Submitted to: Journal of Economic Entomology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 8/11/2008
Publication Date: 4/2/2009
Citation: Snodgrass, G.L., Gore, J., Abel, C.A., Jackson, R.E. 2008. Resistance to Acephate in Tarnished Plant Bug (Heteroptera: Miridae) Populations in the Mississippi River Delta. Journal of Economic Entomology.102:699-707 Interpretive Summary: The tarnish plant bug is controlled mainly with insecticides in cotton. The most widely used and effective insecticide for large populations found in cotton in the Mid-South is the organophosphate acephate (Orthene). In 2005, a resistance monitoring program begun in 1998 detected plant bug populations in the hill and delta regions of Mississippi with resistance to acephate high enough that recommended rates of acephate would not control them in cotton. The percentage of the populations tested with this high level of resistance in 2006 increased to 50% (from 40% in 2005) in the hills, and the increase was to 90% (from 30% in 2005) in the delta. These findings were very alarming and along with control problems experienced by producers with plant bugs in cotton in 2006, it caused entomologists in the mid-South to strongly recommend that growers alternate insecticide classes when controlling plant bugs in 2007. Plant bug pressure was very high in cotton in the delta in 2007 and growers averaged making 7.5 applications of insecticides for plant bug control in cotton (as compared to 3 in 2006), and some growers made as many as 16 applications. Some populations were found with high resistance to carbamate, organophosphate, and pyrethroid insecticides and could not be controlled with recommended rates of these insecticides. Alternation of insecticide classes may not work very well when populations resistant to three of the four main classes of insecticides (the fourth class is the neonicitinoid insecticides) are present. This research documents that insecticide resistance in tarnished plant bug populations is now a critical problem in the mid-South. New insecticides in different classes are badly needed for control of plant bugs in cotton in this region.
Technical Abstract: A monitoring program to detect resistance in tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), populations in the delta of AR, LA, and MS, was conducted by testing populations collected from weeds with a glass-vial bioassay at 20 different delta locations from the fall of 2001 through the fall of 2007. Additional results from field tests using recommended rates of formulated acephate in cotton showed that plant bug populations with RR50 values >3.0 for acephate (from the glass-vial bioassay) would be difficult to control in the field. Over a 4-yr-period from 2001 through 2004, only 1 population tested with the glass-vial bioassay was found with a RR50 >3.0 for acephate, but 6 populations having RR50s >3.0 were found in the delta in 2005. In the fall of 2005, an additional 10 populations from the hill region (the cotton growing areas outside the delta) were tested and 4 of these populations had RR50s >3.0. The number of populations with RR50s >3.0 increased to 5 of 10 and 18 of 20 in the hills and delta, respectively, in the fall of 2006. Because of the large increase in resistant populations and nature of the resistance found in this study, along with control problems experienced by growers in 2006, entomologists in the mid-South strongly recommended that alternation of insecticide classes in field treatments for plant bug control be used by growers in 2007. Plant bug pressure was very high in many parts of the delta in 2007, and 15 of the 20 populations tested in the fall had RR50s >3.0. In one field test, a population with multiple resistance was tested and not controlled in treatments using recommended rates of carbamate, organophosphate, and pyrethroid insecticides. Alternation of insecticide classes may not work very well when populations are present that are resistant to 3 of the 4 main classes of cotton insecticides. New insecticides in different classes are badly needed for control of tarnished plant bugs in cotton in the Mid-South.