Distribution and metabolism of abamectin in larval stages of Spodoptera littoralis boisduval and Heliothis armigera hübner (Lepidoptera: Noctuidae)

Comparisons were made between the amounts of abamectin and total radioactivity recovered from Spodoptera littoralis and Heliothis armigera larvae after topical application of [³H]abamectin. Penetration (as shown by wash-off experiments) did not differ significantly between the Spodoptera instars. Significantly more abamectin was recovered from ventral nerve cord samples of larvae showing symptoms of poisoning than from larvae not showing these symptoms. Fifth-instar S. littoralis larvae had a significantly lower proportion of radioactivity as abamectin in the ventral nerve cord than in sixth-instar S. littoralis or fifth- and sixth-instar H. armigera. The proportion of radioactivity present as abamectin (but not total radioactivity) was significantly increased when the fifth-instar S. littoralis larvae were pre-treated with piperonyl butoxide (PB) suggesting that the relative insensitivity of fifth-instar S. littoralis larvae to abamectin is due at least in part to greater metabolism, particularly by microsomal oxidases. Fat body samples consistently had a greater proportion of radioactivity as abamectin than the nerve cord and the former may act as storage sites for abamectin.     

Insecticidal activity of destruxin, a mycotoxin from Metarhizium anisopliae (Hypocreales), against Spodoptera litura (Lepidoptera: Noctuidae) larval stages

BACKGROUND: The cyclodepsipeptide destruxin produced by the entomopathogen Metarhizium anisopliae (Metch.) was administered by different methods, topical application, ingestion and a combination of the two, in an attempt to minimize the mycotoxin dose for efficient management of the insect pest Spodoptera litura (Fab.).RESULTS: The insecticidal activity of destruxin on the larval stages of S. litura showed an ascending trend in LD(50) values with increasing age. The value for 12-day-old larvae in the combined application assay was as low as 0.045 microg g(-1) body weight of crude destruxin from M-19 strain when compared with the corresponding values of 0.17 microg g(-1) body weight in the ingestion assay and 0.237 microg g(-1) body weight in the topical application assay. On the other hand, values were higher in the treatments with crude destruxin from the low-virulence M-10 strain of M. anisopliae showing the least quantities of A and E components of destruxin.CONCLUSION: Laboratory bioevaluation showed the combination assay of ingestion and topical application of crude destruxin to be efficient in enhancing its insecticidal properties. The adopted combination assay apparently simulates application of the insecticide at field level. Quantitative differences between destruxins from low- and high-virulence strains of M. anisopliae are in accordance with its presumed role in virulence.     

Insensitive acetylcholinesterase causes resistance to organophosphates in Australian Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae)

Organophosphates are valuable insecticides used to control Helicoverpa armigera on cotton in Australia. Those most commonly used for Helicoverpa spp. control are pro-fenofos, parathion-methyl and chlorpyrifos. However, there is an emerging organophosphate-resistance threat in Australian H. armigera, which is compounded by cross-resistance between profenofos and parathion-methyl. An insensitive acetylcholinesterase has been identified as the common resistance mechanism. No resistance to chlorpyrifos has been detected and acetylcholinesterase remains fully sensitive to the chlorpyrifos oxon. © 1998 Society of Chemical Industry     

Impact of a Turkish isolate and a plaque-purified variant of SpliNPV-B on larval stage development of Spodoptera littoralis (Lepidoptera: Noctuidae) Boisd

Baculoviruses can alter the development and physiological status of their insect hosts. In the present study, two Spodoptera littoralis nucleopolyhedroviruses (SpliNPV-TR1 and SpliNPV-M2) were examined in terms of their effect on the stage development of S. littoralis at two doses/concentrations by inoculation of neonates or third instars. Both isolates had an acute pathological effect on neonates. However, larval development was prolonged (6-36 h) by either infection when neonates were infected. When third-instar larvae were inoculated, no mortality occurred until insects moulted to later stages. When the isolates were compared, more mortality occurred in the fifth instar with SpliNPV-M2 than with SpliNPV-TR1, whereas less mortality occurred in the sixth instar with SpliNPV-M2 than with SpliNPV-TR1. However, none of the isolates demonstrated a dose effect. Larvae died at 108-198 h post-inoculation at all infections, and none of them pupated. Larval development was retarded (0-126 h) for each stage when third-instar larvae were inoculated. Consequently, SpliNPV-M2 would be a more effective control agent than SpliNPV-TR1 for control of S. littoralis since it kills larvae at earlier developmental stages.     

Comparative biological activities of a plaque-purified variant and a Turkish native isolate of SpliNPV-B against Spodoptera littoralis (Lepidoptera: Noctuidae)

The noctuid moth Spodoptera littoralis (Boisduval) is an important pest of many cultivated plants worldwide and five different geographical Nucleopolyhedrovirus (NPV) strains of this pest have been isolated to date. Two of these, a plaque-purified variant of the S. littoralis NPV from Morocco (SpliNPV-M2) and a SpliNPV isolated from field-infected S. littoralis larvae found in Turkey (SpliNPV-TR1), were compared biologically in terms of infectiveness (median lethal dose, LD50) for third instars and in terms of virulence (median lethal time, LT50) for neonates and third-instar S. littoralis larvae. The LD50 values of SpliNPV-TR1 and SpliNPV-M2 were 20.73 and 185.21 occlusion bodies (OBs)/larva, respectively, with non-overlapping confidence limits indicating they were significantly different. Thus, SpliNPV-M2 was found to be significantly less infective (about nine times higher LD50) than SpliNPV-TR1. The LT50 values of neonates for SpliNPV-M2 and SpliNPV-TR1 were 37 and 43.9 h at a concentration of 10(6) OBs ml(-1), respectively. For these same isolates, the LT50 values at a concentration of 3 x 10(6) OBs ml(-1) were calculated as 35.6 and 41.7 h, respectively. The LT(50) values of third instars for SpliNPV-M2 and SpliNPV-TR1 were 147.4 and 160.5 h, respectively, at a dose of 3000 OBs/larva and 145.4 and 152.4 h, respectively, for the same isolates at a dose of 20,000 OBs/larva. On the other hand, Helicoverpa armigera (Hübner) and Agrotis ipsilon (Hufnagel) revealed a lack of lethality of the SpliNPV-TR1 isolate.     

Insect deterrent activity of ethanolic leaf extracts of landrace maize and determination of active compounds against Spodoptera littoralis Boisduval (Lepidoptera: Noctuidae)

Journal of Plant Diseases and Protection - The present work was carried out to gain insight into the chemical defense of maize against phytophagous insects. Leaves of sixteen landrace populations...     

Mating,longevity, fertility and fecundity of the cotton leaf-worm,Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

The mechanisms adopted to ensure mating success, fertility and fecundity ofS. littoralis were studied. The male moths usually mate only once a night but they mate repeatedly during most of their life span, and practically all their spermatophores are equally efficient for inseminating a female. Although females are also multiple maters, one spermatophore is sufficient for a female to lay fertile eggs throughout her life with no reduction in potential fecundity. While a male may mate 5.3 times, on the average, a female may mate only 2.3 times. As a pronounced decrease in pheromone release occurs after mating, a repeat mating by a female will occur only after most neighboring competitive virgin females have been inseminated. A male may mate therefore with 5.3 different females, all of which will be thoroughly inseminated. The female moth is ready to mate just after emergence and at any time throughout her life. If mating is delayed the preoviposition period is greatly prolonged and eggs are saved to be laid later, after mating, as fertile eggs. Delay in egg laying due to delayed insemination does not result in reduced fecundity as it is compensated for by prolonged longevity. Even if mating is greatly delayed and occurs after egg laying has already begun, the potential reduction in reproduction is not very great, due to the low daily egg-laying rate and the increased longevity of unmated females. It appears unreasonable to expect any tendency toward reduction of egg production with a decrease in the ratio of adult males in a population; for this purpose the control of males must be essentially complete. Therefore, a behavioral control program by mass trapping ofS. littoralis males is unlikely to be economically feasible.     

广西田间发现2种草地贪夜蛾幼虫寄生蜂

草地贪夜蛾Spodoptera frugiperda (J. E. Smith)是世界性重大迁飞害虫,自2019年入侵我国西南地区后迅速向北扩散,严重威胁我国粮食作物生产安全。挖掘和筛选本地优势天敌,对开展草地贪夜蛾生物防治具有重要意义。2020年夏季在广西南宁市和北海市野外开展草地贪夜蛾及其天敌调查时发现2种草地贪夜蛾幼虫寄生蜂,通过形态学和分子生物学方法鉴定为棉铃虫齿唇姬蜂Campoletis chlorideae Uchida和斜纹夜蛾侧沟茧蜂Microplitis prodeniae Rao & Kurian。本文详细记述了这两种幼虫寄生蜂的形态特征,以期为今后筛选和利用草地贪夜蛾寄生性天敌提供参考。     

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     

Insecticidal toxicity of thirteen commercial plant essential oils against <Emphasis Type="Italic">Spodoptera exigua</Emphasis> (Lepidoptera: Noctuidae)

We evaluated the chemical composition of thirteen commercially available plant essential oils and their insecticidal activity against the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae). Gas chromatography-mass spectrometry was used to characterize the chemical components of the essential oils. A total of 113 compounds were identified, with terpenes (>80%) and aromatic compounds as primary constituents. The toxicity of each pure essential oil was tested separately on third instar larvae and adult beet armyworms by topical application of 0.5 μl oil/ insect. All plant essential oils were found to be harmful to S. exigua, with third instar larvae showing significantly more susceptibility than adults. Essential oils of Cinnamomum zeylanicum and Juniperus virginiana showed the highest toxicity (mortality above 90%) to larvae, while C. zeylanicum and Pogostemon cablin oils were the most harmful compounds (95% mortality) to adults. Cymbopogon winterianus oil caused delayed mortality (similar to the effects of insect growth regulators) as well as malformations in pupae. C. winterianus, Ocimum basilicum and Rosmarinus officinalis oils significantly reduced fecundity, whereas no significant effects were observed on fertility.     

Effects of petroleum spray oils on oviposition behaviour and larval survival of Helicoverpa armigera Hubner (Lepidoptera: Noctuidae) and Ostrinia nubilalis Hubner (Lepidoptera: Pyralidae)

We determined the effects of petroleum spray oil (PSO) (Caltex Canopy®) on oviposition responses of Helicoverpa armigera Hubner and Ostrinia nubilalis Hubner adults, and larval survival of the pest moths on cotton and maize plants in the laboratory. Application of 2% (v/v) of the PSO deterred H. armigera oviposition. Increasing the rate from 2 to 5% (v/v) did not significantly reduce the number of eggs laid by H. armigera on the treated plants. In contrast, the minimum rate at which the oil could deter oviposition of O. nubilalis on maize plants was 5% (v/v). Increasing the rate from 5 to 10% (v/v) did not significantly reduce the number of eggs laid per plant. However, a reduction in the rate of the PSO from 5 to 3% (v/v) resulted in a 73.9% increase in oviposition activity on the maize plants. In wind tunnel bioassay tests, all mated H. armigera females tested could detect and settle on plants treated with water but with plants treated with PSO at various times, only 50% of tested females settled on the plants 4?–?5 days after treatment (DAT) and none on the plants 0?–?2 DAT. A solid phase micro-extraction (SPME) test to determine the effect of the PSO on volatiles released by the cotton plants showed that the quantity of volatiles released by the cotton plants treated with PSO was lower than for water treated plants. This indicates that the PSO sprays may be suppressing or masking the leaf surface volatiles of the cotton plants, thereby deterring oviposition of H. armigera. Larval survival data show that PSO sprays can cause direct mortality of first, second and third instar O. nubilalis larvae. PSOs may have the potential to be integrated into pest management programme targeting H. armigera and O. nubilalis on cotton and maize crops, respectively.     

国外草地贪夜蛾化学防治技术的研究与应用

草地贪夜蛾Spodoptera frugiperda(J.E.Smith)是一种适应性和迁徙能力很强的农业害虫,并具有暴发为害的特点。几十年来,化学防治一直是防治草地贪夜蛾的重要技术措施。20世纪80年代以前,美洲国家防治草地贪夜蛾以有机磷类和氨基甲酸酯类杀虫剂为主;随后拟除虫菊酯类杀虫剂得到了广泛使用;20世纪90年代中后期,美洲特别是美国推广种植转基因Bt玉米后,防治草地贪夜蛾杀虫剂的用量显著减少;近年来,甲氨基阿维菌素苯甲酸盐、乙基多杀菌素、除虫脲、虱螨脲、茚虫威、氯虫苯甲酰胺、氟苯虫酰胺、溴氰虫酰胺等一系列新型杀虫剂品种在防治草地贪夜蛾中发挥了突出的作用。伴随着不同种类杀虫剂的使用,草地贪夜蛾对杀虫剂抗性也相应地呈现出明显的变化,20世纪80年代后,美洲的草地贪夜蛾先后对有机磷类和氨基甲酸酯类杀虫剂产生了抗药性,截至2017年,美洲地区的草地贪夜蛾至少对包括氨基甲酸酯类、有机磷类、拟除虫菊酯类及Bt杀虫蛋白等不同类型共29种杀虫剂产生了抗药性;2016年,采自北美洲波多黎各的草地贪夜蛾田间种群对双酰胺类杀虫剂氟苯虫酰胺和氯虫苯甲酰胺抗性倍数最高分别达500倍和160倍。草地贪夜蛾的抗药性机制主要是解毒代谢增强和靶标基因突变。种子处理可以预防作物苗期草地贪夜蛾的为害,并且有利于天敌保护。雾滴粒径不仅影响杀虫剂对草地贪夜蛾的防治效果,还影响草地贪夜蛾对杀虫剂抗药性的发展,因此,防治田间草地贪夜蛾适宜采用细雾喷雾方式。使用得当,化学杀虫剂可以与天敌和生物杀虫剂协同增效防治草地贪夜蛾。航空施药要和地面施药联合使用才能对玉米田严重发生的草地贪夜蛾达到好的防治效果。     

甜菜夜蛾能源物质积累及其飞行能耗与动态

针对甜菜夜蛾迁飞危害规律及其飞行相关的生理学尚缺乏深入研究的现状,采用吊飞试验及相关生理生化的方法,研究了成虫甘油酯和糖原积累的时间动态及不同日龄成虫飞行后能源物质的变化.结果显示,2日龄蛾虫体干重最高.羽化后2～5日龄雄蛾甘油酯含量显著高于初羽化雄蛾;雌蛾甘油酯积累与雄蛾类似,只有4日龄雌蛾甘油酯含量明显降低.雌蛾糖原含量从初羽化到2日龄急剧升高,然后逐日下降,5日龄又有所回升;雄蛾羽化后到1日龄糖原含量迅速升高,以后的日龄有所波动.不同日龄蛾飞行能源物质的消耗不同.2日龄的成虫飞行,糖类和脂类都有明显的消耗;1、4日龄飞行对糖类的消耗影响不明显.除1日龄雌蛾以外,1、4日龄成虫甘油酯都明显消耗.综合所获结果可以看出,甜菜夜蛾的飞行既能利用脂类,也能利用糖类作为飞行能源,甘油酯是甜菜夜蛾贮备和飞行的主要能源物质.