ELIMINATION, METABOLISM AND ANTICHOLINESTERASE PROPERTIES OF CARBOFURAN IN FRUIT STALK BORER, ORYCTES ELEGANS

Toxicity, anticholinesterase properties, elimination and metabolism of carbofuran applied to the larvae of fruit stalk borer, Oryctes elegan s were investigated. Larvae given 10 or 20 ppm of carbofuran did not s how any observable signs of acute toxicity. The LC50 values were 82, 6 2, and 48 ppm following 24, 48, and 72 hrs, respectively. The activity of brain cholinesterase of the treated larvae at 10 ppm level initial ly decreased during the first three hrs (63.3%), and then the enzyme r ecovered at the end of the experiment (72 hrs). Carbofuran was readily absorbed within 24 hrs following its application at 20 ppm level. The amounts of carbofuran increased to peak value of 20.3, 6.6, and 31.3 mu g/g in brain, fatbody and midgut at 10, 7, and 10 days, respectivel y. These values decreased with time and at the end of the experiment ( 21 days) reached at 4.9, 2.9, and 12.4 mu g/g levels, respectively. Ca rbofuran was metabolized to 3-hydroxy- carbofuran, 3-ketocarbofuran an d 3-ketocarbofuranphenol in the tissues. These metabolic conversions r esulted in the formation of highly polar products which facilitated th eir elimination from the insect body. The daily rate of elimination of carbofuran increased with time following its application. The amount of carbofuran eliminated was 42.9 mu g after one day and then increase d to 163.6 mu g at the end of experimental period days). This indicate s that there was no tendency of the compound to accumulate in the inse ct tissues. Thus carbofuran and its metabolites were rapidly excreted soon after application.