Effect of pyriproxyfen on developing stages and embryogenesis of California red scale (CRS), Aonidiella aurantii

During the past decade, the insect growth regulator pyriproxyfen has been the most used insecticide for controlling the California red scale (CRS), Aonidiella aurantii (Maskell), an important pest in citrus groves worldwide. The aim of the present research was to develop bioassays for determining the effect of pyriproxyfen on developing stages and embryogenesis of CRS that can serve as baselines for monitoring resistance. Pyriproxyfen was very effective against first- and second-instar nymphs of a susceptible strain of CRS; 0.1 and 0.2 mg AI L(-1), resulting in 80 and 100% mortality of first-instar nymphs, and in 62.5 and 91.7% mortality of second-instar nymphs respectively. According to probit analysis, the LC(50) and LC(90) values of pyriproxyfen for first-instar nymphs were 0.03 and 0.15 mg AI L(-1), and for second-instar nymphs they were 0.05 and 0.25 mg AI L(-1) respectively. Pyriproxyfen was quite effective on first-instar nymphs of a CRS field strain originating from a citrus grove where two successive applications of the compound had been applied. Mortality rates were 86 and 100% at concentrations of 0.2 and 0.4 mg AI L(-1) respectively. Pyriproxyfen suppressed embryogenesis when CRS females were treated with pyriproxyfen. Young CRS females treated with 1.0 and 5.0 mg AI L(-1) pyriproxyfen produced 6.6 N(1)/F and 2.4 N(1)/F as compared with 10.9 N(1)/F in untreated control.     

Effect of pyriproxyfen,a juvenile hormone mimic,on egg hatch,nymph development,adult emergence and reproduction of the Asian citrus psyllid,Diaphorina citri Kuwayama

BACKGROUND: The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama, is a vector of bacteria presumably responsible for huanglongbing (HLB) disease in citrus. In this laboratory study, an investigation was made of the activity of pyriproxyfen, a juvenile hormone mimic, on ACP eggs, nymphs and adults to evaluate its potential as a biorational insecticide for inclusion in an integrated pest management (IPM) program for ACP. RESULTS: Irrespective of egg age, timing or method of treatment, a significantly lower percentage of eggs (5–29%) hatched after exposure to 64 and 128 µg mL^?1 of pyriproxyfen. Only 0–36% of early instars (first, second and third) and 25–74% of late instars (fourth and fifth) survived to adults following exposure to 16, 32 and 64 µg mL^?1 of pyriproxyfen. However, 15–20% of adults that emerged following treatment as late instars exhibited morphological abnormalities. Furthermore, pyriproxyfen adversely affected reproduction (fecundity and fertility) of adults that emerged from treated fifth instars or that were treated topically with 0.04 µg as adults. CONCLUSIONS: Application of pyriproxyfen at 64 µg mL^?1 resulted in greater inhibition of egg hatch and suppression of adult emergence compared with lower rates. Pyriproxyfen also markedly reduced female fecundity and egg viability for adults that were exposed either as fifth instars or as newly emerged adults. The ovicidal, larvicidal and reproductive effects against ACP suggest that pyriproxyfen is suitable for integration into an IPM program for ACP. Copyright © 2009 Society of Chemical Industry     

甲胺磷对不同抗性水平褐飞虱品系种群增长的影响

用点滴法测定了甲胺磷对3个褐飞虱品系的毒力,并用5个剂量(LD5、LD10、LD25、LD50和LD75)处理4龄若虫,存活若虫饲养至羽化后单对继续饲养,观察并记录3个品系的繁殖力。结果表明,甲胺磷具有刺激褐飞虱种群增长的作用,但对不同抗性水平品系的刺激作用有很大差异,对田间种群和抗性品系的刺激作用明显小于敏感品系,其中对抗性品系种群增长的刺激作用尤小。     

Toxicity and biochemical study of two insect growth regulators, buprofezin and pyriproxyfen, on cotton leafworm Spodoptera littoralis

Lethal and sublethal effects of two insect growth regulators (IGRs) buprofezin and pyriproxyfen were evaluated on larvae of cotton leafworm Spodoptera littoralis. Activity of chitinase and polyphenol oxidase (PPO) in surviving larvae after treatment was carried out in order to investigate the biochemical influences of these compounds. The compounds were low toxic against the larvae at 0.05, 0.1, 0.25, 0.5, and 1.0-fold of the field application rate. However, the overall mortalities within 6 days of feeding at 2.0-fold were 46.67% and 100% for buprofezin and pyriproxyfen, respectively. Larval weight gain was considerably decreased as concentration increased. Pyriproxyfen showed high antifeedant activity in a concentration-dependent manner, and larvae stopped to eat from the third day with high dose. Conversely, buprofezin did not significantly show antifeedant except with high concentration (3000 mg (a.i.)/kg diet) that gave 80.68%. The high doses of both compounds showed adverse effects on pupae, and emergence of adults. Buprofezin at the recommended dose (1500 mg (a.i.)/kg diet) caused 93.33% pupation and 53.33% emergence of adults. Otherwise, pyriproxyfen caused 21.33% pupation and zere emergence of adults at the recommended dose (75 mg (a.i.)/kg diet) compared to 100% pupation, and 96.30% emergence of adults in the control. Both compounds varied in their influences on chitinase and PPO activity, and these enzymes could have relation with toxicity of buprofezin and pyriproxyfen against S. littoralis larvae.     

Pyriproxyfen,a novel insect growth regulator for controlling whiteflies: Mechanisms and resistance management

Pyriproxyfen, a novel juvenile hormone mimic, is a potent suppressor of embryogenesis and adult formation of the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Dipping of cotton or tomato seedlings infested with 0 to 1-day-old eggs in 0.1 mg litre^?1 resulted in over 90% suppression of egg hatch of both B. tabaci and T. vaporariorum. Older eggs were affected to a lesser extent. Exposure of whitefly females to cotton or tomato seedlings treated with pyriproxyfen resulted in oviposition of non-viable eggs. The LC90 values for egg viability of B. tabaci and T. vaporariorum exposed to treated plants were 0.05 and 0.2 mg litre^?1, respectively. Treatment of whitefly larvae with 0.04–5 mg litre^?1 resulted in normal development until the pupal stage; however, adult emergence was totally suppressed. Second instars of B. tabaci exposed to 5 mg litre^?1 pyriproxyfen, excreted honeydew at a level similar to the control level until the fourth instar (pupation), after which a strong reduction was observed. Inhibition of egg-hatch on the lower surface of cotton leaves was observed when their upper surface was treated with 1–25 mg litre^?1, indicating a pronounced translaminar effect. These findings indicate that pyriproxyfen is an efficient control agent of both B. tabaci and T. vaporariorum. The compound has been used successfully for controlling whiteflies in Israeli cotton fields since 1991. Adults of B. tabaci collected from a rose greenhouse and from adjacent cotton fields were monitored during 1991–1993 for their susceptibility to pyriproxyfen. A high level of resistance was recorded in whiteflies collected from a greenhouse after three successive applications of pyriproxyfen. Based on LC50 values, the resistance ratio for egg-hatch suppression was 554-fold and, for adult emergence failure, 10-fold. However, a single treatment of pyriproxyfen in cotton fields during the summer season (according to an insecticide resistance management (IRM) strategy) did not alter appreciably the susceptibility of B. tabaci to this compound. In order to prevent development of resistance, an attempt should be made to restrict its use to one treatment per crop season applied during the peak activity of the pest. Pyriproxyfen can be alternated with other novel compounds such as buprofezin and diafenthiuron for controlling whiteflies in cotton, vegetables and ornamentals as part of integrated pest management (IPM) and IRM strategies. In pyriproxyfen- or buprofezin-resistant strains of B. tabaci or T. vaporariorum, no appreciable cross-resistance was observed among pyriproxyfen, buprofezin and diafenthiuron.     

Effects of a juvenile hormone analog,pyriproxyfen, on Thrips tabaci (Thysanoptera: Thripidae)

Effects of a juvenile hormone analog, pyriproxyfen, on various developmental stadia of the onion thrips, Thrips tabaci Lindeman, were determined on cabbage leaves in the laboratory. Pyriproxyfen was applied at 0.064 or 0.128 g AI liter(-1) on leaves (residual contact-ingestion), thrips (direct contact) and leaf-thrips (residue contact-ingestion-direct contact). Pyriproxyfen did not have any significant lethal effects on thrips pupae in any treatment. Lethal effects on thrips larvae varied depending on application method and dosage. In the leaf and the leaf-thrips treatments, few larvae and pre-pupae molted to the next stage, and none developed to adults. In contrast, in the thrips-only treatment, pyriproxyfen did not show any significant lethal effects. The developmental times of larvae and pre-pupae were prolonged when larvae were treated with pyriproxyfen, and those of pre-pupae and pupae were shortened when pre-pupae and pupae were treated. The longevity and survival rates of thrips adults were generally shorter when they contacted and ingested pyriproxyfen-treated leaves than those in water control. Significantly fewer progeny (0.22-1.15 larvae per female) were produced by females that had fed on and been in contact with the pyriproxyfen-treated leaves than by those in the water control (11.94 larvae per female). However, the number of progeny produced by the thrips females increased significantly (3.32-7.28 larvae per female) when the females were transferred to untreated leaves after feeding on treated leaves for 5 days; the daily larval hatching pattern was similar to those in water control, indicating that female adults were able to produce viable eggs when untreated food was offered.     

Persistence and residual activity of an organophosphate, pirimiphos-methyl, and three IGRs, hexaflumuron, teflubenzuron and pyriproxyfen, against the cowpea weevil, Callosobruchus maculatus (Coleoptera: Bruchidae)

Three insect growth regulators (IGR), the chitin synthesis inhibitors (CSI) teflubenzuron and hexaflumuron and the juvenile hormone mimic (JHM) pyriproxyfen, as well as the organophosphate (OP) pirimiphos-methyl, were evaluated for their activity against the cowpea weevil, Callosobruchus maculatus (F), in cowpea seeds stored for up to 8 months post-treatment. The initial activity data showed that, based on LC50 level, teflubenzuron had strong ovicidal activity (LC50 = 0.056 mg kg(-1)) followed by pirimiphos-methyl (1.82 mg kg(-1)) and pyriproxyfen (91.9 mg kg(-1)). The residual activity data showed that none of the IGRs tested had strong activity when applied at 200 mg kg(-1) in reducing the oviposition rates of C maculatus at various storage intervals up to 8 months post-treatment. However, teflubenzuron reduced adult emergence (F1 progeny), achieving control ranging from 96.2% at 1 month to 94.3% at 8 months. Hexaflumuron showed a similar trend in its residual activity, ranging between 93.8% control at 1 month to 88.2% control at 8 months post-treatment. However, pyriproxyfen was more active than the CSIs tested and caused complete suppression (100% control) of adult emergence at all storage intervals. Unlike the IGRs tested, pirimiphos-methyl applied at 25 mg kg(-1) was more effective in reducing oviposition rates of C maculatus up to 8 months post-treatment. A strong reduction of adult emergence was also observed at various bimonthly intervals (98.6% control at 1 month to 91.6% control at 8 months post-treatment). The persistence of hexaflumuron and pirimiphos-methyl in cowpea seeds was also studied over a period of 8 months. The loss of hexaflumuron residue in treated cowpeas (200 mg kg(-1)) was very slow during the first month post-treatment (4.43%). At the end of 8 months, the residue level had declined significantly to 46.4% of the initial applied rate. The loss of pirimiphos-methyl residue in treated cowpeas (25 mg kg(-1)) was relatively high during the first month post-treatment (36.7%) and increased to 81.6% after 8 months.     

Disruption of mating in codling moth (Lepidoptera: Tortricidae) by chlorantranilipole, an anthranilic diamide insecticide

The influence of the anthranilic diamide insecticide chlorantranilipole (DPX-E2Y45; Rynaxypyr against the adult stage of codling moth, Cydia pomonella L., was examined. Insecticide residues in plastic cups sprayed with 56 mg AI L(-1) (equivalent to the recommended field rate) had a minimal effect on adult survival or fecundity, but significantly fewer female moths were mated in treated than in untreated cups. Similar results were found in field studies with adults placed in screened cages on treated apple foliage for up to 3 weeks. Mating was disrupted when either sex was topically dosed with technical material (0.01-0.1 microg). Males were more sensitive to the disruptive effects of chlorantranilipole than females. A 2 h exposure significantly reduced male activity (walking and wing fanning), but not female calling. A 25 h exposure significantly reduced the activity of both sexes. The proportion of males landing near a sex pheromone source in a flight tunnel was significantly reduced following exposures of 2-4 h and completely eliminated following a 17 h exposure. Male moths partially recovered from either topical or residual exposure to chlorantranilipole, but the extent of their recovery was dose and time dependent. Male response to sex pheromone recovered within 2 h following a 4 h exposure, but following a 17 h exposure only a partial recovery occurred after 48 h. Mating by moth pairs exposed to chlorantranilipole residues for 24 h did not significantly increase during recovery periods of 24-96 h, except in cups treated with 10% of the standard concentration. The proportion of field-collected female codling moths caught in pear ester-baited traps that were mated was significantly lower in apple orchards treated season-long with chlorantranilipole compared with females caught in either untreated orchards or those treated with sex pheromones to cause mating disruption.     

Thermal behaviour and biological activity against Aedes aegypti (Diptera: Culicidae) of permethrin and pyriproxyfen in a smoke‐generating formulation

BACKGROUND: The most common ways to control dengue vector Aedes aegypti (L.) are larval source reduction in domestic habitats and ground application of small quantities of aerosol insecticide (ultralow volume). Nevertheless, these actions have been shown repeatedly to be ineffective in controlling Ae. aegypti populations. RESULTS: The efficacy of a new smoke‐generating formulation containing pyriproxyfen and permethrin was evaluated in the laboratory. Smoke‐generating tablets containing each insecticide individually or combined were prepared, and the recovery of the insecticides from the smoke was determined. Recovery values of over 90% were obtained for pyriproxyfen, and around 50% for permethrin. The biological efficacy of pyriproxyfen released in the smoke was evaluated in the laboratory, on late third‐instar or early fourth‐instar Ae. aegypti larvae, using different concentrations of pyriproxyfen and exposure times. Adult emergence inhibition (EI) values of 100% were obtained at 30 min, and a dose‐dependent effect was observed at 5 min. The effect of pyriproxyfen released in the smoke was due to direct contact with the larvicide in the water rather than by inhalation of the fumes. The efficacy of permethrin released in the fumes was also evaluated as knockdown effect (KT₅₀) on adults for a tablet containing permethrin alone or permethrin plus pyriproxyfen. There was no significant difference in KT₅₀ values obtained for permethrin (KT₅₀ = 19.9 min) and permethrin plus pyriproxyfen (KT₅₀ = 19.4 min). CONCLUSION: The excellent laboratory performance of this new formulation on immature stages and adults indicates that a smoke‐generating tablet containing pyriproxyfen and permethrin could be a new tool for controlling mosquitoes. Copyright © 2009 Society of Chemical Industry     

Gamma radiation sensitivity of the eggs, larvae and pupae of Indian meal moth Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae)

BACKGROUND: This study focused on determining the minimal effective gamma radiation dose that prevents commodity damage caused by the Indian meal moth Plodia interpunctella (Hübner). The study was also designed to assess the effect of releasing either partially sterilized males alone or both partially sterilized males and females on the reproductive potential of P. interpunctella populations. RESULTS: The dose of radiation required to prevent larval emergence from irradiated eggs was 350 Gy, and the same dose was also required to prevent adult emergence from mature larvae. A dose of 300 Gy was not able to prevent adult emergence from irradiated pupae. The dose at which 100% sterility was achieved in treated females mated to treated males was 300 Gy for the parental generation of irradiated pupae. Fertility of the parental males from irradiated pupae was 48.17% at 300 Gy in treated males crossed with untreated females, but male progeny of irradiated male parents had a residual fertility of 11.06% at the same dose. CONCLUSION: F(1) males from irradiated pupae were more sterile than parental males. To prevent larval emergence from irradiated eggs, a dose of 350 Gy is required. The same dose is required to prevent the larvae from reaching the adult stage.     

小菜蛾对丁烯氟虫腈的抗性选育及生物适合度

用丁烯氟虫腈对小菜蛾敏感品系在室内经7代次药剂汰选,获得了抗性品系(R),与敏感品系(S)比较其抗性指数为77.58倍。抗性汰选前后,采用点滴法测定的结果表明,小菜蛾对阿维菌素、毒死蜱、灭多威、杀虫单和高效氯氰菊酯的敏感性并无明显变化,其抗性指数为0.80~1.36,均不存在交互抗性。通过构建种群生命表,观察比较了小菜蛾抗丁烯氟虫腈品系和敏感品系的一系列生长发育和繁殖特征。结果表明,抗丁烯氟虫腈品系较敏感品系幼虫期和蛹历期延长,低龄幼虫龄期转换时的虫口死亡率增加,蛹重减轻,化蛹率和羽化率降低;在繁殖上表现为产卵量增加,而孵化率和雌雄比降低,雌成虫的数量、寿命减少。抗丁烯氟虫腈种群相对于敏感种群的相对适合度为0.84,抗性种群在繁殖能力上存在明显的生存劣势。     

高效氯氰菊酯和吡丙醚在芥蓝中的残留消解及膳食暴露风险评估

为明确高效氯氰菊酯和吡丙醚在芥蓝上施用后的残留行为和膳食暴露风险, 研究基于规范田间残留试验、目标农药在芥蓝上残留分析方法, 得到芥蓝中2种农药的残留水平, 结合我国膳食结构不同性别/年龄组食物消费量及体重数据评估了高效氯氰菊酯和吡丙醚对各类消费人群的长期和短期膳食摄入风险。结果表明:高效氯氰菊酯和吡丙醚分别在0.01~1.0 mg/L和0.005~1.0 mg/L范围内线性关系良好, 决定系数(R2)≥0.996 7。在3个添加水平下, 芥蓝中2种农药的平均回收率为70.6%~113.4%, 相对标准偏差(RSD)为0.5%~8.5%, 定量限均为0.01 mg/kg。10%高氯·吡丙醚微乳剂以推荐高剂量施药, 高效氯氰菊酯和吡丙醚在芥蓝中的消解符合一级动力学, 半衰期分别为3.9~10.1 d和4.8~6.3 d。最终残留试验结果表明, 最后一次施药3、5、7、10 d后, 芥蓝中高效氯氰菊酯的最终残留量≤0.904 mg/kg, 吡丙醚的最终残留量≤0.202 mg/kg。膳食风险评估表明, 我国不同人群的长期慢性暴露风险最大值为27.26%;短期急性暴露风险最大值为67.17%, 表明对不同年龄段、不同性别人群健康不会产生不可接受的风险。     

硒对亚洲玉米螟生长发育和生殖行为的影响

为探讨硒(selenium)对亚洲玉米螟Ostrinia furnacalis(Guenée)的营养作用及其生长发育、生殖行为的影响,选用添加不同浓度硒的人工饲料饲喂3龄幼虫,观察了蛹、成虫的生长发育及成虫生殖行为情况。结果表明,不同浓度的硒对蛹和成虫的发育影响差异较大,其中硒浓度为0.75 mg/kg时生长发育最好,化蛹率、雄蛹体重和雄蛾寿命显著高于对照,分别提高了7.4%、12.7%和19.1%;硒浓度为5.00 mg/kg时生长发育最差,化蛹率和羽化率最低,雌、雄蛹重最小,成虫寿命最短。当硒浓度为0.75 mg/kg时,雌蛾求偶百分率和求偶持续时间均有所降低,且求偶高峰期推迟1~2 h。以正常雌蛾为诱源时,硒雄蛾的定向能力显著低于对照,而以硒雌蛾为诱源时,硒雄蛾的定向能力显著高于对照雄蛾;硒雌蛾的产卵量和卵孵化率显著提高,硒雌蛾×硒雄蛾组合提高最多,分别为28.9粒和9.3%。研究表明,适量硒可以促进亚洲玉米螟生长发育,并能显著影响成虫的生殖行为。     

Reversal of resistance to pyriproxyfen in the Q biotype of Bemisia tabaci (Hemiptera: Aleyrodidae)

Pyriproxyfen, a juvenile hormone (JH) mimic, is a biorational insecticide that disrupts insect development. It is one of the principal insecticides being used to control Bemisia tabaci (Gennadius) on cotton, and has many environmentally positive attributes that make it compatible with integrated pest management (IPM) programs. In Israel, a high level of resistance to pyriproxyfen has been observed in several isolated regions. Here, tests were conducted to establish whether temporal refuges from exposure to pyriproxyfen could be useful for restoring the effectiveness of the compound. Resistance was found to decrease by a factor of 8 when exposure to pyriproxyfen was ceased for 13 generations. Reversal of resistance was accompanied with increased biotic fitness of the revertant colony. By incorporating experimental estimates of nymph survival, sex ratio, fecundity, egg hatching rate and developmental time, the seasonal cost per generation for resistant insects was estimated to be 25%. A genetic simulation model, optimized by empirical data from bioassays, predicted fitness cost per generation of 19% for resistant homozygous (RR) females and hemizygous (R) males, and produced rates of reversal similar to the experimental results. The model also predicted that, even after 5 years ( approximately 55 generations) without pyriproxyfen treatments, the frequency of the resistance allele (R) will still remain high (0.02). It is therefore concluded, on the basis of experimental and modeling results, that the effectiveness of temporal refuges for reversing development of resistance to pyriproxyfen in B. tabaci may be limited.     

抗三氟氯氰菊酯棉铃虫种群相对适合度研究

应用经三氟氯氰菊酯汰选的棉铃虫种群,在室内条件下分别研究了抗性、敏感及杂交Ｆ_１代（ＲＳ和ＳＲ）基因型相对适合度。结果表明,抗性基因型在产卵量、卵孵化率、幼虫及蛹历期和成虫存活期等方面与敏感基因型相比较存在明显的不利性;与敏感基因型相比,抗性基因型只有０.４５的适合度,ＲＳ和ＳＲ基因型的相对适合度分别为１.１４和１.０８。     

亚致死浓度烯啶虫胺对水稻抗性物质及褐飞虱生殖参数的影响

为明确烯啶虫胺对褐飞虱Nilaparvata lugens的防控效果,采用稻茎浸渍法测定亚致死浓度烯啶虫胺对水稻生理生化指标以及褐飞虱雌成虫繁殖力的影响。结果表明,亚致死浓度烯啶虫胺处理后,水稻中草酸含量在第2天时无明显变化,在第4天时升高了20.5%;类黄酮含量分别升高了9.6%和40.6%;游离氨基酸含量分别下降了20.1%和42.4%;蔗糖含量在第2天时与对照间无显著差异,在第4天时升高了38.5%。亚致死浓度烯啶虫胺对褐飞虱生殖存在显著影响,雌成虫羽化2 d和4 d时,卵巢中可溶性蛋白含量分别下降了31.2%和40.9%;脂肪体中可溶性蛋白含量分别下降了19.0%和38.8%。亚致死浓度烯啶虫胺处理抑制了雌成虫卵巢发育,褐飞虱卵黄原蛋白（Nilaparvata lugens vitellogenin,NlVg）基因表达量在第 2 天时与对照间无显著差异,在第 4 天下降了57.5%;同时显著影响了褐飞虱生殖力,雌成虫产卵量减少了58.1%,产卵历期缩短了36.7%,寿命缩短了28.0%,但对雌成虫产卵前期无显著影响。表明亚致死浓度烯啶虫胺处理后可能通过诱导水稻次生代谢产物含量上升来提高水稻对褐飞虱的抗性,而且对褐飞虱繁殖力也有显著影响。     

伽马辐照对智利小植绥螨生殖及性别决定的影响

辐照可导致染色体变异,是研究生殖机理的常用辅助方法之一。本研究对不同生理状况下智利小植绥螨雌螨、雄螨、不同发育阶段卵进行不同剂量的伽马辐照,探索其后代发育与繁殖情况,以期解释智利小植绥螨性别决定机制及生殖机理。研究结果表明,在160~640 Gy辐照剂量下,辐照的未交配的雄成螨与正常的未交配的雌成螨交配,F1代中只有雄成螨且仅1/3可育。在45~90 Gy辐照剂量下,辐照的未交配的雌成螨与正常的未交配的雄成螨交配,其子代雌性比随着辐照剂量的增加而减小,且至90 Gy处理下无子代完成胚胎发育。辐照交配后产卵前的雌成螨,其子代雌性比间没有显著差异（77.5%~85.0%）。辐照卵龄0~12 h的卵,没有卵发育至成螨;辐照卵龄12~24 h的卵,其中发育至成螨的全为雌螨;辐照卵龄24~48 h的卵,其中发育至成螨的雌性比随着辐照剂量的增加具有增加的趋势。试验结果推测出父系染色体组参与形成配子且对性别起决定作用;父系染色体组异质化的时间可能集中于卵壳形成后至卵期12 h之间。本试验为智利小植绥螨父系染色体组参与性别决定的机制做出了新的诠释,对深入研究性别决定的机理具有重要的意义。     

Effect of exposure period on degree of dominance of phosphine resistance in adults of Rhyzopertha dominica (Coleoptera: Bostrychidae) and Sitophilus oryzae (Coleoptera: Curculionidae)

Degree of dominance of phosphine resistance was investigated in adults of Rhyzopertha dominica F and Sitophilus oryzae L. Efficacy of the grain fumigant phosphine depends on both concentration and exposure period, which raises the possibility that dominance levels vary with exposure period. New and published data were used to test this possibility in adults of R dominica and S oryzae fumigated for periods of up to 144 h. The concentrations required for control of homozygous resistant and susceptible strains and their F1 hybrids decreased with increasing exposure period. For both species the response lines for the homozygous resistant and susceptible strains and their F1 hybrids were parallel. Therefore, neither dominance level nor resistance factor was affected by exposure period. Resistance was incompletely recessive and the level of dominance, calculated at 50% mortality level, was -0.59 for R dominica and -0.65 for S oryzae. The resistant R dominica strain was 30.9 times more resistant than the susceptible strain, compared with 8.9 times for the resistant S oryzae strain. The results suggest that developing discriminating doses for detecting heterozygote adults of either species will be difficult.     

The response of pyriproxyfen-resistant and susceptible Bemisia tabaci Genn (Homoptera: Aleyrodidae) to pyriproxyfen and fenoxycarb alone and in combination with piperonyl butoxide

Pyriproxyfen was effective against susceptible Bemisia tabaci eggs at a LC₅₀ of 0.003 mg litre⁻¹ and against nymphs at 0.02 mg litre⁻¹. In comparison, eggs of a laboratory selected, pyriproxyfen-resistant B tabaci strain, originating in an Israeli greenhouse, exhibited 6500-fold resistance and nymphs exhibited 1100-fold resistance. Eggs and nymphs of a strain from an Israeli sunflower field exhibited 450 and 210-fold resistance in comparison to the susceptible standard. Fenoxycarb was generally less effective than pyriproxyfen against B tabaci eggs and nymphs but was unaffected by pyriproxyfen resistance. Piperonyl butoxide (PB) was antagonistic to pyriproxyfen, and this increased with increasing pyriproxyfen resistance. PB had no effect on the toxicity of fenoxycarb. Collectively, these data imply that the modes of action of pyriproxyfen and fenoxycarb are distinct, despite the structural similarities of these molecules. Possible reasons for the antagonism of PB against pyriproxyfen are discussed. © 1999 Society of Chemical Industry     

Toxicity of the entomopathogenic fungus, Metarhizium anisopliae (Deuteromycotina: Hyphomycetes) to adult females of the blowfly Lucilia sericata (Diptera: Calliphoridae)

The fungus Metarhizium anisopliae (Metchnikoff) (Deuteromycotina: Hyphomycetes) is a natural component of soil flora world-wide and is a causal agent of the green muscardine diseases of insects. The use of this pathogen as a potential biocontrol agent against adult females of the blowfly, Lucilia sericata (Meigen) (Diptera: Calliphoridae) was considered. The blowfly L sericata is an economically important agent of cutaneous myiasis of sheep, particularly in northern Europe. Exposure of flies to suspensions of fungal spores by immersion, topical application or tarsal contact with treated surfaces all resulted in high levels of fatal infection. Spores suspended in silicone oil resulted in higher levels of infection (50-70%) than those formulated in a 0.3 glitre(-1) solution of the detergent Tween 80 (10-20%). Spore concentration had a significant effect on levels of infection of flies, with the highest levels of mortality (64%) resulting from a suspension of 1 x 10(7) conidia ml(-1). The duration of tarsal contact had a significant effect on levels of infection. Mean infection levels of 30% were observed following exposure of free-flying adults to a single spore-treated, 5 x 15 cm2 cloth surface suspended from the roof of a cage (30 cm cube). The implications of the results for the potential use of M anisopliae in the biocontrol of blowflies are discussed.