| Abstract/Contents: | "This study was undertaken to determine extended residual control of a mixed white grub population on a turfgrass area maintained at Penn State's Valentine Turfgrass Research Center at University Park. The turfgrass area consisted primarily of Kentucky bluegrass (25%) and annual bluegrass (75%). Treatment plots were 9 x 6 ft, arranged in a RCB design and replicted 3 times. Liquid formulations were applied by using a CO₂ sprayer with four 8002 TeeJet nozzles mounted on a 6 ft boom, operating at 28 psi, and applied in 817 ml of water/ 54ft² or delivering 4.0 gal/1000ft². Granular formulations were applied with a hand-held shaker and mixed with fine top dressing sand to faciliate product distribution. At the first treatment time (21 May), the following soil and environmental conditions existed: air temp, 53°F; soil temp at 1 inch depth, 52°F; soil temp at 2 inch, 52°F; RH, 72%; amt of thatch, 0.5-0.625 inch; soil percent water content (percent by wt), 16.6; water pH, 7.0; application time, early-morning; and sunny skies. Immediately after application, the experimental area was irrigated with 0.55 inch of water. At the second treatment time (23 Jul), the following soil and environmental conditions existed: air temp, 74°F; soil temp at 1 inch depth, 77°F; soil temp at 2 inch, 77°F; RH, 64%; amt of thatch, 0.5-0.625 inch; soil percent water content (percent by wt), 22.0; water pH, 7.0; application time, mid-morning; and clear skies. Immediately after application the experimental area was irrigated with 0.125 inch of water. At the third treatment time (31 Aug), the following soil and environmental conditions existed: air temp, 54°F; soil temp at 1 inch depth, 60°F; soil temp at 2 inch, 60°F; RH, 90%; amt of thatch, 0.5-0.625 inch; soil percent water content (percent by wt), 19.9% water pH, 7.0; application time, early morning; and clear skies. Immediately after application, the treatments were irrigated with 0.1 inch of water. At the fourth treatment time (15 Sep), the following soil and environmental conditions existed: air temp, 70°F; soil temp at 1 inch depth, 67°F; soil temp at 2 inch, 66°F; RH, 68%; amt of thatch, 5.0-0.625 inch; soil percent water content (percent by wt), 21.2; water pH, 7.0; application time, late-morning; and cloudy skies. Immediately after application, the experimental area was irrigated with 0.3 inch of water. General soil conditions were as follows: soil textural class, silt loam; soil particle analysis: sand, 24.6%; silt, 62.1%; clay, 13.2%; organic matter, 6.4%; and soil pH, 6.4. Three white PVC cylinders (8 inches x 6 inches height were placed in each replicate and 25 JB adults were released inside each cylinder on 6 Jul (60% females) and 12 Jul (60% females). Adult beetles were maintained inside by covering individual cylinders with white shade screen. The latter procedure allowed for oviposition by adult female beetles. All PVC cylinders were removed on 19 Jul. Post-treatment counts were made on 23 Sep. Three ft² sod samples were taken from each replicate. Each ft² sample was centered on turfgrass located within the 8 in PVC cylinder infestation area. The toatl no. of JB and NMC grubs/ft² was recorded. Adult JB's were first observed flying on 20 June in Centre County. The stage of grubs sampled on 26 Aug included second instar JB and NMC grubs, while those sampled on treatment date four (15 Sep) were third instar JB and NMC grubs. Eight treatments provided significant reduction of JB grubs while all treatments, disregarding application timing, provided significant control of NMC on 23 Sep. Severe drought conditions may have influenced whit grub density in 1999. No phytotoxicity was noted." |
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