Identification and Detection of CYP4G68 Overexpression Associated With Cyantraniliprole Resistance in Bemisia tabaci From China

Bemisiatabaci, the tobacco whitefly, is one of the most notorious agricultural sucking insect pests that severely damage a series of crops worldwide. Throughout China, B. tabaci threatens agricultural production with increasing cases of resistance to commonly used insecticides, prompting the widespread use of cyantraniliprole as an alternative to control hemipteran pests. Here, we found overexpression of the CYP4G68 gene conferring cyantraniliprole resistance using quantitative real-time PCR (qPCR) and RNA interference (RNAi) in one lab-selected resistant strain CYAN-R (to about 80-fold higher than control). Furthermore, we measured levels of resistance to cyantraniliprole in whiteflies with 18 field-sampled populations across China and then confirmed that, among them, 14 field-sampled populations showed low-to-high resistance to cyantraniliprole compared with the susceptible strain. We measured CYP4G68 expression in the 14 field populations, and the results of qPCR and RNAi indicated that in two of these populations, Haikou and Wuhan, significant overexpression of CYP4G68 contributed to the development of field-evolved resistance to cyantraniliprole. These results indicate the need to facilitate strategies of management to delay the evolution of resistance to cyantraniliprole and control of whiteflies more sustainably, and to prevent overuse of insecticides in the environment through rational application practices.</jats:p

The Toxicity, Sublethal Effects, and Biochemical Mechanism of &beta;-Asarone, a Potential Plant-Derived Insecticide, against Bemisia tabaci

Bemisia tabaci is a threat to agriculture worldwide because of its potential to cause devastating damage to various crops. &beta;-asarone is a bioactive pesticidal chemical originating from Acorus calamus (or &ldquo;Sweet Flag&rdquo;) plants, and it displays significant lethal effects against insect pests. In this study, we established a baseline of susceptibility to &beta;-asarone from China and patterns of cross-resistance to other popular insecticides. We found that all the 12 field-collected B. tabaci populations exhibited high susceptibility to &beta;-asarone, and there was no cross-resistance detected for other tested insecticides. We subsequently evaluated the sublethal effects of &beta;-asarone on physiology and biochemistry via LC25 treatment (4.7 mg/L). LC25 of &beta;-asarone resulted in prolonged developmental duration and decreased survival rates in B. tabaci nymphs, pseudopupae, and adults. Significant reductions in oviposition duration, fecundity, and hatchability were also observed. Additionally, the metabolic enzyme activity and expression profiles of selected cytochrome P450 monooxygenase (P450) genes following the LC25 treatment of &beta;-asarone suggest that enhanced detoxification via P450s could be involved in the observed sublethal effects. These findings demonstrate the strong toxicity and significant sublethal effects of &beta;-asarone on B. tabaci and suggest that the induced overexpression of P450 genes could be associated with the response to &beta;-asarone

Metabolic Resistance in Abamectin-Resistant Bemisia tabaci Mediterranean from Northern China

Abamectin, produced by the soil-dwelling actinomycete Streptomyces avermitilis, belongs to the macrocyclic lactones class of pesticides, has nematocidal, acaricidal, and insecticidal activity, and is highly effective when used against targeted species. Bemisia tabaci, the tobacco whitefly, is a highly destructive insect to agricultural production worldwide, and various insecticide-resistant strains have been identified in China. Here, we monitored levels of resistance to abamectin in twelve field-collected B. tabaci populations from northern China, and confirmed that, compared with the lab reference strain, six field populations exhibited strong abamectin resistance, while the other six exhibited low-to-medium resistance. Among these, the Xinzheng (XZ) population displayed about a 40-fold increased resistance to abamectin, and experienced significant cross-resistance to chlorpyrifos and imidacloprid. The abamectin resistance of XZ was found to be autosomal and incompletely dominant. Metabolic enzyme and synergism tests were conducted, and two metabolic enzymes, glutathione S-transferase and P450 monooxygenase, were found to be conducive to the field-developed abamectin resistance of the XZ population. The above results provide valuable information that can be used in identifying new pest control strategies and delaying the evolution of resistance to abamectin in field populations of whiteflies

Lethal and sublethal effects of cyantraniliprole, a new anthranilic diamide insecticide, on Bemisia tabaci (Hemiptera: Aleyrodidae) MED

This study was supported partly by research grants from National Science and Technology Support task (2012BAD19B06), the earmarked fund for Beijing Leafy Vegetables Innovation Team of Modern Agro-industry Technology Research System (blvt-13), the earmarked fund for Modern Agro-industry Technology Research System (2013003019) and the earmarked fund from Beijing Academy of Agriculture and Forestry Sciences (QNJJ201610).The Bemisia tabaci (Gennadius) cryptic species complex comprises important insect pests that cause devastating damage to agricultural crops worldwide. In China, the B. tabaci MED species, formerly known as biotype ‘Q’, has surpassed the MEAM1 species, formerly known as biotype ‘B’, which is threatening agricultural production all over the country as an increasing number of resistance cases have been reported. This situation highlights the need for alternative pest control measures. In this study, the lethal effects of six neonicotinoid and two anthranilic diamide insecticides including the novel compound cyantraniliprole on B. tabaci MED were examined. The sublethal effects of cyantraniliprole on the physiology and behavior of B. tabaci MED were also assessed. Among eight insecticides tested, cyantraniliprole was the most toxic to B. tabaci MED with a LC50 of 2.05 mg/L. The sublethal effects of cyantraniliprole to adult B. tabaci MED were observed at LC10 (0.22 mg/L) and LC25 (0.63 mg/L) concentrations. At these concentrations, cyantraniliprole prolonged the developmental duration and decreased the survival rate of nymph stages, pseudopupae and adults. The oviposition duration and fecundity of females were also reduced significantly. The hatching rate of eggs laid by females exposed to LC10 and LC25 concentrations was also reduced. Altogether, these results demonstrate that cyantraniliprole could be an alternative insecticide for efficient control of B. tabaci MED populations in China