Abstract
Abstract The experimental design was a randomized complete block, with 6 treatments and a control replicated 6 times. Cotton was planted on 7 May with plots consisting of 2 rows (on 102 cm centers) × 6.1 m and foliar sprays were applied with a utility tractor equipped with a compressed air system calibrated with water to deliver 76 liters/ha at 2.6 kg/cm2 and 5.5 km/h (2 VS8001 nozzles/row). Treatments were applied on 29 May and plots were evaluated on 31 May and 5 Jun. The plots had not been treated previously and plant height at treatment initiation ranged from 50-75 cm. Effectiveness on aphid populations was evaluated by randomly collecting 25 plant terminals from each plot and placing them immediately into 0.95 liter glass jars. In the laboratory, 10 ml of sodium hypochlorite (5.25%), 5 ml of dilute liquid detergent solution, and 500 ml of tap water were added to the glass jars. Following vigorous agitation, the contents of the jars were poured onto a no. 30 metal sieve and plants were thoroughly washed to dislodge remaining aphids, which were funneled into 300-mesh sieves. Contents of the 300-mesh sieve were backwashed into a Buchner filter apparatus (7 cm diam) containing rules filter paper. Numbers of aphids were determined using a Zeiss binocular stereoscope at 12 × magnification. No rainfall was recorded between 29 and 31 May and a trace (<0.1 cm) of rain occurred on 4 Jun.
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