Sublethal effects of insecticides on the diamondback moth Plutella xylostella (L.)

The effect of sublethal concentrations (LC₁ and LC₅₀) of permethrin, fenvalerate, methamidophos and carbaryl on diamondback moth development, female fecundity and insect behaviour was investigated. All the insecticides had deleterious effects on the number of larvae surviving to pupae, the duration of the pupal period, the number of pupae surviving to adulthood, and cocoon formation in pupae. Prolonged duration of the larval period, from third instar to pupation, and deformed pupae were also observed. Permethrin, fenvalerate and carbaryl caused latent toxicity and deformed wings in the adults. Pyrethroids and methamidophos reduced the longevity of the adults whereas carbaryl increased it. Except for permethrin, the insecticides inhibited female fecundity. At LC₁ and LC₅₀ concentrations, the pyrethroids showed both repellent and antifeedant activity against larvae, and female moths preferred to oviposit on untreated leaf discs rather than on those treated with the pyrethroids at concentrations equal to their LC₅₀ values.     

氯虫苯甲酰胺对小菜蛾亚致死效应的研究

探讨亚致死剂量氯虫苯甲酰胺对小菜蛾2、3龄幼虫的亚致死效应,为氯虫苯甲酰胺的合理使用提供依据。采用药膜法确定氯虫苯甲酰胺对小菜蛾2龄和3龄幼虫的亚致死剂量(LC25、LC40),以试虫死亡率、取食量、化蛹时间、蛹重、羽化率为指标研究其对小菜蛾的亚致死效应。与对照相比,亚致死剂量氯虫苯甲酰胺处理的小菜蛾除死亡率显著增高外,幼虫生长明显受到抑制,幼虫至化蛹平均历期显著延长,取食量、蛹重和化蛹率明显降低。结果表明亚致死剂量氯虫苯甲酰胺对小菜蛾种群增长有一定抑制作用,对小菜蛾综合防治策略的制定有积极意义。     

Effect of antifeedants on the diamondback moth (Plutella xylostella) and its parasitoid Cotesia plutellae

Two neem preparations and the bitter‐tasting synthetic chemical denatonium benzoate were tested in the laboratory as antifeedants against the diamondback moth, Plutella xylostella L. The effects of the three materials on Cotesia plutellae (Kurdjumov), a hymenopteran parasitoid of ­P xylostella, were also recorded. All three materials significantly reduced the food consumption of ­P xylostella larvae. Parasitoid cocoons were formed on approximately half of those larvae which had been exposed to female C plutellae, regardless of antifeedant treatment, but emergence of adult parasitoids from the cocoons was significantly reduced by antifeedant treatment. In terms of food consumption and mortality of unparasitised P xylostella larvae, and emergence of adult C plutellae, the effect of each antifeedant preparation was directly related to the concentration of material used, but the effects of the neem preparations were greater than those of denatonium benzoate. However, no adult P xylostella emerged on any antifeedant treatment, therefore some of the parasitoids survived antifeedant treatments which were fatal to the unparasitised hosts. © 2000 Society of Chemical Industry     

Efficacy of crude seed extracts of Annona squamosa against diamondback moth,Plutella xylostella L. in the greenhouse

Experiments were conducted to assess the efficacy of crude seed extracts of Annona squamosa collected from Ambon (Maluku, Indonesia) against larvae of the diamondback moth, Plutella xylostella L., feeding on cabbage. Three greenhouse trials were carried out using aqueous seed extracts and an aqueous emulsion of ethanolic seed extracts. At a concentration of 0.5% (w/v), an aqueous emulsion of an ethanolic seed extract was 2.5 fold more effective than 1% rotenone, a commercial botanical insecticide. Crude aqueous seed extracts showed efficacy comparable to pyrethrum, the most widely used botanical insecticide. Seed extract of A. squamosa is a promising candidate for development as a simple botanical insecticide for local use in rural Indonesia.     

Differential toxicity of Bacillus thuringiensis strains and their crystal toxins against high-altitude Himalayan populations of diamondback moth, Plutella xylostella L

BACKGROUND: Diamondback moth, Plutella xylostella (L.), is a major insect pest of crucifers in the biodiversity‐rich north‐western Indian Himalayan hills. The present investigation was aimed at determining the susceptibility pattern of P. xylostella populations collected from different locations of this region to autochthonous and standard Bacillus thuringiensis strains. RESULTS: Among the reference as well as indigenous B. thuringiensis strains tested, sub spp. kurstaki HD‐1, kurstaki HD‐73, galleriae HD‐8, local galleriae/colmeri strain BtOa1 and some of their Cry1 class toxins were found to be highly toxic. Surprisingly, the sub sp. tolworthi HD‐125, local tolworthi strain BtHa1 and Cry9 class toxins were found to be non‐toxic. Midgut homogenate from fourth‐instar larvae was found to activate 130 kDa protoxin from the local tolworthi strain BtHa1 into 68 kDa toxin, but failed to exert any larval mortality, probably owing to lack of receptor binding. CONCLUSION: The present study provides valuable baseline susceptibility data for the deployment of B. thuringiensis‐based control methods, as well as for future monitoring of development of resistance in P. xylostella to B. thuringiensis in this ecologically sensitive region. Copyright © 2008 Society of Chemical Industry     

春甘蓝田小菜蛾及主要捕食性天敌时空生态位

在田间系统调查的基础上,研究了春甘蓝田小菜蛾及主要捕食性天敌的时空生态位。结果表明,小菜蛾的时间生态位宽度较小而空间生态位宽度相对较大,说明小菜蛾种群的发生有高峰期明显和全株为害的特点。小菜蛾的时间动态、空间生态位宽度与种群密度无显著相关性,说明小菜蛾对甘蓝的为害情况比较复杂。田间调查共记录捕食性天敌13种,主要优势种依次为草间钻头蛛、七星瓢虫、血色高亮腹蛛、八斑鞘腹蛛、四点高亮腹蛛和三突花蛛。主要捕食性天敌中,七星瓢虫和三突花蛛与小菜蛾的时空二维生态位重叠度最大,其次为四点高亮腹蛛和血色高亮腹蛛,八斑鞘腹蛛和草间钻头蛛最小。这表明七星瓢虫和三突花蛛对小菜蛾有较好的跟随和潜在控制作用。     

半闭弯尾姬蜂寄生对寄主小菜蛾幼虫体液免疫的影响

研究半闭弯尾姬蜂Diadegma semiclausum对寄主小菜蛾Plutella xylostella幼虫体液免疫系统的影响。结果表明,半闭弯尾姬蜂寄生能够显著抑制小菜蛾血淋巴内酚氧化酶前体激活,导致体外处理中血淋巴黑化的时间被延长;同时,抑菌物质的产生也受抑制并最终造成离体培养中血细胞的感菌率提高。     

小菜蛾GluCl受体α亚基cDNA基因克隆和序列分析

利用RT-PCR和RACE技术对小菜蛾[Plutella xylostella(L.)]4龄幼虫谷氨酸门控的氯离子通道(GluCl)受体cDNA全长进行了克隆和序列分析。通过设计简并性上、下游引物扩增出小菜蛾GluCl受体α亚基基因192bp的cDNA片段,根据得到的片段序列设计3′和5′特异性引物采用RACE技术进行3′和5′末端的克隆,获得了小菜蛾GluCl受体的cDNA的完整序列,GenBank登录号为GQ221939。该基因全长2144bp,其开放阅读框(ORF)1344bp,编码447个氨基酸。相似性分析表明:它与果蝇和赤拟谷盗的相似性均为73%,与埃及伊蚊的相似性为75%,与东亚飞蝗的相似性为79%;氨基酸分析后显示它具有GluClα亚基的典型特征,表明克隆的cDNA序列是小菜蛾GluClα亚基基因的序列。     

Genetic basis of resistance and studies on cross-resistance in a population of diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae)

The genetic basis of abamectin resistance was studied in a strain of the diamondback moth, Plutella xylostella (L), following laboratory selection of a field population collected at Xuanhua, Hebei Province, China. Data from the testing of F1 progeny from reciprocal crosses between abamectin-resistant and abamectin-susceptible strains indicated that resistance might be autosomal and incompletely recessive with a degree of dominance of -0.13. Chi-squared analyses from the response of a backcross of crossed F1 progeny and the resistant strain and F2 progeny were highly significant, suggesting that the resistance was probably controlled by more than one gene. The results of cross-resistance studies showed that there was little cross-resistance between abamectin and four pyrethroid insecticides (deltamethrin, beta-cypermethrin, fenvalerate and bifenthrin) and no cross-resistance between abamectin and the acylureas chlorfluazuron or flufenoxuron.     

小菜蛾在春茬甘蓝上的分布及其防治研究

系统调查了小菜蛾在春茬甘蓝不同生育期的分布规律。结果表明,在甘蓝莲座期,小菜蛾的卵主要产在甘蓝近地面的茎部、叶柄和叶背等比较隐蔽的部位,包心初期,大量的小菜蛾幼虫集中在甘蓝的心叶进行为害,进入包心后期,小菜蛾主要在甘蓝的内叶为害,进入收获初期,小菜蛾转移到外叶为害。〖JP2〗据此,甘蓝的包心初期和后期是对小菜蛾进行防治的两个重点时期,结合科学合理施药,在甘蓝的整个生长季节施药2~3次即可有效控制小菜蛾的为害。     

沙冬青茎甲醇提取物对小菜蛾幼虫生长发育抑制作用研究

室内测定了沙冬青茎甲醇提取物对小菜蛾幼虫生长发育的抑制作用。研究结果表明,其提取物对小菜蛾幼虫相对生长率(RGR)、近似消化率(AD)、食物利用率(ECI)和食物转化率(ECD)虽在一段时间内连续发生变化,但最高浓度为0.2g/mL时,这4项指标始终低于其他处理。沙冬青茎甲醇提取物对小菜蛾幼虫历期的影响不明显,但使蛹期延长,幼虫死亡率升高,且提取物浓度越高,这些作用效果越明显。     

Microdroplet application for determination of comparative topical and residual efficacy of formulated permethrin to two populations of diamond back moth (plutella xylostella L.)

An on-demand, uniform droplet generator was used to apply 120 μm diameter drops of formulated permethrin either directly onto 3rd-instar Plutella xylostella, of two Ohio populations, or onto the abaxial surface of leaf discs (1-1000 drops cm^?2) to which those larvae were subsequently exposed. Incorporating a fluorescent tracer (Saturn Yellow GT-17N) in the spray mixture confirmed that ?direct hit”? larvae had received a topical dose from a single droplet. There was little difference in the LC₅₀/LD₅₀ for either population of P. xylostella when 24 and 48 h mortality assessments from direct hits were compared, but the LD₅₀ of Celeryville larvae was 6-8 times greater than that of Fremont larvae. Residual deposits of 120 μm drops containing approximately the LC₅₀, based on the topical assays, revealed that a droplet density providing a dose per cm² leaf surface of more than 1000 times the LD₅₀ was required to cause median mortality. The efficiency of utilisation, based on the topical LD₉₅ values, was 0.0006% and 0.072% for Fremont and Celeryville larvae, respectively.     

Testing and improving the effectiveness of trap crops for management of the diamondback moth Plutella xylostella (L.): a laboratory‐based study

BACKGROUND: The aim of this study was to assess white mustard (Sinapis alba L.) as a trap crop for diamondback moth [Plutella xylostella (L.)] on cauliflower [Brassica oleracea (L.) var. Lateman]. Moth behaviour on these plants and the importance of plant age and size in maintaining pest preference for trap crop plants were also investigated. RESULTS: Three times as many eggs were laid on cauliflower plants that were unprotected than on plants protected by a trap crop of white mustard. Moths remained longer on the mustard plants as a result of a doubling in the mean duration of information‐providing behaviours. Plant age had little effect on P. xylostella host preference. When plant age was constant, percentage oviposition on mustard was higher when these were larger (93%) than copresented cauliflower plants, compared with when they were smaller (68%). CONCLUSION: Trap cropping with white mustard may reduce the incidence of P. xylostella in cauliflower crops. The pest management benefits of trap crops may be maximised by using trap crop plants that are larger than the main crop plants, although relatively smaller trap crop plants may still be preferred as hosts for P. xylostella per se. Copyright © 2009 Society of Chemical Industry     

Susceptibility pattern and development of resistance in the diamondback moth,Plutella xylostella L,to Bacillus thuringiensis Berl var kurstaki in India

Base‐line susceptibility for six‐day‐old larvae of the diamondback moth, Plutella xylostella, against Bacillus thuringiensis var kurstaki (Biobit^®) was studied by a cabbage leaf disc dip bioassay technique. Diamondback moth from 13 locations in seven different states spread over a distance of about 3000 km longitudinally was used for these studies. Forty‐eight‐hour LC₅₀ values varied from 1.0 to 10.97 mg AI litre⁻¹. Further investigations on the development of resistance under laboratory conditions showed an increase in LC₅₀ from 2.76 (for unselected F₁ generation) to 5.28 mg AI litre⁻¹ (for selected F₉ generation), using a selection concentration of 6.4 mg AI litre⁻¹. This suggested a possibility of the development of resistance under field conditions if there were to be extensive and indiscriminate use of B thuringiensis. These findings are discussed in relation to integrated pest management and the mechanisms of resistance in resistance management tactics. © 2000 Society of Chemical Industry