About pencycuron: Effects of selected chemical pesticides on Agamermis unka (Nematoda: Mermithidae), a parasite of the brown plant hopper, Nilaparvata lugens

By: Choo HoYul Kim HyeongHwan Kaya HK Choo HY Kim HH Selected commercial and technical grade pesticides were tested against the egg, preparasite and adult stages of Agamermis unka, a nematode parasite of Nilaparvata lugens. The commercial insecticide, diazinon (LC50=0.37 ppm), was most toxic to the preparasites, followed by phenthoate (LC50=0.43 ppm), BPMC (LC50=0.44 ppm), IBP (LC50=0.46 ppm), cartap hydrochloride (LC50=0.82 ppm) and buprofezin + isoprocarb (LC50=1.11 ppm). The least toxic commercial pesticide tested was the fungicide, pencycuron (LC50=2.19 ppm). Out of 12 technical grade insecticides tested, phenthoate, monocrotophos, diazinon and carbofuran (LC50 = 0.37 - 0.46 ppm) were highly toxic to the preparasites, followed by buprofezin, BPMC and fenitrothion (LC50 = 0.74 - 0.86 ppm). Fenthion, etofenprox, chlorpyrifos, imidacloprid and MIPC (LC50=1.11-2.19 ppm) were the technical grade insecticides least toxic to the preparasites. Most preparasites survived for up to 24 h at the low insecticide concentrations (0.63 and 0.31 ppm). Preparasites that were exposed to BPMC for 24 h at concentrations as high as 5.0 ppm and survived the treatments infected brown planthopper nymphs. Four selected insecticides - chlorpyrifos, BPMC, imidacloprid and carbofuran - had significant adverse effects on A. unka egg hatching. Eggs that were in the insecticide solution for 168 h fared poorly with imidacloprid having the best survival (> 2% of the eggs hatching at 0.04 ppm). No eggs hatched from the other insecticide treatments. Three selected insecticides,BPMC, imidacloprid and chlorpyrifos, tested against adult A. unka showed that most adults survived the exposure to the insecticides between 0.31 and 2.5 ppm. At 5.0 ppm of BPMC or chlorpyrifos none of the adults survived, whereas with imidacloprid 70% of the adults survived. Egg deposition by the surviving adults was greatly reduced in those treated with the insecticides compared with those in the controls. Imidacloprid had some negative impact on the preparasites" ability

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