Reproductive behaviour and vibratory communication of the neotropical predatory stink bug Podisus nigrispinus

Vibratory communication during reproductive behaviour is less well described in predatory (Asopinae) than in phytophagous (Pentatominae) stink bugs. Different steps in the mating behaviour of the predatory stink bug Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae; Asopinae) are described in the present study, together with vibratory signals emitted on artificial and natural substrate during courtship and copulation. Vibratory signals in Podisus nigrispinus have a decisive role in copulation success and are produced in both sexes by abdominal vibration and tremulation. In P. nigrispinus, one species‐specific female and two male songs, which do not show the calling function typically found in phytophagous stink bugs, are produced by abdominal vibration and are emitted during reproductive behaviour. Additionally, P. nigrispinus produces tremulatory signals that have no species or sex specificity. Tremulatory signals emitted spontaneously on a plant as a sequence of readily repeated pulses are similar to the calling songs of the Pentatominae stink bug. These signals may carry information on the presence of a mate; however, in other behavioural contexts, they may have a different function, such as advertisement or even alarm signals. Plants transmit vibratory signals produced by both mechanisms as a low‐pass filter, increasing the amount of low‐frequency components. The results of the present study raise important questions about the interaction between chemical and vibratory signals in the mating behaviour of predatory stink bugs.     

Maternal age and egg weight affect offspring performance in the predatory stink bug Podisus nigrispinus

To investigate influences of maternal age and egg weight on developmental time and body weight of offspring in the Neotropical pentatomid Podisus nigrispinus, a study was carried out using large (0.36 mg) and small (0.32 mg) eggs of young (two-week- old) females and large eggs of old (seven-week-old) females. Incubation period of eggs was influenced only by egg weight, i.e. small eggs took a relatively shorter time to hatch. Both maternal age and egg weight had significant effects on total nymphal and egg-to- adult developmental times. Overall, offspring of young parents had shorter developmental times. None of the developmental periods were significantly affected by sex. No significant differences were found among various offspring groups for percentages of egg hatch, nymphal survival, and sex ratio. Variation of egg weight in relation to the number of eggs per day observed within the first month of life suggests a trade-off between weight of individual eggs and oviposition rate. It is concluded that for mass production of the predators in view of their use in augmentative biocontrol programmes, young parents (2–4 weeks old) should be preferred.     

Interaction between the predator Xylocoris sordidus and Bacillus thuringiensis bioinsecticides

Xylocoris species (Hemiptera: Anthocoridae) are known to occur in various habitats and attack a diversity of agriculturally important prey. Other groups of organisms, such as strains of Bacillus thuringiensis Berliner (Bt) bacteria, also have been extensively studied and applied as biological control agents. The use of these Bt-bioinsecticides in association with predators may be a good strategy in integrated pest management. This work had the objective to study predator behaviour, predatory capacity, and functional response of fifth-instar nymphs of Xylocoris sordidus (Reuter) to eggs of Plutella xylostella (L.) (Lepidoptera: Plutellidae) and Corcyra cephalonica (Stainton) (Lepidoptera: Pyralidae) treated with one of three commercial Bt-bioinsecticides. The predator presented a type II functional response to untreated P. xylostella eggs (control) and to eggs treated with Agree, whereas the response was type III to P. xylostella eggs treated with Xentari and Dipel. However, on a diet of C. cephalonica eggs the predator displayed a type II response curve on eggs treated with each of the three bioinsecticides, and a type III response on untreated eggs. Bioinsecticides based on B. thuringiensis may be used in association with X. sordidus predators to control lepidopterous pest species.     

Control of Plutella xylostella using polymer-formulated Steinernema carpocapsae and Bacillus thuringiensis in cabbage fields

Abstract:  Field trials evaluating the potential of the entomopathogenic nematode Steinernema carpocapsae and the feasibility to combine nematodes with Bacillus thuringiensis for sustainable control of the diamondback moth (DBM) Plutella xylostella were conducted in cabbage cultivated in the province Probolinggo, east Java and Indonesia. A single use of 0.5 million S. carpocapsae  m⁻² applied with a surfactant-polymer-formulation containing 0.3% xanthan and 0.3% Rimulgan^® achieved a significant reduction of the insects per plant with >50% control after 7 days. Even 14 days after the application about 45% control was recorded and dead larvae containing nematodes were found. No significant effects were recorded when the formulation was compared with nematodes applied in water or with a surfactant alone. This was attributed to high humidity in the experimental area at the end of the rainy season and a microclimate in the cabbage heads favouring nematode survival. Weekly applications of B. thuringiensis (Turex^®) or alternating applications of Turex^® and the nematodes achieved >80% control. The application of both biological agents together every second week reached insignificant lower efficacy (70%). Nematodes can be used to substitute ineffective chemical insecticides and alterations with B. thuringiensis can prevent the further development of resistance against the bacterial control agent.     

Relationship between predation by Podisus nigrispinus and developmental phase and density of its prey,Plutella xylostella

This study evaluated the predation by Podisus nigrispinus (Dallas) (Hemiptera: Pentatomidae) at various densities of larvae and pupae of the pest Plutella xylostella (L.) (Lepidoptera: Plutellidae). We tested predator behavior of female P. nigrispinus at six experimental densities (1, 5, 10, 15, 20, or 25 prey items in a 1‐l transparent plastic container, replicated 15 times for each density) of both the fourth instar and pupae of P. xylostella. The number of prey consumed was monitored every 15 min for 12 h and was subsequently monitored at 24 h. Podisus nigrispinus females were weighed before and after the experiments to determine the effect of different densities of prey on their weight gain. Female predators had a Type‐II functional response, with attack rate estimated at 1.387 and 0.260 and a handling time of 0.091 and 0.183 h^?1 for larvae and pupae, respectively. Podisus nigrispinus consumed on average 10.9 larvae or 5.5 pupae in 24 h. Despite the similarity of the response type, P. nigrispinus preferred to feed on larvae, rather than on pupae.     

Pathogenicity of Heterorhabditis nematodes isolated from north-western Himalaya against the larvae of Plutella xylostella (L.) (Lepidoptera: Plutellidae)

The efficacy of three entomopathogenic nematodes (Heterorhabditis spp.), from north western Himalaya, India was studied against the diamondback moth, Plutella xylostella (Linnaeus, 1758) (Lepidoptera: Plutellidae), under laboratory conditions. The larvae were exposed to 10, 20, 30 and 40 infective juveniles (IJs) of each nematode species for different time periods and they were found to be susceptible to all the EPNs tested. However, the susceptibility of larvae to nematode infection varied according to the dosages of IJs and their exposure periods. The efficacy of these indigenous entomopathogenic nematodes was also evaluated against the commercially available entomopathogenic nematode H. indica. An indigenous isolate, H. bacteriophora (HRJ), along with the commercial isolate H. indica recorded 100.0% mortality of insect larvae in 96 h exposure time against third instar larvae of P. xylostella. However, it was noticed that with the advancement of larval stage its mortality rate reduces and vice versa with the exposure period. All the tested nematode species were also found to reproduce within the host and produced infective juveniles. In conclusion, the evidence obtained in this study suggests that all the three indigenous EPN species are virulent enough to produce 100% mortality of larvae of P. xylostella. These EPN species thus have potential for the management of P. xylostella under integrated management practices.     

Genetic control of Plutella xylostella in omics era

Diamondback moth, Plutella xylostella (L.), is a specialist pest on cruciferous crops of economic importance. The large‐scale use of chemical insecticides for the control of this insect pest has caused a number of challenges to agro‐ecosystems. With the advent of the omics era, genetic pest management strategies are becoming increasingly feasible and show a powerful potential for pest control. Here, we review strategies for using transgenic plants and sterile insect techniques for genetic pest management and introduce the major advances in the control of P. xylostella using a female‐specific RIDL (release of insects carrying a dominant lethal gene) strategy. Further, the advantages of gene drive developed in combination with sex determination and CRISPR/Cas9 systems are addressed, and the corresponding prospects and implementation issues are discussed. It is predictable that under the policy and regulation of professional committees, the genetic pest control strategy, especially for gene drive, will open a new avenue to sustainable pest management not only for P. xylostella but also for other insect pests.     

Bacteria abundance and diversity of different life stages of Plutella xylostella (Lepidoptera: Plutellidae), revealed by bacteria culture‐dependent and PCR‐DGGE methods

Microbial abundance and diversity of different life stages (fourth instar larvae, pupae and adults) of the diamondback moth, Plutella xylostella L., collected from field and reared in laboratory, were investigated using bacteria culture‐dependent method and PCR‐DGGE analysis based on the sequence of bacteria 16S rRNA V3 region gene. A large quantity of bacteria was found in all life stages of P. xylostella. Field population had higher quantity of bacteria than laboratory population, and larval gut had higher quantity than pupae and adults. Culturable bacteria differed in different life stages of P. xylostella. Twenty‐five different bacterial strains were identified in total, among them 20 strains were presented in larval gut, only 8 strains in pupae and 14 strains in adults were detected. Firmicutes bacteria, Bacillus sp., were the most dominant species in every life stage. 15 distinct bands were obtained from DGGE electrophoresis gel. The sequences blasted in GenBank database showed these bacteria belonged to six different genera. Phylogenetic analysis showed the sequences of the bacteria belonged to the Actinobacteri, Proteobacteria and Firmicutes. Serratia sp. in Proteobacteria was the most abundant species in larval gut. In pupae, unculturable bacteria were the most dominant species, and unculturable bacteria and Serratia sp. were the most dominant species in adults. Our study suggested that a combination of molecular and traditional culturing methods can be effectively used to analyze and to determine the diversity of gut microflora. These known bacteria may play important roles in development of P. xylostella.     

The ability of synthetic sex pheromone traps to forecast Plutella xylostella infestations depends on survival of immature stages

The potential for using synthetic sex pheromone traps as a simple and practical method of monitoring population densities of insect pests has been investigated in many crop systems. Yet, factors enabling the forecast of infestations based on pheromone trap catches are not fully understood. This study tested the prediction that high survival of immature stages of the target pest is a pre‐requisite for trap catches to correlate well with future infestations on the crop. The influence of parasitoids, as an important natural mortality factor of diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), larvae and pupae in South Africa, on the ability of pheromone traps to forecast infestations was investigated continuously at weekly intervals over 6 years on unsprayed cabbage. During late October–May, when parasitism levels were high (≥50%), infestations and trap catches were significantly lower than during low parasitism (<50%) observed during June–early October. Because infestations were negatively related to parasitism level, trap catches correlated with infestations better when observations were made in the same week during periods of high parasitism. Conversely, when survival of P. xylostella immature stages was high due to low parasitism levels, trap catches correlated with future infestations well for up to 2 weeks. Thus, trap catches can be used to forecast infestations during September–October, a period that coincides with high P. xylostella infestations as a consequence of low natural control by parasitoids. This is the first study to show that the ability of pheromone trap catches to forecast infestations depends on survival of the immature stages of the target pest.     

Bacillus thuringiensis isolates from northeastern Brazil and their activities against Plutella xylostella (Lepidoptera: Plutellidae) and Spodoptera frugiperda (Lepidoptera: Noctuidae)

Northeastern Brazil has been little explored in the search for Bacillus thuringiensis (Berliner) variants for the control of agricultural pests such as Plutella xylostella (L.) and Spodoptera frugiperda (J.E. Smith). The aim of this study was to isolate B. thuringiensis from soil and insect samples collected from the northeastern states and to evaluate their lethal and sublethal activities against the neonate larvae of P. xylostella and S. frugiperda. One hundred and four isolates were bioassayed and visualised for the presence of crystals. Bipyramidal crystals were present in 31% of the isolates. In pathogenicity tests, 13 and 19 isolates caused >30% mortality in P. xylostella and S. frugiperda, respectively. The Laboratory of Insect-Toxic Interactions (LIIT)-4311 isolate was the most toxic for P. xylostella, with toxicity similar to B. thuringiensis var. kurstaki (Dipel® WP) and B. thuringiensis var. aizawai (Xentari® WDG). For S. frugiperda, the LIIT-4311, LIIT-4306 and LIIT-4406 isolates were more active than B. thuringiensis var. aizawai. The LIIT-4311 and LIIT-4306 isolates caused high rates of larval growth inhibition in both P. xylostella and S. frugiperda. These results suggest a broad distribution of B. thuringiensis variants in areas of northeastern Brazil. Because LIIT-4306 and LIIT-4311 provided the highest levels of toxicity and larval growth inhibition for both P. xylostella and S. frugiperda, these isolates can be exploited to develop new technologies for pest management.     

Predicting the impacts of climate change on the biological control of Plutella xylostella by Diadegma semiclausum

1. The parasitoid Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae) has been widely adopted as a biological control agent for Plutella xylostella L. (Lepidoptera: Plutellidae) over the last 80 years. Earlier studies have found differential responses to temperature between the host and its parasitoid and demonstrated the multiple ways in which the parasitoid is more susceptible to elevated temperatures.
2. Using data from experimental studies, the modelling package CLIMEX was used to investigate the suitability of current climates for the host and its parasitoid and the effects on their potential global geographical distributions. The study was then extended to investigate possible changes to these distributions that might result under different climate change scenarios by 2080. The models predict that the global distributions of both the host and parasitoid will be reduced. These changes will not be proportionate and many areas in tropical, sub-tropical, and temperate regions that are currently suitable for D. semiclausum are predicted to become unsuitable for the parasitoid, whereas retaining suitability for P. xylostella. The seasonal dynamics of both the host and parasitoid are also predicted to be significantly reshaped under climate change.
3. Analysis of associations between annual P. xylostella outbreaks and weather conditions in three provinces in China with field data collected between 1995 and 2017 indicated significant effects of temperature on P. xylostella outbreaks at the beginning of the peak season in warmer provinces where P. xylostella can overwinter; such associations were not found in the colder provinces where it is unable to survive harsh winters.

     

小菜蛾抗性治理及可持续防控技术研究与示范——公益性行业(农业)科研专项“小菜蛾可持续防控技术研究与示范”进展

针对我国小菜蛾Plutella xylostella(L.)严重为害及高抗药性的现状,在华南、华中、华东、华北和西南等具代表性地区开展小菜蛾灾变规律、抗性监测及治理、越冬迁飞、抗性机理及可持续防控技术研究集成与示范。灾变规律研究结果表明,我国各地小菜蛾的年发生世代从北至南呈逐渐增加趋势,各地小菜蛾发生起始峰时间从南至北逐渐向后推移,每年不同区域有一至两个发生高峰,年度间受温度和降水等气候因素、天敌等生物因子以及耕作制度等人为操作等多种因素的影响。抗性监测及治理研究显示,全国5个十字花科蔬菜主产区小菜蛾对11种代表性杀虫剂都有较强的抗药性,不同药剂在全国的抗药性水平有很大差异,在华南、西南和华东十字花科蔬菜主产区抗性水平相对较高,华中和华北呈现抗性上升趋势,并根据抗性监测结果制定区域性抗性治理策略。越冬和迁飞研究证明,武汉至驻马店区域为小菜蛾的越冬北限,小菜蛾存在远距离迁移的特性,并确定小菜蛾有迁入迁出和迁入定殖两种迁飞模式。抗性机理研究结果表明,小菜蛾对Bt制剂、阿维菌素、氟虫腈、茚虫威和丁醚脲的抗性遗传方式不同,各药剂交互抗性普也存在差异。可持续防控技术方面,制定了适合各区域的小菜蛾可持续防控技术体系,并在华南、华东、华北、华中和西南等地区建立了45个示范基地,依区域不同分别示范推广具区域特色的以农业措施、生物防治、生态调控和合理用药为主的可持续防控等技术,累计印刷技术宣传手册16万份,培训各类农民和基层农技人员5.19万人次,累计示范面积近4万公顷,带动技术示范近20万公顷,取得了显著的经济、社会和生态效益。     

Quantifying the reproduction of Bacillus thuringiensis HD1 in cadavers and live larvae of Plutella xylostella

The Bacillus cereus group comprises a range of micro-organisms with diverse habits, including gut commensals, opportunistic pathogens and soil saprophytes. Using quantitative microbiological methods we tested whether Bacillus thuringiensis (Bt) could reproduce in cadavers of Plutella xylostella killed by Bt, or in the gut of live insects, or be transmitted vertically from females to their offspring. We also tested whether diverse Bt strains could grow in high nutrient broth at a pH similar to that in the larval midgut. Low levels of reproduction were found in insect cadavers but there was no evidence of vertical transmission, or of significant reproduction in live insects. Four strains of B. thuringiensis var. kurstaki and one of B. thuringiensis var. tenebrionis were found to be capable of growth at high pH. Greater spore recovery rates in frass were found in hosts that were resistant or tolerant of infection. We concluded that that spores recovered in frass represent, in general, an ungerminated fraction of ingested inoculum and that germination rates are reduced in unsuitable hosts.     

一株对小菜蛾高毒力的苏云金杆菌的选育及研究

利用醋酸钠 抗生素法从土壤中分离出 1株对小菜蛾 (Plutellaxylostella)高毒力的苏云金杆菌Bt 990 5。该菌对小菜蛾 4 8h的平均死亡率为 98.5 %。高于标准菌株HD 1(81.2 % )。同时 ,对该菌的形态、培养特征 ,生化特性和杀虫晶体蛋白的分子量的测定以及cry基因类型的鉴定进行了研究。     

小菜蛾在温带地区越冬研究进展

小菜蛾是世界性重要害虫。在热带和亚热带地区冬季的十字花科植物上能正常发育繁殖,可见到各种虫态。但在温带冬季十字花科植物不能生长的地区,小菜蛾的越冬成为一个重要生态学问题。综述了亚洲、北美洲和欧洲小菜蛾越冬的研究进展。小菜蛾在日本的北海道、本州岛的北陆和东北大部分地区不能越冬,越冬北限相当于冬季积雪覆盖时间为60d的区域;在中国,小菜蛾不能在寒冷的东北地区越冬,在长江中下游以南地区冬季可见各虫态,但越冬北限尚不清楚;小菜蛾在冬天气候温和的韩国以及澳大利亚东南部继续发生;北美洲的加拿大西部和安大略地区大量的试验证明小菜蛾不能成功越冬,在美国南部小菜蛾冬季可正常发生,北部小菜蛾的越冬尚未见系统研究报道,但确认春季从南部运输的受小菜蛾感染的甘蓝等种苗是美国北部的重要虫源。小菜蛾在欧洲各地越冬的系统研究未见报道,没有证据表明在英国小菜蛾会发生有显著意义的越冬。目前小菜蛾越冬研究主要采用冬季直接试验观察和基于耐寒性试验的越冬预测两种方法。冬季直接试验观察法包括:(1)利用人工饲养的小菜蛾在田间各种潜在的越冬场所的越冬试验;(2)在秋播、野生或残留的十字花科植物上进行冬季种群的系统抽样调查;(3)越冬前后在前茬为十字花科植物的田块广泛搜寻普查小菜蛾的存活个体。基于耐寒性试验的越冬预测法:在获取小菜蛾越冬场所温度的基础上设计低温处理模式,试验低温处理后小菜蛾的存活率及后续发育和生殖。将试验数据和各地气温或小气候相结合,对小菜蛾在的越冬可能性进行推断。     

Sublethal effects of hexaflumuron on development and reproduction of the diamondback moth,Plutella xylostella (Lepidoptera: Yponomeutidae)

Abstract Effects of hexaflumuron at 10% lethal concentration (LC₁₀) and LC₂₅ on development and reproduction parameters of the diamondback moth, Plutella xylostella (Linnaeus, 1753) (Lep.: Yponomeutidae) were investigated. Estimated LC₅₀, LC₁₀ and LC₂₅ values of leaf dip bioassay of hexaflumuron on the third instar larvae of the P. xylostella were 1.48, 0.59 and 0.91 mg/L, respectively. Hexaflumuron decreased pupal weight in the parent generation at sublethal concentrations but in the offspring generation, this effect was not observed. Sublethal concentrations increased egg, first and second larval instar and pupa developmental time and shortened life span of adults, but did not change the third and fourth larval instars and pre‐pupa developmental period. Also fecundity of females reduced significantly but hatchability of treatments and control were similar. Survival rate of pre‐adult stages declined significantly at LC₂₅ concentration. Reproduction parameters such as reproductive rate (R₀) and intrinsic rate of increase in sublethal concentrations were significantly lower compared with control, but gross reproduction rate (GRR) at the LC₁₀ concentration was increased and it could be hormoligosis. Also hexaflumuron significantly increased doubling time (Dt). We conclude that the sublethal effects of hexaflumuron might exhibit significant effects on the population dynamics of P. xylostella.     

植物保护剂保卫德对小菜蛾种群控制效应评价

室内外试验表明,植物保护剂保卫德（BIOACT－T35）对小菜蛾种群具有较好的控制效应,其显的控制机理主要表现在对成虫产卵的忌避作用和对幼虫的拒食作用。保卫德10．00ml／L处理对成虫的忌避率为81．43％,对幼虫的选择和非选择性拒食率为96．32％和93．17％,小菜蛾种群趋势指数I值由对照的18．2840降为1．9492,干扰作用控制指数为0．1066。     

Isolation and characterization of trinucleotide repeat microsatellite markers for Plutella xylostella L.

Thirteen microsatellite markers generating high quality patterns have been developed and characterized for diamondback moth (Plutella xylostella L.), of which 11 are based on trinucleotide repeats. These markers are polymorphic, generating up to 15 alleles in a test set of 12 caterpillars. The markers will be useful to assess the differentiation of P. xylostella populations and the exchange of pest populations between sites with crops, green manure crops and weeds.     

Insecticidal potential of Bacillus thuringiensis for the biological control of neotropical brown stink bug

Euschistus heros (Hemiptera: Pentatomidae) is considered a major insect pest in soybean production in Brazil. The indiscriminate application of pesticides to fields leads to reduction in biodiversity, selection of resistant populations, emergence of new pest outbreaks, and damage to non‐target organisms. The objective of this research was to evaluate the effects of exposure to Cry proteins present in new isolates of Bacillus thuringiensis Berliner, commercial formulations, and Bt soybean on E. heros development. The feeding preference of E. heros for Bt‐ vs. non‐Bt soybean was also evaluated. All treatments caused significant mortality to E. heros except the Bt soybean. Tests with combinations of isolated Bt‐toxins indicated that combinations had greater efficacy than other treatments (>98% mortality). The results demonstrate that E. heros is susceptible to B. thuringiensis toxins, which may contribute to the management of this insect in soybean agro‐ecosystems.     

Complex inheritance of larval adaptation in Plutella xylostella to a novel host plant

Studying the genetics of host shifts and range expansions in phytophagous insects contributes to our understanding of the evolution of host plant adaptation. We investigated the recent host range expansion to pea, in the pea-adapted strain (P-strain) of the crucifer-specialist diamondback moth, Plutella xylostella (Lepidoptera: Plutellidae). Larval survivorship on the novel host plant pea and a typical crucifer host (kale) was measured in reciprocal F(1), F(2) and backcrosses between the P-strain and a strain reared only on crucifers (C-strain). Reciprocal F(1) hybrids differed: offspring from P-strain mothers survived better on pea, indicating a maternal effect. However, no evidence for sex-linkage was found. Backcrosses to the P-strain produced higher survivorship on pea than C-strain backcrosses, suggesting recessive inheritance. In a linkage analysis with amplified fragment length polymorphism markers using P-strain backcrosses, two, four and five linkage groups contributing to survival on pea were identified in three different families respectively, indicating oligogenic inheritance. Thus, the newly evolved ability to survive on pea has a complex genetic basis, and the P-strain is still genetically heterogeneous and not yet fixed for all the alleles enabling it to survive on pea. Survivorship on kale was variable, but not related to survivorship on pea. This pattern may characterize the genetic inheritance of early host plant adaptation in oligophagous insect species.