Effectiveness of thiamethoxam and imidacloprid seed treatments against Bemisia tabaci (Hemiptera: Aleyrodidae) on cotton

BACKGROUND: Bemisia tabaci (Gennadius) biotype B is one of the most important pests on cotton around the world. Laboratory, greenhouse and field experiments were conducted to determine the efficacy of thiamethoxam and imidacloprid seed treatments against B. tabaci on cotton. RESULTS: Under laboratory conditions, the two treatments caused whitefly adult mortality, reduced oviposition and increased mortality of nymphs at 10, 20, 30 and 40 days after germination (DAG). The longer the adults fed on plants from treated seeds, the higher the mortality. The two treatments did not have any effect on eggs. The efficacy of the treated seeds against B. tabaci gradually decreased from 10 to 40 DAG, being the lowest at 40 DAG. In laboratory experiments, the efficacies between the two treatments were similar. In greenhouse experiments, the two treatments were equally effective with lower numbers of whiteflies than untreated controls. With both treatments the concentrations of the active ingredient were gradually reduced with aging of the plants and from the bottom to the top leaves of the plants. Numbers of live whiteflies were well correlated with the dosage of active ingredients. Under field conditions, the seeds treated with both insecticides exhibited similar efficacy against B. tabaci for up to ～2 months. CONCLUSION: Cotton seeds treated with imidacloprid and thiamethoxam were effective against B. tabaci for up to 45 days under laboratory and greenhouse conditions, and up to ～2 months under field conditions. Use of imidacloprid‐ and thiamethoxam‐treated seeds can be an important alternative for management of whiteflies on cotton. Copyright © 2010 Society of Chemical Industry     

Transmission of the Pepino mosaic virus by whitefly

Two experiments were conducted to investigate the transmission of the Pepino mosaic virus (PepMV) by the greenhouse whitefly (Trialeurodes vaporariorum) from tomato to tomato. In the 1:1 system (in which a single virus-contaminated plant was placed next to a healthy plant in a cage containing 469 whiteflies on average) the virus was transmitted to three out of 10 plants. In the 1:4 system (in which a virus-contaminated plant was surrounded by four healthy plants in a cage with 601 whiteflies on average) the virus was transmitted to five out of 32 plants. In order to investigate the mechanism involved in the transmission, the insect bodies were washed to determine the external presence of viral particles. The results showed that the number of PepMV particles carried on whitefly bodies was low, with an average occurrence of 1.33 on the 55 whiteflies tested after the insects were in contact with infected plants for 5 days. This low occurrence was confirmed by observation under microscope, which showed an absence of PepMV-contaminated tomato sap on the insect bodies, suggesting that PepMV transmission by whiteflies could occur when they feed on the plant.     

Identification of whitefly transmitted tomato yellow leaf curl geminivirus from Iran and a survey of its distribution with molecular probes

A virus causing a disease of tomato, prevalent in the southern provinces of Iran, with symptoms of leaf-curling, stunting, reduction of leaf size, leaf corrugation, shortening of internodes and severe reduction in fruit yield, was shown to be transmissible to healthy tomato plants by grafting and by whiteflies ( Bemisia tabaci ), but not by sap inoculation. Geminivirus DNA was detected in extracts of diseased tomato plants by dot-blot hybridization assays using as probes full-length cloned DNA of Australian, Italian (Sardinian) or Jordanian strains of tomato yellow leaf curl virus (TYLCV). Geminivirus coat protein was detected in whitefly inoculated plants by dot immunobinding assay using polyclonal antibody raised against Jordanian TYLCV. A limited survey using the dot-blot hybridization assay for virus detection indicated the presence of the virus in tomato-growing provinces of southern but not northern Iran. Whitefly transmission experiments to tomato under controlled greenhouse conditions showed that some isolates of TYLCV-like geminiviruses from different parts of Iran differ in symptomatology.     

正交试验法研究黄板对3种温室西葫芦害虫的诱杀作用

应用正交试验法研究了黄板悬挂高度、黄板形状、黄板距温室出口距离、黄板距北墙距离4个因素对黄板诱杀3种温室西葫芦害虫的影响。结果表明:4个因素对诱杀温室白粉虱都具有显著、极显著影响,黄板悬挂高度和黄板距出口距离对诱杀美洲斑潜蝇有显著影响;黄板距北墙距离对诱杀有翅瓜蚜具有极显著影响。黄板诱杀害虫的4因素组合为黄板高出植株0.2 m、平板形、距出口91 m、距北墙距离0.7 m时诱杀虫量最大。     

Pyriproxyfen,a novel insect growth regulator for controlling whiteflies: Mechanisms and resistance management

Pyriproxyfen, a novel juvenile hormone mimic, is a potent suppressor of embryogenesis and adult formation of the sweetpotato whitefly, Bemisia tabaci (Gennadius), and the greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Dipping of cotton or tomato seedlings infested with 0 to 1-day-old eggs in 0.1 mg litre^?1 resulted in over 90% suppression of egg hatch of both B. tabaci and T. vaporariorum. Older eggs were affected to a lesser extent. Exposure of whitefly females to cotton or tomato seedlings treated with pyriproxyfen resulted in oviposition of non-viable eggs. The LC90 values for egg viability of B. tabaci and T. vaporariorum exposed to treated plants were 0.05 and 0.2 mg litre^?1, respectively. Treatment of whitefly larvae with 0.04–5 mg litre^?1 resulted in normal development until the pupal stage; however, adult emergence was totally suppressed. Second instars of B. tabaci exposed to 5 mg litre^?1 pyriproxyfen, excreted honeydew at a level similar to the control level until the fourth instar (pupation), after which a strong reduction was observed. Inhibition of egg-hatch on the lower surface of cotton leaves was observed when their upper surface was treated with 1–25 mg litre^?1, indicating a pronounced translaminar effect. These findings indicate that pyriproxyfen is an efficient control agent of both B. tabaci and T. vaporariorum. The compound has been used successfully for controlling whiteflies in Israeli cotton fields since 1991. Adults of B. tabaci collected from a rose greenhouse and from adjacent cotton fields were monitored during 1991–1993 for their susceptibility to pyriproxyfen. A high level of resistance was recorded in whiteflies collected from a greenhouse after three successive applications of pyriproxyfen. Based on LC50 values, the resistance ratio for egg-hatch suppression was 554-fold and, for adult emergence failure, 10-fold. However, a single treatment of pyriproxyfen in cotton fields during the summer season (according to an insecticide resistance management (IRM) strategy) did not alter appreciably the susceptibility of B. tabaci to this compound. In order to prevent development of resistance, an attempt should be made to restrict its use to one treatment per crop season applied during the peak activity of the pest. Pyriproxyfen can be alternated with other novel compounds such as buprofezin and diafenthiuron for controlling whiteflies in cotton, vegetables and ornamentals as part of integrated pest management (IPM) and IRM strategies. In pyriproxyfen- or buprofezin-resistant strains of B. tabaci or T. vaporariorum, no appreciable cross-resistance was observed among pyriproxyfen, buprofezin and diafenthiuron.     

水氮供应对温室黄瓜叶绿素含量及光合速率的影响

利用温室小区试验,以黄瓜"博耐9-1"为供试品种,设置3个灌水水平:低水W1(60%ET0)、中水W2(80%ET0)和高水W3(100%ET0),全生育期灌水量分别为126、152 mm和177 mm;4个施氮水平:无氮N0(0)、低氮N1(180 kg·hm-2)、中氮N2(360 kg·hm-2)和高氮N3(540 kg·hm-2),共12个处理,研究了不同水氮供应对温室黄瓜叶绿素含量和光合速率的影响。结果表明:黄瓜叶绿素含量随着生育期的推进呈现先增加后降低的趋势,在盛果期取得最大值。在同一施氮水平条件下,灌水量的提高对叶绿素含量的提高均起到了促进作用。其中叶绿素总含量在W3N3处理下取得最大值,为12.32 mg·g-1,且与W2N2处理之间无显著差异。在各水氮供应条件下,黄瓜叶片的净光合速率日变化呈现单峰曲线,不施氮肥或严重亏水均会显著影响作物的净光合速率,而适量的节水节肥不仅能节约农业成本,且相比于充分灌水施肥,作物也能达到较好的净光合速率。在光照较强较稳定的情况下,W2处理下黄瓜叶片净光合速率达到最大值。从总体变化趋势看,W2N2处理(80%ET0,N 360 kg·hm-2)可认为是基于本试验条件下较适宜的水氮组合。     

Pymetrozine interferes with transmission of<Emphasis Type="Italic">Tomato yellow leaf curl virus</Emphasis> by the whitefly<Emphasis Type="Italic">Bemisia tabaci</Emphasis>

Pymetrozine, a novel compound belonging to the class pyridine-azomethines, is a feeding inhibitor labeled for use against plant pests in the order Hemiptera. Pymetrozine was evaluated for its ability to interfere with whitefly transmission of the begomovirusTomato yellow leaf curl virus (TYLCV). Pymetrozine was applied as Fulfill ^TM 50 WG at two rates (0.291 and 0.582 g formulationl ⁻¹) to tomato seedlings with four to six true leaves. Viruliferous whiteflies (three to five per plant) were added 1, 4, 7 and 11 d after a single application of pymetrozine, and transmission rates were determined 4 wk after the addition of whiteflies. Pymetrozine provided protection against transmission of TYLCV by viruliferous whiteflies for up to 1 wk after a single apliation. No phytotoxicity was observed on tomato transplants. These results indicate that pymetrozine could be an effective tool for tomato transplant producers to protect susceptible transplants from infection by begomoviruses, such as TYLCV. Pymetrozine might also work well as part of an integrated approach to begomovirus management in greenhouse tomato fruit production. http://www.phytoparasitica.org positing Oct. 20, 2003.     

茄田和菜用大豆田烟粉虱成虫数量及空间格局动态差异

运用随机抽样方法进行田间系统调查,并用t检验法、种群聚集强度指标及地统计学方法,对茄田和菜用大豆田烟粉虱成虫数量及空间格局差异进行研究。结果表明,7月7日至8月25日茄田烟粉虱成虫种群增长模型为y=3053e0.0053x(r=0.823*),菜用大豆田烟粉虱成虫种群增长模型为y=2356e-0.1662x(r=-0.9631**),对茄田和菜用大豆田烟粉虱成虫种群数量之间的差异性进行t检验,t值为3.3333,df=7时,t0.05=2.365,两者之间差异显著。这期间两种作物上烟粉虱成虫的田间水平分布和在茄株叶片上的垂直分布均呈聚集分布格局。     

Guideline for the evaluation of side-effects of pesticides. Encarsia formosa

This guideline is concerned with the evaluation of the side-effects of pesticides on Encarsia formosa (ENCAFO) in the glasshouse. Encarsia formosa is used for biological or integrated control of greenhouse whitefly ( Trialeurodes vaporariorum (TRIAVA)). Because field-testing is laborious and costly, this guideline includes a sequential testing scheme involving three laboratory tests, which may serve to classify many pesticides as definitely harmless or harmful without having recourse to field tests. In particular, the very stringent residual contact test on adults (the most sensitive stage) allows products to be classed as definitely harmless, since experience has shown that no product so classed by this test is ever harmful in field tests. The direct contact test on pupae (the most insensitive stage) makes it possible to exclude as definitely harmful products which have ≥ 50% effect. Products which are not harmful to pupae in this test could still kill adults after emergence if they are sufficiently persistent. So a 3-day persistence test makes it possible to exclude further products as too persistent. Finally, only products which appeared potentially harmful in the first test, but were harmless to pupae and non-persistent, have to be field tested, by comparison with harmful and harmless reference products, to decide on the final rating.     

Screening for Resistance to Bacterial Blight in Cowpea

Abstract

The evaluation of greenhouse and field screening methods for the identification of resistance to bacterial blight (Xanthomonas vignicola Burkh.) amongst germplasm and breeding lines of cowpea (Vigna unguiculata(L.) Walp.) is described. A stem injection technique and a leaf infiltration method were found reliable under greenhouse conditions while foliar spray inoculation was appropriate for use in both greenhouse and field experiments. A seed inoculation technique for evaluating seedling mortality may prove useful although only one susceptible cowpea accession was used in this study. Since distinct syndromes of bacterial blight (seedling mortality, stem canker and foliar blight) are recognised, it may be advantageous to adopt a different inoculation method for each syndrome to establish the relationship between the resistance of different plant parts within cowpea genotypes. Results confirm the existence of at least two distinct mechanisms of resistance to bacterial blight in cowpea. Hypersensitive resistance was clearly demonstrated in the accession TVu 410 by the leaf injection infiltration method; VITA 3 was shown to possess a field resistance, expressed as reduced and delayed disease development. The probable stability of these mechanisms is discussed with regard to their suitability as breeding objectives.     

Screening Luffa germplasm and advanced breeding lines for resistance to Tomato leaf curl New Delhi virus

The two cultivated Luffa species can be severely infected by Tomato leaf curl New Delhi virus (ToLCNDV) with up to 100% yield loss. Here, 52 Luffa genotypes were screened for ToLCNDV resistance after natural field infection. Mean vulnerability index (VI) ranged from 0.00 to 75.33; genotypes IIHR-137 and IIHR-138 had no symptoms (VI 0), 16 genotypes were resistant (VI 0–25), 15 were moderately resistant (VI 26–50), and 19 were moderate to susceptible (VI?>?50). Ten of the most resistant genotypes and five susceptible checks were then challenge-inoculated using whiteflies or sap in an insect-proof net house; only IIHR-137 [L. cylindrica (L.) Roem.] was symptomless (VI 0.00), and 3–5% of plants of IIHR-138 [L. cylindrica (L.) Roem.] and IIHR-Sel-1 [L. acutangula (L.) Roxb.] had only mild symptoms; genotype Arka Prasan was most susceptible (VI 80.96). Asymptomatic plants were confirmed as infected using polymerase chain reaction. Susceptible genotypes rapidly developed leaf curling, then a severe mosaic 10 days post-inoculation. The resistant inbred lines identified are good candidates for a breeding program for ToLCNDV-resistant cultivars.

     

The virus-vector relationship of the tomato leafcurl virus (TLCV) and its vector,Bemisia tabaci gennadius (Hemiptera: aleyrodidae)

Basic studies carried out in India showed that the incubation period of TLCV in plants varied from 8 days in August to 90 days in winter. The acquisition threshold for the whitefly,Bemisia tabaci Gen., was 31 min; it resulted in 3% transmission. An acquisition access of 24 h for a female whitefly on a TLCV source resulted in 30% transmission. A minimum feeding period of 32 min was required by a viruliferous whitefly to cause infection on tomato test plants; this gave 4% transmission. With inoculation access of 24 h on tomato test plants, the transmission rose to 24%. Starving the vector for 1 h pre-acquisition or 1 h pre-inoculation resulted in higher levels of transmission of TLCV: 36 and 40%, respectively, compared with 20% for non-starved whiteflies. Extending the fasting period beyond 1 h resulted in a reduced transmission level. The whiteflies could acquire the virus from the cotyledonary leaves of an infected tomato plant, with a resultant 28% transmission; but infection did not occur when the whiteflies had an inoculation access to such leaves. Higher transmission rates were obtained when the younger leaves on tomato plants were used for acquisition and inoculation. Transmission was 8 and 38% when five whiteflies per plant were allowed 24 h of acquisition access to 11- and 2-month-old virus sources, respectively. After an acquisition access of 24 h to a TLCV source, male and female whiteflies retained their infectivity for 5 and 53 days, respectively. Nymphs can acquire and transmit the virus. When ten whiteflies of each sex were given 24 h of acquisition and of inoculation access, the subsequent transmission rate of males and females was 56 and 86%, respectively. This virus is not transovarially transmitted. Whitefly colonies raised on brinjal were more efficient (70 and 84% transmission in two experiments) than those raised on chilli, cotton, cowpea, tobacco or tomato.     

Tracing the geminivirus-whitefly transmission pathway by polymerase chain reaction in whitefly extracts, saliva, hemolymph, and honeydew

ABSTRACT A membrane feeding system and polymerase chain reaction (PCR) were used to track squash leaf curl virus (SLCV) DNA in whole whitefly body extracts and in saliva, honeydew, and hemolymph of its whitefly vector, Bemisia tabaci, and a whitefly nonvector, Trialeurodes vaporariorum. SLCV ingestion was monitored by PCR in whiteflies that were given acquisition access periods (AAPs) ranging from 0.5 to 96 h on virus-infected plants. SLCV detection by PCR in whole body extracts was considered reflective of virus ingestion. As whiteflies were given longer AAPs, the number of whiteflies that ingested SLCV increased. SLCV DNA was detected in honeydew of vector and nonvector whiteflies, indicating that virions, viral DNA, or both passed unimpeded through the digestive system. SLCV DNA was detected in saliva and hemolymph of B. tabaci, but not in these fractions from nonvector whiteflies, despite virus ingestion by both. Although vector and nonvector whiteflies both ingested SLCV, only in the vector, B. tabaci, did virus cross the gut barrier, enter the hemolymph, or pass into the salivary system. These results suggest that digestive epithelia of nonvector whiteflies did not permit SLCV passage from the gut to hemocoel, whereas virus effectively crossed the analogous gut barrier in vector whiteflies.     

东亚小花蝽携带绿僵菌防控西花蓟马和烟粉虱的效果评价

天敌昆虫和生防菌的联合应用对害虫防控具有潜在的增效作用。东亚小花蝽Orius sauteri是目前常用的捕食性天敌之一, 被广泛用于温室蓟马、粉虱等害虫的防治。金龟子绿僵菌Metarhizium anisopliae寄主广泛, 可有效防治多种温室害虫, 且相对安全。为探索东亚小花蝽与金龟子绿僵菌联用的控害效果, 本文在室内和田间条件下研究了二者对烟粉虱Bemisia tabaci和西花蓟马Frankliniella occidentalis的协同控害作用。室内测定结果表明, 绿僵菌孢子悬浮液浓度不大于5×107孢子/mL时, 不会对东亚小花蝽5龄若虫的存活和羽化造成负面影响。室内与温室笼罩条件下, 东亚小花蝽携带绿僵菌的处理能够降低辣椒上的西花蓟马和烟粉虱发生量, 表明东亚小花蝽携带绿僵菌可提高对西花蓟马和烟粉虱的防治效果, 证明了天敌昆虫和生防菌联合应用的可行性, 为生物防治方式多元化应用与推广提供了实践指导。     

28%三环唑·嘧菌酯悬浮剂对水稻稻瘟病的防治效果

为科学合理地选择和使用田间控制稻瘟病的杀菌剂,本研究通过室内苗期测定和大田试验,评价复配剂28%三环唑·嘧菌酯SC对水稻稻瘟病的防治效果。结果表明,28%三环唑·嘧菌酯SC对水稻苗瘟及穗瘟均有很好的预防和治疗效果。在温室人工控制条件下,施药后接种的防效高于接种后施药的防效,最高防效分别为97.35%和92.70%。在田间对穗瘟的最高防效达到91.11%,与对照药剂75%三环唑WP和250 g/L嘧菌酯SC的平均防效相当,可以在生产上推广使用,推荐有效成分用量为252～420 g/hm~2。     

Biotechnische Regulierung der Kohlmottenschildlaus in Kohlgem��se �C Sachstand und Perspektiven

The cabbage whitefly,Aleyrodes proletella, has developed to a key pest in brassica vegetable crops throughout Germany. In a 3-year project we investigated a biotechnical approach employing netting (0.8?×?0.8 mm meshsize) in combination with the native parasitoidEncarsia tricolor in an inoculative-inundative approach in organic Brussels sprouts under field conditions. In small scale plot experiments continuous netting from transplanting in May till October alone reduced whitefly larval densities by 77 % at peak infestation in all years. Remaining whitefly infestation under net was associated with the necessity of temporary net removal for the purpose of mechanical weeding, which caused primary whitefly infestation. Release of mass rearedE. tricolour under net at the first signs of larval infestation significantly increasedA. proletella-parasitation and reduced infestation compared to netted controls without release. Furthermore, at highest dosage in 2009,E. tricolor had a significant enhancing effect on raw yield and the quality level of marketable yield. Additional on-farm experiments without netting in 2008 and 2009 confirmed the control potential ofE. tricolor. Although the most important project mile stones have been achieved, namely (a)E. tricolour-establishment under net and in the open field, (b) enhanced parasitation corresponding with pest density decline and (c) a positive impact on yield and quality parameters, further research will be necessary. The focus should be on the initial infestation period, optimizing the timing, frequency and required dosage.     

4LZY-7型全喂入油菜联合收获机的设计与试验

为解决西北地区油菜机械化收获中存在损失率高、作业效率低等问题,设计并试制了一种可一次性完成收割、脱粒、分离、清选、入仓等一体化作业的4LZY-7型全喂入油菜联合收获机。结合现有稻麦联合收获机,并针对油菜的生物特性及其收获时的农艺要求,对样机核心部件的作业机理进行了分析,并对样机关键部件进行了设计,确定了割台系统、脱粒系统和清选系统的工作参数。田间试验结果表明,当作业速度在0.8~1.2 m·s^-1之间,拨禾轮线速度在1.4~1.8 m·s^-1之间,即速比取1.5~2.25时割台损失率为2.35%;脱粒滚筒的圆周速度在15~20 m·s^-1之间,脱粒间隙为20 mm时,滚筒的脱净率大于96.9%;风机出口处风速为4.07 m·s^-1,筛面倾斜角度为16±2°时,筛出物菜籽含量为0.11%,粮仓含杂率为2.83%。即整机损失率最高为3.95%,粮仓含杂率最高为2.83%,机械破碎率最高为0.2%。各项试验指标均符合国家和行业标准要求,试验结果满足设计和实际作业要求。     

Efficacy of insect nets for cabbage production and pest management depending on the net removal frequency and microclimate

In Africa, synthetic pesticide applications are overly frequent and above labelled rates. We assessed the efficacy of an insect net physical control system on field cabbage (Brassica oleracea var. capitata) production in France and Benin. Various mesh sizes and netting removal frequencies were compared under contrasting climatic conditions. Studies under Mediterranean climatic conditions (spring season) compared two mesh sizes (0.73 mm and 1.6 mm). Studies under subequatorial climatic conditions (cool and hot seasons) tested nets of mesh size 0.4 mm and 0.9 mm used either as permanent cover, removed daily, or 3 days per week. The results showed that a fine mesh did not improve the netting efficacy against pests but had a major impact on the microclimate. In Mediterranean climatic conditions, the netting efficacy and beneficial microclimate improved crop yields. In subequatorial conditions, crop yields were lowest with permanent net protection due to high temperatures under the nets and poor aphid and Spodoptera littoralis control. Removing the nets 3 days per week was a good technical/economic trade-off, ensuring acceptable efficacy with minimal effects on the microclimate.     

Assessment of Partial Resistance to Powdery Mildew (Podosphaera pannosa) in a Tetraploid Rose Population Using a Spore-suspension Inoculation Method

Powdery mildew (Podosphaera pannosa) is the most important fungal disease in greenhouse roses and is in practice controlled by fungicides. The creation of novel cultivars with durable resistance to powdery mildew is highly desirable. To understand the inheritance of mildew resistance, a tetraploid rose population with a size of 181 seedlings was obtained by crossing two tetraploid genotypes each having partial resistance. The population and its parents were tested under greenhouse conditions with two well-defined monospore isolates (2 and F1) using artificial inoculation with spore suspensions. Disease score at 11 days post-inoculation, latent period and rate of symptom development were used to describe seedling resistance. The tests for both isolates exhibited a wide and significant variation among genotypes for resistance. The distribution of the genotypic means of the disease scores was continuous and showed a considerable transgression. Statistical analysis, scatter plot of disease scores for the isolates, and correlation analyses indicated that the two isolates differed in pathogenicity. The outcome of the tests showed that the inoculation assay with spore suspensions was a reliable and effective way to screen large numbers of genotypes under greenhouse conditions for genetic and breeding studies. This is the first report on spore-suspension inoculation to be used successfully in rose.     

浙南菜区番茄曲叶病毒病发生规律

通过两年调查,明确了浙南菜区越冬番茄曲叶病毒病的主要侵染期在9月下旬至10月上旬,即番茄苗龄20~30 d。温州近郊常年蔬菜生产基地,番茄曲叶病毒病的侵染循环主要通过携毒烟粉虱在越冬番茄和早春番茄间传播完成。苍南、瑞安等季节性番茄生产基地,该病的侵染循环主要通过携毒烟粉虱在越冬番茄、大田番茄苗和夏季南瓜等中间寄主传播完成。随着播种期推迟,番茄曲叶病毒病发生轻,目前浙南菜区生产上‘托马雷斯’、‘好韦斯特’、‘合作903’等主栽番茄品种均表现感病。田间调查还表明,通过50目防虫网覆盖育苗栽培可以有效控制番茄曲叶病毒病发生,防控效果达到90%以上。