| In order to clarify the toxcity of chlorantraniliprole to Pieris rapae and the metabolic detoxification mechanisms in the Pieris rapae. We evaluated the toxicity of chlorantraniliprole against Pieris rapae (L.)(Lepidoptera:Pieridae) on cabbage (Brassicae oleracea variety capitata L.), and examined the persistence of chlorantraniliprole on field-aged cabbage leaf residues against5-day-old larvae. Efficacies of chlorantraniliprole and other insecticides to P. rapae (L.) were tested under field conditions for two seasons in Hunan province, south-central China. By using the leaf-dip method, effects of sublethal concentrations of chlorantraniliprole on the larvae of Pieris rapae.The expression of ryanodine receptor (RyR) gene from Pieris rapae (L.)3rd larvae at continuous and intermittent treatment with below the sublethal dose of chlorantranilipole and the RyR gene expression from P. rapae that susceptible and resistant to chlorantraniliprole were studied by quantitive RT-PCR method.1、the LC50value of chlorantraniliprole for early and later instar ranged from5.07to12.13mg/L and7.12to19.71mg/L by contact, in respectively, the LC90value of chlorantraniliprole for early and later instar ranged from22.58to122.98mg/L and33.10to156.09mg/L by contact, in respectively. Chlorantraniliprole exhibit high level contact activity on Pieris rapae larvae. Similarly, chlorantraniliprole are highly toxic to Pieris rapae larvae through ingestion. the LC50and LC90value by ingestion were relatively low compared with those by contact. The LC50and LC90value for early and later instar by ingestion were, respectively,0.95(0.41-2.57),4.32(2.79-6.00) and7.01(2.53-20.34)19.65(12.7-44.40). The results indicated that chlorantraniliprole is primarily active on chewing pests by ingestion and secondarily by contact, showing good and larvicidal activity. The LC50and LC90values of chlorantraniliprole to young larvae (first and second instars) and older larvae (third and fourth instars) were significantly different because the95%FL did not overlap. Younger larvae were significantly more susceptible to chlorantraniliprole than the older larvae.respectively. The toxicity of chlorantraniliprole on0to28day-old leaf residues declined gradually under the field conditions. Almost all larvae died on day5after being fed with0to21-day-old leaf residues, and the mortalities were as high as83.3%and72.5%after being fed with21-and25-day-old leaf residues, respectively.With one application, chlorantraniliprole suppressed P. rapae (L.) larvae below the economic threshold for21-28days. The results of two field trials showed that chlorantraniliprole applied at52mg active ingredient (a.i.)/l was effective against P. rapae (L.) larvae on cabbage. In addition, we showed that chlorantraniliprole was as effective as indoxacarb and spinosad, and was significantly more effective than emamectin benzoate. These results indicated that it is possible to provide marketable cabbages with three applications of chlorantraniliprole per season. When the3rd instar larvae were treated with chlorantraniliprole at the concentration for12,24,48and72h.2、After continuous treatment with LC25of chlorantraniliprole of carboxyleaterase(C arE) was increased, but the specific activity of glutathione S-transferase (GSTs) were significantly lower than the untreated control. These results suggested that the carboxylesterase may be involved the metabolic detoxification mechanisms in the Pieris rapae.3、The results show that lower dose of chalorantraniliprole can induce the expression of RyR gene from pupae of P. rapae; moreover, compared with intermittent treatment, continuous treatment can significant enhance RyR gene expression from P. rapae, and the relative expression of RyR gene from chlorantraniliprole resistant strain was6.32-fold compared with that of the susceptible strain. These results would be conductive to clarify the mechanism of chlorantraniliprole, and also provide a foundation to screen the compounds targeting at RyR. |
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