Resistance of Pakistani field populations of spotted bollworm Earias vittella (Lepidoptera: Noctuidae) to pyrethroid,organophosphorus and new chemical insecticides

BACKGROUND: The spotted bollworm Earias vittella (Fab.) is a serious pest of cotton and okra in Pakistan. Owing to persistent use of insecticides, this pest has developed resistance, especially to pyrethroids. The present studies aimed at determining the extent of resistance to pyrethroid, organophosphorus and new chemical insecticides in Pakistani populations of E. vittella. RESULTS: Field populations of E. vittella were monitored at Multan, Pakistan, from 1999 to 2007 for their resistance against six pyrethroid, four organophosphorus and six new chemical insecticides using a leaf‐dip bioassay. Of the pyrethroids, resistance was generally low to zeta‐cypermethrin and moderate to high or very high to cypermethrin, deltamethrin, esfenvalerate, bifenthrin and lambda‐cyhalothrin. Resistance to organophosphates chlorpyrifos, profenofos, triazophos and phoxim was recorded at very low to low levels. Among new chemicals, E. vittella had no or a very low resistance to spinosad, emamectin benzoate and methoxyfenozide, a very low to low resistance to abamectin, a very low to moderate resistance to indoxacarb and a moderate resistance to chlorfenapyr. CONCLUSION: The results indicate a lack of cross‐resistance between pyrethroid and organophosphorus insecticides in E. vittella. Rotation of insecticides showing no, very low or low resistance, but belonging to different insecticide classes with unrelated modes of action, may prevent or mitigate insecticide resistance in E. vittella. Copyright © 2009 Society of Chemical Industry     

Potentiation/antagonism of deltamethrin and cypermethrins with organophosphate insecticides in the cotton bollworm, Helicoverpa armigera (Lepidoptera: Noctuidae)

The joint action of pyrethroids deltamethrin and cypermethrins in combination with organophosphates ethion, profenofos, chlorpyrifos, quinalphos, and triazophos was studied on putatively resistant field populations of Helicoverpa armigera from Pakistan by using a leaf-dip method. Ethion produced a good potentiation with deltamethrin, cypermethrin, alphacypermethrin, and zetacypermethrin, whereas profenofos, chlorpyrifos, quinalphos, and triazophos exhibited an antagonism with deltamethrin as well as cypermethrins. Implications of using mixtures for counteracting insecticide resistance are discussed.     

Efficacy of insecticide mixtures against pyrethroid‐ and organophosphate‐resistant populations of Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) is an important pest worldwide, with over 112 host plants, and is exposed to insecticides throughout the year, resulting in the rapid development of resistance. Insecticide mixtures can delay the development of resistance more effectively than sequences or rotations. Cypermethrin, deltamethrin, profenofos, chlorpyrifos and fipronil were assessed separately and in mixtures against laboratory susceptible S. litura and two field‐collected populations. RESULTS: The field‐collected population from Khanewal (KWL) was significantly more resistant to cypermethrin, deltamethrin, chlorpyrifos and profenofos than one collected from Muzaffar Garh (MGH). Mixtures of cypermethrin + chlorpyrifos or profenofos and of deltamethrin + chlorpyrifos or profenofos at 1:1, 1:10 and 1:20 ratios significantly increased (P < 0.01) toxicity to cypermethrin and deltamethrin in field populations. The combination indices of cypermethrin + chlorpyrifos at 1:1 and 1:10 ratios and cypermethrin + fipronil at 1:1, 1:10 and 1:20 ratios for the KWL strain and of cypermethrin + profenofos or fipronil at 1:1, 1:10 and 1:20 ratios for MGH were significantly below 1, suggesting synergistic interactions. The inhibitors DEF and PBO largely overcame resistance to deltamethrin, cypermethrin and profenofos, suggesting that resistance to the insecticides was associated with esterase and monooxygenase detoxification respectively. CONCLUSION: Chlorpyrifos, profenofos and fipronil could be used in mixtures to restore cypermethrin and deltamethrin susceptibility. These findings may have considerable practical implications for S. litura resistance management. Copyright © 2008 Society of Chemical Industry     

Toxicity of butene-fipronil,in comparison with seven other insecticides,in <Emphasis Type="Italic">Leptinotarsa decemlineata</Emphasis> and <Emphasis Type="Italic">Drosophila melanogaster</Emphasis>

The speed of toxic action of an insecticide is an indicator for control efficacy and has considerable practical importance. For agricultural pest control, fast-acting is an important feature for an insecticide to consistently reduce the amount of feeding damage. Butene-fipronil is a novel compound obtained via the structural modification of fipronil. However, information about the toxicity and speed of toxic action is still limited. In the present paper, we compared the toxic feature of butene-fipronil with seven other insecticides, of which imidacloprid and abamectin are slow-acting insecticides, and acephate, endosulfan, methomyl, α-cypermethrin and spinosad are fast-acting insecticides. We found that the contact and stomach toxicities of butene-fipronil were among the highest ever estimated to Leptinotarsa decemlineata and Drosophila melanogaster. The speed of toxic action of butene-fipronil was determined using median lethal time (LT₅₀) at a dose (concentration) equivalent to LD₈₀ values. For L. decemlineata, the values for butene-fipronil, imidacloprid, abamectin, acephate, endosulfan, methomyl, cypermethrin and spinosad were calculated to be 39.9, 36.5, 37.5, 20.2, 22.4, 23.8, 16.4 and 23.1 h, respectively. Those for D. melanogaster were 29.8, 31.5, 29.4, 14.0, 20.3, 18.1, 13.5, and 20.1 h, respectively. ANOVA analysis showed that butene-fipronil, imidacloprid, abamectin had similar LT₅₀ values, whereas acephate, endosulfan, methomyl, spinosad and cypermethrin had comparable LT₅₀ values. Thus, butene-fipronil belongs to slow-acting insecticides. Our results provide more empirical information for butene-fipronil potential application.     

Synergist induced susceptibility of tobacco caterpillar, <Emphasis Type="Italic">Spodoptera litura</Emphasis> (Fabricius) from Kerala,India exposed to conventional insecticides

The present study was undertaken to assess the insecticide resistance developed in various field collected population of S. litura and to induce susceptibility by using the synergists. Third-instar larvae collected from three different locations of Kerala viz., Thiruvananthapuram (TVM), Pathanamthitta (PTA) and Alappuzha (ALP) were exposed to conventional insecticides like chlorpyriphos, quinalphos, lambda-cyhalothrin and cypermethrin by leaf dip bioassay and resistance ratios were calculated by using the baseline data generated for respective insecticides using susceptible strain. Resistance ratios recorded were 1965, 840 and 320 against chlorpyriphos, 605, 255 and 59 against quinalphos, 926, 250 and 108 against lambda-cyahlothrin and 2566, 534 and 396 against cypermethrin respectively for TVM, PTA and ALP populations. The effect of selected synergists viz., piperonyl butoxide (PBO), diethyl maleate (DEM) and triphenyl phosphate (TPP) was studied in combination with respective test insecticides against the highly resistant population of S.litura collected from TVM of Kerala. The population was tested with insecticide in combination of the above synergists at different ratios. When PBO, TPP and DEM at ratio of 1:4 were used the synergistic ratio was 8.47, 7.26 and 3.98 for chlorpyriphos, 6.09, 5.26 and 3.05 for quinalphos, 13.37, 4.53 and 7.39 for lambda cyhalothrin and 4.77, 3.36 and 3.40 for cypermethrin respectively. PBO showed highest synergistic activity against both the organophosphates tested followed by DEM and TPP. Highest synergistic activity against synthetic pyrethroids also was shown by PBO, followed by TPP and DEM. The results obtained from the present study revealed that PBO at 1:4 ratio showed higher synergism with the test insecticides against the resistant populations of S.litura and proved to be an effective molecule alternate for breaking the resistance against conventional organophosphates and synthetic pyrethroids.     

Broad-spectrum insecticide resistance in obliquebanded leafroller Choristoneura rosaceana (Lepidoptera: Tortricidae) from Michigan

Nineteen insecticides, belonging to nine chemical classes, were bioassayed by dietary exposure against two strains of obliquebanded leafroller, Choristoneura rosaceana, collected from Michigan apple orchards. Berrien is a putatively organophosphate-resistant strain from a commercial orchard with a history of insecticide use, and Kalamazoo a susceptible strain from an isolated and unsprayed orchard. The Berrien strain was moderately resistant (about 25-fold) to organophosphates such as azinphos-methyl and chlorpyrifos. Very low resistance (< 10-fold) was also observed to pyrethroids such as cypermethrin, zeta-cypermethrin, bifenthrin, deltamethrin and esfenvalerate, to the ecdysone agonists tebufenozide and methoxyfenozide, and to the chlorinated pyrrole chlorfenapyr. Endosulfan and carbamates such as thiodicarb, methomyl and carbaryl had low intrinsic toxicities against both strains, with little difference in sensitivity between them. There was no resistance to spinosad. Emamectin benzoate was found to be the most toxic insecticide against C rosaceana, with slightly higher lethal doses required for the Berrien strain. Unexpectedly, Berrien exhibited a very high level of resistance (> 700-fold) to indoxacarb, which has never been used in Michigan to control this insect pest. The active metabolite of indoxacarb, DCJW, was considerably more toxic than the parent compound, but the resistance against DCJW was comparable to that seen with indoxacarb. This indicates that a failure to activate indoxacarb was not the mechanism of resistance in Berrien. The low level of resistance to several chemistries recorded in Michigan C rosaceana can be managed at this stage by adopting a rotation of chemistries having different modes of action.     

Deltamethrin resistance in the cotton mealybug, <Emphasis Type="Italic">Phenacoccus solenopsis</Emphasis> Tinsley: Cross-resistance to other insecticides,fitness cost analysis and realized heritability

The cotton mealybug, Phenacoccus solenopsis Tinsley (Homoptera: Pseudococcidae) is a devastating pest that cause rigorous damage to the number of crops through feeding, managed by using various insecticides. To assess the risk of resistance and design a strategy for resistance management, a field collected population of P. solenopsis was selected with deltamethrin in the laboratory for six generations to investigate the cost to its fitness and to examine cross resistance to different insecticides. Bioassay results at G₈ showed that the deltamethrin selected population (Delta-SEL) developed a resistance ratio of 100-fold compared to that of the unselected population (UNSEL). The deltamethrin resistance population exhibited strong cross-resistance to acetamiprid and lambda-cyhalothrin, but no cross-resistance to profenofos when compared to that of the UNSEL. The relative fitness of the Delta-SEL population was 0.37, with considerably lower survival rates from crawler to second instar, fecundity, hatchability, number of next generation nymphs, net reproductive rate and biotic potential compared with that of the UNSEL. The cost of fitness associated with deltamethrin resistance was evident in the Delta-SEL population. The present study provided useful information for management strategies to overcome development of resistance.     

Resistance in field populations of <Emphasis Type="Italic">Amrasca devastans</Emphasis> (Hemiptera: Cicadellidae) to new insecticides in Southern Punjab,Pakistan

Cotton jassid, Amrasca devastans (Distant), is an economically important pest of various crops (i.e. cotton, okra, brinjal) and has the potential to become resistant against insecticides due to the intense use of insecticides in the region which entails high selection pressure. To monitor the resistance levels against recently used new chemistry insecticides (nitenpyram, spirotetramat, chlorfenapyr, fipronil, emamectin benzoate, sulfoxaflor, and flonicamid), four field populations of A. devastans collected from Khanewal, Multan, Muzaffargarh and Lodhran districts were examined by leaf dip bioassays. The results revealed the 32.95–136.47 fold resistance to nitenpyram, 23.03–56.74 fold to spirotetramat, 10.84–31.33 fold to chlorfenapyr, 1.20–9.43 fold to fipronil, 3.27–43.77 fold to emamectin benzoate, 0.66–2.81 fold to sulfoxaflor and 0.59–1.25 fold to flonicamid in different field populations, compared to the susceptible strain. Based on present study findings, it may be suggested to discontinue the use of nitenpyram, spirotetramat, chlorfenapyr and emamectin benzoate for which the populations were resistant and the rotational use of fipronil, sulfoxaflor and flonicamid for which the populations were susceptible. Proactive resistance management approaches such as judicious use of insecticides with proper dose selection, time of spray on early stages and correct method of application are necessary to prevent the development of resistance.     

Genetics and mechanism of resistance to deltamethrin in a field population of Spodoptera litura (Lepidoptera: Noctuidae)

BACKGROUND: Spodoptera litura (F.) causes enormous losses in many economically important crops. The genetics of insecticide resistance has been extensively studied in several insect pests, but there is a lack of information on S. litura. Therefore, the genetics and mechanisms of the resistance of S. litura to deltamethrin were investigated. RESULTS: Bioassays at generation G1 gave resistance ratios of 9, 5, 41, 52 and 49 for deltamethrin, cypermethrin, profenofos, chlorpyrifos and triazofos respectively, when compared with the susceptible Lab-PK strain. Bioassays at G4 with a deltamethrin-selected population (Delta-SEL) showed that selection gave resistance ratios of 63 and 7 for deltamethrin when compared with the Lab-PK and UNSEL strains respectively. Cross-resistance to other insecticides tested was observed in the selected population. A notable feature of the Delta-SEL strain was that resistance to deltamethrin, cypermethrin, profenofos and chlorpyrifos did not decline over the course of five generations. Synergism tests with microsomal oxidase (MO) and esterase-specific inhibitors indicated that the deltamethrin resistance was associated with MO and, possibly, esterase activity. Reciprocal crosses between the Delta-SEL and Lab-PK strains indicated that resistance was autosomal and incompletely dominant. A direct test of monogenic inheritance suggested that resistance to deltamethrin was controlled by more than one locus. CONCLUSION: Stability and dominance of resistance and cross-resistance suggest that insecticides with different modes of action should be recommended to reduce pyrethroid selection pressure.     

Mechanisms for multiple resistances in field populations of common cutworm, Spodoptera litura (Fabricius) in China

The mechanisms for multiple resistances had been studied with two field resistant strains and the selected susceptible and resistant strains of Spodoptera litura (Fabricius). Bioassay revealed that the two field strains were both with high resistance to pyrethroids (RR: 63-530), low to medium resistance to organophosphates and carbamates, AChE targeted insecticides (RR: 5.7-26), and no resistance to fipronil (RR: 2.0-2.2). Selection with deltamethrin in laboratory could obviously enhance the resistance of this pest to both pyrethroids and AChE targeted insecticides. Synergism test, enzyme analysis and target comparison proved that the pyrethroid resistance in this pest associated only with the enhanced activity of cytochrome P450 monooxygenase (MFO) and esterase. However the resistance to the AChE targeted insecticides depended on the target insensitivity and also the enhanced activity of MFO and esterase. Thus, the cross-resistance between pyrethroids and the AChE targeted insecticides was thought to be resulted from the enhanced activity of MFO and esterase.     

棉铃虫抗药性监测及其化学防治

1997～1998年,用浸叶接虫法测定了山西省南部棉区永济县棉铃虫对常用5种农药的抗药性,同时进行了多种农药防治棉铃虫田间药效试验研究。结果表明,永济县棉铃虫对氯氰菊酯已产生了高等水平的抗药性,对久效磷产生了中等水平的抗药性,但对灭多威仍未产生明显的抗药性。水胺硫磷、甲基对硫磷、氯氟氰菊酯、氯氰菊酯、丙·辛乳油和甲对·氯乳油等农药防治永济县二代棉铃虫效果较好     

美洲斑潜蝇幼虫对杀虫剂的敏感性研究

利用浸叶法测定了美洲斑潜蝇幼虫对１１种不同类型杀虫剂的敏感性。实验结果表明,齐墩螨素对美洲斑潜蝇具有较高的毒力,其ＬＣ_５０仅为０.０８１８ｍｇ／Ｌ,其次是菊酯类杀虫剂溴氰菊酯和高效氯氰菊酯。美洲斑潜蝇对有机磷杀虫剂马拉硫磷、敌敌畏、乙酰甲胺磷、氨基甲酸酯类杀虫剂灭多威和丁硫克百威具有较强的耐药性。     

Cross-resistance, genetics and stability of resistance to deltamethrin in a population of Chrysoperla carnea from Multan, Pakistan

Broad-spectrum insecticides are still widely being used. Chrysoperla carnea has been shown to develop resistance to the insecticides in the field. Knowledge of the evolution and genetics of resistance to insecticides in natural enemies could enable to explain how effectively natural enemies can be implemented in different IPM systems. To examine this, a population of C. carnea from Multan Pakistan was collected and was subjected to deltamethrin selection in the laboratory. Bioassays at generation G₁ gave resistance ratios of 47, 86, 137, 76 and 110 for deltamethrin, alphamethrin lambdacyhalothrin, chlorpyrifos and profenofos respectively compared with susceptible Lab-PK. Bioassays at G₄ with a deltamethrin-selected population (Delta-SEL) showed that selection gave resistance ratios of 896 and 30 for deltamethrin compared with the Lab-PK and UNSEL, respectively. Cross-resistance to other insecticides tested was observed in the selected population. A notable feature of the Delta-SEL strain was that resistance to deltamethrin, alphamethrin, lambdacyhalothrin, chlorpyrifos and profenofos did not decline over the course of four generations. Synergism tests with microsomal oxidase (MO) and esterase-specific inhibitors indicated that the deltamethrin resistance was associated with MO and, possibly, esterase activity. Reciprocal crosses between the Delta-SEL and Lab-PK strains indicated that resistance was autosomal and incompletely dominant. A direct test of monogenic inheritance suggested that resistance to deltamethrin was controlled by more than one locus. The broad spectrum of resistance, cross resistance, incompletely dominant mode of inheritance and stability of resistance to insecticides suggest that Delta-SEL population of C. carnea could be compatible with most spray programs.     

Association between insecticide use and greenhouse whitefly (Trialeurodes vaporariorum westwood) resistance to insecticides in hawaii

Susceptibility to acephate, methomyl, and permethrin was determined with laboratory bioassays for adults of greenhouse whitefly, Trialeurodes vaporariorum Westwood, from 12 to 14 sites in Hawaii. Comparisons at LC₅₀ showed up to 42-fold resistance to acephate, 36-fold resistance to methomyl, and 8-fold resistance to permethrin. Higher levels of resistance to acephate and methomyl than to permethrin are consistent with greater use of organophosphates and carbamates than pyrethroids by growers. Insecticide use varied from 1 to 98 insecticide sprays per site per season. Significant positive associations between LC₅₀ for each insecticide and frequency of application of the same insecticide were found across sites. This finding suggests that local variation in insecticide use was an important cause of variation in susceptibility.     

Dissipation of acephate, chlorpyrifos, cypermethrin and their metabolites in a humid-tropical vegetable production system

BACKGROUND: High amounts of insecticides are often used in intensive tropical vegetable production systems. Their persistence and residues in vegetables and soils need to be studied to ensure food safety and environmental stability. The dissipation of acephate, chlorpyrifos, cypermethrin and their metabolites was studied in green mustard [Brassica juncea (L.) Coss.] and soils. Two treatments, Impact 75 (acephate) and Agent 505 (cypermethrin plus chlorpyrifos), were applied 4 times at weekly intervals. RESULTS: Dissipation of acephate, chlorpyrifos and cypermethrin in green mustard and topsoils followed first‐order kinetics, with half‐lives of between 1.1 and 3.1 days in green mustard and between 1.4 and 9.4 days in topsoils (26 °C). Higher vapour pressure of insecticides and higher rainfall appeared to stimulate dissipation from the vegetable, with least effect of rainfall on chlorpyrifos. Dissipation rates in the vegetable were faster or similar (cypermethrin) to rates observed for temperate areas. Preharvest intervals of 13, 4 and 3 days were required for acephate, chlorpyrifos, cypermethrin and their metabolites to comply with the tolerance levels. The pesticide dissipation rates in soils varied by less than a factor of 3 between sites. The metabolites methamidophos and TCP derived from acephate and chlorpyrifos amounted to less than 10 and 25% by mass of the parent compounds in soils. Vegetable shading possibly retarded pesticide degradation in soil. CONCLUSION: The dissipation of pesticides and their metabolites in the vegetable was rapid and faster than the dissipation in temperate climates. The degradation rates of pesticides in the soil were equal to or slightly faster than the degradation rates in temperate soils. Copyright © 2008 Society of Chemical Industry     

Cotton whitefly (Bemisia tabaci) resistance to organophosphate and pyrethroid insecticides in Pakistan

Resistance to three organophosphate and four pyrethroid insecticides was monitored from 1992 to 2000 in field populations of adult whiteflies, Bemisia tabaci, from Pakistan using a leaf-dip method. There was generally a very high resistance to dimethoate and deltamethrin, and a moderate resistance to monocrotophos during 1992 to 1996. From 1997 to 2000, resistance to these insecticides dropped to low levels because of less reliance on them for whitefly control, and introduction of new chemistries with novel modes of action that had no cross-resistance to conventional insecticides. Concurrently, whitefly resistance to acephate, fenpropathrin, lambda-cyhalothrin and bifenthrin mostly remained low. An insecticide resistance management strategy is recommended that particularly emphasizes the rotation of still-effective insecticides from different chemical classes along with the use of novel chemicals and other tactics of integrated pest management.     

杀虫剂对甜菜夜蛾不同世代及幼虫龄期的毒力变化

甜菜夜蛾 ( Spodoptera exigua Hübner)属鳞翅目夜蛾科 ,是一种世界性的农业害虫。该虫为杂食性 ,寄主范围广[1 ] 。自 80年代以来 ,由于种植结构及栽培管理方式不当、气候条件、农药对天敌的影响、抗药性、迁飞性等各方面的因素 ,致使甜菜夜蛾发生呈上升趋势。目前 ,对甜菜夜蛾的研究主要局限在生物学、生态学、防治等方面 ,而对其抗药性规律尚缺乏深入研究。作者主要研究了杀虫剂对甜菜夜蛾的不同发生世代和不同幼虫龄期的毒力变化 ,对该虫的化学防治有一定指导意义。1　材料与方法1 .1　供试药剂氟啶脲 ,92 .5 %原药 (日本石原产业株式…     

小菜蛾对溴氰菊酯抗性选育及其机理

本研究用溴氰菊酯在室内以点滴法处理小菜蛾４龄幼虫，连续继代药剂淘汰选育其抗药性，至Ｆ６５代，抗药性提高到１１６３倍，已形成高抗生品系。其抗性的形成发展趋势为前期相对缓慢，中期较快，后期迅速增长。于１９９２、１９９３、１９９４年分别以氯氰菊酯、敌敌畏、杀虫双、灭虫剂有明显 正交互抗性，对其它非菊酯类杀虫虫没有产生交互抗性。用聚丙烯酰胺凝胶电泳地（ＰＡＧＥ）测定表明，小菜蛾对溴氰菊酯抗性的产生可能与非     

小菜蛾对阿维菌素B_1抗药性选育及交互抗性

用阿维菌素B_1(abamectin)对小菜蛾敏感种群在室内进行抗性品系选育。经过25代连续汰选,获得抗性种群Laba-R,与选育前比较,抗性提高100倍。Laba-R种群在不接触任何药剂条件下饲养20代,抗性逐渐下降,很难恢复到选育前的敏感状态。抗性汰选前后分别测定10种药剂的剂量-死亡率毒力回归线,发现Laba-R抗性种群对乙酰甲胺磷、锐劲特、灭多威、敌敌畏不存在交互抗性;对溴氰菊酯、氯氰菊酯、杀虫双、巴丹和Bt的敏感性略有下降,但无明显交互抗性。活体增效剂试验表明,增效醚(PBO)和磷酸三苯酯(TPP)对阿维菌素B_1均有明显的增效作用,其中PBO的增效活性尤为显著,它能使对阿维菌素B_1产生100多倍抗药性的小菜蛾完全恢复其敏感性。说明多功能氧化酶解毒代谢增强可能是小菜蛾对阿维菌素B_1产生抗性的主导因素之一。