Resistance to the twospotted spider mite (Tetranychus urticae Koch) of 18 cultivars of ivy geranium [Pelargonium peltatum (L.) L’Her ex Ait.] was evaluated under greenhouse conditions by mass screening, by measuring fecundity on isolated leaves, and by paired leaf tests for selected cultivars. ‘Sybil Holmes’, ‘Yale’, and ‘Cornell’ were among the most susceptible, whereas ‘Double Lilac White’, ‘Sunset’, and ‘Salmon Queen’ were relatively mite-free. ‘Madeline Crozy’ and ‘Cornell’ were preferred for oviposition over the resistant ‘Double Lilac White’. Mite resistance was not related to density of simple or glandular leaf trichomes, but there was an apparent relationship between mite susceptibility and severity of oedema.
Although the number and weight of worms was quite variable, there were some significant differences from the check. Furadan exhibited the most pronounced effect on earthworm populations, reducing both numbers and biomass relative to the untreated check. Benomyl and diazinon also significantly reduced the earthworm numbers. However, the effect of diazinon was not as severe as that of Furadan.
CThis study was conducted in a 2-yr old stand of tall fescue at Elkhorn Springs Sod Farm, near Frankfort, KY. The turf was on a Maury silt loam soil (fine-silty, mixed, mesic Typic Paleudalf). Soil texture was 23% clay, 74% silt, and 3% sand, with 8.8% organic matter and pH = 6.4 Thatch accumulation was negligible. Plots (7 x 10 ft) were established in a RCB with five replications, with 2 ft untreated boundaries between plots. The turf was mown to 3" height before treatment, with the clippings raked and removed. Treatments were applied on 18 Aug. Liquid formulations were applied with a high pressure CO2 sprayer that delivered 2 gal of spray per 1000 ft2. Granular treatments were diluted with dry sand and applied to the plots by gloved hand. Nematode treatments were applied last, after which all plots were irrigated with about 0.5 inch of water, beginning 5-10 min after the final treatment was applied. Conditions at the time of application were sunny, 78°F, 57% relative humidity, and 5 mph winds. The soil was moist due to the 0.45 of rain that had fallen in the previous 4 d. The grub population at the time of treatment consisted of a mixture of 2nd and 3rd instars of each species. Treatment effectiveness was assessed 29-30 DAT by cutting a strip (25 X 18 inches, 2.5 inches deep) from the center of each plot with a motorized sod cutter. The sod strips were broken apart and examined for living grubs in the field. Data were analyzed by ANOVA followed by Fisher's protected LSD test to separate treatment means.
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