Start Date: Oct 01, 2010
End Date: Jan 12, 2012
Because we have established the baseline susceptibility of the boll weevil to Malathion we will determine if certain metabolic and/or physiological mechanisms for detoxifying this class of insecticide are correlated with the observed variability of survival. This also will reveal how detoxification works with adult boll weevils and organophosphate insecticides. Collections will be made from infested cotton squares from volunteer and commercial cotton fields. The resulting cohort of immature boll weevils will then be reared to adulthood in the laboratory. We will then conduct dose-mortality bioassay and compare to determined detoxification mechanisms. We will also examine the role of volunteer cotton that may be a source or sink for boll weevil's ability to infest commercial cotton fields. Appropriate non-crop habitats (ditches, roadsides, waste areas) within these quadrates will be identified and systematically sampled for volunteer cotton plants to generate estimates of the distribution and densities of volunteer plants for the entire Lower Rio Grande Valley. In addition, a sub-sample of sites detected with volunteer cotton will be sampled for determining and recording selected life history parameters such as damage and infestation, life stage characterization, and mortality factors (desiccation, predation by ants, parasitims). The model will be developed to simulate boll weevil populatioin dynamics and to forecast weevil densitities in volunter cotton stands. Once the model has been field validated, it will be used to simulate weevil dynamics in spatially explicit context to incorporate landscape characteristics, and used to examine the interaction between commerical cotton practices, landscape features, and the metapopulation of volunteer cotton stands. We will also investigate the reproductive biology, sampling schemes, and economic injury levels for Creotiades signatus in cotton and non-cotton landcapes. In the laboratory, the crop species that this pest utilizes will be exposed to mature, mated female C. signatus where the development of F populations will be reared on a minimum of three phenological states to determine the oviposition sites and reproductive potential (i.e., number of eggs, nymphs, and adults). In addition, multiple samples for all life-stages will be recorded during the growing season from several large-scale production fields to further determine the distribution of the life-stages and reproductive potential within the given crop species. Lastly, we will examine the influence of soybean planting date and insecticide seed treatments on early season pests found in the Lower Rio Grande Valley. For both spring and fall soybeans, experimental plots will be planted in a split-block design (commonly referred to as a strip-split plot) on an in-house ARS research farm as well as an additional location on a cooperator's research farm. For fall soybean plantings, the three dates will also be approximately 30 days apart, but the first planting date will be decided based on local grower recommendations. Soybean planting date will be the main factor with common insecticide treatments being the subfactors.