|Teran-Vargas, A. - INIFAP, MEXICO|
|MORALES RAMOS, JUAN|
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 7, 2008
Publication Date: December 1, 2008
Citation: Blanco, C.A., Teran-Vargas, A.P., Abel, C.A., Portilla, M., Rojas, M.G., Morales Ramos, J.A. 2008. Plant Host Effect on the Development of Heliothis virescens (F.) (Lepidoptera: noctuidae). Environmental Entomology. 37(6):1538-1547. Interpretive Summary: The preservation of transgenic Bacillus thuringiensis (Bt-expressing cotton depends on its effectiveness against targeted pests such as Heliothis virescens (tobacco budworm). This pest, according to reports produced over 15 years ago, develops in high numbers in weeds of agricultural field margins. Mathematical models used to predict the development of resistance to Bt-cotton, still uses information from these reports. To find out if there has been a change in abundance of this pest on its host plants, a two year field study was conducted. Previously reported weedy hosts were low in abundance and tobacco budworms were not found on any of them. Feeding the weedy hosts to tobacco budworm in the laboratory determined that white clover, a host growing around agricultural fields year round, is likely the most suitable host plant for the tobacco budworm. Two species of Geranium, previously reported as being important for building the population of the pest in the spring, was an inferior food source when compared to white clover. Cotton perhaps the most important crop source of tobacco budworm in the region produced low life table parameters. Our results indicate that the population density of the pest is not supported by the wild hosts we studied. The tobacco budworms may be developing on other, unknown, hosts or migration may play a larger role than expected.
Technical Abstract: Heliothis virescens F. is an important polyphagous pest that can develop on ˜20 crops and ˜80 uncultivated plants. Populations of this insect are believed to be locally maintained on a few of these crops and weed hosts in Washington County, Mississippi. To find out the abundance of this pest on those plants, and their intrinsic value for the development of H. virescens populations, we conducted a two-year field survey and we fed different laboratory colonies with fresh and lyophilized plant tissue under a constant temperature. We found that weedy hosts have lower abundance as previously reported around agricultural fields and no H. virescens was found on them during the 2006-2007 survey. Development of this insect under laboratory conditions varied up to 10 days between plant hosts, but it was dependent on the type of plant tissue, fresh or lyophilized. Life table parameters indicate that Trifolium repens, a host growing around agricultural fields year round, could be one of the most suitable plant hosts for the development of H. virescens. Two species of Geranium, previously reported as the source of the first H. virescens generation in the region, did not have any larvae feeding on them and their intrinsic value as food source was lower than T. repens. Gossipium hirsutum, perhaps the most important crop source of H. virescens in the region produced low life table parameters. Results indicate that H. virescens population(s) on this region is not supported by the uncultivated plant species growing around agricultural fields.