Submitted to: Southwestern Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 15, 2000
Publication Date: December 2, 2001
Citation: Mulrooney, J.E., Smith, L.A. 2001. Application of reduced rates of technical malathion applied as ultra low volume in oil. Southwestern Entomologist. Supplement No. 24:41-48. Interpretive Summary: Application research was conducted to reduce the cost of utra- low-volume (ULV) application of malathion for boll weevil eradication. This research demonstrated that once-refined cottonseed oil (CSO) enhances the efficacy of technical malathion. Boll weevil mortality in laboratory bioassays of leaves treated with 8:8 and 6:26 ounce mixtures of malation:CSO was the same as a 10 oz/A application of undiluted technical malathion for the first 2 days after application. Application of the 8:8 mixture of malathion:CSO is 20 cents per acre per application cheaper than an application of 10 oz/A of technical malathion. With millions of acres of cotton being treated across the country, the reduced cost of low rate applications of malathion in CSO is substantial. Substantial reductions in the cost of eradication are possible if reduced rates of malathion are applied in CSO.
Technical Abstract: Aerial application tests of malathion ULV mixed in once-refined cottonseed (CSO) and horticultural mineral oils (HMO) were conducted in 1998 and 1999 to determine toxicity to boll weevils with leaf bioassays. The HMO's used in these tests were: Orchex 796, and WS2908, an Orchex 796 formulation with drift retardant. Mortalities showed that a 6 oz/A rate of malathion ULV mixed with 26 oz/A of CSO was as effective against boll weevils as a 12 oz/A rate of undiluted malathion ULV. In July and August 1999, efficacy of 6:26, 6:10, 7:18, 8:8, and 10:0 oz/A ratios of malathion ULV:CSO against boll weevils was determined. Plots were 1.34 and 10 A and were replicated six times. Results showed that 6 and 8 oz/A rates of malathion ULV can be as effective as an undiluted 10 oz/A rate for the first 2 - 3 days after treatment if the volume of the application is sufficiently high. Malathion residues accumulated on leaf surfaces during rain free periods in August after repeated applications of both undiluted and malathion ULV diluted in CSO.