Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: January 9, 2007
Publication Date: June 1, 2007
Citation: Snodgrass, G.L. 2007. Current Status of Insecticide Resistance in Tarnished Plant Bug Poplations in the Mid-South in 2006. National Cotton Council Beltwide Cotton Conference. Available: http://www.cotton.org/beltwide. Interpretive Summary: The tarnished plant bug is a major pest of cotton grown in the mid-South. Plant bugs are controlled in cotton exclusively with insecticides, and became resistant to the pyrethroid insecticides in the mid 1990’s. Following the loss of pyrethroid insecticides, the main insecticide used for plant bug control was acephate (Orthene).
Because of the importance of acephate for plant bug control, resistance levels to acephate in plant bug populations have been monitored at 20 locations scattered in the Delta of AR, LA, and MS since 1998. The resistance monitoring used a glass-vial bioassay in the laboratory and required testing of over 4,000 adults each year. Resistance to acephate remained about the same from 1998 through 2004. In 2005, populations at six locations were found to have elevated resistance to acephate. This was alarming in that in the previous seven years only 3 populations with elevated resistance were found. One of the six populations was tested in the field and acephate would not control them. In 2006, 18 of the populations at the 20 locations had elevated resistance to acephate. If similar results are found in 2007, it is likely that acephate will no longer be effective for plant bug control in the mid-South. This will make control and resistance management of this pest in cotton a great deal more difficult and expensive.
Technical Abstract: A survey was conducted in August and September 2006 in which tarnished plant bugs, Lygus lineolaris (Palisot de Beauvois), were collected from wild hosts near cotton and tested for resistance to acephate with a glass-vial bioassay. Plant bug populations from twenty locations in the Mississippi River Delta and ten locations in the “hills” of Mississippi were tested. Eighteen populations from the Delta and five from the hills were found to have elevated resistance to acephate as indicated by three-fold or higher resistance as compared to a susceptible population. This was a large increase in the number of locations with elevated resistance in the Delta as compared to 2005. At the same locations in 2005, only six of the populations had elevated resistance to acephate. The average LC50 value for acephate for the 20 Delta locations went from 6.8 µg/vial in 2005 to 16.1 µg/vial in 2006 which was a 2.4-fold increase in one year. Adults from a population found in cotton near Vance, MS that had 7.1-fold resistance to acephate were tested by caging them on cotton treated with commercial insecticides. Mortalities in treatments with acephate at 0.5 and 1.0 lbs AI/acre at 48 h after treatment were 33 and 23%, respectively. Mortalites in treatments with dicrotophos (0.5 lbs AI/acre), and thiamethoxam (2 oz/acre) were 88 and 95%, respectively. These results showed that the plant bug population from Vance could not be controlled with acephate. Plant bug populations from all thirty sample locations will be tested in 2007 to again determine their insecticide resistance.