Olfactory cues used in host‐habitat location and host location by the parasitoid Cotesia urabae

There is a growing body of evidence that many hymenopteran parasitoids make use of olfaction as the primary mechanism to detect and locate hosts. In this study, a series of bioassays was conducted to investigate the orientation behaviour of the gum leaf skeletonizer larval parasitoid Cotesia urabae Austin & Allen (Hymenoptera: Braconidae) in both Y‐tube and four‐arm olfactometers. In a Y‐tube olfactometer, male C. urabae were attracted only to virgin conspecific females. Host‐plant leaves, damaged leaves, host larvae, and host larvae feeding on leaves were highly attractive to female C. urabae, whereas host frass and conspecific males were not. The multiple‐comparison bioassay conducted in a four‐arm olfactometer clearly indicates that C. urabae females were significantly more attracted to the host Uraba lugens Walker (Lepidoptera: Nolidae) larvae feeding on Eucalyptus fastigata H Deane & Maiden (Myrtaceae) leaves than to any other of the odour sources tested. The results of this study show that C. urabae individuals responded to chemical cues specific to the host plant and target host insect, and support hypotheses that unreliable cues are not utilized for host location by specific natural enemies.     

The Wiggle Index: An Open Source Bioassay to Assess Sub-Lethal Insecticide Response in Drosophila melanogaster

Toxicological assays measuring mortality are routinely used to describe insecticide response, but sub-lethal exposures to insecticides can select for resistance and yield additional biological information describing the ways in which an insecticide impacts the insect. Here we present the Wiggle Index (WI), a high-throughput method to quantify insecticide response by measuring the reduction in motility during sub-lethal exposures in larvae of the vinegar fly Drosophila melanogaster. A susceptible wild type strain was exposed to the insecticides chlorantraniliprole, imidacloprid, spinosad, and ivermectin. Each insecticide reduced larval motility, but response times and profiles differed among insecticides. Two sets of target site mutants previously identified in mortality studies on the basis of imidacloprid or spinosad resistance phenotypes were tested. In each case the resistant mutant responded significantly less than the control. The WI was also able to detect a spinosad response in the absence of the primary spinosad target site. This response was not detected in mortality assays suggesting that spinosad, like many other insecticides, may have secondary targets affecting behaviour. The ability of the WI to detect changes in insecticide metabolism was confirmed by overexpressing the imidacloprid metabolizing Cyp6g1 gene in digestive tissues or the central nervous system. The data presented here validate the WI as an inexpensive, generic, sub-lethal assay that can complement information gained from mortality assays, extending our understanding of the genetic basis of insecticide response in D. melanogaster.     

Effects of two biorational insecticides, spinosad and methoxyfenozide, on Spodoptera littoralis (Lepidoptera: Noctuidae) under laboratory conditions

The toxicity of two biorational insecticides, spinosad (Tracer) and methoxyfenozide (RH-2485), was tested against eggs, larvae, and pupae of the noctuid Spodoptera littoralis (Boisduval). In the first experiment, filter paper circles containing egg masses of two different age classes, young (<24 h old) and old (24-48 h old), were dipped in different concentrations of each insecticide diluted in either water or acetone. No ovicidal activity was recorded when insecticides were diluted in water. In contrast, when insecticides were diluted in acetone, both egg age classes generally showed a concentration-dependent response for both compounds. Mortality of larvae that hatched from both egg age classes was significantly increased, compared with control larvae, at all concentrations of both insecticides when diluted in water or acetone alike. The prevalence of mortality was similar with each insecticide. In the second experiment, third instars of S. littoralis were fed semisynthetic diet containing different concentrations of both insecticides. According to LC50 values, no significant differences were observed between spinosad (2.11 mg [AI]/kg diet) and methoxyfenozide (3.98 mg [AI]/kg diet) after 48 h of treatment, based on the overlap of 95% CL. Toxic effects on the mortality of pupae, adult emergence, and the prevalence of deformed adults after topical application on young pupae also were examined. Only methoxyfenozide caused pupal mortality and deformed adults. Our results suggest that spinosad and methoxyfenozide are potentially potent compounds for control of S. littoralis.     

Compatibility of Spinosad, Tebufenozide and Azadirachtin with Eggs and Pupae of the Predator Chrysoperla carnea (Stephens) Under Laboratory Conditions

Under laboratory conditions, the toxicity of three novel insecticides, spinosad (Tracer ® ), tebufenozide (Mimic ® ) and azadirachtin (Align ® ), was tested against eggs and pupae of the predator Chrysoperla carnea (Stephens). In a first series of assays, eggs were dipped in an aqueous concentration and no ovicidal activity was scored for the three insecticides. In the second, when females were ovipositing on treated substrate for 24 h, fecundity and hatching percentages were similar as compared to controls and the offspring developed normally until the adult stage. However, spinosad, at the highest concentrations tested, caused a slight, significant reduction in the adult life span and fecundity. In a third series of experiments, pupae developed into normal adults after topical treatment for the three insecticides. Herewith, a pharmacokinetic study indicated low accumulation in the body after pupal cuticle penetration when administrating 14 C-labelled insecticide. Fourthly, pupation of last-instar larvae in treated substrate was normal for spinosad and tebufenozide. Only azadirachtin caused a slight reduction in the number of pupae and adults; however, fecundity and fertility of surviving adults was normal. In conclusion, the current results indicate that the three insecticides are not toxic to eggs and pupae of C. carnea .     

Insecticide susceptibility of Cnaphalocrocis medinalis (Lepidoptera: Pyralidae) in China

Insecticide control is the major measure for suppression of Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae) damage, and a few insecticides used for long time have proved to fail to control this pest in China. Several new chemicals have been introduced for control of C. medinalis. However, there was no baseline susceptibility data of C. medinalis to insecticides used or will be in use. In this study, a seedling dipping method was developed for bioassay of insecticide susceptibility of C. medinalis. Dose responses of C. medinalis to 11 insecticides were tested. Interpopulation sensitivity to insecticides was compared. Based on LC50 values, C. medinalis was most susceptible to antibiotic insecticides (abamectin, emamectin benzoate, and spinosad) and least sensitive to monosultap and a Bacillus thuringiensis (Bt) product. Chlorantraniliprole and insect growth regulator (IGR) insecticides (tebufenozide and hexaflumuron) exhibited great efficacy against C. medinalis. No susceptibility difference was observed for antibiotic insecticide and IGR insecticides among three populations. Narrow variation in tolerant level was detected for organophosphates insecticides, chlorantraniliprole, monosultap, and Bt. The results in this study provided baseline susceptibility data of C. medinalis to 11 insecticides and also offered useful information for choice of alternative insecticide and for integrated resistance management of C. medinalis.     

Chemical composition and fumigant toxicity of the essential oils from 16 species of Eucalyptus against Haematobia irritans (Diptera: Muscidae) adults

Oils extracted from various species of Eucalyptus (Eucalyptus badjensis Beuzev & Welch, Eucalyptus badjensis x Eucalyptus nitens, Eucalyptus benthamii variety dorrigoensis Maiden & Cambage, Eucalyptus botryoides Smith, Eucalyptus dalrympleana Maiden, Eucalyptus fastigata Deane & Maiden, Eucalyptus nobilis L.A.S. Johnson & K. D. Hill, Eucalyptus polybractea R. Baker, Eucalyptus radiata ssp. radiata Sieber ex Spreng, Eucalyptus resinifera Smith, Eucalyptus robertsonii Blakely, Eucalyptus rubida Deane & Maiden, Eucalyptus smithii R. Baker, Eucalyptus elata Dehnh, Eucalyptus fraxinoides Deane & Maiden, E. obliqua L'Hér) were obtained by hydrodistillation. The chemical composition of essential oils was determined by gas chromatography coupled to mass spectrometry. Essential oils were mainly composed of 1,8-cineole, alpha-pinene, alpha-terpineol, 4-terpineol, and p-cymene. Vapors from these essential oils and their major components were found to be toxic to Haematobia irritans (L.) (Diptera: Muscidae) adults. An aliquot of each oil was placed in a cylindrical test chamber, and the number of knocked down flies was recorded as a function of time. Knockdown time 50% was then calculated. Results showed that essential oil of E. polybractea had the highest knockdown activity of 3.44 min. A correlation was observed between the content of 1,8-cineole in the Eucalyptus essential oils and the corresponding toxic effect.     

无公害水稻生产的病虫草调控技术及其效应的研究

利用无公害农药和农业措施防治水稻主要病虫草试验结果表明,井·腊芽、井冈霉素和多抗霉素在水稻分蘖末期和孕穗末期各喷施1次,对纹枯病防效达75.16％～94．27％,优于化学杀菌剂三唑酮;春雷霉素和灭瘟素在叶瘟病发生初期及破肚期、齐穗期各喷施1次,对叶瘟防效为50．54％～72．67％,穗瘟为76．66％～8742％,与化学杀菌剂三环唑相当3种无公害农药在二化螟和稻纵卷叶螟1～2龄幼虫期使用,苏云金杆菌防效优于化学杀虫剂杀虫双,皂素·烟碱和苦参碱与杀虫双相当;皂素·烟碱和苦参碱在稻飞虱1～2龄若虫期使用,药后3～30d防效均在70％以上,低于化学杀虫剂吡虫啉,在水稻移栽前耕地2次,再配合施用适量的未腐熟有机质或人工除草,能控制杂草发生和提高产量,采用无公害农药和农业措施防治水稻病虫草,产量较常规化防区略有增加,稻谷中农药残留量较化防区低,符合绿色食品卫生指标要求。     

杀虫剂胁迫下褐飞虱迁飞虫和本地虫后代体内粗脂肪、可溶性糖及氨基酸含量的比较

为了解迁飞种群与居留种群后代发生再猖獗的生理生化差异,探讨再猖獗的机制,比较研究了在两个水稻品种（TN1和协优963）上施用杀虫剂后褐飞虱Nilaparvata lugens (Stål)迁飞虫和本地虫后代3龄、5龄若虫和成虫体内可溶性糖和粗脂肪含量以及迁飞成虫与其后代成虫体内游离氨基酸含量的变化。结果表明： 施药以及未施药处理(对照)TN1水稻品种上的迁飞后代3龄、5龄若虫和成虫体内的可溶性糖含量均显著高于本地虫。与可溶性糖含量相比,施药以及对照TN1水稻品种上的迁飞后代3龄、5龄若虫和成虫体内的粗脂肪含量均显著低于本地虫。协优963上3龄、5龄若虫体内可溶性糖含量的变化趋势与TN1上相同。对照水稻上迁飞成虫的粗脂肪含量显著高于本地种群,迁飞与本地3龄、5龄若虫间粗脂肪含量没有显著差异。杀虫剂处理后的水稻上迁飞后代5龄若虫和成虫体内粗脂肪含量显著高于本地虫。方差分析结果也显示,可溶性糖和粗脂肪含量的变化在虫源和杀虫剂,虫源和杀虫剂浓度以及杀虫剂类型和浓度方面有显著交互作用。两种水稻品种上,迁飞当代成虫体内的游离氨基酸含量显著低于其后代成虫。在经3种杀虫剂处理后,TN1上施用三唑磷后成虫体内的氨基酸含量显著高于施用溴氰菊酯和吡虫啉的处理,而协优963上施用溴氰菊酯和吡虫啉显著高于施用三唑磷的处理。本研究结果对深入阐明农药诱导褐飞虱再猖獗的机制具有参考价值。     

Effects of spinosad, spinosad bait, and chloronicotinyl insecticides on mortality and control of adult and larval western cherry fruit fly (Diptera: Tephritidae)

Effects of spinosad, spinosad bait, and the chloronicotinyl insecticides imidacloprid and thiacloprid on mortality of the adults and larvae of western cherry fruit fly, Rhagoletis indifferens Curran (Diptera: Tephritidae), were determined in the laboratory and the field. Spinosad and spinosad bait caused higher adult mortality than imidacloprid, which caused higher mortality than thiacloprid. Only spinosad bait prevented oviposition. All materials were more toxic to adults when ingested than when topically applied. Spinosad bait had the greatest residual toxicity on leaves, killing 100% of adults when aged for 14 d in the field. When materials were sprayed on infested cherries, numbers of live larvae in fruit after 8 d were lower in imidacloprid and thiacloprid than in spinosad and spinosad bait treatments, which did not differ from the control, but all materials reduced larval emergence over 30 d. In the field, spinosad and spinosad bait were as effective in suppressing larval infestations as azinphos-methyl and carbaryl, whereas imidacloprid was effective in most cases and thiacloprid was generally less effective than azinphos-methyl and carbaryl. Overall, results in the laboratory and field show that spinosad and chloronicotinyl insecticides differed significantly in their effectiveness against adults and larvae of R. indifferens but that spinosad, spinosad bait, and imidacloprid seem to be acceptable substitutes for organophosphate and carbamate insecticides for controlling this fruit fly.     

Reduced-risk insecticides for control of grape berry moth (Lepidoptera: Tortricidae) and conservation of natural enemies

A 3-yr field study was conducted at commercial grape (Vitis spp.) farms to evaluate insect management programs for control of the grape berry moth, Paralobesia viteana Clemens (Lepidoptera: Tortricidae) and conservation of natural enemies. At each farm, one vineyard received only reduced-risk insecticides for control of second and third generation P. viteana, whereas the comparison vineyard received conventional insecticides. Both vineyards received a conventional insecticide application for control of first generation P. viteana and other insect pests. Monitoring with pheromone traps showed no differences between programs in the total number of adult male moths trapped in vineyards, and oviposition by P. viteana was similar between the two programs in all 3 yr. During weekly samples of crop infestation, both programs had a similar percentage of clusters infested by P. viteana larvae. Berries infested by P. viteana were collected from vineyard borders during the second and third P. viteana generations and held under controlled conditions. In eight of the nine berry samples, survival of larvae was significantly lower in berries collected from vineyards managed under the reduced-risk insecticide program compared with the conventional program. Parasitism of P. citeana larvae in these samples was not consistently different between the two insecticide programs over 3 yr, and similar captures of natural enemies were found on yellow sticky traps in the two programs throughout the study. Our results indicate that integrated pest management programs incorporating reduced-risk insecticides for control of P. viteana can obtain similar or greater control of P. viteana compared with programs based solely on conventional insecticides, but they may not lead to measurable long-term increases in parasitism of P. viteana.     

褐飞虱对吡虫啉的抗性机理和靶标分子毒理学

褐飞虱Nilaparvata lugens是水稻最重要的害虫之一,长期依赖化学防治导致了该害虫对不同类型杀虫剂抗性的产生,对新烟碱类杀虫剂吡虫啉高水平抗性的产生更是造成了巨大的粮食生产损失。近年来在褐飞虱对吡虫啉抗性机理,以及在抗药性机理研究推动下吡虫啉作用靶标褐飞虱神经系统烟碱型乙酰胆碱受体（nicotinic acetylcholine receptors, nAChRs）毒理学等方面取得了许多研究进展。nAChRs是昆虫神经系统中最重要的神经递质受体,是几类重要杀虫剂的作用靶标,其中以新烟碱类杀虫剂为代表。通过对比敏感品系和室内连续筛选获得的高抗吡虫啉品系,在褐飞虱两个nAChRs亚基Nlα1和Nlα3中均发现了抗性相关点突变Y151S,该突变导致了受体与吡虫啉结合亲和力的显著下降,而对内源神经递质乙酰胆碱的亲和力影响很小。Nlα1与褐飞虱另外两个亚基Nlα2和Nlβ1共聚成一个受体,构成吡虫啉低亲和力结合位点;Nlα3与褐飞虱另外两个亚基Nlα8和Nlβ1共聚成一个受体,构成吡虫啉高亲和力结合位点。不仅褐飞虱nAChRs与吡虫啉抗性相关,某些nAChRs附属蛋白也直接影响褐飞虱对吡虫啉的抗性,如Lynx蛋白。关于褐飞虱nAChRs组成、抗药性相关变异、受体附属蛋白对抗药性的影响等方面的研究,均为国内外前沿报道,不仅有助于对新烟碱类杀虫剂抗性机理的理解,对昆虫nAChRs毒理学同样具有很大的推动作用。     

Ultralow rates of spinosad in phagostimulant granules provide control of Spodoptera frugiperda (Lepidoptera: Noctuidae) in maize

Field trails in 2002 and 2003 were performed to determine the efficacy of maize flour-based granular formulations with ultralow rates of the naturally derived insecticide spinosad (0.1, 0.3, and 1.0 g [AI]/ha), for control of Spodoptera frugiperda (J.E. Smith) in maize, Zea mays L., in southern Mexico. Spinosad formulations were compared with a chemical standard, a commercial granular formulation of chlorpyrifos (150 g [AI]/ha). In both years, application of spinosad resulted in excellent levels of control, indicated by the number of living S. frugiperda larvae recovered from experimental plots. The efficacy of spinosad applied at 0.3 and 1.0 g (AI)/ha was very similar to that of chlorpyrifos. Natural reinfestation caused S. frugiperda numbers in insecticide treated plots to return to values similar to the control treatmentby 10-15d postapplication. Many spinosad-intoxicated larvae collected in the field died later in the laboratory in 2002, but not in 2003. Percentage mortality due to parasitoid emergence did not differ in any treatment in either field trial. The number of parasitoids that emerged from S. frugiperda collected in each treatment was significantly reduced after application of spinosad (all rates) or chlorpyrifos due to a reduction in the number of host larvae. Parasitoid numbers returned to control values by 9-15 d postapplication in all treatments. The most prevalent parasitoid was the braconid Chelonus insularis Cresson, which represented approximately 80% of emerging parasitoids in both years. We conclude that appropriate formulation technology can greatly enhance the performance of this naturally derived, biorational insecticide.     

Susceptibility of the adult eye gnat Liohippelates collusor (Diptera: Chloropidae) to neonicotinoids and spinosad insecticides.

Imidacloprid, thiamethoxam (first and second generation neonicotinoid insecticides), and spinosad (a naturally derived biorational insecticide) were evaluated in the laboratory against adult eye gnats, Liohippelates collusor (Townsend), using two modes of exposure. Ingestion experiments revealed that toxicity was the highest for thiamethoxam (Platinum soluble concentrate) followed by technical thiamethoxam, imidacloprid (Admire 2 flowable concentrate), and spinosad (Success* soluble concentrate). When incorporated into 5% sucrose solutions, eye gnat mortality was significantly increased compared to the same concentrations of aqueous insecticide solutions. Contact toxicity experiments revealed that thiamethoxam formulation (Platinum) was the most toxic, followed by technical thiamethoxam, imidacloprid, and spinosad. Increasing the duration of exposure time from 15 min to 30 min significantly increased adult eye gnat mortality, but no further mortality occurred by extending exposure from 30 min to 60 min. Our results suggest that Platinum has good ingestion and contact activity against adult eye gnats. Admire and Success have appreciable ingestion toxicity but low contact activity against adult eye gnats.     

褐飞虱抗药性研究现状

褐飞虱Nilaparvata lugens(Stal)对杀虫剂产生抗药性是其近年来暴发频繁的重要原因。文章综述国内外关于褐飞虱抗药性的研究成果,包括褐飞虱抗性测定方法、抗药性的发展、交互抗性、抗性遗传、抗性机理及抗性治理等。田间褐飞虱种群对新烟碱类药剂产生不同程度的抗药性,其中对吡虫啉产生高水平到极高水平抗性,对氯噻啉和噻虫嗪分别产生中等水平和低水平的抗药性,对呋虫胺和烯啶虫胺仍然处于敏感性阶段。此外,褐飞虱种群对噻嗪酮(昆虫生长调节剂)产生低水平到中等水平抗性。长期大面积使用化学药剂是褐飞虱产生抗药性的重要原因。因此,必须加强褐飞虱的抗性治理,以延缓其抗药性进一步发展。     

Insecticidal resistance and cross-resistance in populations of Cydia pomonella (Lepidoptera: Tortricidae) in central Europe

Insecticide bioassays were used to investigate resistance of Cydia pomonella (L.) (Lepidoptera: Tortricidae) to insecticides with various types of active ingredients. The efficacy baselines of selected insect growth regulators (fenoxycarb), insect growth inhibitors (diflubenzuron and teflubenzuron), organophoshorous insecticides (phosalone), and neonicotinoids (thiacloprid) against the eggs and first and fifth instars of sensitive laboratory strains of codling moth were determined. According to concentration-mortality baseline, 50% lethality concentration values and 90% lethality concentration values were determined for all the tested insecticides. The lethal concentration ratio quantified the relation between the efficacy of selected insecticides against fifth instars found by topical application and against first instars found by diet-treated bioassay. No difference was detected when the efficacy of technical grade diflubenzuron diluted in tetrahydrofuran and diflubenzuron in the formulated product Dimilin 48 SC diluted in water was compared. However, just before the application of insecticide, the integument of larvae must be treated with acetone. Two bioassays were used to monitor the resistance of codling moths collected in 2003-2005 in two apple (Malus spp.) orchards with different intensities of chemical control. Resistance ratios (RRs) to the tested insecticides were determined for both field populations of codling moth. For the population of codling moth from a commercial apple orchard in Velké Bílovice, cross-resistance to fenoxycarb, teflubenzuron, and phosalone was detected after the topical application of insecticides to fifth instars. The population of codling moth from Prague-Ruzyne was slightly resistant to phosalone and teflubenzuron. No resistance to diflubenzuron was detected in either tested population.     

Protection of fruit against infestation by apple maggot and blueberry maggot (Diptera: Tephritidae) using compounds containing spinosad

Two insecticide formulations containing the naturalyte insecticide spinosad, GF-120 Fruit Fly Bait and SpinTor 2 SC, were compared for control of apple maggot, Rhagoletis pomonella (Walsh), and blueberry maggot, Rhagoletis mendax Curran. In 2002 and 2003, larval infestation in blueberries and apples was significantly lower in plots treated with GF-120 (spinosad bait) or SpinTor than in untreated control plots. Fruit fly infestation in apples was reduced by 67% in 2002 after weekly application of GF-120 for 6 wk. Six weeks of GF-120 treatment reduced infestation in blueberries by 85% in 2002 and 98% in 2003. Plots treated weekly with the bait component of GF-120 for 6 wk had significantly higher infestation of blueberry maggot larvae compared with untreated plots in 2002. Observations of wild R. mendax flies revealed that similar numbers of flies landed on blueberry foliage treated with spinosad bait, the bait component alone, or water droplets. However, flies on spinosad bait and bait treated plants spent significantly more time within 5 cm of the treatment droplets compared with control (water) droplets. Overall, the results demonstrate a high degree of efficacy of baited spinosad formulations against these key pests of temperate fruit and suggest that GF-120 is an arrestant for foraging flies.     

Effects of selected insecticides on Diadegma insulare (Hymenoptera: Ichneumonidae), a parasitoid of Plutella xylostella (Lepidoptera: Plutellidae)

Effects of eight insecticides on Diadegma insulare (Cresson), a parasitoid of the diamondback moth, Plutella xylostella L., were evaluated under the laboratory conditions. The insecticides were three azadirachtin-based products (Ecozin, Agroneem and Neemix), two Bacillus thuringiensis (Bt) products (Xentari and Crymax), indoxacarb, spinosad, and λ-cyhalothrin. When D. insulare pupae were treated, none of the insecticide treatments except λ-cyhalothrin significantly reduced adult emergence, with 76-90% adults emerged from the treated pupae. In the λ-cyhalothrin treatment, only 10% D. insulare pupae produced adult wasps. Indoxacarb, spinosad, and λ-cyhalothrin caused 100% D. insulare adult mortality in 24 h in Petri dishes sprayed with insecticides in the contact bioassays, and 95.8, 100 and 95.8% adult mortality in 24 h in the ingestion bioassays, respectively. In contrast, all three azadirachtin-based insecticides and the two Bt-insecticides caused only 0-10.4% mortality of D. insulare adults after ingestion. The surviving D. insulare from ingestion treatments with Bt- and azadirachtin-insecticides parasitized 50.8-67.6% of P. xylostella larvae, respectively, compare to 72.1% for the water control. After ingesting indoxacarb, spinosad and λ-cyhalothrin mixed in honey-water, both the females and the males lived significantly shorter than those ingesting Bt- and azadirachtin-insecticides and the non-insecticide honey-water. Effects of leaf residues of indoxacarb, spinosad and λ-cyhalothrin varied significantly. The leaf residues of spinosad had the least effects on D. insulare adults, and 7- and 10-day-old residue only caused 5.6 and 7.4% mortality in 24 h, whereas 10-day-old leaf residues of indoxacarb and λ-cyhalothrin caused 40.7 and 57.4% mortality in 24 h, respectively.     

Effect of selected pesticides on larval mortality of the neuropteran predator,Chrysopa lacciperda Kimmins,of the lac insect,Kerria lacca (Kerr)

Laboratory bioassays were carried out to evaluate the bioefficacy of some pesticides against larval Chrysopa lacciperda Kimmins, a lac insect predator, to develop a suitable strategy for field management of this serious neuropteran pest of Indian lac insect, Kerria lacca (Kerr). Seven insecticides (lambdacyhalothrin, carbosulfan, spinosad, indoxacarb, fipronil, alphamethrin and ethofenprox) were identified based on field trials against the lac insect. They were evaluated for their bioefficacy against C. lacciperda by spraying the insect directly and by exposing the insect to a residual film. Direct spray of lambdacyhalothrin (0.005 and 0.008% a.i.), carbosulfan (0.02 and 0.03% a.i.), fipronil (0.005 and 0.01% a.i.), alphamethrin (0.005 and 0.01% a.i.), spinosad (0.02% a.i.), indoxacarb (0.02% a.i.), and ethofenprox (0.02% a.i.) exhibited 100% mortality of C. lacciperda within 24 h of treatment. Fipronil (0.005 and 0.01% a.i.) and indoxacarb (0.02% a.i.) were equally effective as 100% mortality was observed within 24 h of treatment with both modes of treatment. For most insecticides, direct spray was more effective compared to residual films. It is therefore, suggested that lambdacyhalothrin, carbosulfan, indoxacarb, spinosad, fipronil, alphamethrin and ethofenprox shall be incorporated in IPM programs for the effective management of this neuropteran predator of lac insect without adversely affecting the lac insect.     

Development and stability of insecticide resistance in the leafminer Liriomyza trifolii (Diptera: Agromyzidae) to cyromazine, abamectin, and spinosad

Three populations of the leafminer, Liriomyza trifolii (Burgess), were collected from commercial ornamental production greenhouses in the United States and tested for susceptibility to three commercial insecticides. A leaf dip bioassay of leaves containing young (1-2-d-old) larvae was used. Based on larval mortality and compared with a susceptible laboratory reference colony, the three strains varied in spectrum and level of resistance to the insecticides. CA-1, collected from Gerbera daisy, was moderately resistant to cyromazine (18.1-fold) and abamectin (22.0-fold), but highly resistant to spinosad (> 188-fold). CA-2, collected from chrysanthemums, was not resistant to abamectin, had a low level of resistance to cyromazine (8.2-fold), but was extremely resistant to spinosad (1,192-fold). GA-1, collected from chrysanthemums, had very low levels of resistance to cyromazine (5.4-fold) and spinosad (1.9-fold) but was moderately resistant to abamectin (30.6-fold). When reared in the absence of insecticide selection pressure, all three strains reverted to approximately the level of the reference strain. The CA-1 strain reverted in nine generations to cyromazine; however, the lowest levels of abamectin and spinosad resistance reverted to was 3.1-fold at F8 and 3.2 at the F10, respectively. The CA-2 strain reverted in five generations to both cyromazine and spinosad. GA-1 reverted in five generations to abamectin. Based on the results, resistance to these three insecticides was unstable. Additionally, there was no cross-resistance among these three insecticides.     

Acaricidal properties of spinosad against Tetranychus urticae and Panonychus ulmi (Acari: Tetranychidae)

Laboratory bioassays were conducted to characterize the activity of the insecticide spinosad against the twospotted spider mite, Tetranychus urticae Koch, and European red mite, Panonychus ulmi (Koch) (Acari: Tetranychidae). T. urticae females and larvae were individually placed on bean, Phaseolus vulgaris L. (Fabaceae), leaf disks treated with four rates of spinosad (25, 55, 121, and 266 ppm) and a water control. Significantly fewer T. urticae completed development on any spinosad rates (<15%) compared with the control (>85%), whereas spinosad exhibited no significant effects on P. ulmi development; 72.5 and 83.1% of P. ulmi completed development on apple (Malus pumila P. Mill, Rosaceae) leaf disks treated with 75 ppm spinosad and the control, respectively. T. urticae adult females placed on spinosad-treated disks had significantly higher mortality and lower oviposition rates compared with the water control; no significant mortality effects were observed until 3 d after placing adults on leaf disks. In choice tests where half of a bean leaf was treated with 55 ppm spinosad transversally or longitudinally, T. urticae females were repelled by spinosad and largely oviposited and fed on nonspinosad treated areas. Spinosad did not affect the behavior of P. ulmi females. When T. urticae females were released on potted bean plants (two-leaf stage) in which leaves received spinosad sprays on the adaxial or abaxial leaf surfaces, or complete spinosad coverage on one or two of the leaves, mite population increase lagged significantly behind those released on control plants. These results indicate that spinosad has significant acaricidal effects against T. urticae but not P. ulmi.