Assessment of Potential Sublethal Effects of Various Insecticides on Key Biological Traits of The Tobacco Whitefly,Bemisia tabaci

The tobacco whitefly Bemisia tabaci is one of the most devastating pests worldwide. Current management of B. tabaci relies upon the frequent applications of insecticides. In addition to direct mortality by typical acute toxicity (lethal effect), insecticides may also impair various key biological traits of the exposed insects through physiological and behavioral sublethal effects. Identifying and characterizing such effects could be crucial for understanding the global effects of insecticides on the pest and therefore for optimizing its management in the crops. We assessed the effects of sublethal and low-lethal concentrations of four widely used insecticides on the fecundity, honeydew excretion and feeding behavior of B. tabaci adults. The probing activity of the whiteflies feeding on treated cotton seedlings was recorded by an Electrical Penetration Graph (EPG). The results showed that imidacloprid and bifenthrin caused a reduction in phloem feeding even at sublethal concentrations. In addition, the honeydew excretions and fecundity levels of adults feeding on leaf discs treated with these concentrations were significantly lower than the untreated ones. While, sublethal concentrations of chlorpyrifos and carbosulfan did not affect feeding behavior, honeydew excretion and fecundity of the whitefly. We demonstrated an antifeedant effect of the imidacloprid and bifenthrin on B. tabaci, whereas behavioral changes in adults feeding on leaves treated with chlorpyrifos and carbosulfan were more likely caused by the direct effects of the insecticides on the insects'' nervous system itself. Our results show that aside from the lethal effect, the sublethal concentration of imidacloprid and bifenthrin impairs the phloem feeding, i.e. the most important feeding trait in a plant protection perspective. Indeed, this antifeedant property would give these insecticides potential to control insect pests indirectly. Therefore, the behavioral effects of sublethal concentrations of imidacloprid and bifenthrin may play an important role in the control of whitefly pests by increasing the toxicity persistence in treated crops.     

Host plant influence on susceptibility of Bemisia tabaci (Hemiptera: Aleyrodidae) to insecticides

A resistance monitoring program conducted for the polyphagous whitefly, Bemisia tabaci (Gennadius), in Imperial Valley, CA, USA generated a large set of LC50s for adults collected from broccoli, cantaloupe and cotton crops over a four-year period. A vial bioassay and, subsequently, a yellow-sticky card bioassay produced similar temporal profiles of relative susceptibilities to the pyrethroid insecticide bifenthrin. Both bioassays revealed that whiteflies collected from broccoli were significantly less susceptible to bifenthrin compared to the other two crops. A similar finding was observed for endosulfan and the mixture of bifenthrin+endosulfan in the yellow-sticky card bioassay. The possibility that seasonal differences contributed to the observed differences in susceptibility provided the impetus to conduct a reciprocal transfer experiment using broccoli (or kale) and cantaloupe grown simultaneously in the field and greenhouse. Whitefly adults collected from an organic farm over three consecutive weeks had significantly higher LC50s on kale than those collected the same day on cantaloupe. After culturing in the greenhouse on broccoli or cantaloupe and testing again, LC50s remained significantly higher on broccoli after one week and again at the F1 generation. In contrast, whiteflies originating on kale in the field and transferred to cantaloupes in the greenhouse had significantly reduced LC50s at the F1 generation. When tested against the bifenthrin+endosulfan mixture, significantly higher LC50s were generated for whiteflies reared on broccoli in the greenhouse at one week and the F1 compared to the field source from cantaloupes. The consistently higher LC50s for whiteflies on broccoli and other Brassica spp. crops, compared to cantaloupes or cotton, point to statistically significant host-plant influences that are expressed in both field-collected and greenhouse-reared populations of whiteflies.     

Establishment of baseline susceptibility data to various insecticides for Homalodisca coagulata (Homoptera: Cicadellidae) by comparative bioassay techniques

Homalodisca coagulata Say, adults from three locations in California were subjected to insecticide bioassays to establish baseline toxicity. Initially, two bioassay techniques, petri dish and leaf dip, were compared to determine the most useful method to establish baseline susceptibility data under laboratory and greenhouse conditions. Comparative dose-response data were determined by both techniques to endosulfan, dimethoate, cyfluthrin, and acetamiprid. Toxic values were similar to some insecticides with both techniques but not for all insecticides, revealing susceptibility differences among the three populations of H. coagulata. In subsequent tests, the petri dish technique was selected to establish baseline susceptibility data to various contact insecticides. A systemic uptake bioassay was adapted to estimate dose-mortality responses to a systemic insecticide, imidacloprid. A 2-yr comparison of toxicological responses showed all three populations of H. coagulata to be highly susceptible to 10 insecticides, including chlorpyrifos, dimethoate, endosulfan, bifenthrin, cyfluthrin, esfenvalerate, fenpropathrin, acetamiprid, imidacloprid, and thiamethoxam. In general, two pyrethroids, bifenthrin and esfenvalerate, were the most toxic compounds, followed by two neonicotinoids, acetamiprid and imidacloprid. The LC50 values for all insecticides tested were lower than concentrations used as recommended field rates. Baseline data varied for the three geographically distinct H. coagulata populations with the petri dish technique. Adult H. coagulata collected from San Bernardino County were significantly more susceptible to select pyrethroids compared with adults from Riverside or Kern counties. Adults from San Bernardino County also were more sensitive to two neonicotinoids, acetamiprid and imidacloprid. The highest LC50 values were to endosulfan, which nonetheless proved highly toxic to H. coagulata from all three regions. In the majority of the tests, mortality increased over time resulting in increased susceptibility at 48 h compared with 24 h. These results indicate a wide selection of highly effective insecticides that could aid in managing H. coagulata populations in California.     

不同作物田烟粉虱发生的时空动态

2008～2009年连续2年系统调查了番茄、茄子、棉花、大豆、玉米等寄主植物上烟粉虱种群发生的时间与空间动态。结果表明：不同寄主植物上的烟粉虱成虫及其伪蛹数量有显著性差异,其密度大小依次为：茄子>棉花>番茄>大豆>玉米。其中,在玉米上除了发现极少量的成虫逗留外,没有发现烟粉虱的卵及若虫。在发生的时间序列上,烟粉虱成虫及伪蛹的数量呈现为先逐渐上升后又下降的变化过程,发生高峰期集中在8月5日到8月31日,9月初以后烟粉虱数量慢慢减少。在空间分布上,表现为烟粉虱成虫喜食寄主的上部叶片。统计分析显示,寄主对烟粉虱成虫和伪蛹的数量的影响极显著,而年份对其数量的影响没有显著差异。由此得出的烟粉虱发生和达到高峰的时间,可为烟粉虱预测预报和区域性综合治理提供重要理论依据。     

Methods of analysing data to compare effects on populations of carrot fly (Psila rosae) larvae on carrots of treatments with exponentially-increasing doses of granular insecticide formulations

Effects of insecticide treatments were assessed by comparing the percentages of undamaged carrot roots on insecticide-treated and untreated check plots. A dose-response relationship based on a log-log transformation was derived and illustrated with data for six insecticides from two field experiments. Formulae are provided for estimating doses corresponding to given levels of decrease in the numbers of carrot fly larvae. Guidance is given on sample sizes needed and constraints on the accuracy of the estimates are stated. Examples are given of the use of the dose-response relationship to compare insecticide treatments within and between experiments.     

Lethal and sublethal effects of insecticide residues on Orius insidiosus (Hemiptera: Anthocoridae) and Geocoris punctipes (Hemiptera: Lygaeidae)

Laboratory-reared predators, the insidious flower bug, Orius insidiosus (Say), and big-eyed bug Geocoris punctipes (Say), were exposed to 10 insecticides, including three newer insecticides with novel modes of action, using a residual insecticide bioassay. These species are important predators of several economic pests of cotton. Insecticides tested were: azinphos-methyl, imidacloprid, spinosad, tebufenozide, fipronil, endosulfan, chlorfenapyr, cyfluthrin, profenofos, and malathion. There was considerable variation in response between both species tested to the insecticides. Tebufenozide and cyfluthrin were significantly less toxic to male O. insidiosus than malathion. Tebufenozide was also significantly less toxic to female O. insidiosus than malathion. Imidacloprid, tebufenozide, and spinosad were significantly less toxic to male G. punctipes than chlorfenapyr, endosulfan, and fipronil. Spinosad, tebufenozide, and azinphos-methyl were significantly less toxic to female G. punctipes than fipronil and endosulfan. Fecundity of O. insidiosus was significantly greater in the spinosad treatment compared with other treatments including the control. Consumption of bollworm, Helicoverpa zea (Boddie), eggs by O. insidiosus was significantly lower in the fipronil, profenofos, and cyfluthrin treatments compared with other treatments including the control. Consumption of H. zea eggs by G. punctipes was significantly lower in the malathion, profenofos, endosulfan, fipronil, azinphos-methyl, and imidacloprid treatments compared with the control. Egg consumption by G. punctipes was not significantly different in the tebufenozide treatment compared with the control. The lower toxicity of spinosad to G. punctipes is consistent with other reports. Based on these results, the following insecticides are not compatible with integrated pest management of cotton pests: malathion, endosulfan, profenofos, fipronil, and cyfluthrin; while imidacloprid, tebufenozide, azinphos-methyl, and spinosad should provide pest control while sparing beneficial species.     

Effect of delayed toxicity of chemical barriers to control Argentine ants (Hymenoptera: Formicidae)

Brief exposures of Argentine ants to four different insecticide treatments, bifenthrin, beta-cyfluthrin, bifenthrin + beta-cyfluthrin, and fipronil, were conducted to determine Kaplan-Meier product limit survivorship percentiles (SPs) at 21-23 and 27-29 degrees C. Bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin provided rapid kill at 21-23 degrees C with SP10 values ranging from 11.2 to 33.7 min. Fipronil provided delayed toxicity at 21-23 degrees C with SP10 values ranging from 270 to 960 min. At 27-29 degrees C, all of the SP10 values significantly decreased. Field tests in which Argentine ants were induced to forage across insecticide-treated surfaces were used to determine the effect that speed of action has on foraging and recruitment ability, and whether these insecticides are repellent. The slower-acting fipronil allowed a greater amount of foraging and consequently a greater fraction of the colony to be exposed, whereas fast-acting bifenthrin, beta-cyfluthrin, and bifenthrin + beta-cyfluthrin inhibited recruitment, resulting in fewer ants being exposed and killed. Implications for controlling ants by using perimeter barrier treatments are discussed.     

Conservation of predatory arthropods in cotton: role of action thresholds for Bemisia tabaci (Homoptera: Aleyrodidae)

Studies were conducted in 1994 and 1995 to examine the effects of a range of action thresholds for managing Bemisia tabaci (Gennadius) Biotype B (= B. argentifolii Bellows & Perring) with insecticides in cotton on populations of arthropod predators in Imperial Valley, CA, and Maricopa, AZ. Application of insecticides significantly reduced population densities of spiders, Geocoris punctipes (Say), G. pallens (St?l), Orius tristicolor (White), Nabis alternatus Parshley, Zelus renardii Kolenati, Hippodamia convergens Guerin-Méneville, Spanogonicus albofasciatus (Reuter), Drapetis sp., and Chrysoperla carnea Stephens in one or both years and sites compared with untreated controls. Use of higher B. tabaci thresholds conserved some species and groups relative to lower thresholds. Stepwise regression analyses indicated that reductions in predator populations were generally influenced more strongly by the timing of the first insecticide application than by the total number of sprays necessary to maintain suppression of the pest below any given action threshold. A predation index, which weights the importance of each predator species based on their known frequency of predation on B. tabaci and another key pest, Pectinophora gossypiella (Saunders), was developed and analyzed. Patterns were similar to results based on changes in abundance alone, but the index generally revealed less severe effects of insecticides on overall predator function. The current action threshold for conventional insecticidal control of B. tabaci in Arizona and southern California is five adults per leaf. Results here suggest that predator conservation may be enhanced by raising the initial threshold to delay the first application or initially using more selective materials such as insect growth regulators.     

Insecticidal control of the mealybug Phenacoccus gossypiphilous (Hemiptera: Pseudococcidae), a new pest of cotton in Pakistan

The mealybug Phenacoccus gossypiphilous (Stanley) played havoc with the cotton crop in Pakistan during 2005. To control this pest, insecticides of different groups were evaluated in both the laboratory and in field conditions. In the laboratory, bifenthrin, profenofos and chlorpyrifos proved to be the best insecticides for mealybug control, based on their susceptibility with the leaf dip method for their LC₅₀. In field conditions, the recommended application rates of methomyl, profenofos and chlorpyrifos provided the best control: the lethal time studies proved their efficiency for better and timely control of this sporadic pest. The present study has shown that the insecticides tested, in particular profenofos, chlorpyrifos, methomyl and bifenthrin, provide satisfactory control of the cotton mealybug. The control of the insect pest complex throughout the cotton crop predominantly depends on wise and justified use of these chemicals, and necessitates development of an integrated pest management strategy.     

Prevalence and stability of insecticide resistances in field population of Spodoptera litura (Lepidoptera: Noctuidae) from Huizhou,Guangdong Province,China

The field population of Spodoptera litura from Huizhou, Guangdong Province, China was evaluated for resistance to 21 insecticides, including conventional and new chemistry insecticides. Extreme levels of resistance were observed to metaflumizone and emamectin benzoate with resistance factors of 234.1 and 183.3, respectively. Resistance to abamectin was also high (perhaps extremely high) and over 71.9-fold. The Huizhou population of S. litura possessed high resistance to deltamethrin (96.5-fold) and moderate resistance to beta cyfluthrin and lambda cyhalothrin but remained susceptible to bifenthrin. Moderate resistance to chlorantraniliprole (22.3-fold), endosulfan (22.2-fold), tebufenozide (10.7-fold) and thiodicarb (14.3-fold), and low-level resistance to fipronil, indoxacarb and spinosad were also reported in this population. This field population remained susceptible to acetamiprid, chlorfenapyr, chlorfluazuron, hexaflumuron, chlorpyrifos, pyridalyl and spinetoram. The stabilities of resistance to metaflumizone, emamectin benzoate, deltamethrin, chlorantraniliprole and endosulfan were evaluated, the resistance level decreased when the insecticide stress was removed, suggesting stop of the application of insecticides with high level resistance could be implemented into the resistance management. Because S. litura from Huizhou developed resistance to multiple insecticides, integration of different control practices, especially the rotation of insecticides with biocontrol agents, should be performed in the management of this pest. The results suggested the suspension of the application of insecticide to which S. litura had developed high level of resistance in order to mitigate the resistance status, and the use of the insecticides to which this pest remained sensitive, including spinetoram, pyridalyl, indoxacarb, hexaflumuron, chlorfluazuron, chlorfenapyr and bifenthrin, could be incorporated into the alternating application for resistance management.     

Patterns of insecticide resistance in onion thrips (Thysanoptera: Thripidae) in onion fields in New York

To develop an insecticide resistance management program for onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), on onions (Allium spp.), we surveyed populations in commercial onion fields in New York and evaluated their susceptibility to the two most widely used classes of insecticides plus two new insecticides during 2003-2005. All insecticide evaluations were conducted using the Thrips Insecticide Bioassay System (TIBS). As in our surveys conducted during 2002-2003, there were large temporal and spatial variations in susceptibility to the pyrethroid lambda-cyhalothrin (Warrior) across onion-growing regions in 2003. New data indicate that the field rate of methomyl (Lannate LV) still provides control but that the genes for resistance to methomyl are present in some populations. Tests with the two new insecticides, acetamiprid (Assail 70 WP) and spinosad (SpinTor 2CS), indicated they provided > 85% mortality at the field rate. To determine the spatial variation in insecticide susceptibility within a region, a series of systematic assays were conducted with lambda-cyhalothrin and methomyl. In 2004 and 2005, our data indicated that the within-region spatial variation in susceptibility to lambda-cyhalothrin was not large at the field rate or for the 100 ppm rate of methomyl. In 2005, a year in which T. tabaci densities in most fields were much higher than in 2004, growers were unable to control T. tabaci in particular fields and attributed this lack of control to resistance. Yet, we found similar levels of high susceptibility in all fields when using TIBS. This finding suggests that resistance had not developed and that variation in control may have been due to other factors, such as localized higher populations, poor spray coverage, too much time between spray applications, or different onion varieties.     

不同类型杀虫剂对烟粉虱捕食性天敌日本刀角瓢虫的毒力

采用试管药膜法,测定了不同类型杀虫剂对日本刀角瓢虫Serangium japonicum Chapin的毒力。结果表明,灭多威和敌敌畏对日本刀角瓢虫具有极强的毒力,其25%推荐剂量即可导致日本刀角瓢虫全部死亡;氯虫苯甲酰胺、吡虫啉和噻虫嗪对日本刀角瓢虫也具有很强的毒力,其田间推荐剂量可导致日本刀角瓢虫全部死亡,其50%推荐剂量对日本刀角瓢虫的致死率也高达73.33%～100.00%;乐果、烯啶虫胺、丁醚脲田间推荐剂量对日本刀角瓢虫的致死率分别为40.00%、56.67%、50.00%,预示着上述这些杀虫剂的田间应用对刀角瓢虫具有很高的直接杀伤风险。高效氯氰菊酯、联苯菊酯、毒死蜱、甲氰菊酯、高效氯氟氰菊酯、虫螨腈、阿维菌素、吡蚜酮、噻嗪酮、定虫隆和氟虫脲对日本刀角瓢虫的毒力较低甚至没有直接致死作用。研究结果将为合理使用杀虫剂,协调利用化学防治与生物防治对烟粉虱进行综合防治提供依据。     

Digging behavior of Solenopsis invicta workers when exposed to contact insecticides

ABSTRACT Contact between ants and insecticides is a prerequisite for contact insecticides to be effective in the control of red imported fire ants, Solenopsis invicta Buren. Typically, passive contact occurs in the insecticide application process, but ants also may actively contact insecticides by digging in treated soil or walking on a treated soil surface. Laboratory experiments were conducted to determine whether fire ant workers would dig sand treated with contact insecticides in two different scenarios: (1) no-choice bioassays where insecticide-treated sand was the only available digging substrate, and (2) two-choice bioassays where nontoxicant sand was also available for digging. Eight insecticides that are currently registered in the United States for imported fire ant control were tested. They include acephate, bifenthrin, carbaryl, cyfluthrin, deltamethrin, gamma-cyhalothrin, permethrin, and pyrethrin. Workers dug the treated sand for every insecticide tested, even at concentrations up to 10 times of the lowest lethal concentration (LLC) which caused 100% mortality in a toxicity bioassay. However, generally, insecticides significantly reduced the digging effort, even at a concentration that did not cause any significant mortality in the toxicity bioassay.     

Impact of straw mulch on populations of onion thrips (Thysanoptera: Thripidae) in onion

Development of insecticide resistance in onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), populations in onion (Allium spp.) fields and the incidence of the T. tabaci transmitted Iris yellow spot virus have stimulated interest in evaluating alternative management tactics. Effects of straw mulch applied in commercial onion fields in muck areas of western New York were assessed in 2006 and 2007 as a possible onion thrips management strategy. In trials in which no insecticides were applied for thrips control, straw mulch-treated plots supported significantly lower T. tabaci populations compared with control plots. In both years, the action thresholds of one or three larvae per leaf were reached in straw mulch treatments between 7 and 14 d later than in the control. Ground predatory fauna, as evaluated by pitfall trapping, was not increased by straw mulch in 2006; however, populations of the common predatory thrips Aeolothrips fasciatus (L.) (Thysanoptera: Aeolothripidae) were significantly lower in straw mulch plots in both years. Interference of straw mulch in the pupation and emergence of T. tabaci was investigated in the lab and their emergence was reduced by 54% compared with bare soil. In the field the overall yield of onions was not affected by the straw mulch treatment; however, the presence of jumbo grade onions (>77 mm) was increased in 2006, but not in 2007. These results indicate that populations of T. tabaci adults and larvae can be significantly reduced by the use of straw mulch without compromising overall onion yield. The use of this cultural practice in an onion integrated pest management program seems promising.     

山东省五个棉花产区绿盲蝽对药剂的敏感性检测（英文）

利用闪烁管药膜法测定了2009年山东省德州、滨州、梁山、曲阜和聊城5个棉花产区绿盲蝽Lygus lucorum Meyer-Dür对硫丹、马拉硫磷、毒死蜱、灭多威、丁硫克百威、吡虫啉、联苯菊酯和氟虫腈8种杀虫剂的敏感性,筛选出适合各地区的高效防治药剂。结果表明：5个地区绿盲蝽种群对马拉硫磷、毒死蜱、丁硫克百威、联苯菊酯和吡虫啉处于敏感性阶段。不同种群之间对灭多威、硫丹和氟虫腈的敏感性差异较大,其中聊城种群为最敏感种群,滨州种群对灭多威、 硫丹和氟虫腈的LC₅₀值分别为聊城种群的5.12,6.04和39.80倍;曲阜种群对灭多威、硫丹和氟虫腈的LC₅₀值分别为聊城种群的22.12,5.48和22.80倍。两种群对此3种药剂的敏感性下降,而其余种群仍处于较敏感阶段。8种药剂对绿盲蝽成虫的毒力按大小依次排序为：氟虫腈＞灭多威、联苯菊酯、硫丹＞马拉硫磷、毒死蜱＞丁硫克百威＞吡虫啉。2009年7-10月间德州夏津绿盲蝽种群对8种杀虫剂的敏感性变化极微。     

Utilizing the assassin bug, Pristhesancus plagipennis (Hemiptera: Reduviidae), as a biological control agent within an integrated pest management programme for Helicoverpa spp. (Lepidoptera: Noctuidae) and Creontiades spp. (Hemiptera: Miridae) in cotton

Helicoverpa spp. and mirids, Creontiades spp., have been difficult to control biologically in cotton due to their unpredictable temporal abundance combined with a cropping environment often made hostile by frequent usage of broad spectrum insecticides. To address this problem, a range of new generation insecticides registered for use in cotton were tested for compatibility with the assassin bug, Pristhesancus plagipennis (Walker), a potential biological control agent for Helicoverpa spp. and Creontiades spp. Indoxacarb, pyriproxifen, buprofezin, spinosad and fipronil were found to be of low to moderate toxicity on P. plagipennis whilst emamectin benzoate, abamectin, diafenthiuron, imidacloprid and omethaote were moderate to highly toxic. Inundative releases of P. plagipennis integrated with insecticides identified as being of low toxicity were then tested and compared with treatments of P. plagipennis and the compatible insecticides used alone, conventionally sprayed usage practice and an untreated control during two field experiments in cotton. The biological control provided by P. plagipennis nymphs when combined with compatible insecticides provided significant (P<0.001) reductions in Helicoverpa and Creontiades spp. on cotton and provided equivalent yields to conventionally sprayed cotton with half of the synthetic insecticide input. Despite this, the utilization of P. plagipennis in cotton as part of an integrated pest management programme remains unlikely due to high inundative release costs relative to other control technologies such as insecticides and transgenic (Bt) cotton varieties.     

Augmentation of the assassin bug Pristhesancus plagipennis (Walker) (Hemiptera: Reduviidae) as a biological control agent for Helicoverpa spp. in cotton

Third-instar nymphs of the Australian assassin bug, Pristhesancus plagipennis (Walker), were released into cotton plots at two release densities and two crop growth stages to test their biological control potential. Release rates of 2 and 5 nymphs per metre row resulted in field populations of 0.51 and 1.38 nymphs per metre row, respectively, indicating that over 70% of nymphs died or emigrated within two weeks of release. Effective release rates of 1.38 nymphs per metre row reduced the number of Helicoverpa spp. larvae in the plots for a 7-week period. Crop yields were significantly greater in the plots to which P. plagipennis nymphs were released, with the effective release rate of 1.38 nymphs per metre row providing equivalent yields as insecticide treated plots. The data suggest that P. plagipennis has the capacity to reduce Helicoverpa spp. larvae densities in cotton crops when augmented through inundative release.     

Pyrethroid-Acarophenax lacunatus interaction in suppressing the beetle Rhyzopertha dominica on stored wheat

Any biocontrol agent used against stored grain insects will have to interact with insecticides used as grain protectants due to their heavy use especially in tropical areas. Therefore, the interaction between the pyrethroid insecticides bifenthrin and deltamethrin and Acarophenax lacunatus (Cross & Krantz) (Prostigmata: Acarophenacidae), an egg parasite of the stored cereal pest Rhyzopertha dominica(F.) (Coleoptera: Bostrichidae), was assessed in a range of mite densities and insecticide doses for each compound. Despite the mite species presence on all insecticide doses, the lowest instantaneous rate of increase of A.lacunatus was recorded with the highest doses of insecticides. The presence of the biological control agent at all doses of both insecticides suggests its tolerance to these compounds. A. lacunatusshowed higher parasitism rate with bifenthrin than with deltamethrin indicating a higher selectivity of the first compound to the biocontrol agent. This revised version was published online in August 2006 with corrections to the Cover Date.     

Susceptibility of immature stages of Homalodisca coagulata (Hemiptera: Cicadellidae) to selected insecticides

Susceptibility of immatures of the glassy-winged sharpshooter, Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), to 10 insecticides that included chlorpyrifos, dimethoate, endosulfan, bifenthrin, cyfluthrin, esfenvalerate, fenpropathrin, acetamiprid, imidacloprid, and thiamethoxam was evaluated in the laboratory. All five instars were exposed to different doses of each foliar insecticide by the petri dish technique, whereas a systemic uptake method was used to assess the toxicity to imidacloprid and thiamethoxam. All test insecticides exhibited high toxicity to all immature stages of H. coagulata at concentrations below the field recommended rates of each insecticide. Although all five instars were susceptible to test insecticides, mortality was significantly higher in first instars than in the older immatures based on low LC50 values (ranging from 0.017 to 5.75 ng(AI)/ml) with susceptibility decreasing with each successive stage. Fifth instars were generally the least sensitive (LC50 values ranging from 0.325 to 216.63 ng (AI)/ml). These results show that mortality was directly related to age of the insect and suggest that chemical treatment at early stages is more effective than at late stages. Acetamiprid (neonicotinoid) and bifenthrin (pyrethroid) were the most toxic to all five instars, inducing most mortality within 24 h and showing lower LC50 values ranging from 0.017 to 0.686 ng/ml compared with other insecticides (LC50 values ranging from 0.191 to 216.63 ng(AI)/ml). Our data suggest that a diverse group of very effective insecticides are available to growers for controlling all stages of H. coagulata. Knowledge on toxicity of select insecticides to H. coagulata immatures may contribute to our understanding of resistance management in future for this pest by targeting specific life stages instead of the adult stage alone.     

烟粉虱抗药性的研究进展

烟粉虱是一种世界性的重要害虫,目前已对有机磷、拟除虫菊酯和氨基甲酸酯等许多常规杀虫剂产生高水平抗性,在一些地区烟粉虱对昆虫生长调节剂和烟碱类杀虫剂的抗性也是十分普遍.文中综述了世界范围内烟粉虱的抗药性现状、抗药性机理、以及抗药性与生物型的关系,并介绍了美国和以色列较为成功的烟粉虱抗药性治理计划.