Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2000
Publication Date: 12/1/2001
Citation: MULROONEY, J.E. ENHANCEMENT OF TRANSFER OF TECHNICAL MALATHION FROM COTTON LEAVES TO BOLL WEEVILS, ANTHONOMUS GRANDIS GRANDIS, BOHEMAN (COLEOPTERA: CURCULIONIDAE) USING COTTONSEED OIL. SOUTHWESTERN ENTOMOLOGIST. Supplment 24, p 29-40 Interpretive Summary: A method was developed in the laboratory for determining the amount of malathion transferred from cotton leaves to boll weevils. Using a laboratory spray tower, a motion analysis system, and gas chromatography, the effect of cottonseed oil on the transfer and efficacy of malathion was determined. Malathion transfer and subsequent boll weevil mortality increased with increased rate of application as expected. Increasing the volume of cottonseed oil also increased malathion transfer and boll weevil mortality. This research demonstrates that reduced rates of malathion can be effective against boll weevils if a sufficient volume of cottonseed oil is used to apply malathion. Using cottonseed oil to enhance the transfer and efficacy of reduced rates of malathion is both economically and environmentally sound.
Technical Abstract: Transfer tests of technical malathion alone and in mixtures of different ratios of cottonseed oil (CSO) were conducted in the laboratory. A Potter spray tower was used to treat excised cotton leaves collected from plants grown in a greenhouse. Mixtures of malathion:CSO were applied first at constant volume and then at constant rate. CSO was found to enhance transfer of malathion from cotton leaves into boll weevils. Mortality and the amount of malathion transferred to weevils were related to the amount of CSO in the mixture and to the volume applied. A three-parameter modified Weibull Function was found to best fit the data. Two types of data were fit. First, maximum cumulative mortality was found to increase with increasing volumes of malathion and a steady state of insecticide transfer to the boll weevil was reached within 5 - 15 cm of travel across a treated cotton leaf. The distance at which half of the maximum cumulative mortality occurred was shortest when malathion was mixed in CSO at a 1:9 ratio. Also, the rate of cumulative mortality over distance traveled increased when malathion was mixed with CSO. All mixtures except the 1:1 ratio of malathion:CSO had greater maximum cumulative mortalities than undiluted applications of malathion. The highest ratio, 1:9, produced the greatest maximum cumulative mortality (99%) and transferred the greatest amount of malathion from cotton leaves to boll weevils. The second type of data modeled by the cumulative Weibull function was the malathion residue that accumulated on boll weevils as they traveled various distances across leaves treated with various mixtures. Cumulative malathion residue on boll weevils for each treatment followed similar trends as cumulative mortality.