Laboratory and field evaluation of spinosad against the gypsy moth,Lymantria dispar

The toxicity of the naturally derived insecticide spinosad was tested against the gypsy moth, Lymantria dispar. Bioassays using red oak leaf disks, treated with spinosad in a Potter spray tower, yielded an LC₅₀ value of 0.0015 µg AI cm⁻² (3‐day exposure; 13‐day evaluation; 2nd instar larvae). Applied to foliage to run‐off in the laboratory (potted red oak seedlings) and the field (4 m‐tall birch trees), spinosad effectively controlled 2nd instar larvae at concentrations ranging from 3 to 50 mg litre⁻¹. Toxicity in the laboratory, and efficacy and persistence in the field, were comparable to those achieved with the insecticide permethrin. Laboratory studies supported field observations that control was achieved in part by knockdown due to paralysis. In addition, laboratory results demonstrated that crawling contact activity may play an important role in field efficacy; 50% of treated larvae were paralyzed 16 h after a 2‐min crawling exposure to glass coated with a 4 mg litre⁻¹ spinosad solution. © 2000 Society of Chemical Industry     

Susceptibility of tomato borer,Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) populations from Turkey to 7 different insecticides in laboratory bioassay

The tomato borer, Tuta absoluta (Meyrick), was first recorded in Turkey in August 2009 and rapidly became a serious pest in the Mediterranean and Aegean coastal regions in field and greenhouse grown tomatoes. Currently, insecticides are considered one of the major tools for the management of T. absoluta in Turkey. This study, investigated the efficacy of 7 different insecticides, against T. absoluta in laboratory bioassays. To determine the lethal concentration (LC) values and feeding activity of the larvae, tomato leaf parts mined by 1–3 day old L1 larvae were dipped into different insecticide concentrations. Mortality was recorded 5 days after insecticide treatments. Spinosad, chlorantraniliprole + abamectin or indoxacarb treatment resulted in 100% mortality with minimal or no feeding in all populations at their recommended doses of 120, 50.4 and 60 mg a.s. L^?1, respectively. In general, the LC₉₉ values of populations for these insecticides were similar and also lower than that of the recommended field doses. The effect of pyridalyl was low, resulting in low mortality with serious feeding damage at the dose of 125 mg a.s. L^?1. The efficacies of abamectin, metaflumizone and azadirachtin were found to be moderate to low at the recommended doses (4.5, 240 and 50 mg a.s. L^?1, respectively). However, these insecticides may affect pupation and adult emergence rates hence further studies are recommended to investigate these insecticides.     

Beet armyworm (Spodoptera exigua) resistance to spinosad

Susceptibility to spinosad (Success®/Tracer®) of beet armyworm (Spodoptera exigua) from the southern USA and Southeast Asia was determined through exposure of second‐ and third‐instar larvae to dipped cotton leaves. LC₅₀ estimates of susceptibility of second‐ and third‐instar larvae of field populations ranged from 0.279 to 6.14 and 0.589 to 14.0 mg spinosad litre⁻¹, respectively. A Thailand population was 22‐ and 24‐fold less susceptible than the six other US field populations evaluated, and 85‐ and 58‐fold less susceptible than a reference laboratory population, respectively. From these results, we initiated experiments to test the hypothesis that the Thailand population was resistant to spinosad. F₁ crosses between the resistant Thailand population and a susceptible reference strain yielded individuals that were 22‐fold less sensitive to spinosad than the susceptible parent. This same resistant strain exhibited significantly greater survivorship on plants treated with spinosad in the field. Lastly, selection of an Arizona population resulted in a significant reduction in susceptibility to spinosad, further substantiating the hypothesis of a genetic basis for resistance to spinosad. These findings indicate a vulnerability of this new insecticide to resistance development in beet armyworm and should serve as a warning against excessive use of it. © 2000 Society of Chemical Industry     

Mortality and reproductive effects of ingested spinosad on adult bollworms

BACKGROUND: Upon emergence from their pupal cells, bollworm, Helicoverpa zea (Boddie), adults actively seek and feed on plant exudates before they disperse and reproduce on suitable host plants. This nocturnal behavior of the bollworm may be exploited as a pest management strategy for suppression of the insect by using an attractant/stimulant mixed with an insecticide to induce feeding to cause adult mortality or reproductive reduction/inhibition. This study aimed to determine in the laboratory whether or not spinosad when mixed with sucrose solution as a feeding stimulant and ingested by bollworm could influence mortality and reproduction of the insect. RESULTS: Sublethal concentrations of spinosad fed to laboratory‐reared females confined with males significantly reduced percentage hatch of eggs at 0.1 mg L^?1, and it was reduced to near zero at 2.5 mg L^?1 when compared with females fed 2.5 M sucrose solutions only. The lethal concentration (LC₉₉) for males captured from the field in sex‐pheromone‐baited traps was 73 mg L^?1 for 24 h response. Proboscis extension response was not inhibited significantly even at 10 g L^?1. In spite of a 137‐fold increase in lethal dose concentration, spinosad did not inhibit feeding. CONCLUSION: A detailed study of laboratory‐reared and field‐collected bollworm adults relative to mortality and reproduction after ingestion of spinosad indicates that spinosad would be useful in an attract‐and‐kill strategy to control the insect when mixed with a feeding attractant/stimulant. Field validation of the data is warranted. Published 2010 by John Wiley & Sons, Ltd.     

Systemic effects of thiamethoxam and chlorantraniliprole seed treatments on adult Lissorhoptrus oryzophilus (Coleoptera: Curculionidae) in rice

BACKGROUND: Feeding assays using adult rice water weevils and foliage of plants treated as seeds with chlorantraniliprole and thiamethoxam at different rates were conducted to evaluate the systemic adulticidal and feeding effects. Dose–mortality relationships were determined for thiamethoxam seed treatments by combining leaf area lost due to feeding and insecticide residues analyzed by LC/MS/MS. Changes in adulticidal activity of thiamethoxam were also investigated by contrasting adult mortalities at the 5–6‐leaf and tillering stages of rice. RESULTS: Adult weevil mortalities and leaf consumption rates on foliage were affected in thiamethoxam but not in chlorantraniliprole treatments when rice was at the 6–7‐leaf stage. The LD₅₀ for weevils feeding on thiamethoxam‐treated rice at the 2–3‐leaf stage was 447 pg insecticide weevil^?1 (95% CL: 25–830 pg weevil^?1) but was lower (142 pg weevil^?1; 95% CL: 102–180 pg weevil^?1) in experiments with 3–4‐leaf‐stage plants. Mortalities on leaves from 5–6‐leaf‐stage plants were consistently higher than on leaves from tillering plants. Thiamethoxam residues measured by ELISA increased with seed treatment rate and differed between plant stages. CONCLUSION: The LD₅₀ values developed in this study are the first values for leaf‐feeding insects on foliage of plants treated as seeds with thiamethoxam. The attrition of adulticidal activity of thiamethoxam in foliage of older plants may help to explain the reduced effectiveness of seed treatments against rice water larvae that is seen at later stages of rice growth in field studies. The differential activity of these two seed treatments on adults suggests that adult mortality contributes to the field efficacy of thiamethoxam but not to that of chlorantraniliprole. Copyright © 2012 Society of Chemical Industry     

Residual toxicity and sublethal effects of chlorantraniliprole on Plutella xylostella (lepidoptera: plutellidae)

BACKGROUND: The diamondback moth (DBM), Plutella xylostella (L.), is the most important pest of cruciferous vegetables in the world. Chlorantraniliprole is a novel anthranilic diamide insecticide registered for the control of lepidopteran pests. The dose response, residual toxicity and sublethal effects of chlorantraniliprole applied for 48 h at LC₁₀ (0.02 mg L^?1) and LC₂₅ (0.06 mg L^?1) on P. xylostella were investigated. RESULTS: Leaf‐dip bioassays showed that chlorantraniliprole had a high level of toxicity against larvae of P. xylostella, and the 48 h LC₅₀ values were 0.23 and 0.25 mg L^?1 for a susceptible and field strain respectively. Chlorantraniliprole also had a long‐lasting effect when the larvae were exposed to chlorantraniliprole field sprayed on radish seedlings. Sublethal effects of chlorantraniliprole were indicated by reduced pupation, pupal weight and adult emergence rates. There was also an increase in the duration of female preoviposition period, decreased fecundity and egg hatch and decreased survival rates of the offspring. The mean values of the net reproductive rate (R₀), intrinsic rate of increase (r_m), finite rate of increase (λ) were significantly lower in the treatment than in control groups. CONCLUSIONS: These results indicate that chlorantraniliprole is effective against P. xylostella. The sublethal concentrations of chlorantraniliprole may reduce the population growth of P. xylostella by decreasing its survival and reproduction, and by delaying its development. Copyright © 2012 Society of Chemical Industry     

多杀菌素对菜蛾绒茧蜂的致死和亚致死效应

以对多杀菌素高抗的小菜蛾纯合子品系作寄主饲养菜蛾绒茧蜂,用多杀菌素田间推荐使用浓度(25 mg/L)分别处理处于卵期、幼虫期和蛹期的绒茧蜂,其中卵期和幼虫期通过处理寄主幼虫间接处理,并测定该药剂对成虫的毒力,系统观察该杀虫剂对绒茧蜂各虫期的致死和亚致死作用。与对照相比,绒茧蜂卵期或幼虫期其寄主受药后,可导致蜂幼虫死于寄主体内或啮出寄主的过程中,使结茧化蛹率下降43% ~56%,成虫羽化率下降19% ~33%,成蜂雌性比下降11% ~25%,而成虫大小、寿命和寄生力未受显著影响;在蛹期受药使成虫羽化率下降10%,成蜂寿命缩短,但对成虫寄生力无显著影响;对成虫24 h的LC99为4.31 mg/L。结果表明,多杀菌素可进入寄主作用于其体内的蜂卵和幼虫,或直接作用于蜂蛹和成虫,从而对绒茧蜂各个虫态产生显著的致死和亚致死效应,尤以对成虫高毒。     

Paradoxical effects of sublethal exposure to the naturally derived insecticide spinosad in the dengue vector mosquito,Aedes aegypti

BACKGROUND: Recent studies have indicated that spinosad, a mixture of two tetracyclic macrolide compounds produced during the fermentation of a soil actinomycete, may be suitable for controlling a number of medically important mosquito species, including the dengue vector, Aedes aegypti L. The authors determined the effects of a 1 h exposure to a 50% lethal concentration (LC₅₀) of spinosad in the larval stage on the wing length, longevity and reproductive capacity of the adult survivors. RESULTS: The LC₅₀ of spinosad for a wild‐caught population of Ae. aegypti from Chiapas, southern Mexico, was estimated to be 0.06 mg AI L^?1 in late third instars. Paradoxically, the female survivors of exposure to this concentration were significantly larger (as determined by wing length) laid more eggs, but were slightly less fertile than control females. This was probably due to elimination of the smaller and more susceptible fraction of mosquito larvae from the experimental population following spinosad treatment. Male survivors, in contrast, were significantly smaller than controls. No significant differences were detected in the adult longevity of treated and control insects of either sex. CONCLUSIONS: The increase in reproductive capacity of spinosad‐treated females did not compensate for mortality in the larval stage and would be unlikely to result in population increase in this mosquito under the conditions that were employed. Sustained‐release formulations would likely assist in minimizing the occurrence of sublethal concentrations of this naturally derived product in mosquito breeding sites. Copyright © 2008 Society of Chemical Industry     

Residual activity of spinosad applied as a soil drench to tomato seedlings for control of Tuta absoluta

BACKGROUND

Tuta absoluta (Lepidoptera: Gelechiidae) is difficult to control by means of foliar insecticides, partly because of the endophytic feeding behavior of its larvae. The biopesticide spinosad is applied as a foliar spray for control of T. absoluta and has systemic properties when applied as a soil drench to the growing medium of tomato plants. The aims of this study were to determine the: (i) instar-dependent tolerance of larvae to spinosad; (ii) efficacy of spinosad drench application for the control of larvae; (iii) residual period of systemic activity of spinosad in leaves and fruit after drenching; and (iv) effect of spinosad drenching on tomato plant growth parameters.

RESULTS

The estimated LC₅₀ value (Lethal Concentration at which 50% of the larvae died) differed between instars. The LC₅₀ for second-instar larvae (0.41 ppm) to spinosad was significantly lower than that for third- (0.64 ppm) and fourth-instar (0.63 ppm) larvae. The LC₈₀ value (Concentration at which 80% of the larvae died) for fourth-instar larvae (2.48 ppm) was 2.6- and 1.7-fold higher than that for the second- and third-instar larvae, respectively. The spinosad concentration recorded in leaves at 25 days after treatment (DAT; 0.26 μg g⁻¹) was significantly lower than that in leaves sampled at 3, 10 and 15 DAT. High larval mortalities were, however, recorded for the duration of the experiment, which lasted 25 days (equivalent to one T. absoluta generation).

CONCLUSION

Systemic spinosad effectively controlled T. absoluta larvae over a prolonged period. However, drenching this insecticide violates the recommendation of the Insecticide Resistance Action Committee to avoid treating consecutive insect generations with the same mode of action and can therefore result in the evolution of insecticide resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Identification of new limonoids from Swietenia and their biological activity against insects

BACKGROUND: Natural limonoids are one group of compounds being studied for their insecticidal properties. To discover new limonoids with better activities, analogs were prepared via acylation and hydrolysis, and bioassayed. RESULTS: Analogs were identified using one‐ and two‐dimensional (COSY, HMQC and HMBC) ¹H and ¹³C NMR, IR and MS. 3‐O‐Isovalerylswietenolide (13) and 3‐O‐isobutyrylswietenolide (14) showed excellent antifeedant activity, with DC₅₀ values of 0.19 and 0.009 mg L^?1 respectively, compared with the natural limonoid swietenolide (80.6 mg L^?1) against fourth‐instar Spodoptera frugiperda (JE Smith) larvae. CONCLUSION: This work shows that limonoid analogs prepared through semi‐synthesis can be used as lead compounds for the development of new insecticides. Copyright © 2010 Society of Chemical Industry     

Design, synthesis and insecticidal activities of novel pyrazole amides containing hydrazone substructures

BACKGROUND: Pyrazole and hydrazone derivatives possess good insecticidal activities; their substructural units are widely used in pesticide design. In an effort to discover new molecules with good insecticidal activities, a series of pyrazole amide derivatives containing hydrazone substructures were synthesised and bioassayed. RESULTS: Bioassays demonstrated that some of the title compounds exhibited notable control of Plutella xylostella (Linnaeus), Helicoverpa armigera (Hübner), Culex pipiens pallens, Laphygma exigua (Hübner), Spodoptera litura (Fabricius), Nilaparvata lugens (Stål) and Rhopalosiphum maidis (Fitch) at 5, 10, 0.25, 200, 20, 100 and 500 mg L^?1 respectively. Comparative molecular field analysis (CoMFA) based on the bioactivities for P. xylostella was studied; the values of q² and r² for the CoMFA model were 0.701 and 0.964 respectively. CONCLUSION: Some of the title compounds displayed good and broad‐spectrum insecticidal activities against different insect species; the CoMFA model revealed that a bulky and negatively charged group at the 4‐position of benzene could enhance insecticidal activity. These results could provide useful information for the design of novel insecticide containing substructural units of pyrazole amide and hydrazone. Copyright © 2011 Society of Chemical Industry     

Compatibility of spinosad with predaceous mites (Acari) used to control Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

BACKGROUND: Spinosad is a biopesticide widely used for control of Frankliniella occidentalis (Pergande). It is reported to be non‐toxic to several predatory mite species used for the biological control of thrips. Predatory mites Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) and Hypoaspis miles (Berlese) have been used for control of F. occidentalis. This study investigated the impact of direct and residual toxicity of spinosad on F. occidentalis and predatory mites. The repellency of spinosad residues to these predatory mites was also investigated. RESULTS: Direct contact to spinosad effectively reduced the number of F. occidentalis adults and larvae, causing > 96% mortality. Spinosad residues aged 2–96 h were also toxic to F. occidentalis. Direct exposure to spinosad resulted in > 90% mortality of all three mite species. Thresholds for the residual toxicity (contact) of spinosad (LT₂₅) were estimated as 4.2, 3.2 and 5.8 days for T. montdorensis, N. cucumeris and H. miles respectively. When mites were simultaneously exposed to spinosad residues and fed spinosad‐intoxicated thrips larvae, toxicity increased. Residual thresholds were re‐estimated as 5.4, 3.9 and 6.1 days for T. montdorensis, N. cucumeris and H. miles respectively. Residues aged 2–48 h repelled T. montdorensis and H. miles, and residues aged 2–24 h repelled N. cucumeris. CONCLUSION: Predatory mites can be safely released 6 days after spinosad is applied for the management of F. occidentalis. Copyright © 2011 Society of Chemical Industry     

Larvicidal activity of Cnidium monnieri fruit coumarins and structurally related compounds against insecticide-susceptible and insecticide-resistant Culex pipiens pallens and Aedes aegypti

BACKGROUND: An assessment was made of the toxicity of imperatorin and osthole identified in Cnidium monnieri fruit, 11 related compounds and five insecticides to larvae from insecticide‐susceptible Culex pipiens pallens (KS‐CP strain) and Aedes aegypti and wild C.p. pallens (YS‐CP colony) using a direct‐contact mortality bioassay. Results were compared with those of the conventional larvicide temephos. RESULTS: Imperatorin (LC₅₀ = 3.14 and 2.88 mg L^?1) was 1.9‐, 3.7‐ and 4.2‐fold and 2.4‐, 4.5‐ and 4.6‐fold more toxic than isopimpinellin, isoimperatorin and osthole against susceptible C. p. pallens and A. aegypti larvae respectively. Overall, all of the compounds were less toxic than temephos (0.011 and 0.019 mg L^?1). The toxicity of these compounds was virtually identical against larvae from the two Culex strains, even though YS‐CP larvae were resistant to fenthion (resistance ratio RR = 390), deltamethrin (RR = 164), cyfluthrin (RR = 14) and temephos (RR = 14). This finding indicates that the coumarins and the insecticides do not share a common mode of action. The structure–activity relationship indicates that the chemical structure and alkoxy substitution and length of the alkoxyl side chain at the C8 position are essential for imparting toxicity. CONCLUSION: The C. monnieri fruit‐derived coumarins and the related coumarins described merit further study as potential insecticides or lead molecules for the control of insecticide‐resistant mosquito populations. Copyright © 2012 Society of Chemical Industry     

Lethal and sublethal side-effect assessment supports a more benign profile of spinetoram compared with spinosad in the bumblebee Bombus terrestris

BACKGROUND: This study was undertaken to identify the potential side effects of the novel naturalyte insecticide spinetoram in comparison with spinosad on the bumblebee Bombus terrestris L. The potential lethal effects together with the ecologically relevant sublethal effects on aspects of bumblebee reproduction and foraging behaviour were evaluated. Bumblebee workers were exposed via direct contact with wet and dry residues under laboratory conditions to spinetoram at different concentrations, starting from the maximum field recommended concentration (MFRC) and then different dilutions (1/10, 1/100, 1/1000 and 1/10 000 of the MFRC), and compared with spinosad. In addition, the side effects via oral exposure in supplemented sugar water were assessed. RESULTS: Direct contact of B. terrestris workers with wet residues of spinosad and spinetoram showed spinetoram to be approximately 52 times less toxic than spinosad, while exposure to dry residues of spinetoram was about 8 times less toxic than exposure to those of spinosad. Oral treatment for 72 h (acute) indicated that spinetoram is about 4 times less toxic to B. terrestris workers compared with spinosad, while exposure for a longer period (i.e. 11 weeks) showed spinetoram to be 24 times less toxic. In addition, oral exposure to the two spinosyns resulted in detrimental sublethal effects on bumblebee reproduction. The no observed effect concentration (NOEC) for spinosad was 1/1000 of the MFRC, and 1/100 of the MFRC for spinetoram. Comparison between the chronic exposure bioassays assessing the sublethal effects on nest reproduction, with and without allowing for foraging behaviour, showed that the respective NOEC values for spinosad and spinetoram were similar over the two bioassays, indicating that there were no adverse effects by either spinosyn on the foraging of B. terrestris workers. CONCLUSION: Overall, the present results indicate that the use of spinetoram is safer for bumblebees by direct contact and oral exposure than the use of spinosad, and therefore it can be applied safely in combination with B. terrestris. Another important conclusion is that the present data provide strong evidence that neither spinosyn has a negative effect on the foraging behaviour of these beneficial insects. However, before drawing final conclusions, spinetoram and spinosad should also be evaluated in more realistic field‐related situations for the assessment of potentially deleterious effects on foraging behaviour with the use of queenright colonies of B. terrestris. Copyright © 2011 Society of Chemical Industry     

多杀霉素亚致死浓度对棉铃虫幼虫生理及代谢的影响

为明确田间使用多杀霉素亚致死浓度对棉铃虫Helicoverpa armigera幼虫的影响,用含多杀霉素亚致死浓度LC₂₅的人工饲料持续饲喂棉铃虫3龄幼虫,并对饲喂后其体重、取食量、累计蛹化率、蛹发育历期和蛹重等生长发育及脂肪体内甘油三脂（triglyceride,TG）含量和相关基因SREBP、FAS和HSL表达情况进行测定。结果表明,多杀霉素对棉铃虫的亚致死浓度LC₂₅为0.21 mg/kg;多杀霉素亚致死浓度处理4~6 d后,棉铃虫3龄幼虫体重分别为0.065、0.263和0.329 g,较对照显著降低;处理6 d后,其取食量为0.082 g,较对照显著降低;处理4~7 d后,其累计化蛹率分别为60.90%、63.20%、65.50%和65.50%,较对照显著降低。多杀霉素亚致死浓度处理后,棉铃虫蛹发育历期由对照9.89 d显著延长至10.74 d,单头蛹重为0.274 g,显著低于对照的0.324 g;其脂肪体TG含量较对照显著降低。多杀霉素亚致死浓度处理24~72 h后,参与脂肪酸合成信号通路中重要基因SREBP和FAS的相对表达量较对照均显著下调,而参与脂肪代谢的重要基因HSL则较对照显著上调。     

Risk assessment of thiacloprid and its chemical decontamination on eggplant,Solanum melongena L.

BACKGROUND: Thiacloprid [(Z)‐3‐(6‐chloro‐3‐pyridylmethyl)‐1,3‐thiazolidin‐2‐ylidenecyanamide; Calypso^?] is a systemic insecticide having persistence in the plant system. It was chosen for the management of the eggplant shoot and fruit borer, Leucinodes orbonalis Guen. Management of this insect pest is difficult because it harbours inside the shoot and fruit portions of eggplant. The persistence of thiacloprid on eggplant has not been studied in India. The Food and Agriculture Organisation (FAO) has proposed its maximum residue limit (MRL) on eggplant as 0.7 mg kg^?1, and there is a need to validate this value. Since residues were found to be above this level, five different decontamination agents were tested for the decontamination of thiacloprid from eggplant. RESULTS: The half‐life of thiacloprid was 11.1 and 11.6 days from trials in 2 years. Safety factors such as theoretical maximum daily intake (TMDI) and maximum permissible intake (MPI) were used to arrive at a risk assessment to human health from the analytical data obtained from the field trials. Thiacloprid at the doses tested (30 and 60 g AI ha^?1) was not effective in managing eggplant fruit borer. A waiting period of 3 days before harvest of the fruits after insecticide application and a processing factor (PF) could not ensure a sufficient margin of safety (MOS). Subjecting the data to a processing factor of 60% could not bring the residues below the proposed MRL. CONCLUSION: Thiacloprid is not found to be an appropriate and effective agent for application to eggplant. Either the proposed MRL needs to be revised or good agricultural practice involving thiacloprid for plant protection in eggplant cultivation is required. Copyright © 2008 Society of Chemical Industry     

The discovery of SYP‐10913 and SYP‐11277: novel strobilurin acaricides

BACKGROUND: As previously reported, methyl (E)‐2‐[2‐(2‐phenylamino‐6‐trifluoromethylpyrimidin‐4‐yloxymethyl)phenyl]‐3‐methoxyacrylate has proven to be a new lead with highly acaricidal activity. Following on from this, in an effort to discover new strobilurin analogues with improved activity, a series of substituted pyrimidines were synthesised and bioassayed. RESULTS: All compounds were characterised by ¹H NMR, IR, MS and elemental analysis. Preliminary bioassays demonstrated that some of the title compounds exhibited notable control of Tetranychus cinnabarinus (Boisd.) at 1.25 mg L^?1. The relationship between structure and acaricidal activity is discussed. CONCLUSION: Two compounds of particular interest, 6j (SYP‐10913) and 6k (SYP‐11277), exhibited potent acaricidal activity. The acaricidal potencies of these analogues are higher than that of fluacrypyrim in greenhouse applications, and are comparable with those of commercial acaricides such as spirodiclofen and propargite in field trials. Copyright © 2011 Society of Chemical Industry     

Toxicological and biochemical response to azinphos-methyl in Cydia pomonella L. (Lepidoptera: Tortricidae) among orchards from the Argentinian Patagonia

BACKGROUND: Azinphos‐methyl is the main insecticide used to control codling moth on apple and pears in Northern Patagonia. The aim of this study was to evaluate the toxicological and biochemical response of diapausing larvae of codling moth in orchards subjected to different insecticide selection pressure. RESULTS: Dose–mortality assays with azinphos‐methyl in diapausing larvae of Cydia pomonella L. showed significant differences between the LD₉₅ from a population collected in one untreated orchard (2.52 µg moth^?1) compared with that in a laboratory‐susceptible population (0.33 µg moth^?1). Toxicity to azinphos‐methyl in field populations of diapausing larvae collected during 2003–2005 was evaluated by topical application of a discriminating dose (2.5 µg moth^?1) that was obtained from larvae collected in the untreated orchard (field reference strain). Significantly lower mortality (37.71–84.21%) was observed in three out of eight field populations compared with that in the field reference strain. Most of the field populations showed higher esterase activity than that determined in both the laboratory susceptible and the field reference strains. Moreover, there was a high association between esterase activity and mortality (R² = 0.64) among the field populations. On the other hand, a poor correlation was observed between glutathione S‐transferase activity and mortality (R² = 0.33) among larvae collected from different orchards. CONCLUSIONS: All the field populations evaluated exhibited some degree of azinphos‐methyl tolerance in relation to the laboratory susceptible strain. Biochemical results demonstrated that esterases are at least one of the principal mechanisms involved in tolerance to this insecticide. Copyright © 2008 Society of Chemical Industry     

Toxicity,persistence and efficacy of indoxacarb and two other insecticides on Plutella xylostella (Lepidoptera: Plutellidae) immatures in cabbage

Toxicities of indoxacarb on eggs and 5-day-old larvae of diamondback moth, Plutella xylostella L., on cabbage and those of field-aged leaf residues on 5-day-old larvae were determined in the laboratory. The persistence and efficacies of indoxacarb and two other newer insecticides (spinosad and emamectin benzoate) to P. xylostella were tested under field conditions. Results from laboratory bioassays indicate that indoxacarb was highly toxic to P. xylostella larvae through food ingestion, with LC₅₀ and LC₉₀ values of 24.1 and 90.1 mg AI l ^{- 1}, respectively. However, indoxacarb had no significant effects on eggs and larvae through direct contact compared with water control. The toxicity of field-aged leaf residues of indoxacarb (0-, 3-, 5-, 7-, 10-, 14-, 17- and 21-day-old residues) declined slowly and gradually under the field conditions in South Texas. Almost all larvae died on day 5 after feeding on the leaves with 0 - 14-day residue, and the mortalities were as high as 94 and 78% for the 14- and 17-day-old leaf residues. With one application, indoxacarb suppressed P. xylostella larvae below the economic threshold for 14 - 21 days. Two field trials showed that indoxacarb at 0.05 - 0.07 kg AI ha ^{- 1} was effective against P. xylostella, providing marketable cabbage with three applications per season. In addition, indoxacarb was as effective as spinosad, and significantly more effective than emamectin benzoate.     

Testing insecticide resistance management strategies: mosaic versus rotations

BACKGROUND: Developing scientifically valid, economically acceptable insecticide resistance management (IRM) programs is critical for sustainable insect management. The diamondback moth, Plutella xylostella (L.), has demonstrated an ability to develop resistance to many different classes of insecticides, including proteins produced by the bacterium Bacillus thuringiensis Berliner (Bt). Recently it has developed resistance to the novel compounds spinosad and indoxacarb. In greenhouse cage experiments, a laboratory‐selected population of P. xylostella resistant to spinosad, indoxacarb and Bt was used to compare population growth and resistance evolution if these three insecticides were rotated or used in a mosaic fashion. RESULTS: The average population density through nine generations was lowest in the treatment in which the insecticide was rotated every generation (R‐1) (x? = 20.7 ± 3.20) compared with the treatment in which the insecticide was rotated every third generation (R‐3) (x? = 41.4 ± 17.6) or where the insecticides were applied as a mosaic (M) (x? = 41.8 ± 6.53). After nine generations, the survival of resistant individuals increased for each insecticide (7.2–73.5%) compared with the population without selection (CK) (0.73–3.1%). Survival on spinosad was significantly lower (23.7%) in the single‐generation rotation than for the other two treatments, both of which exceeded 72%. The calculated survival on all three insecticides treated simultaneously, according to the survival on each insecticide, was 0.26, 0.81 and 1.6% for R‐1, R‐3 and M treatments respectively. CONCLUSION: Results of both population density and resistance development indicated that insecticide rotation every generation was better for IRM than if the insecticide was rotated every third generation or if the three insecticides were applied as a mosaic. Copyright © 2010 Society of Chemical Industry