Impact of deltamethrin aerial sprays on adult Cyrtobagous salviniae in Botswana

The risk and effect of the insecticide deltamethrin, applied aerially in Botswana to control and eradicate tsetse fly, was studied on the non-target weevil Cyrtobagous salviniae, a biocontrol agent of the aquatic weed Salvinia molesta. Environmentally-simulated short-term toxicity bioassay used open iron cages and closed plastic basins containing weevils and salvinia placed in riverine water bodies, where they were exposed to the aerial applications of deltamethrin over the Kwando–Linyanti system in 2006. Control samples were placed 40 km outside the sprayed area. Weevil mortality, determined at 12, 36 and 60 hours after the aerial application, reached a maximum of 27%. No significant difference in mortalities was observed between the closed basins and the open cages. The amount of deltamethrin deposited at ground level was between 1.2 and 6.4 μg m^?2  and the insecticide toxicity was related to the weevil mortality. Simultaneous field monitoring through five spray applications showed that weevil abundance declined in late winter. Deltamethrin had a negligible impact on the weevil's ability to control salvinia under field conditions, probably due to the weevils’ protective mechanism and because vegetation could act as a barrier, preventing the insecticide from reaching the weevils. Minimum impacts of deltamethrin on the weevils in the present study and their recovery in the field are consistent with those of earlier spray applications in the Okavango Delta, Botswana.     

基于转录组的苹小卷叶蛾杀虫剂靶标及解毒代谢相关基因分析

【目的】建立苹小卷叶蛾Adoxophyes orana转录组数据库,挖掘杀虫剂靶标及解毒代谢相关基因。【方法】采用Illumina HiSeq~(TM) 2000高通量测序技术对苹小卷叶蛾进行转录组测序,挖掘并分析杀虫剂靶标基因;利用qPCR检测6个杀虫剂靶标基因在苹小卷叶蛾卵、幼虫、蛹和成虫各不同发育阶段的表达;挖掘并分析苹小卷叶蛾转录组中解毒代谢相关基因的代谢通路及进化关系。【结果】通过组装有效序列共获得48 610条unigene(GenBank登录号:GGMW00000000)。挖掘鉴定到155个杀虫剂靶标unigene;qPCR结果显示,1个蜕皮激素受体(ecdysone receptor, ECR)、2个乙酰胆碱酯酶(acetylcholinesterase, AChE)、1个氯离子通道蛋白(chloride channel, CLC)、1个几丁质酶(chitinase, CS)和1个鱼尼丁受体(ryanodine receptor, RyR)基因在苹小卷叶蛾不同发育阶段均存在表达差异。挖掘鉴定到69个羧酸酯酶(carboxylesterase, CarE)unigene、66个谷胱甘肽S-转移酶(glutathion S-transferase, GST)unigene和205个细胞色素P450(cytochrome P450)unigene等解毒代谢相关基因,共鉴定20个CarE unigene, 32个GST unigene和30个P450 unigene与有毒物质代谢相关的通路有关。基于氨基酸序列对具有完整ORF的unigene聚类分析结果显示:12个CarEs中9个为G类,即鳞翅目保幼激素类;分别有10个AoGSTs属于Delta和Epsilon亚家族;18个P450全部聚到CYP3集团。【结论】该研究有助于苹小卷叶蛾杀虫剂靶标基因的挖掘及抗药性的研究。     

The antagonistic/synergistic effects of some medicinal plant essential oils,extracts and powders combined with Diatomaceous earth on red flour beetle,Tribolium castaneum Herbst (Coleoptera: Tenebrionidae)

Abstract

Red flour beetle, Tribolium castaneum Herbst (Coleoptera: Tenebrionidae) is a prominent pest of stored products particularly cereal flour. Since resistance of this pest to common chemical insecticides is well documented, we were examined the synergistic/antagonistic interaction between Satureja hortensis L., Trachyspermum ammi L., Ziziphora tenuior L., Cuminum cyminum L. and Foeniculum vulgare Miller essential oils, ethanolic extracts and powders with Diatomaceous earth (DE) against T. castaneum adults under laboratory conditions at 27 ± 1 °C, 65 ± 5% RH and continuous darkness. We assayed repellency of ethanolic extracts and essential oils of mentioned plants on the pest. Results showed that DE had high toxicity to the pest. Plant essential oils and ethanolic extracts (except ziziphora) synergized the performance of DE. Nevertheless, plant powders elicited antagonistic effects (except ziziphora that exhibited synergistic effect). The most repellent EO and extract was cumin which exhibited mean repellency value on adult insect equivalent to 92.58 and 51.47%, respectively.     

The impact of strain diversity and mixed infections on the evolution of resistance to Bacillus thuringiensis

Pesticide mixtures can reduce the rate at which insects evolve pesticide resistance. However, with live biopesticides such as the naturally abundant pathogen Bacillus thuringiensis (Bt), a range of additional biological considerations might affect the evolution of resistance. These can include ecological interactions in mixed infections, the different rates of transmission post-application and the impact of the native biodiversity on the frequency of mixed infections. Using multi-generation selection experiments, we tested how applications of single and mixed strains of Bt from diverse sources (natural isolates and biopesticides) affected the evolution of resistance in the diamondback moth, Plutella xylostella, to a focal strain. There was no significant difference in the rate of evolution of resistance between single and mixed-strain applications although the latter did result in lower insect populations. The relative survivorship of Bt-resistant genotypes was higher in the mixed-strain treatment, in part owing to elevated mortality of susceptible larvae in mixtures. Resistance evolved more quickly with treatments that contained natural isolates, and biological differences in transmission rate may have contributed to this. Our data indicate that the use of mixtures can have unexpected consequences on the fitness of resistant and susceptible insects.     

Control efficacy of Bacillus thuringiensis and a new granulovirus isolate against Cydia pomonella in orchards

Abstract

Codling moth, Cydia pomonella, is one of the most serious pests of apple and pear worldwide. This study evaluates the efficacies of a granulovirus, a Bacillus thuringiensis (Bt) strain and their combination in the control of C. pomonella in China. A Cydia pomonella granulovirus (CpGV) was isolated from C. pomonella cadavers in an orchard in Gansu, China. Droplet-feeding bioassays showed the median lethal concentration (LC₅₀) of this CpGV isolate (CpGV-C1) against the third instar C. pomonella larvae was 770 OBs µl^?1. The LC₅₀ values of Bt C-33 and kurstaki HD-1 against the third instar larvae were 26.3 µg ml^?1 and 15.7 µg ml^?1, respectively. Field tests indicated the control efficacies of CpGV-C1 and the combination of CpGV-C1 and Bt against C. pomonella larvae in apple orchards were similar to that of beta-cypermethrin. Our data demonstrated that the combination of CpGV and Bt might effectively protect apple fruits from the damage of C. pomonella larvae and had the potential to be developed as a low-cost, highly effective insecticide.     

Epigeic spiders are not affected by the genetically modified maize MON 88017

The genetically modified (GM) maize MON 88017 facilitates weed management owing to its tolerance to glyphosate, and resists western corn rootworm (WCR), Diabrotica virgifera virgifera, owing to the expression of Cry3Bb1 toxin. MON 88017 could therefore contribute to the solution of two major problems of European agriculture: continuous WCR spreading and high use of herbicides. To assess possible unwanted environmental impacts of MON 88017, we compared communities of spiders in plots planted in three successive years with this maize, its near isogenic non‐GM cultivar treated or not treated with an insecticide and two unrelated maize cultivars. Each of the five treatments was applied on five 0.5 ha plots in a 14 ha field. Spiders were collected in five pitfall traps per plot five times per year. Upon reaching the waxy ripening stage, all plants of first‐year cultivation were shredded to small pieces and ploughed into the soil in the respective plot, whereas in the 2nd and 3rd year the harvest was used for biogas production and only digestate was returned to the field. Out of 79 spider species, Pardosa agrestis, Pachygnatha degeeri and Oedothorax apicatus made up 28%, 25% and 23% of the total spider count in the 1st year of study; 2%, 8% and 84% in the 2nd; and 40%, 8% and 35% in the 3rd year. Statistical analysis did not reveal any influence of GM maize on the spider abundance and biodiversity. The abundance, and in two years also the species diversity, was insignificantly higher on the plots with GM maize than on plots with the insecticide‐treated non‐GM maize. The composition and size of spider community varied year to year, probably reflecting weather conditions and differences in field fertilization with organic matter.     

Characterization of a Degraded Product Derived from Serratia piscatorum Polysaccharide by Ultrasonication

Acidic polysaccharide, PLS F–II, was prepared from Serratia piscatorum polysaccharide, PLS N–I, by a sequence of ultrasonication and gel filtration and was examined for chemical composition and biological activity.

The purified PLS F–II preparation was shown to be homogeneous by ultracentrifugation, zone electrophoresis and column chromatography. The molecular weight was estimated to be about 2 × 10⁴ by the Archibald method. PLS F–II was composed of l-rhamnose, d-galactose and d-galacturonic acid in the molar ratio of 2: 1: 1 and was partially acylated on the galacturonic acid residues.

PLS F–II was found to enhance the antibody formation in mice, although it showed no anti-inflammatory activity.     

Comparative effects of insecticides with different mechanisms of action on Chrysoperla externa (Neuroptera: Chrysopidae): Lethal,sublethal and dose–response effects

The comprehensive knowledge that the delayed systemic and reproduction side effects can be even more deleterious than acute toxicity, has caused a shift in focus toward sublethal effects assessment on physiology and behavior of beneficial insects. In this study, we assessed the risks posed by some insecticides with different mode of action through lethal and delayed systemic sublethal effects on the pupation, adult emergence, and reproduction of the chrysopid Chrysoperla externa (Hagen, 1861; Neuroptera: Chrysopidae), an important predator in pest biological control. The maximum field recommended dose (MFRD) and twice (2×MFRD) for chlorantraniliprole, tebufenozide, and pyriproxyfen were harmless to C. externa. In contrast, all the tested chitin synthesis inhibitors (CSIs) were highly detrimental to the predator, despite of their lack of acute lethal toxicity. Therefore, the safety assumed by using IGRs toward beneficial insects is not valid for chrysopids. Dose–response data showed that although all CSIs have a similar mechanism of action, the relative extent of toxicity may differ (novaluron > lufenuron > teflubenzuron). For CSIs, the delayed systemic effects became obvious at adult emergence, where the predicted no observable effect dose (NOED) was 1/2 048 of the MFRD for novaluron (0.085 ng/insect), and 1/256 of the MFRD for both lufenuron (0.25 ng/insect) and teflubenzuron (0.6 ng/insect). Finally, this work emphasized the significance of performing toxicity risk assessments with an adequate posttreatment period to avoid underestimating the toxicities of insecticides, as the acute lethal toxicity assays may not provide accurate information regarding the long‐range effects of hazardous compounds.     

Ecological genetics of Italian peach‐potato aphid (Myzus persicae) populations in relation to geography,dispersal and insecticide resistance as studied using microsatellite and resistance markers

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