Monitoring for Pyrethroid Resistance in Bollworm (Helicoverpa zea) Populations in Texas: Trends from 2003-2005

Abstract

The purpose of this study was to assess the susceptibility of the bollworm, Helicoverpa zea (Boddie), to the pyrethroid cypermethrin in the primary crop production areas of Texas. Pyrethroid insecticides are widely used in cotton and in other production systems, such as grain sorghum and corn. The statewide monitoring program that evaluated resistance in male H. zea was conducted from April to September 2005, surveying nine Texas counties with a total of 5,041 moths from all areas used for analysis. Data from all areas were sent to Texas A&M University Toxicology Laboratory for analysis. Considerable variability in response to cypermethrin was detected in H. zea across the state. Based on LC50 data, the most resistant populations were from Nueces, Uvalde, and Williamson counties while the most susceptible populations were from Ellis, Fisher and Mitchell, Hockley, and Swisher counties. Accepted for publication 2 October 2006. Published 19 July 2007.

Evidence for Decreasing Helicoverpa zea Susceptibility to Pyrethroid Insecticides in the Midwestern United States

“…The decline in susceptibility of CEW to synthetic pyrethroids, including cypermethrin and lambda-cyhalothrin are not surprising given the continued and long-term exposure of CEW to these insecticides throughout many cropping systems in the southern (7,17,20) and northern US (22). Prior to our findings, a CEW population also collected from sweet corn in Illinois during 1991, was found to be resistant to another pyrethroid, permethrin (1).…”

“…To assess the level of resistance in CEW adults to pyrethroids, the standard Adult Vial Test (AVT), developed in the 1980s (7,14) was used to assess the level of susceptibility in CEW adults collected in Illinois, Minnesota, and Wisconsin from 2003 to 2005. This procedure has been used extensively in the southern US to monitor susceptibility of CEW and tobacco budworm, Heliothis virescens (F.), to pyrethroids (7,17,19,20). However, rather than collecting adults directly from pheromone traps, as in the southern US (20), we reared adults from field collected larvae, typically taken from small-plot insecticide trials (non-treated plots, as well as pyrethroid treated plots), or commercial sweet corn fields (previously treated with pyrethroids).…”

“…As illustrated in Fig. 2, there is also evidence of increasing tolerance to cypermethrin, a standard pyrethroid used for resistance monitoring purposes, in the southern US (7,14,17,19,20). Because CEW is not known to successfully overwinter at latitudes north of the 40th parallel, we believe that most of the CEW populations, particularly in the upper Midwestern regions of Minnesota, Wisconsin, and Michigan, likely result from migrating moths that have originated in the southern US (13,23).…”

“…1, most moth flights into Minnesota do not occur until late July or early August. Given the continued exposure of CEW to pyrethroids in the southern US in several crops (3,7,17,20), it is not surprising that moths immigrating into the northern US each year may carry genes for pyrethroid resistance. The purpose of this paper is to review the results of field efficacy trials for pyrethroid insecticides used against CEW in the Midwest, and the results of adult and larval assays to assess CEW resistance to selected pyrethroids, from 2003 to 2005.…”

Value of an Insecticide Added to a Fungicide for Soybean during Drought

“…Corn earworm is a migratory insect that utilizes cotton (Gossypium hirsutum L.), grain sorghum (Sorghum bicolor L.), corn (Zea mays L.), and many plants in nonagricultural settings as hosts. This pest is often exposed to pyrethroid insecticides in multiple crops throughout a growing season from south Texas to southern Canada, and it has developed resistance to some pyrethroid insecticides (Martin et al, 2000;Hutchison et al, 2007;Pietrantonio et al, 2007;Jacobson et al, 2009).…”