吡虫啉对烟田节肢动物群落的影响研究

利用群落参数分析了吡虫啉对烟田节肢动物群落及其各亚群落的影响。结果表明,施药后对烟田节肢动物群落、害虫亚群落的物种数有一定的影响,对天敌昆虫和蜘蛛亚群落物种数的影响不明显。5月23日施药后至6月13日施药区(Ⅱ)和对照区节肢动物群落、害虫亚群落个体数均下降,下降程度施药区大于对照区。6月14日施药后施药区节肢动物群落、害虫亚群落个体数下降,对照区显著上升。两次施药对天敌昆虫和蜘蛛亚群落个体数的影响不明显,施药后一段时间内优势种烟蚜种群个体数量显著下降,使节肢动物群落和害虫亚群落优势集中性下降,多样性指数和稳定性增加。     

噻虫嗪对昆虫病原线虫侵染韭菜迟眼蕈蚊能力的影响

【目的】为提高昆虫病原线虫对韭菜迟眼蕈蚊Bradysia odoriphaga Yang et Zhang幼虫的防治效果,将昆虫病原线虫与环境友好型化学杀虫剂混用是一条有效途径。【方法】测定了噻虫嗪与6个昆虫病原线虫品系混用对韭菜迟眼蕈蚊的作用效果,以及温度和土壤含水量对作用效果的影响,并进行了田间验证。【结果】田间推荐浓度噻虫嗪(100 mg·L~(-1))对6种供试线虫存活无显著影响。处理后3 d,低浓度噻虫嗪(15 mg·L~(-1))分别与6品系线虫混合后处理韭菜迟眼蕈蚊幼虫,其死亡率明显高于线虫和噻虫嗪单用处理。小卷蛾斯氏线虫SF-SN+噻虫嗪、印度异小杆线虫LN2+噻虫嗪和小卷蛾斯氏线虫All+噻虫嗪3种组合发挥杀虫作用的最适温度范围分别为20~25℃、25~30℃和25~30℃,显著高于其他温度;最适土壤含水量范围为10%~18%,也显著高于其他湿度。大田条件下,施用后7 d,单用噻虫嗪、线虫+噻虫嗪组合处理对韭菜迟眼蕈蚊的防治效果显著高于单线虫,且以芫菁夜蛾斯氏线虫SF-SN+噻虫嗪的防治效果最高,达到93%以上。【结论】芫菁夜蛾斯氏线虫SF-SN品系与噻虫嗪组合联合防治韭菜迟眼蕈蚊效果最好。     

叶喷和土施化学药剂对柑橘木虱的防效研究

【目的】筛选对柑橘木虱Diaphorina citri Kuwayama成虫具有高防效、低毒作用的杀虫剂,旨在为柑橘黄龙病(Huanglongbing,HLB)的综合防控提供理论依据。【方法】采用室内药膜法和田间生物测定,评价了12种化学药剂的毒力和防治效果,筛选出适合叶面喷雾和土壤淋施的高效低毒化学农药及其最佳使用浓度,为柑橘木虱化学防治的科学精准用药提供参考。【结果】对12种药剂室内毒力测定结果表明,对柑橘木虱成虫毒力效果较好的是48%噻虫胺、45%毒死蜱、10%溴氰虫酰胺和20%呋虫胺,LC50分别为1.42、1.48、1.49、1.60 mg/L。田间叶面喷雾生测结果表明,20%呋虫胺和10%溴氰虫酰胺施药后7 d,防效均达到90%以上,综合防效优于其他10种药剂。土壤淋施生测结果表明,30%噻虫嗪的累积减退率在12 d时达到100%,显著高于其他4种药剂,不同浓度筛选结果表明在施药后第7天,100 mg/L和150 mg/L的30%噻虫嗪防效均达到100%,且在施药30 d后其防效均在60%以上。【结论】柑橘木虱化学防治田间叶面喷雾以150 mg/L的20%呋虫胺或100 mg/L的10%溴氰虫酰胺防治效果较好,且持效期长,而土壤淋施则100 mg/L的30%噻虫嗪防治效果最好,且持效期长,具有较大的应用价值。     

小型植保无人机超低量喷雾防治稻水象甲

【目的】通过建立适宜新疆荒漠绿洲特殊生态环境的稻水象甲超低量喷雾技术,为稻水象甲的大面积统防统治提供新型施药技术。【方法】以小型遥控多旋翼植保无人机(UAV)为施药机械,以稻水象甲常规喷雾防效大于90%的药剂为首选药剂,开展了药剂、施药量、助剂以及施药机型的筛选试验。【结果】施药后3、7、14和21 d虫口密度高于防治指标的样地所占比例依次为35.71%、21.43%、35.71%和78.57%。30%氯虫·噻虫嗪187.5 mL·hm~(-2)防效最佳,14 d药效高达93.43%;药后21 d,球孢白僵菌3000 mL·hm~(-2)的防效最高,达84.65%。各药剂施药量与防效呈正相关。此外,UAV喷雾防治稻水象甲时,添加助剂的平均防效可提高22.29%~28.49%。【结论】在农业精准施药、绿色生产中,综合考虑供试药剂的施药量、持效期、防效和药后存活虫量,建议以30%氯虫·噻虫嗪SC和14%氯虫·高氯氟CS作为全程以UAV为施药机械防治稻水象甲的首选药剂,在稻水象甲种群发展前中期优先考虑低浓度施药量;同时,为避免UAV在实际作业中药液雾滴发生飘失和流失问题,可以考虑添加飞防助剂提升防效。     

12种杀虫剂及5种天敌昆虫对梧桐木虱的田间控害评价

梧桐木虱是一种危害园林植物梧桐的重大害虫。本研究分别测定了12种杀虫剂和5种天敌昆虫对梧桐木虱的防治效果。结果表明: 12种杀虫剂中噻虫嗪和吡虫啉对梧桐木虱的防治效果最好,螺虫乙酯次之。在喷雾法、注射法和灌根法等3种施药方式中,应尽量避免使用喷雾法,优先选择注射法,在条件允许的情况下可使用灌根法作为补充手段。5种天敌昆虫中以中华通草蛉和赤星瓢虫对梧桐木虱的防治效果最佳,在长期防治效果上可以起到代替杀虫剂的作用。因此,中华通草蛉及赤星瓢虫可作为园林环境中长期安全环保防治梧桐木虱的重要方法,而以注射法使用噻虫嗪和吡虫啉可作为短期快速防治手段。     

采用两种不同施药方法评价八种药剂对韭蛆的防治效果

【目的】为筛选有效防治韭蛆Bradysia odoriphaga Yang et Zhang的药剂及科学合理的施药方法。【方法】本试验充分抓住韭蛆喜湿这一生物学特性,采用两种不同的施药方法(单次定点淋根法和二次灌根法)评价8种药剂对韭蛆的防治效果。【结果】同种药剂不同的施药方法,二次灌根法在韭蛆防效、韭菜保苗率和韭菜增产率三方面均明显高于单次定点淋根法。同时,噻虫胺、噻虫嗪和吡虫啉3种药剂单独使用,或分别与辣根素混配,对韭蛆均表现出最佳的防治效果。【结论】本研究提出了一种科学合理的施药方法,对防治韭蛆具有重要的意义。     

烟草连作障碍与土壤理化性质及微生物多样性特征的关联

【背景】烟草是我国最重要的经济作物之一,其忌连作的特点严重影响了我国烟草产业的发展。【目的】通过研究烟草连作障碍、土壤理化性质和微生物多样性特征的关系,为解决烟草连作障碍问题、制定有效的烟草生产技术提供理论基础。【方法】选择连作障碍严重烟田和克服连作障碍烟田作为研究对象,基于高通量测序技术,探究烟田连作障碍情况、烟田理化性质与土壤微生物多样性的联系。【结果】克服连作障碍的烟田土壤pH、总氮和有机质含量显著高于连作障碍严重的烟田土壤,克服连作障碍烟田和连作障碍严重烟田土壤微生物多样性之间不存在显著差异,但土壤微生物优势群落发生了显著改变,烟田土壤的pH、有机质、有效磷、总氮都与微生物群落显著相关。【结论】烟田克服连作障碍的差异,可能与烟田土壤的理化性质以及微生物组成的差异有关,此研究为解决湘西烟区连作障碍问题提供理论基础和技术支持。     

噻虫嗪施用对二斑叶螨种群动态的影响

为了明确新烟碱类杀虫剂噻虫嗪对非靶标害虫二斑叶螨Tetranychus urticae种群的影响,本研究在玻璃温室的盆栽苗和设施大棚内,采用噻虫嗪灌根、喷雾等不同施用方式,研究了二斑叶螨的种群动态变化。盆栽苗的模拟结果表明,噻虫嗪施用后,二斑叶螨卵和成若螨的数量均显著高于清水处理;而噻虫嗪灌根处理叶螨数量在初期显著高于喷雾处理,后期无显著差异;设施棚内采用噻虫嗪进行灌根施用,发现二斑叶螨雌成螨自然种群数量也显著高于对照处理区。结果表明,噻虫嗪灌根会刺激田间叶螨种群的快速增长,因此在田间施用噻虫嗪时应特别注意对叶螨的防控。     

Q型烟粉虱UDP-糖基转移酶UGT354A1基因克隆及其在噻虫嗪抗性中的作用

【目的】UDP-糖基转移酶（UGTs）是昆虫主要的Ⅱ期解毒酶,可能参与昆虫抗药性的形成。本研究旨在探究Q型烟粉虱中UGT基因是否参与其对噻虫嗪的抗药性。【方法】依据烟粉虱基因组数据库设计引物,克隆其UGT354A1基因的全长序列;采用qRT-PCR技术检测UGT354A1基因在烟粉虱不同发育阶段、不同组织部位以及抗敏品系中的表达量;通过RNA干扰试验,验证UGT354A1基因在烟粉虱噻虫嗪抗性中的作用。【结果】序列生物信息学分析发现,UGT354A1基因属于典型的昆虫UGTs,包括两个糖基供体（DBR1和DBR2）和一个保守特征性基序。qRT-PCR结果显示,UGT354A1基因在噻虫嗪抗性品系（THQR）中的表达量为敏感品系（THQS）的2.60倍,且噻虫嗪可显著诱导该基因的表达。在不同发育阶段和组织部位中,发现UGT354A1基因在烟粉虱若虫和成虫阶段及头部和胸部表达丰富。RNAi后,沉默UGT354A1基因能够显著增加噻虫嗪对Q型烟粉虱的毒杀作用。【结论】UGT354A1基因在Q型烟粉虱中对噻虫嗪具有重要的解毒作用,可能参与了抗性的形成。     

七种杀虫剂对小麦吸浆虫和麦蚜防治效果研究

【目的】明确25%吡蚜酮SC、3%甲氨基阿维菌素苯甲酸盐ME、25%噻虫嗪WG、14%氯虫·高氯氟ZC、15%高氯·毒死蜱EC、2.5%高效氯氟氰菊酯EW和40%毒死蜱EC 7种杀虫剂对小麦吸浆虫和蚜虫的防治效果,为科学、合理用药防治小麦害虫提供参考。【方法】采用喷雾法和剥穗调查法,研究它们对小麦吸浆虫成虫和麦蚜的防效,及防后对小麦吸浆虫幼虫危害损失的影响。【结果】参试药剂药后1 d对小麦吸浆虫成虫防效均高于90%,药后3~5 d防效为84.81%~93.93%,防后挽回损失76%以上;对麦蚜药后1、3、5 d防效分别高于75%、80%和85%。在供试的7种药剂中,15%高氯·毒死蜱EC药后3~5 d对两种害虫防效、挽回吸浆虫危害均超过90%,应用效果最好;其次为25%噻虫嗪WG和40%毒死蜱EC,药后3~5 d对吸浆虫防效高于90%、对麦蚜防效分别高于86%和90%,挽回吸浆虫危害损失88%以上。【结论】供试药剂对小麦吸浆虫和麦蚜防效存在显著差异,15%高氯·毒死蜱EC对两种害虫防治效果最好。     

Response of old and new cowpea varieties to insecticide spray regimes in the Sudan savanna of Nigeria

Insect pests are major constraint to cowpea production in northern Nigeria causing yield losses up to 70%. Several cowpea varieties have been developed and delivered to farmers by IITA over the past four decades. These varieties have varying degrees of resistance to insect pest attacks. A field study was established in northern Nigeria to determine the response to insecticide spraying of old cowpea varieties developed in the late 1970s and new varieties developed in the 2000s in order to determine whether new varieties have lesser requirement for spraying with insecticides than the old ones. The result revealed that the new cowpea varieties developed in the 2000s require more spraying than the old varieties developed in the 1970s. Infestations by the insect pests, maruca (Maruca virata Fabricius) and flower thrips (Megalurothrips sjostedti Trybom) were significantly less at zero and 1 spray for old varieties than for the new varieties. Old varieties also produced significant higher grain yield at zero and 1 spray compared with new varieties. Newer varieties require more spray to maximise yield gain.     

Lethal and sub‐lethal effects of spinosad on the life‐history traits of army worm,Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), and its fitness cost of resistance

Spodoptera litura is one of the most destructive polyphagous insect pests, with more than 120 host‐plant species. In our present study, a field‐collected population of S. litura when selected with spinosad for 11 consecutive generations resulted in the development of 3921‐fold resistance to spinosad as compared to the susceptible strain. The spinosad‐resistant strain of S. litura had a relatively high fitness cost (0.17) as compared to the susceptible strain. Furthermore, the lethal and sub‐lethal effects of different concentrations of spinosad were checked on the susceptible strain at different levels; i.e., LC₄₀, LC₃₀, LC₂₀ and LC₁₀, which revealed that the impact of spinosad on the life‐history traits of S. litura increased with the increase in concentration of spinosad. A significant impact of spinosad was recorded on the larval duration, pre‐pupal weight, pupal duration, pupal weight, reproductive potential and adult emergence. The outcomes of the current research clearly indicate that fitness cost of spinosad and its sub‐lethal effects have a significant impact on population dynamics of S. litura, for which it can be incorporated in integrated pest management.     

Accumulation of a chymotrypsin inhibitor in transgenic tobacco can affect the growth of insect pests

A member of the potato proteinase inhibitor II (PPI II) gene family that encodes for a chymotrypsin iso-inhibitor has been introduced into tobacco (Nicotiana tabacum) usingAgrobacterium tumefaciens-mediated T-DNA transfer. Analysis of the primary transgenic plants (designated R₀) confirmed that the introduced gene is being expressed and the inhibitor accumulates as an intact and fully functional protein. For insect feeding trials, progeny from the self-fertilization of R₀ plants (designated R₁) were used. Leaf tissue, either from transgenic or from control (non-transgenic) plants, was fed to larvae ofChrysodeixis eriosoma (Lepidoptera: Noctuidae, green looper),Spodoptera litura (F.) (Lepidoptera: Noctuidae) andThysanoplusia orichalcea (F.) (Lepidoptera: Noctuidae) and insect weight gain (increase in fresh weight) measured. Consistently,C. eriosoma larvae fed leaf tissue from transgenic plants expressing thePPI II gene grew slower than insects fed leaf tissue from non-transgenic plants or transgenic plants with no detectablePPI II protein accumulation. However, larvae of bothS. litura andT. orichalcea consistently demonstrated similar or faster growth when fed leaf tissue from transgenic plants compared with those fed non-transgenic plants. In agreement with the feeding trials, the chymotrypsin iso-inhibitor extracted from transgenic tobacco effectively retarded chymotrypsin-like activity measured inC. eriosoma digestive tract extracts, but not in extracts fromS. litura. We conclude, therefore, that for certain insects the use of chymotrypsin inhibitors should now be evaluated as an effective strategy to provide field resistance against insect pests in transgenic plants, but further, that a single proteinase inhibitor gene may not be universally effective against a range of insect pests. The significance of these observations is discussed with respect to the inclusion of chymotrypsin inhibitors in the composite of insect pest resistance factors that have been proposed for introduction into crop plants.     

Biocontrol efficacy of protoplast fusants between Bacillus thuringiensis and Bacillus subtilis against Spodoptera litura Fabr.

Bacillus thuringiensis (Bt) is a microbial pesticide widely used to control crop pests. Its strains have good biocontrol activity against crop insect pest, but lack some desirable characteristics that are found in Bacillus subtilis. An attempt has been made to combine those desirable characteristics; we used a highly effective biocontrol strain of B. thuringiensis in protoplast fusions with a strain of B. subtilis. The fusants were identified through cell culture and stained with crystal violet. The Bt and B. subtilis protoplasts were induced to fuse by PEG 6000. The fusants were produced almost 95% mortality in first instar larvae of Spodoptera litura. The lethal doses (The LC₅₀ and LC₉₀) for mortality of S. litura values were significantly in lower level in the fusant-treated larvae, when compared with Bt and B. subtilis individual treatment. The consumption and digestion of S. litura significantly decreased after treatment with fusant. Also the approximate digestibility of S. litura increased significantly.     

Temperature Impacts the Development and Survival of Common Cutworm (Spodoptera litura): Simulation and Visualization of Potential Population Growth in India under Warmer Temperatures through Life Cycle Modelling and Spatial Mapping

The common cutworm, Spodoptera litura, has become a major pest of soybean (Glycine max) throughout its Indian range. With a changing climate, there is the potential for this insect to become an increasingly severe pest in certain regions due to increased habitat suitability. To examine this possibility, we developed temperature-based phenology model for S. litura, by constructing thermal reaction norms for cohorts of single life stages, at both constant and fluctuating temperatures within the ecologically relevant range (15–38°C) for its development. Life table parameters were estimated stochastically using cohort updating and rate summation approach. The model was implemented in the geographic information system to examine the potential future pest status of S. litura using temperature change projections from SRES A₁B climate change scenario for the year 2050. The changes were visualized by means of three spatial indices demonstrating the risks for establishment, number of generations per year and pest abundance according to the temperature conditions. The results revealed that the development rate as a function of temperature increased linearly for all the immature stages of S. litura until approximately 34–36°C, after which it became non-linear. The extreme temperature of 38°C was found lethal to larval and pupal stages of S. litura wherein no development to the next stage occurred. Females could lay no eggs at the extreme low (15°C) and high (> 35°C) test temperatures, demonstrating the importance of optimum temperature in determining the suitability of climate for the mating and reproduction in S. litura. The risk mapping predicts that due to temperature increase under future climate change, much of the soybean areas in Indian states like Madhya Pradesh, Maharashtra and Rajasthan, will become suitable for S. litura establishment and increased pest activity, indicating the expansion of the suitable and favourable areas over time. This has serious implication in terms of soybean production since these areas produce approximately 95% of the total soybeans in India. As the present model results are based on temperature only, and the effects of other abiotic and biotic factors determining the pest population dynamics were excluded, it presents only the potential population growth parameters for S. litura. However, if combined with the field observations, the model results could certainly contribute to gaining insight into the field dynamics of S. litura.     

Biological and genetic characterization of a Pakistani isolate of Spodoptera litura nucleopolyhedrovirus

Spodoptera litura is an emerging insect pest in a wide range of crops worldwide. The insect is difficult to control because of resistance development to synthetic insecticides and emerging resistance to Bacillus thuringiensis toxins. Therefore, there is a need to develop biological control agents, preferably from an indigenous source to avoid risks associated with the importation of exotic natural antagonists. A Pakistani isolate of S. litura nucleopolyhedrovirus (SpltNPV, Baculoviridae), SpltNPV-Pak-BNG, was obtained from the field and characterized biologically and genetically, and compared to a SpltNPV reference isolate, SpltNPV-G1, thought to be of Chinese origin. The dose–mortality response (LD₅₀) of SpltNPV-Pak-BNG was not significantly different from that of the reference isolate SpltNPV-G1, but the time-to-death (LT₅₀) was significantly shorter for SpltNPV-Pak-BNG than for SpltNPV-G1. DNA restriction enzyme profiling indicated that SpltNPV-Pak-BNG and SpltNPV-G1 are different viruses. Sequence analysis of ‘ORF24’, specific for SpltNPV (and S. littoralis NPV as ORF21), and the conserved baculovirus core genes polyhedrin, DNApol, pif-2 and lef-8 confirmed that this was indeed the case and that SpltNPV-Pak-BNG is a genuine SpltNPV variant, whereas the SpltNPV-G1 isolate we used is, in fact, a SpliNPV variant, renamed to SpliNPV-G1. The newly isolated SpltNPV-Pak-BNG has the potential for development as a biocontrol agent of S. litura in Pakistan.     

A field study investigating the insecticidal efficacy against Diaphorina citri Kuwayama on Kinnow mandarin,Citrus reticulata Blanco trees

Asian citrus psyllid is a most damaging insect pest of citrus. In this field study, the efficacy of seven insecticides (emamectin benzoate, bifenthrin, chlorfenapyr, fipronil, imidacloprid, pyriproxyfen and thiamethoxam) was evaluated against Diaphorina citri Kuwayama in the citrus orchard of Kinnow mandarin, Citrus reticulata Blanco. The insecticides revealed a differential and substantial relative efficacy against D. citri compared to the untreated plants. The insecticidal effect attributed as percent reduction in insect population was more prominent after three days of spray: highest reduction values were recorded with thiamethoxam (50.89%), imidacloprid (44.27%) and bifenthrin (42.94%) after first spray, and thiamethoxam (83.36%), imidacloprid (73.20%) and bifenthrin (72.66%) after second spray. Thus, neonicotinoids (thiamethoxam and imidacloprid) and pyrethroid (bifenthrin) resulted as highly effective against D. citri at three days after both sprays. At seven days, imidacloprid (63.53%) and fipronil (62.47%) presented relatively higher population reduction after first spray, and thiamethoxam (92.66%) and chlorfenapyr (89.59%) after second spray. At 12 days, the insecticidal effect on insect population became significantly at par after each spray except chlorfenapyr that reflected high population reduction (93.17%) only after second spray. It is also obvious from the data that there is need of regular monitoring to suppress the psyllids population below threshold level by timely application of the second insecticidal spray.     

Induction of 2-cyanoethyl-isoxazolin-5-one as an antifeedant against the tobacco cutworm (Spodoptera litura) by jasmonic acid in sweet pea leaf

ABSTRACT

Although sweet pea (Lathyrus odoratus) beans contain toxic β-aminopropionitrile, the plant itself is readily attacked by insects and is, therefore, protected through the use of pesticides. Consequently, the induction of L. odoratus resistance to insect attack via exogenous treatment is promising for pest control development. Screening of inducible elicitor effects showed that treatment of sweet pea foliage with jasmonic acid (JA) can induce antifeeding-based resistance to tobacco cutworm (Spodoptera litura) larvae. Spectroscopic analysis identified 2-cyanoethyl-isoxazolin-5-one (2-CEIX) as the antifeedant with a half-maximal effective concentration of 33.6 µmol/g fr. wt., i.e., exogenous JA treatment induced antifeeding activity due to the accumulation of 2-CEIX. Moreover, 2-CEIX-induced mortality of S. litura larvae was evaluated by a dipping test and the half-maximal lethal dose was determined to be 5.9 mg/mL. Therefore, 2-CEIX was concluded to be a suitable induced resistance target for elicitors or a lead compound for insecticide development.     

Knockdown of dorsal/relish increases larvae susceptibility to microbes in Spodoptera litura

The tobacco cutworm, Spodoptera litura has developed high levels of resistance to frequently-used insecticides, and failures of chemical control has frequently been reported in China. Moreover, the control efficiency of biological control agents was not satisfactory by farmers, and thus the development of novel or combined techniques for such pest control becomes an imperative requirement. In this study the potential application of innate immune-related genes in insect control was investigated. Sldorsal and Slrelish were identified from S. litura. Sldorsals were mainly expressed in epidermal and fatbody of larvae, and Slrelish highly expressed in fatbody and haemolymph of larvae. Their expression characteristic suggests potential roles in defense against fungi or bacteria. The expression of Sldorsal was up-regulated by the challenge of entomogenous fungi Isaria javanica and Beauveria bassiana, however, the expression of Slrelish could only be induced by Escherichia coli challenge. Injection of Sldorsal or Slrelish dsRNA down-regulated the expression level of the corresponding gene and broke specific signaling transduction pathway of innate immunity in S. litura. Knockdown of Sldorsal by RNAi significantly increased the mortality of S. litura larvae caused by I. javanica and B. bassiana, and Slrelish RNAi highly increased the mortality caused by E. coli. Sldorsal and Slrelish are essential genes for innate immunity, their knockdown by RNAi increases S. litura susceptibility to insect pathogens, therefore enhances the mortalities caused by I. javanica, B. bassiana and E. coli respectively.