 2008, and 2009, respectively. The LC50‘s for these collections ranged from 1.63-32.36 µg/vial. Resistance ratios (RR) were calculated relative to a susceptible standard population (LC50 = 3.1 µg/vial) and ranged from 0.52-10.44 among populations. Field control failures with acephate are likely when RR’s >3.0 and when persistent infestations exceed the action threshold for foliar sprays. Twenty field trials were conducted during 2007-2009 to determine acephate performance against native infestations. Five treatments (0[control], and acephate at 0.54, 0.82, 1.1, 1.34 kg AI/ha) were arranged in a Latin square design and were placed in commercial production fields and on LSU AgCenter Research Stations. Acephate efficacy was collected five to seven days after treatment using a one meter black shake sheet. The lowest acephate rate (0.54 kg AI/ha) significantly reduced tarnished plant bugs compared to that in the non-treated plots at 17 locations. However, this rate only reduced numbers below the action threshold in the 2007 trials. During 2008 and 2009, acephate rates of 0.82-1.34 kg AI/ha were needed to adequately control infestations. These results indicate that acephate susceptibility in Louisiana populations of tarnished plant bug is shifting and field performance is decreasing.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Leonard, Billy Rogers



Included in

Entomology Commons