Toxical Effects And Evaluations Of Neonicotinoid Insecticides To Bradysia Odoriphaga

Bradysia odoriphaga Yang et Zhang, commonly called as chive maggot, belongs to Sciaridae Diptera. It is the very important underground pest that damages Allium tuberosum, Allium sativum, Allium cepa, Allium fistulosum and other plants, which is the heaviest in Allium tuberosum. The highly-toxic pesticides were used to control it and caused the pollution seriously on security of china chives, it made a potential threat to the health of consumers, at the same time, it also becomes the important obstacle of restricting Chinese chives production. This article using the neonicotinoid insecticides as object of research, determined the toxicity of neonicotinoid insecticides to the different stages of odoriphaga, studied on the temperature effect of different kinds of insecticides to odoriphaga, observed the sublethal effects of insecticides on the growth, development and reproduction of neonicotinoid insecticides to odoriphaga, and insecticide using technology was also been studied. This objectives of this paper is to select new security insecticide and study its technology, all of this can provided theoretical basis and technical guidance for odoriphaga decontamination control. The main results are as follows:1. In order to determine the pesticide toxicity,6insecticides to different stages of odoriphaga was detected using the dripping ration liquid methods. Toxicity of the6insecticides to eggs are low, but clothianidin showed higher toxicity to it with LC₅₀ up to82.562mg/L, LC50of abamectin was606.507mg/L, toxicity of the6pesticides to the eggs of odoriphaga was declining in the order as following:clothianidin> imidacloprid> methomyl> thiamethoxam> emamectin benzoate> abamectin. The2nd instars of odoriphaga was the most sensitive to the6pesticides, and clothianidin showed the highest toxicity to it with LC₅₀ up to0.339mg/L, and abamectin showed the lowest toxicity, its LC₅₀ was9.154mg/L, toxicity of the6pesticides to the2nd instars of odoriphaga was declining in the order as following:clothianidin> imidacloprid> methomyl> thiamethoxam> emamectin benzoate> abamectin. Toxicity of the6kinds of insecticides to the4th instars of odoriphaga showed that clothianidin had the highest toxicity, and abamectin oppositely, their LC₅₀ were1.020mg/L and25.712mg/L respectively. Toxicity of6pesticides to the4th instars of odoriphaga was declining in the order as following:clothianidin> methomyl> imidacloprid> thiamethoxam> emamectin benzoate> abamectin. Along with the extending of time, toxicity of the6 pesticides as increased. The toxicity differences between2nd instars and4th instars of odoriphaga of clothianidin was not apparently. It is worth to be extending and applicating.2. Toxicity of the6insecticides was detected at different temperatures. Under three different given temperatures, methomyl, clothianidin, imidacloprid, thiamethoxam and emamectin benzoate were showed the positive temperature effect. Among the6insecticides, imidacloprid showed the most obviously positive temperature effect, toxicity of imidacloprid in24℃is4.67times higher than in8℃; secondly, methomyl, clothianidin and thiamethoxam’s positive temperature effect were similarly, and toxicity of clothianidin in24℃is3.11times higher than in8℃; and the positive temperature effect of emamectin benzoate was minimum, toxicity of clothianidin in24℃is only1.86times higher than in8℃.3. The effects of neonicotinoid insecticides were treated on sublethal dose on development and adult fecundity of odoriphaga. When the4th instars were treated by sublethal dose of clothianidin, compared to control larvae of larval developmental period prolonged3.61days, pupation rate reduced by66.31%, Pupal stage prolonged0.48days, emergence rate reduced by58.93%, female and male pupae weight decreased by19.82%and28.55%respectively, eggs laid per female reduced by45.71%, Egg hatch rate reduced by23.33%, and it showed that clothianidin had obviously adverse effects on surviving4th larval development and adult fecundity, especially on pupation rate, emergence rate and fecundity.4. In pot test, when clothianidin50mg/L irrigating roots, odoriphaga emendation of larve mortality was73.35%, and24.17%,14.17%and27.51%higher than methomyl, imidacloprid and thiamethoxam50mg/L irrigating roots respectively. The results of field experiment demonstrated that clothianidin200mg/L and100mg/L, imidacloprid200mg/L, clothianidin200mg/L and betacypermethrin18mg/L, clothianidin200mg/L and hexaflumuron25mg/L irrigating roots, the second generation of Bradysia odoriphaga emendation of larve mortality was up to100%. Clothianidin and other neonicotinoids irrigating roots at growing time have a good affect for Bradysia odoriphaga control, and has a simple, less drug use characteristics, it is worth to be extending and applicating.