| Grub, the general term of Scarabaeoidea larvae, is one of the most serious soil-inhabiting pests. Chemical control is the main prevention and treatment methods at the present stage. Chlorpyrifos, the most commonly used in underground pest control, is generally processed into emulsifiable concentrate(EC). The use of large quantity of organic solvents puts pressure on environments and the acute toxicity of that to aquatic creatures is high toxicity. So it is resolved with the development of capsule suspension(CS) of chlorpyrifos. Studys on development of chlorpyrifos CS have been reported largely while there are few reports on release behavior in soils and toxicity of chlorpyrifos CS to environmental organisms. So we have studied persistance of chlorpyrifos CS in soils, toxicity of chlorpyrifos CS to environmental organisms and pesticide application technology about control of white grubs in peanuts field, and main contents is as the following aspects:1. The toxicity of chlorpyrifos CS to 4 species of environmental organisms were evaluated. The result showed that compared with chlorpyrifos EC, the toxicity of chlorpyrifos EC to Brachydanio rerio was 69.55 as high as chlorpyrifos CS, and chlorpyrifos CS was low toxic to Brachydanio rerio. The results also showed that the LD50 of chlorpyrifos EC to quail(Coturnix japonica)was 7.45 mg·kg-1, but the different formulation of chlorpyrifos CS to the same tested bird was 56.97 mg·kg-1. Chlorpyrifos EC was highly toxic to Coturnix japonica while chlorpyrifos CS was low toxic to that. Meanwhile, the toxicities of the different insecticide formulations to silkworm(Bombyx mori L.)were evaluated in the laboratory using the leaf dipping method. The results indicated that the difference of LC50 (24 h, 25℃) to silkworm between chlorpyrifos CS and chlorpyrifos EC was not significant while LC50 of chlorpyrifos CS (48 h, 25℃) to silkworm was significantly lower than the other formulation of the insecticide. After contact of silkworm with filter paper treated by chlorpyrifos in time of 1, 10, 30 and 60 min, the LD50 (48 h, 25℃) of chlorpyrifos EC to third-instar larvae was 3.18, 0.68, 0.41, 0.38μg·cm-2 and the LD50 (48 h, 25℃) of chlorpyrifos CS to silkworm was 6.92, 1.58, 1.18, 0.48μg·cm-2, respectively. The results also indicated that the LC50 (48 h) to bee(Apis mellifera L.) of chlorpyrifos EC or chlorpyrifos CS was 0.53 mg·L-1 or 2.32 mg·L-1, respectively. The results indicated that the safety of chlorpyrifos CS to 4 species of environmental organisms was obviously higher than that of chlorpyrifos EC. 2. Effects of environmental factors on persistence of microcapsule suspension of chlorpyrifos in soils were studied by bioassay using the larva of Holotrichia parallela and compared with emulsifiable concentrate of chlorpyrifos. The results indicated that persistence of microcapsule suspension of chlorpyrifos and the releasing rate within capsule decreased with increasing of soil moisture under the same conditions of other soil media. Persistence of chlorpyrifos in soil decreased with increasing of soil temperature. The active ingredient was trapped by organic soil, so toxicity against target organism decreased but its persistence extended.3. The residual dynamic of chlorpyrifos urea-formaldehyde resin (UF) microcapsulesand and chlorpyrifos polyurethane microcapsules in soil was investigated compared with chlorpyrifos EC and chlorpyrifos granules(GR). The result showed that the degradation of four types of chlorpyrifos in soil could be described with equation: Ct=C0e-kt. Degradation rate of four types of chlorpyrifos in soil : chlorpyrifos EC≈chlorpyrifos urea-formaldehyde resin microcapsules>chlorpyrifos granules > chlorpyrifos polyurethane microcapsules.4. Field efficacy trials of 30% chlorpyrifos CS against peanut white grub was investigated compared with chlorpyrifos EC and chlorpyrifos granules. The results indicated that the control effects of seed dressing with irrigation were obviously higher than other application methods. The control effects of chlorpyrifos polyurethane microcapsules against peanut white grub were higher than that of chlorpyrifos urea-formaldehyde resin microcapsules, and the control effects of chlorpyrifos EC and chlorpyrifos granules were not as high as that of chlorpyrifos CS.
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