[Occurrence regularity and integrated control of leaf miner in safflower].

Leaf miner is one of the major pests on safflower, which causes yield loss and poor quality seriously. "Weihonghua", "nine safflower varieties" and "three chemical insecticides" as materials that used to evaluate variety and regularity of leaf miner, safflower resistant level, and different proportions insecticides in field efficiency test. The results showed that Liriomyza sativae and L. huidobrensis accounted for 80%, the peak period of two pests was all in July; but Phytomyza horticola is relative less, its peak period occured in June. Three were great difference of resistance to leaf miner among safflower varieties, FQ12 and YJ65 expressed higher resistibility to leaf miner by ratio method. With abamectin 2% emulsifiable concentrate diluted for 2 000 times, or the mixture three insecticides(bifenthrin 20% water emulsions, thiamethoxam 25% water dispersible granule, abamectin 2% emulsifiable concentrate=1∶1∶1) diluted for 3 000 times, which were sprayed on leaves at squaring stage and lethal rate was 96% after 48 h in the study. Through comparative study on the variety and regularity of leaf miner, screen for resistant varieties to leaf miner and for high efficiency pesticide. The study provides theoretical basis and reference for integrated pest management of leaf miner.

Silencing of an aphid carboxylesterase gene by use of plant-mediated RNAi impairs Sitobion avenae tolerance of Phoxim insecticides.

RNA interference (RNAi) describes the ability of double-stranded RNA (dsRNA) to inhibit homologous gene expression at the RNA level. Its specificity is sequence-based and depends on the sequence of one strand of the dsRNA corresponding to part or all of a specific gene transcript. In this study we adopted plant-mediated RNAi technology that targets Sitobion avenae (S. avenae) to enable gene silencing in the aphid and to minimize handling of the insects during experiments. S. avenae was selected for this study because it causes serious economic losses to wheat throughout the world. The carboxylesterase (CbE E4) gene in S. avenae was homologously cloned, which increased synthesis of a protein known to be critical to the resistance (tolerance) this species has developed to a wide range of pesticides. A plant RNAi vector was constructed, and transgenic Triticum aestivum (dsCbE1-5 and dsCbE2-2 lines) expressing CbE E4 dsRNA were developed. S. avenae were fed on dsCbE1-5 and dsCbE2-2 lines stably producing the CbE E4 dsRNA. CbE E4 gene expression in S. avenae was reduced by up to 30-60%. The number of aphids raised on dsCbE1-5 and dsCbE2-2 was lower than the number raised on non-transgenic plants. A solution of CbE E4 enzyme from S. avenae fed on dsCbE1-5 and dsCbE2-2 plants hydrolyzed only up to 20-30% Phoxim solution within 40 min whereas a solution of the enzyme from CbE E4 fed on control plants hydrolyzed 60% of Phoxim solution within 40 min. CbE E4 gene silencing was achieved by our wheat-mediated RNAi approach. This plant-mediated RNAi approach for addressing degradation-based pesticide resistance mechanisms in aphids and may prove useful in pest management for diverse agro-ecosystems.