1a.Objectives (from AD-416)
Establish baseline responses to insecticides where feasible and evaluate longer term performance to safeguard against resistance development. Incorporate resistance management strategies into pest management programs for particular pests of cotton and associated crops including silverleaf whitefly, glassy-winged sharpshooter, and Lygus spp.
1b.Approach (from AD-416)
Develop bioassay methods for various insect pests that realistically depict the type of exposures that occur in the field. Collect target pests in their crop habitat and establish and maintain cultures for repetitive testing. Evaluate relative susceptibilities to crucial insecticides by examining dose-mortality responses of immature and adults stages. Determine stability of resistance when it occurs in populations and formulate effective strategies for mitigating resistance by incorporating information on resistance stability. Documents SCA with UC Riverside. Formerly 5347-22620-017-12S (6/09) & 5347-22620-018-02S (12/09).
Research concentrated on three major pests of agriculture, i.e. the vine mealybug that infests wine, table and raisin grapes throughout California; various spider mites that are pests of grapes, cotton and many other crops; and the sweetpotato whitefly that infests cotton and vegetable crops in the southwestern US.
For the vine mealybug, field trials were established in three table grape vineyards in Kern County, CA to evaluate efficacies of various insecticide regimens. Vine mealybug infestation pressure varied among the three vineyards, but in each case a single application of Movento® (spirotetramat) proved to be highly effective at suppressing infestations over a period of months. Effective treatment responses were also observed for Applaud® (buprofezin) which showed an effective persistence period of weeks rather than months as for Movento. The responses of vine mealybug infestations to Admire Pro® (imidacloprid) treatments proved to be much more variable. Further evaluation of imidacloprid uptake differences among the three vineyards is progressing as soil samples were collected from multiple sites within each vineyard. Soil composition analyses will be performed as well as HPLC detection of imidacloprid to determine if residues are still present.
Laboratory studies were carried out to ascertain the current susceptibility status of adult and immature stages of the bank grass mites, Oligonychus pratensis, to various acaricides/insecticides that are commonly used for mite control. Tests were conducted with 10 compounds to evaluate their efficacy against Bank grass mites. Adult and/or immature mites revealed a general susceptibility trend towards all test acaricides/insecticides in the present study. Bifenthrin was significantly the most effective compound against adult bank grass mites based on the lowest LC50 value (0.136¿g/ml A.I.). Fenpropathrin and abamectin were also quite effective against adult mites with little difference in susceptibility. Additional studies were carried out to ascertain the effectiveness of four formulations of hexythiazox on the susceptibility of adult and immature stages of the two spotted spider mites, Tetranychus urticae. Of the four formulations of hexythiazox, 11.8% formulation was the most effective against all immature stages of the two spotted spider mites. Both knockdown effect and high mortality was observed suggesting that the immature stages are highly susceptible to this formulation.
In addition to being an important direct pest of crops, the sweetpotato whitefly (SPW) is also a vector of more than 110 plant viruses. Work this year focused on an experimental insecticide, pyrifluquinazon, is a promising whitefly control agent as well as a potential suppressor of virus transmission. It proved highly toxic against SPW based on leaf bioassays in clip cages (LC50 < 0.1 ppm) and contact bioassays in coated glass vials. Pyrifluquinazon represents a promising new chemistry with a probable unique mode of action that will represent a very effective compound to be used in rotation with other selective insecticides for managing B. tabaci.
Project is monitored through site visits and email correspondence.