Resistance Monitoring. Insects are well known to develop resistance to insecticides. There is increasing documentation of insecticide resistance in populations of bollworm, tarnished plant bug and cotton aphids in the Midsouth. Therefore, an insecticide resistance monitoring program was instigated in 2006 for both bollworm and tarnished plant bug populations collected in West Tennessee. Monitoring resistance of key insect pests helps to document resistance and implement insect resistance management plans. Vial assays of adults are used in both cases. In 2012, no monitoring was done for tarnished plant bug, although insecticide testing indicates high resistance to the pyrethroid insecticides (data not shown). Vial assays using 5 ug/vial cypermethrin, a synthetic pyrethroid, were again performed on bollworm moths. This represents a discriminating dose where 90% or higher of susceptible moths are expected to die after 24 h exposure. Fresh bollworm (i.e., corn earworm) moths were collected from traps that were baited with pheromone lure on the previous night. All moths were collected in Madison County at the West Tennessee Research and Education Center (WTREC). For several years and as part of a cooperative effort, moths from the above tests have been submitted to scientists in Mississippi (X. Xxxxxx, X. Xxxxxxx) who are assaying moths using a technique that determines if the larval host was a C3 or C4 plant. These data are being collected to better understand the population dynamics of bollworm and determine the impact of host origin on resistance levels. C3 plants are broadleaves such as cotton and soybean. C4 plants are usually grasses, and presumably any bollworms testing positive for C4 plants developed on corn or sorghum because these are primary hosts during the time frame of moth trapping.
Resistance Monitoring. Insects are well known to develop resistance to insecticides. There is increasing documentation of bollworm resistance to pyrethroid insecticides in parts of the lower Midsouth. Although pyrethroid and acephate resistance in some tarnished plant bug populations has also been documented in at least part of the Midsouth, until recently there have been no monitoring efforts in Tennessee. Therefore, an insecticide resistance monitoring program was instigated in 2006 for both bollworm and tarnished plant bug populations collected in West Tennessee. Monitoring resistance of key insect pests helps to document resistance and implement insect resistance management plans. Vial assays of adults are used in both cases. Populations of tarnished plant bugs were not tested in 2009, in part because excessive rainfall in September prevented their timely collection. Vial assays using 5 ug/vial cypermethrin, a synthetic pyrethroid, were again performed on bollworm moths in 2009. This represents a discriminating dose where 90% or higher of susceptible moths are expected to die after 24 h exposure. Fresh bollworm (i.e., corn earworm) moths were collected from traps that were baited with pheromone lure on the previous night. All moths were collected in Madison County at the West Tennessee Research and Education Center. For several years and as part of a cooperative effort, moths from the above tests have been submitted to scientists in Mississippi (X. Xxxxxx, X. Xxxxxxx) who are assaying moths using a technique that determines if the larval host was a C3 or C4 plant. These data are being collected to better understand the population dynamics of bollworm and determine the impact of host origin on resistance levels. C3 plants are broadleaves such as cotton and soybean. C4 plants are usually grasses, and presumably any bollworms testing positive for C4 plants developed on corn or sorghum because these are primary hosts during the time frame of moth trapping. Outcomes: 1277 moths were used in the vial tests that were done between 6 July and 21 September, 2009. Percent survival after 24 h was recorded for moths in treated and untreated vials (see figure below). The average, corrected percent survival of moths to the 5 ug/vial dose of cypermethrin was about 10%, similar to 2008 and less than observed in 2006 (16%) and 2007 (21%). These data indicate some level of resistance but not to the levels that result in field control insecticide failures when spraying pyrethroid insecticides f...
Resistance Monitoring. Insects are well known to develop resistance to insecticides. There is increasing documentation of bollworm resistance to pyrethroid insecticides in parts of the lower Midsouth. Although pyrethroid and acephate resistance in some tarnished plant bug populations has also been documented in at least parts the Midsouth, until recently there have been no monitoring efforts in Tennessee. Therefore, an insecticide resistance monitoring program was instigated in 2006 for both bollworm and tarnished plant bug populations collected in West Tennessee. Monitoring resistance of key insect pests helps to document resistance and implement insect resistance management plans. Vial assays of adults were used in both cases.
