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Preliminary Research on Toxicity of Some Miticides and Use of GreenSeeker ™ to Detect Plant Damage by Two-spotted Spider Mite, Tetranychus urticae Koch. Juan D. López Jr., D. E. Martin, and Y. Lan USDA-ARS, Areawide Pest Management Research Unit College Station, TX.
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Preliminary Research on Toxicity of Some Miticides and Use of GreenSeeker™ to Detect Plant Damage by Two-spotted Spider Mite, Tetranychusurticae Koch. Juan D. López Jr., D. E. Martin, and Y. Lan USDA-ARS, Areawide Pest Management Research Unit College Station, TX
Two-spotted Spider Mite • Tetranychusurticae Koch. • Serious pest worldwide on many different crops. • Recently has become an important pest in cotton especially in the Mid-South of the Cotton Belt. • Only control option is miticides. • Research needed on aerial application technology.
Preliminary Research Objectives • Rear two-spotted spider mites for testing. • Determine toxicity to two-spotted spider mites of selected miticides using the adult glass vial technique. • Use GreenSeeker ™ to detect two-spotted spider mite damage on cotton and pinto beans. • Initiate spray table evaluation of deposition parameters that contribute to specific miticide efficacy.
Rearing Two-spotted Spider Mites • Initial natural infestation on cotton being grown in greenhouse. • Placed mite infested cotton leaves on pinto beans, PhaseolusvulgarisL. , variety Dwarf Hort/Improved, obtained from BWI, Schulenburg, TX. • Grown in Standard NCR Flats (22”x11”x2”-LxWxH), BWI. • Used Baccto™ Premium Potting Medium, BWI
Rearing Two-Spotted Spider Mites • Initially had very good bean plant establishment in the flats, but as conditions got hotter in the greenhouse, observed lots of plant mortality due to pathogens. • Sprayed the seeds with a fungicide to get a good stand in the flats. • Young plants were infested by putting parts of previously infested bean plants on which the mites were massing.
Use of Glass Vial Bioassay to Determine Miticide Toxicity • Adult mites obtained from bean plants when they were massing. • Placed in 20 ml glass scintillation vials with coating inside of technical miticides deposited while dissolved in acetone. • Miticide concentrations based on µg/vial at intervals from none to as high as necessary to kill all the mites. • Acetone evaporated by placing vials on hot dog roller until dry.
Glass Vial Bioassays of Miticides • Adult mites confined in vials for 24 hours. • Considered dead if they did not move or could not right themselves when prodded if they were still moving. • Dosage mortality equations were calculated for each miticide. • Significant differences were based on the lack of overlap of the 95% confidence limits.
Use of GreenSeeker to Detect Mite Damage on Beans and Cotton • Commercial hand-held GreenSeeker optical sensor was used to take NDVI measurements. • Flats with pinto beans and cotton were infested by placing infested bean leaves over the plants. Each infested flat was paired with an uninfested flat for comparison. • Measurements collected daily starting with the day of infestation and until the infested plants died or about 14 days.
GreenSeeker Detection of Mite Damage • Maximum NDVI values from 3 readings of each flat were used in data calculations for each day.
Spectoradiometer • FieldSpec HandHeld (Analytical Spectral Devices, Inc.) • A useful tool for detection and monitoring of crop growing status • Collect spectral data from the target ranging from blue, green, red and NIR wavebands (325-1075nm) • Reflectance spectra of healthy plant canopy
Conclusions • Two spotted spider mite rearing system developed. • Observed major differences in toxicity of miticides to adult mites • Will proceed to spray table evaluation of deposition patterns for increased efficacy. • GreenSeeker shows promise for use in remote sensing of mite damage on beans and cotton.
