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.     

Beetle-specific Bacillus thuringiensis Cry3Aa toxin reduces larval growth and curbs reproduction in Spodoptera littoralis (Boisd.)

Application of Bacillus thuringiensis tenebrionis (Bt) and expression of the Bt protein Cry3Aa in genetically modified crops are used for targeted control of the Colorado potato beetle Leptinotarsa decemlineata (Say). The Cry3A proteins are selectively toxic for the beetles but the present study describes effects of Cry3Aa on the Egyptian armyworm, Spodoptera littoralis (Boisduval). Cry3Aa expressed in potatoes or added to an agar-base wheat-germ diet reduced the growth of S. littoralis caterpillars and the fertility of adults. The effect of 1.4 mg kg(-1) Cry3Aa in potato leaves was comparable with that of 3.3 mg kg(-1) in the diet. This difference in activity was correlated with better digestibility and higher conversion efficiency of the diet that also supported higher reproduction rate: S. littoralis grown on the potatoes reached a similar size to those on the diet but laid only 702 instead of 1077 eggs per female. Cry3Aa consumption reduced body growth as a consequence of lower food intake without significantly affecting food digestibility and the conversion efficiency of nutrients. The 11% and 5% body weight reductions caused by 1.4 mg kg(-1) Cry3Aa in potatoes and 3.3 mg kg(-1) in the diet, respectively, were associated with 74% and 65% reduction in the number of progeny; S littoralis grown on a diet with 9.1 mg kg(-1) Cry3Aa were 10% smaller and produced no viable progeny. These data suggest that the curtailment of reproduction was not caused by a general shortage of nutrient reserves but by a more direct Cry3Aa effect on the reproduction process.     

DPX-MP062—a potent compound for controlling the Egyptian cotton leafworm Spodoptera littoralis (Boisd.)

The effects of DPX-MP062 [methyl 7-chloro-2,3,4a,5-tetrahydro-2-[methoxycarbonyl(4-trifluoromethoxyphenyl)carbamoyl] indeno[1,2-e][1,3,4] oxadiazine-4a-carboxylate] a broad-spectrum insecticide with a novel mode of action, on the Egyptian cotton leafworm, Spodoptera littoralis, were studied in laboratory experiments. Egg hatch was affected by high concentrations (125 mg AI litre^-1) of DPX-MP062. Larvae that hatched from treated eggs were significantly affected at concentrations of 12·5 mg AI litre^-1 and greater. Larvae were fed castor bean leaves treated with DPX-MP062; 1st-instar larvae were the most susceptible development stage. Pupation and adult formation were determined in assays with 5th-instar larvae. There was strong suppression of adult formation; 65 and 91% at 0·5 and 0·75 mg AI litre^-1, respectively. Highly affected larvae died before pupation; slightly affected ones reached pupation 2–4 days later, were smaller than larvae in the untreated control, and were sometimes unable to develop into normal adults. Comparatively high concentrations (50 and 100 mg AI litre^-1) of the test compound were necessary to affect adults by ingestion, but no effects from contact application could be determined at a concentration of 100 mg AI litre^-1. © 1998 Society of Chemical Industry     

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。     

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.     

斜纹夜蛾幼虫游泳行为初步观察

在实验条件下,初步观察了斜纹夜蛾幼虫游泳行为,结果表明:(1)幼虫泳姿有侧面游泳、弹射游泳、平行游泳和仰面游泳4种姿势;(2)游泳总时间因温度不同而异;(3)仰面游泳持续时间最短,时间分配率和发生率最低。观察结果可为深入研究该幼虫游泳行为及生理机制提供参考。     

Synthetic bis- and mono-chalcones with insecticide effects on Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

This is the first report on the antifeedant, toxic and nutritional effects produced by the synthetic chalcones on the lepidopteran Spodoptera frugiperda followed by structure-activity relationship. Bis (5a-c) and mono (8a-d) chalcones have been synthesized via Claisen-Schmidt condensation and have been purified and characterized. The mono chalcones 8b and 8d displayed toxic effects on early larval instars when incorporated to the larval diet at 100?µg per g of diet (40 and 60%, respectively) and low adults emergency with malformations leading to death. The remaining chalcones 8a, 8c, 5a, 5b and 5c do not displayed toxic effects at the same dose. The evaluation of nutritional indices indicated that 8a and 8c were the only tested chalcones to produce decrease in the growth rate and to reduce the efficiency with which larvae converted ingested food into biomass.     

草地贪夜蛾在小麦和不同玉米品种上的种群适合度比较

草地贪夜蛾Spodoptera frugiperda(J.E.Smith)是新入侵我国的重大迁飞性害虫,2019年在我国黄淮海冬小麦-夏玉米轮作主产区河南省呈点片发生,主要为害玉米,特别偏好取食晚播的甜糯玉米。为明确草地贪夜蛾在小麦和不同玉米品种上的种群适合度是否存在差异,本研究在室内(26±1)℃,RH(65±5)%和L//D=16 h//8 h光周期条件下比较了草地贪夜蛾在普通玉米‘郑单958’‘郑单1002’‘豫研1501’和糯玉米‘郑黄糯2号’以及小麦‘郑麦366’上生长发育指标。结果表明:取食‘郑麦366’的草地贪夜蛾的化蛹率(44.00±3.40)%、蛹重(138.62±6.76)mg、羽化率(35.00±3.07)%和单雌产卵量(971.70±125.63)粒均低于取食4个玉米品种的化蛹率(73.33%～80.00%)、蛹重(154.94～176.40)mg、羽化率(73.33%～79.33%)和单雌产卵量(1 052.00～1 322.60)粒(P0.05);草地贪夜蛾取食不同寄主植物的种群趋势指数由大到小顺序为:‘郑黄糯2号’(578.38)‘豫研1501’(493.40)和‘郑单958’(437.06)‘郑单1002’(321.47)‘郑麦366’(133.56)。综上表明,草地贪夜蛾在小麦上的适合度低于在玉米上的适合度,但其能够在小麦上完成生长发育并实现种群扩繁;其在糯玉米上的种群适合度大于普通玉米。因此应密切监测草地贪夜蛾在小麦上的发生和为害,并提出适时种植糯玉米作为诱集带并集中喷施杀虫剂来压低草地贪夜蛾种群数量的防控措施。     

一株莱氏绿僵菌的筛选及其对草地贪夜蛾的毒力

开展草地贪夜蛾病原真菌的筛选和毒力测定可为草地贪夜蛾的绿色防控提供新的生物制剂.本研究从广西南宁田间采集的草地贪夜蛾幼虫僵虫上分离获得一株病原真菌,采用形态学和ITS-rDNA序列分析相结合的方法对该菌株进行了鉴定,并采用浸虫法测定了该菌株对草地贪夜蛾的致病力.结果表明新分离的菌株为莱氏绿僵菌Metarhizium r...     

3种寄主植物饲养的草地贪夜蛾种群生命表

入侵我国的草地贪夜蛾Spodoptera frugiperda(J.E.Smith)(Lepidoptera:Noctuidae)经研究目前均认为主要是玉米型,而该虫能否在甘蔗、水稻上完成其生活史并对我国甘蔗、水稻的种植构成威胁值得探讨。本研究对采自玉米上的草地贪夜蛾自然种群用3种不同寄主植物饲养,并分别构建草地贪夜蛾两性生命表,比较不同寄主植物对其种群参数的影响。结果表明:取食甘蔗、水稻的草地贪夜蛾低龄幼虫存活率明显低于取食玉米的幼虫;取食水稻的成虫前期最长(27.75 d±0.50 d),且雄蛹体重最轻(153.3 mg±9.1 mg);草地贪夜蛾取食甘蔗、水稻、玉米后其产卵量无显著差异,平均世代周期依次为31.46 d、33.92 d和29.53 d,种群内禀增长率(r)分别为0.19、0.14和0.16,周限增长率(λ)分别为1.21、1.16和1.17,净增殖率(R_0)分别为367.01、135.44和101.25。总体而言,采自玉米的草地贪夜蛾在水稻上的适合度低于甘蔗和玉米上,但在甘蔗、水稻上该虫能够完成其生活史实现种群繁衍,本研究为草地贪夜蛾的预测预报和防治提供了理论依据。     

双斑青步甲幼虫对草地贪夜蛾幼虫的捕食能力

在云南德宏州芒市玉米田调查发现一种草地贪夜蛾Spodoptera frugiperda（J.E.Smith）的捕食性天敌昆虫双斑青步甲Chlaenius bioculatus Chaudoi,为探究其对草地贪夜蛾的生物防治潜能,在室内条件下测定了双斑青步甲3龄幼虫对草地贪夜蛾6个龄期幼虫的捕食能力。试验结果表明：双斑青步甲3龄幼虫对草地贪夜蛾6个龄期幼虫的瞬时攻击率分别为1.1478、1.3386、1.3949、1.2745、1.3599和1.4227。处置时间分别为0.0036、0.0068、0.0137、0.0554、0.2895、0.4356 d。日最大捕食量分别为278.39、146.30、73.26、18.06、3.45和2.29头。试验表明,双斑青步甲幼虫对草地贪夜蛾具有良好的捕食作用,有应用于生物防治的潜力。     

Toxicity and kinetics of methoxyfenozide in greenhouse-selected Spodoptera exigua (Lepidoptera: Noctuidae)

Methoxyfenozide (RH-2485) was found to be 7.5-fold less toxic in terms of LD50 values against last-instar larvae of a greenhouse-selected strain of the beet armyworm Spodoptera exigua (Hübner) that was collected in July 2001 in an experimental greenhouse for resistance at Murcia in southern Spain, in comparison with a laboratory susceptible strain. To date, the compound is the newest member of this new group of moulting hormone accelerating IGRs to reach the marketplace against Lepidoptera. To understand this different potency in the greenhouse-selected S exigua, oxidative metabolism and acetylcholinesterase activities were measured in last-instar larvae and adults. In addition, we determined, by the use of 14C-labelled methoxyfenozide, the pattern of absorption in body tissues and excretion via faeces in last-instar larvae of the greenhouse-selected strain and compared the results with those from the laboratory susceptible strain. It was striking that the rate of excretion was about twice as high in the greenhouse-selected strain, resulting in a more rapid clearance of insecticide amounts from the insect body. Data are discussed in relation to mechanisms of lower toxicities for this new group of IGRs.     

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.     

草地贪夜蛾病原白僵菌的分离鉴定及其致病力研究

草地贪夜蛾Spodoptera frugiperda (J. E. Smith)是一种全球性重大玉米害虫, 于2019年入侵我国云南并快速蔓延, 对我国的粮食安全造成重大威胁。本研究从玉米地块自然罹病的草地贪夜蛾幼虫僵虫中分离纯化致病菌, 并回接验证, 获得一株虫生真菌菌株, 结合形态学和rDNA-ITS序列分析, 确认该菌株属于球孢白僵菌Beauveria bassiana, 编号为SfG01。采用浸虫法测定了该菌株对草地贪夜蛾2龄幼虫的致病活性。结果表明, 孢子悬浮液浓度为1.00×109个/mL时, 草地贪夜蛾2龄幼虫第11天累计死亡率达86.67%, LC50为4.85×107个/mL, LT50为6.50 d。表现出一定的生防潜力, 具有进一步研究价值。     

草地贪夜蛾对小麦和玉米的产卵选择性及其种群生命表

为明确草地贪夜蛾对小麦的产卵选择性及其是否对小麦安全生产构成威胁,本研究以玉米和小麦作为测试寄主,比较分析了草地贪夜蛾对两种作物不同部位的产卵选择性,并利用两性生命表方法研究了取食小麦、玉米对其生命参数的影响。结果表明:草地贪夜蛾更喜欢在玉米上产卵,其在玉米、小麦叶片、玉米和小麦茎秆上的产卵量存在显著差异(df=102,F=15.593,P<0.05),以玉米叶片背面卵块数量(7.11±1.55)块/笼最高;草地贪夜蛾取食小麦可以完成生活史,但幼虫存活率、化蛹率、羽化率和世代存活率低于取食玉米。取食玉米的幼虫发育历期为(16.31±0.15)d,显著高于取食小麦的(14.66±0.12)d,蛹期、蛹重、产卵前期、成虫寿命和世代周期无显著差异。取食小麦羽化出的雌虫寿命、平均单雌产卵量显著高于取食玉米,分别为(16.39±0.40)d、(976.31±57.21)粒和(14.64±0.32)d、(831.57±30.55)粒。生命表参数显示取食玉米的净增殖率为363.14,显著高于小麦的258.63,但内禀增长率、周限增长率和平均世代周期无显著差异。研究结果为草地贪夜蛾在小麦上的预测预报和有效防控提供了基础数据。