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.     

Biorational insecticides: mechanism and cross-resistance

Potency and cross-resistance of various biorational insecticides, exemplified by the whitefly Bemisia tabaci, have been studied. Bemisia tabaci were exposed to the juvenile hormone mimic pyriproxyfen for the past 12 years resulting in an over 2,000-fold resistance, but there was no appreciable cross-resistance with the benzoylphenyl urea novaluron. Similarly, no cross-resistance was found between pyriproxyfen and the two neonicotinoids, acetamiprid and imidacloprid. On the other hand, a slight cross-resistance of 5-13-fold was observed with another neonicotinoid thiamethoxam. Among the neonicotinoids, a resistant strain of B. tabaci to thiamethoxam (approximately 100-fold) showed no appreciable cross-resistance to either acetamiprid or imidacloprid, while another strain 500-fold resistant to thiamethoxam resulted in a mild of 4-6-fold resistance to acetamiprid and imidacloprid. In other assays, B. tabaci strain resistant to thiamethoxam (approximately 100-fold) had no cross-resistance to pyriproxyfen. Our findings indicate that no appreciable cross-resistance was observed between the benzoylphenyl urea novaluron, the juvenile hormone mimic pyriproxyfen, and the neonicotinoids acetamiprid and imidacloprid. Hence, these compounds could be used as components in insecticide resistance management programs.     

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.     

Development, oviposition, and mortality of Neoseiulus fallacis (Acari: Phytoseiidae) in response to reduced-risk insecticides

Eight reduced-risk insecticides (acetamiprid, thiamethoxam, imidacloprid, thiacloprid, methoxyfenozide, pyriproxyfen, indoxacarb, and spinosad) and three conventional insecticides (azinphosmethyl, fenpropathrin, and esfenvalerate) were tested against Neoseiulus fallacis (Garman) (Acari: Phytoseiidae), the most abundant predacious mite in North Carolina apple (Malus spp.) orchards. To assess the effect of insecticides on development and mortality of N. fallacis immatures, 12-h-old eggs were individually placed on bean leaf disks previously dipped in insecticide solutions. Tetranychus urticae Koch (Acari: Tetranychidae) females were added as a food source. None of the reduced-risk insecticides significantly affected immature N. fallacis compared with the control; however, the pyrethroids esfenvalerate and fenpropathrin were highly toxic to immatures. To evaluate the effect of insecticides on mortality and oviposition of adult N. fallacis, 7- to 8-d-old females were confined on insecticide-treated bean leaves with Malephora crocea (Aizoaceae) pollen added as a food source. Spinosad resulted in the highest mortality, whereas azinphosmethyl, acetamiprid, fenpropathrin, and imidacloprid were moderately toxic, and mortality from esfenvalerate, indoxacarb, thiacloprid, methoxyfenozide, pyriproxyfen, and thiamethoxam did not differ significantly from the control. Oviposition was affected in a similar manner, with the exception of acetamiprid that did not affect oviposition, and thiamethoxam that reduced oviposition.     

杀虫剂对烟粉虱成虫毒力的微量筛选方法

采用直径为18mm的指形管代替常规浸叶法中的培养皿,研究不同寄主植物叶片和琼脂浓度对烟粉虱Bemisia tabaci(Gennadius)成虫自然死亡的影响,并用吡虫啉和啶虫脒为供试药剂对烟粉虱成虫毒力的筛选方法进行比较。结果表明:选用棉花叶片和14g.L-1的琼脂时,指形管内烟粉虱成虫72h自然死亡率最低,只有(5.4±1.5)%;采用此方法就吡虫啉和啶虫脒对烟粉虱成虫的毒力进行测定,测定结果重复性较好,节省药剂用量,无需对烟粉虱成虫麻醉,操作简便,达到微量活体筛选的目标。     

Assessment of cross-resistance potential to neonicotinoid insecticides in Bemisia tabaci (Hemiptera: Aleyrodidae)

Laboratory bioassays were carried out with four neonicotinoid insecticides on multiple strains of Bemisia tabaci (Gennadius) to evaluate resistance and cross-resistance patterns. Three imidacloprid-resistant strains and field populations from three different locations in the southwestern USA were compared in systemic uptake bioassays with acetamiprid, dinotefuran, imidacloprid and thiamethoxam. An imidacloprid-resistant strain (IM-R) with 120-fold resistance originally collected from Imperial Valley, California, did not show cross-resistance to acetamiprid, dinotefuran or thiamethoxam. The Guatemala-resistant strain (GU-R) that was also highly resistant to imidacloprid (RR=109-fold) showed low levels of cross-resistance when bioassayed with acetamiprid and thiamethoxam. However, dinotefuran was more toxic than either imidacloprid or thiamethoxam to both IM-R and GU-R strains as indicated by low LC50s. By contrast, a Q-biotype Spanish-resistant strain (SQ-R) of B. tabaci highly resistant to imidacloprid demonstrated high cross-resistance to the two related neonicotinoids. Field populations from Imperial Valley (California), Maricopa and Yuma (Arizona), showed variable susceptibility to imidacloprid (LC50s ranging from 3.39 to 115 microg ml(-1)) but did not exhibit cross-resistance to the three neonicotinoids suggesting that all three compounds would be effective in managing whiteflies. Yuma populations were the most susceptible to imidacloprid. Dinotefuran was the most toxic of the four neonicotinoids against field populations. Although differences in binding at the target site and metabolic pathways may influence the variability in cross-resistance patterns among whitefly populations, comparison of whitefly responses from various geographic regions to the four neonicotinoids indicates the importance of ecological and operational factors on development of cross-resistance to the neonicotinoids.     

Investigation on the optimal term of one-fold insecticide application for decreasing onion thrips ( Thrips tabaci Lindeman, Thysanoptera, Thripidae) damage on early white cabbage

An impact of the term of one-fold insecticide application to reduce the damage of the onion thrips in early white cabbage was established. During the growing season plants were treated with insecticide (abamectin) in three different terms (treatment 1: 9 June, treatment 2: 16 June, treatment 3: 23 June, and treatment 4: untreated). On the exterior leaves of cabbage heads, treated with the insecticide, statistically significantly lower mean index of damage was determined as compared to the untreated plants. No significant differences were found between three different terms of application. The majority of the economically important damages in all of the treatments was found between the 3rd and 6th exterior leaf in the head. The highest mean weight of heads (1517.3 g) and mean net weight of heads I = mean weight of heads - weight of damaged and removed leavesl (1166.3 g) were established in plants which were treated the last. These parameters were the lowest in untreated plants (1083.3 g / 805.6 g). The yield loss due to damaged leaves removal amounted from 22.9% (treatment 2) to 25.6% (treatment 4). Based on the results obtained in this research we concluded that yield loss due to onion thrips attack in plants with one-fold insecticide application is not substantially lower as in untreated plants (though statistically significant differences between them were established), because insecticide cannot reach the interior leaves in the head. Substantial differences in the total and net weight of heads between the treatments and especially between the treated and untreated plants are explained by the fact that feeding of numerous thrips populations in the heads and on the exterior cabbage leaves negatively affects plant physiology and yield. The highest average yield in plants which were treated the last indicates a possibility that insecticide also inhibits plant growth and development to a certain extent.     

Response of arthropods associated with the canopy of common beans subjected to imidacloprid spraying

Abstract:   Imidacloprid, the first neonicotinoid of potential use in agriculture, became an important agent for controlling leafhoppers, aphids, thrips and whiteflies. The use of this compound was extended to common beans in Brazil, a crop of great socio-economic value throughout Latin America, and the aim of the present work was to assess the temporal effectiveness and environmental safety of this insecticide to the arthropod community associated with the canopy of this crop plant. Thirty six species of phytophagous and detritivorous species were collected, as well as 37 species of predators and parasitoids. However, there was no significant impact of imidacloprid on species richness. In contrast, the insecticide significantly decrease the arthropod abundance for over a 30-day period. This impact is probably a reflection of the effect of this insecticide on Thrips tabaci and Caliothrips brasiliensis (Thysan., Thripidae) the most frequent and abundant species present in the area, and important pests of common beans in Brazil. Among the other most frequent taxa (present in over 50% of the samples), Araneae (predators) and the green leafhopper Empoasca kraemeri (Hom., Cicadellidae), another important bean pest in Brazil, were not significantly affected by imidacloprid, unlike the thrips species T. babaci and C. brasiliensis which showed decreased population levels until 8 days after imidacloprid application.     

Stink bug Agonoscelis spp. (Heteroptera: Pentatomidae) – An emerging threat for seed production in alfalfa crop (Medicago sativa L.) and their successful management

Fodder crops play an important role in sustainable agriculture as they provide feed for animals, which is ultimately converted to human food. Alfalfa is one of the most important fodder crops having high nutritive value for livestock. However, seed production of alfalfa crop is seriously affected by several factors and the highest reduction in seed yield is caused by stink bug infestation. The current study evaluated different insecticides to control stink bugs during 2016–17. The efficacy of ten insecticides, i.e., acephate, dimethoate, malathion, chlorpyriphos, bifenthrin, lambdacyhalothrin, deltamethrin, acetamiprid, imidacloprid and carbosulfan was tested on Agonoscelis spp. (Heteroptera Pentatomidae). The mortality of stink bug was recorded at one, three, five, seven, ten and fifteen days after insecticide application. Similarly, the population of pollinators was recorded before and one, three and five days after the application of insecticides. It was observed that acetamiprid (81.14%) and acephate (80.65%) caused the highest mortality of stink bug and proved most effective. Insecticides application decreased the pollinators’ population one day after spray; however, it was rehabilitated three days after insecticide application. Insecticide application increased seed yield from 28.05 kg/acre (during last four year without chemical control) to 116 kg/acre in 2016–17 (with chemical control). It is concluded that acetamiprid and acephate can be successfully used in integrated management program of increasing alfalfa seed production.     

Baseline susceptibility of Planococcus ficus (Hemiptera: Pseudococcidae) from California to select insecticides

Between 2006 and 2008, 20 populations of Planococcus ficus (Signoret), from Coachella and San Joaquin Valleys of California were measured in the laboratory for susceptibility to buprofezin, chlorpyrifos, dimethoate, methomyl, and imidacloprid. Toxicity was assessed using a petri dish bioassay technique for contact insecticides and by a systemic uptake technique for imidacloprid. Mixed life stages were tested for susceptibility to all insecticides except for buprofezin, which was measured against early and late instars (first, second, and third). Dose-response regression lines from the mortality data established LC50 and LC99 values by both techniques. Responses of populations from the two geographical locations to all five insecticides varied, in some cases significantly. Variations in susceptibility to each insecticide among sample sites showed a sevenfold difference for buprofezin, 11-fold to chlorpyrifos, ninefold to dimethoate, 24-fold to methomyl, and 8.5-fold to imidacloprid. In spite of susceptibility differences between populations, baseline toxicity data revealed that all five insecticides were quite effective based on low LC50s. Chlorpyrifos was the most toxic compound to Planococcus ficus populations as shown by lowest LC50s. Buprofezin was toxic to all immature stages but was more potent to first instars. The highest LC99 estimated by probit analysis of the bioassay data of all 20 populations for each compound was selected as a candidate discriminating dose for use in future resistance monitoring efforts. Establishment of baseline data and development of resistance monitoring tools such as bioassay methods and discriminating doses are essential elements of a sustainable management program for Planococcus ficus.     

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.     

内共生菌Cardinium对烟粉虱MED隐种耐药性的影响

【目的】次生内共生菌感染可影响烟粉虱Bemisia tabaci对杀虫剂的敏感性。本研究旨在揭示内共生菌Cardinium感染对烟粉虱B. tabaci MED隐种耐药性的影响。【方法】室内测定海南陵水与山东寿光烟粉虱MED隐种种群内遗传背景一致的Cardinium感染与未感染品系对不同浓度新烟碱类杀虫剂噻虫嗪和吡虫啉的耐药性。【结果】各浓度噻虫嗪和吡虫啉处理后,烟粉虱陵水种群感染Cardinium品系死亡率比未感染品系显著降低;100, 150, 175和200 mg/L噻虫嗪以及175和200 mg/L吡虫啉处理后,烟粉虱寿光种群感染Cardinium品系死亡率比未感染品系显著上升。相对于未感染品系,烟粉虱陵水种群感染Cardinium品系对噻虫嗪、吡虫啉的抗性倍数(RR)分别是1.355和1.847,烟粉虱寿光种群感染Cardinium品系的RR分别是0.790和0.847。【结论】内共生菌Cardinium感染能影响烟粉虱MED隐种对噻虫嗪和吡虫啉的耐药性,且这种影响在不同种群间存在差异。研究结果对于揭示烟粉虱MED隐种的种群适应性及扩张机制具有重要参考价值。     

Incidence of thrips and tomato spotted wilt Tospovirus in fluecured tobacco protected from early season insect pest infestations

The relative impacts of early season thrips exclusion (cages) and thrips suppression (pesticides) on tomato spotted wilt (family Bunyaviridae, genus Tospovirus, TSW) Tospovirus infection in flue-cured tobacco, Nicotiana tobaccum L., were examined in field trials in 2001-2004. There were fewer TSW symptomatic plants when plants were covered by exclusion cages for 6 wk than when they were uncaged or caged for 2 or 4 wk after transplanting. Plant height, leaves per plant, and total leaf weight per plant were lower in TSW symptomatic plants compared with nonsymptomatic plants for the uncaged plus 2- and 4-wk caged duration treatments but not different when caged 6 wk. Weekly acephate (Orthene) foliar sprays for 2 or 4 wk after transplanting reduced thrips populations for up to 5 wk after transplanting, whereas the 6-wk sprays had lower thrips populations for up to 8 wk. TSW was lower in both the 4- and 6-wk acephate treatments than in the untreated. A tray drench application of imidacloprid (Admire) reduced thrips populations in early season plus lowered the percentage of TSW compared with no tray drench treatment. The tobacco thrips, Frankliniella fusca (Hinds), was the predominate thrips species on tobacco foliage, and 1.9-4.9% tested positive for nonstructural TSW protein. The imidacloprid tray drench treatment and 6-wk acephate foliar sprays had lower densities of the tobacco-adapted form of Myzus persicae (Sulzer). Suppressing early season thrips populations with foliar acephate or imidacloprid tray drench are management option that can effectively reduce the incidence of TSW in flue-cured tobacco plus suppress aphids.     

Systemic insecticide and gibberellin reduced cone damage and increased flowering in a spruce seed orchard

Insects feeding in conifer cones are difficult to control with nonsystemic insecticides. Newly developed systemic insecticides that can be injected into tree trunks may be a possible way of reducing both insect damage and negative side-effects to the surrounding environment, compared with conventional spraying. Several insecticides that could be injected into tree stems were tested on Picea abies (L.) Karst. In one experiment, insecticides (bifenthrin, deltamethrin, abamectin, and imidacloprid) were injected during flowering; in a second experiment two of these insecticides (abamectin and imidacloprid) were injected 1 yr before the expected flowering. In the second experiment insecticide treatment was also combined with treatments with the flower stimulating hormone, gibberellin (GA(4/7)). The only insecticide that reduced damage was abamectin, both after injection during flowering and after injection 1 yr before the expected flowering. Injections with GA(4/7) increased flowering and were as efficient as the conventional application method of drilling but abamectin was not effective in combination with the drilling method. There was no negative effect of the insecticide injections on seed quality. The injections were ineffective against the seed chalcid Megastigmus strobilobius (Ratzeburg), which was found to have an unexpected, negative effect on seed quality. Our results suggest that it may be possible to reduce damage from certain insect species, and to increase flowering by injecting abamectin and GA(4/7) in the year before a cone crop.     

Conserving vedalia beetle, Rodolia cardinalis (Mulsant) (Coleoptera: Coccinellidae), in citrus: a continuing challenge as new insecticides gain registration

The effects of insecticides used for California citrus pest management were evaluated using larval and adult stages of vedalia beetle, Rodolia cardinalis (Mulsant). This predatory beetle is essential for control of cottony cushion scale Icerya purchasi (Williston) (Homoptera: Margarodidae) in San Joaquin Valley citrus. When adult beetles were exposed to treated citrus leaves, adult survival was significantly reduced by the foliar neonicotinoid imidacloprid and the pyrethroid cyfluthrin. Progeny production was significantly reduced by imidacloprid, cyfluthrin, fenpropathrin, and buprofezin. Buprofezin, pyriproxifen, and foliar imidacloprid also significantly reduced successful development of larvae into the adult stage. When vedalia stages were fed insecticide-treated cottony cushion scale reared on Pittosporum tobira (Thunb.) Ait, toxic effects were more severe than contact toxicity alone. Adult beetle survival was most profoundly reduced by the pyrethroids and to a lesser extent the foliar neonicotinoids acetamiprid and imidacloprid. Progeny production and larval development to adulthood were reduced by all insecticides but were most severely affected by pyriproxifen and the pyrethroids. Systemically applied neonicotinoids were toxic to vedalia larvae feeding on cottony cushion scale that had ingested these insecticides. These data demonstrate that IGRs, neonicotinoid insecticides, and pyrethroid insecticides have a significant, negative impact on vedalia beetles. Depending on the rate of insecticide used, the number and timing of applications, and the level of coverage of the tree, disruption of vedalia can be minimized. However, the situation is made difficult when pests such as citrus thrips Scirtothrips citri (Moulton) (Thysanoptera: Thripidae), forktailed bush katydid Scuddaria furcata Brunner von Wattenwyl (Orthoptera: Tettigoiniidae), or glassy-winged sharpshooter Homalodisca coagulata Say (Homoptera: Cicadellidae) require these pesticide treatments during periods of vedalia beetle activity.     

西花蓟马田间种群对常用杀虫剂的抗性现状及防治对策

【目的】西花蓟马Frankliniella occidentalis在中国是一种严重危害温室蔬菜的入侵害虫。本研究旨在了解该害虫在中国的抗药性现状,为防治该害虫提供理论支持。【方法】采用Munger cell法测定了北京,山东寿光和青岛以及云南晋宁和呈贡等5个地区西花蓟马田间种群对多杀菌素、毒死蜱、阿维菌素、甲维盐、氟氯氰菊酯、溴虫腈、灭多威、吡虫啉和啶虫脒9种杀虫剂的抗药性水平,同时利用这些田间种群测定了多功能氧化酶抑制剂胡椒基丁醚（PBO）、谷胱甘肽S 转移酶抑制剂顺丁烯二酸二乙酯（DEM）和羧酸酯酶抑制剂三丁基三硫磷酸酯（DEF）对多杀菌素、吡虫啉和甲维盐的增效作用。【结果】生物测定结果表明,北京、晋宁及呈贡种群分别对多杀菌素产生了34.45, 47.45和64.45倍的高水平抗性;晋宁种群对灭多威和甲维盐分别产生了16.58和11.03倍的中等水平抗性;呈贡种群对甲维盐、啶虫脒、吡虫啉、阿维菌素、溴虫腈分别产生了24.17, 21.69, 20.05, 16.45和10.31的中等水平抗性;青岛种群对啶虫脒和吡虫啉产生了17.70和12.49倍的中等水平抗性;寿光种群没有对任何杀虫剂产生高等或中等水平抗性。增效剂生物测定结果表明,对于吡虫啉和甲维盐,多功能氧化酶抑制剂PBO在所有田间种群上均有显著的增效作用。谷胱甘肽S-转移酶抑制剂DEM在呈贡、寿光和青岛种群中对吡虫啉存在显著增效作用;在北京、呈贡和寿光种群中,DEM对甲维盐存在显著增效作用。羧酸酯酶抑制剂DEF在呈贡、晋宁和青岛种群中对吡虫啉存在显著增效作用;在北京、呈贡和晋宁种群中,DEF对吡虫啉存在显著增效作用。但所有增效剂在各田间种群中对多杀菌素均无显著增效作用。【结论】结果提示：在使用多杀菌素防治西花蓟马时,应与其他杀虫剂轮换使用;此外,可通过添加酶抑制剂来增强甲维盐和吡虫啉对西花蓟马的防效。     

Evaluation of insecticides and application methods against Contarinia nasturtii (Diptera: Cecidomyiidae), a new invasive insect pest in the United States

The midge Contarinia nasturtii (Keiffer), a serious gall-forming insect pest of cruciferous plants in Europe and southwestern Asia, was first reported in the United States in summer 2004. It had not been recorded in North America until its discovery in Ontario, Canada, in 2000. Efficacy of 20 insecticides belonging to 12 different classes was evaluated by using a foliar spray, soil drench, or seed treatment method. The broccoli cultivar 'Packman' was used in all tests at the suitable stage of four to five true leaves. Results indicated that foliar sprays of lambda-cyhalothrin, acephate, acetamiprid, chlorpyrifos, and methomyl reduced C. nasturtii larval populations by 96.7-100%. Except for acetamiprid, the other four insecticides also were effective against adults and provided 100% mortality after 24 h. When applied by drench, acetamiprid, imidacloprid, and thiamethoxam provided 100% control of C. nasturtii larvae, and the duration of efficacy lasted at least 7 wk. When applied as seed treatment, clothianidin and thiamethoxam provided 100% control of larvae and did not significantly affect seed germination. Imidacloprid also provided 100% control but the percentage of germination after treatment was only 62% (96.9% in check). These results indicate that several insecticides may significantly reduce midge populations. The nicotinoid class of insecticides, which has strong systemic activity, is likely to be the first choice. It is necessary to explore and develop other control methods such as cultural control and host resistance to develop an effective integrated pest management system.     

Impact of whole-canopy and systemic insecticidal treatments on Callirhytis cornigera (Hymenoptera: Cynipidae) and associated parasitoids on pin oak

The gall wasp Callirhytis cornigera (Osten Sacken) is a cynipid with alternating generations that produce large, woody stem galls and tiny blister-like leaf galls on pin oak, Quercus palustris Muenchhausen, in the United States. We tested 3 approaches to control the leaf-galling generation, and determined their impact on associated parasitoids and effectiveness in reducing numbers of new stem galls. First, trees were sprayed with bifenthrin or chlorpyrifos in late March to kill females emerging from stem galls before they oviposited into buds. Second, concentrated solutions of abamectin, imidacloprid, or bidrin were injected from pressurized containers into tree sapwood to control larvae developing in young leaf galls. Finally, systemic insecticides (acephate, abamectin, dimethoate, or imidacloprid) were sprayed at early leaf expansion (2 May) or to young, expanded leaves (17 May) to target larvae in leaf galls. Parasitoids, mostly eulophids, accounted for approximately 70% mortality of leaf-galling C. cornigera larvae on untreated trees. Whole-canopy sprays during C. cornigera emergence from stem galls reduced overall numbers of galled leaves and leaf galls. Trunk injections of bidrin or abamectin resulted in significant mortality of gall inhabitants, including parasitoids. However, neither of the aforementioned approaches significantly reduced numbers of new stem galls. Sprays of abamectin, dimethoate, or imidacloprid applied on 2 May caused high mortality of all gall inhabitants. There was no net benefit, however, because parasitism caused a similar reduction in C. cornigera survival on unsprayed shoots. Sprays applied later in leaf expansion had little impact on gall inhabitants. Of the treatments tested, bifenthrin sprays at bud break provided the greatest reduction in new leaf galls, whereas bidrin injections provided the greatest reduction in gall wasps emerging from galled leaves. This study suggests that gall wasp outbreaks are unlikely to be controlled by a single treatment, regardless of application method.     

Impact of neonicotinoid seed treatments on thrips (Thysanoptera: Thripidae) and soybean yield in Virginia and North Carolina

Currently there are several neonicotinoid insecticide seed treatments registered for use on soybean (Glycine max L.), with disparity in adoption rates in the eastern United States. A complex of seedling insect pests is found in mid-south soybean, but thrips are the primary early season pest of soybean in Virginia and North Carolina. Published knowledge regarding their impact on soybean yield is minimal, as is the impact of thrips on soybean yield; thrips species composition is also understudied. In 2008 through 2010, nine field experiments in Virginia and North Carolina were conducted to evaluate the impact on thrips population dynamics; the influence on yield of neonicotinoid seed treatments, imidacloprid and thiamethoxam, was reported from nine of these experiments. Moreover, thrips species abundance was recorded in three of these experiments. Both imidacloprid and thiamethoxam reduced thrips densities compared with untreated soybean. Thiamethoxam was more effective than imidacloprid in reducing adult thrips densities at 5 wk after planting. Adult densities peaked at 3 wk after planting, followed by larval densities, which peaked at 4 wk after planting. The most abundant thrips species was Frankliniella fusca (Hinds), followed by Neohydatothrips variabilis (Beach). Other common species included F. occidentalis (Pergande) and F. tritici (Fitch). In general, F. fusca was more common earlier in the season, while N. variabilis was more common later in the season. There were no significant differences in yield among any of the treatments or in the untreated controls. Although neonicotinoid insecticides reduced thrips abundance, data collected in these studies demonstrated that there was no positive yield response.     

An aphid-dip bioassay to evaluate susceptibility of soybean aphid (Hemiptera: Aphididae) to pyrethroid, organophosphate, and neonicotinoid insecticides

Since the discovery of the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in North America in 2000, chemical control has been the most effective method to manage aphid outbreaks. Increased insecticide use in soybean raises the possibility of developing insecticide resistance in soybean aphid, and monitoring insecticide susceptibility is essential to maintain pesticide tools. We developed a simple and reliable aphid-dip bioassay by using a tea strainer that resulted in -90% survival in controls. Using this technique, we tested susceptibility of a greenhouse strain of soybean aphid that has never been exposed to insecticides, and field-collected aphid strains from two counties in Michigan. Aphid susceptibility was tested for five insecticides by dipping groups of five aphids in each insecticide dose for 10 s. After 48 h, aphids were classified as dead or alive, and counted. Aphids from all strains were highly susceptible to chlorpyrifos, lambda-cyhalothrin, esfenvalerate, and dimethoate, with LC50 and LC90 values well below the recommended application rates. However, aphids showed less susceptibility after 48 h to neonicotinoid imidacloprid, with higher LC90s and wider fiducial limits. This illustrated the potential limitation of using a 48-h assay to evaluate insecticides with longer-term, sublethal impacts. Nevertheless, this study made use of a simple aphid-dip method to test and compare insecticide susceptibility of soybean aphid. In the event of a field failure, the aphid populations involved can be tested in comparison to a susceptible greenhouse strain to determine the extent of resistance development.