Endophytic Colonization of Onions Induces Resistance Against Viruliferous Thrips and Virus Replication.

In agricultural ecosystems, insect pests, pathogens, weather patterns, and reduced soil fertility pose major challenges to crop productivity and are responsible for significant yield losses worldwide. Iris yellow spot virus (IYSV) vectored by Thrips tabaci Lindeman, is a major hindrance to onion production in eastern Africa. Control measures often rely on insecticides with deleterious effects. Endophytes are one key alternative as they can play important roles in mediating induced systemic resistance. Hence, we examined the potential effect of endophytic fungus Hypocrea lixii (F3ST1) on feeding and replication of IYSV on endophyte-colonized (E+) and endophyte-free (E-) onion plants. For more precise assessment, replication was also tested using leaf disk bioassays and individual thrips. The number of feeding punctures was significantly lower in E+ as compared to E- plants. Disease level was significantly lower in E+ as compared to E- plants for four weeks post-exposure to thrips. IYSV replication was reduced by 2.5-fold in endophytic treatment on both whole plant and leaf disk assays. Thrips tabaci showed 2 times higher feeding activities on endophyte-free onion leaf disks as compared to the endophyte-inoculated leaf disks. Our results suggest potential utility of the endophytes to reduce feeding damage and virus infection on onion plants. Further studies should be conducted to elucidate the secondary metabolites involved in such endophyte-thrips-virus mediated interaction and determine whether the interactions extend for this and other onion varieties and viruses under field conditions.

Can narrow-bandwidth light from UV-A to green alter secondary plant metabolism and increase Brassica plant defenses against aphids?

Light of different wavelengths is essential for plant growth and development. Short-wavelength radiation such as UV can shift the composition of flavonoids, glucosinolates, and other plant metabolites responsible for enhanced defense against certain herbivorous insects. The intensity of light-induced, metabolite-based resistance is plant- and insect species-specific and depends on herbivore feeding guild and specialization. The increasing use of light-emitting diodes (LEDs) in horticultural plant production systems in protected environments enables the creation of tailor-made light scenarios for improved plant cultivation and induced defense against herbivorous insects. In this study, broccoli (Brassica oleracea var. italica) plants were grown in a climate chamber under broad spectra photosynthetic active radiation (PAR) and were additionally treated with the following narrow-bandwidth light generated with LEDs: UV-A (365 nm), violet (420 nm), blue (470 nm), or green (515 nm). We determined the influence of narrow-bandwidth light on broccoli plant growth, secondary plant metabolism (flavonol glycosides and glucosinolates), and plant-mediated light effects on the performance and behavior of the specialized cabbage aphid Brevicoryne brassicae. Green light increased plant height more than UV-A, violet, or blue LED treatments. Among flavonol glycosides, specific quercetin and kaempferol glycosides were increased under violet light. The concentration of 3-indolylmethyl glucosinolate in plants was increased by UV-A treatment. B. brassicae performance was not influenced by the different light qualities, but in host-choice tests, B. brassicae preferred previously blue-illuminated plants (but not UV-A-, violet-, or green-illuminated plants) over control plants.

Differential proteomics analysis of Frankliniella occidentalis immune response after infection with Tomato spotted wilt virus (Tospovirus).

Tomato spotted wilt virus (TSWV) is mainly vectored by Frankliniella occidentalis Pergande, and it potentially activates the vector's immune response. However, molecular background of the altered immune response is not clearly understood. Therefore, using a proteomic approach, we investigated the immune pathways that are activated in F. occidentalis larvae after 24 h exposure to TSWV. Two-dimensional isoelectric focusing/sodium dodecyl sulfate polyacrylamide gel electrophoresis (2D-IEF/SDS/PAGE) combined with mass spectrometry (MS), were used to identify proteins that were differentially expressed upon viral infection. High numbers of proteins were abundantly expressed in F. occidentalis exposed to TSWV (73%) compared to the non-exposed (27%), with the majority functionally linked to the innate immune system such as: signaling, stress response, defense response, translation, cellular lipids and nucleotide metabolism. Key proteins included: 70 kDa heat shock proteins, Ubiquitin and Dermcidin, among others, indicative of a responsive pattern of the vector's innate immune system to viral infection.

Different Narrow-Band Light Ranges Alter Plant Secondary Metabolism and Plant Defense Response to Aphids.

Light of different wavelengths affects various physiological processes in plants. Short-wavelength radiation (like UV) can activate defense pathways in plants and enhance the biosynthesis of secondary metabolites (such as flavonoids and glucosinolates) responsible for resistance against certain herbivorous insects. The intensity of light-induced, metabolite-based resistance is plant- and insect species-specific and depends on herbivore feeding guild and specialization. In this study, broccoli (Brassica oleracea var. italica) plants were grown for 4 weeks in a climate chamber under conventional fluorescent tubes and were additionally treated with UV-B (310 nm), UV-A (365 or 385 nm), or violet (420 nm) light generated with UV-B tubes or light-emitting diodes (LEDs). The objective was to determine the influence of narrow bandwidths of light (from UV-B to violet) on plant secondary metabolism and on the performance of the cabbage aphid Brevicoryne brassicae (a specialist) and the green peach aphid Myzus persicae (a generalist). Among flavonol glycosides, specific quercetin and kaempferol glycosides increased markedly under UV-B, while among glucosinolates only 4-methoxy-3-indolylmethyl showed a 2-fold increase in plants exposed to UV-B and UV-A. The concentration of 3-indolylmethyl glucosinolate in broccoli plants increased with UV-B treatment. Brevicoryne brassicae adult weights and fecundity were lower on UV-B treated plants compared to UV-A or violet light-treated plants. Adult weights and fecundity of M. persicae were increased under UV-B and UV-A treatments. When specific light wavelengths are used to induce metabolic changes in plants, the specificity of the induced effects on herbivores should be considered.

Towards a Collaborative Research: A Case Study on Linking Science to Farmers' Perceptions and Knowledge on Arabica Coffee Pests and Diseases and Its Management.

The scientific community has recognized the importance of integrating farmer's perceptions and knowledge (FPK) for the development of sustainable pest and disease management strategies. However, the knowledge gap between indigenous and scientific knowledge still contributes to misidentification of plant health constraints and poor adoption of management solutions. This is particularly the case in the context of smallholder farming in developing countries. In this paper, we present a case study on coffee production in Uganda, a sector depending mostly on smallholder farming facing a simultaneous and increasing number of socio-ecological pressures. The objectives of this study were (i) to examine and relate FPK on Arabica Coffee Pests and Diseases (CPaD) to altitude and the vegetation structure of the production systems; (ii) to contrast results with perceptions from experts and (iii) to compare results with field observations, in order to identify constraints for improving the information flow between scientists and farmers. Data were acquired by means of interviews and workshops. One hundred and fifty farmer households managing coffee either at sun exposure, under shade trees or inter-cropped with bananas and spread across an altitudinal gradient were selected. Field sampling of the two most important CPaD was conducted on a subset of 34 plots. The study revealed the following findings: (i) Perceptions on CPaD with respect to their distribution across altitudes and perceived impact are partially concordant among farmers, experts and field observations (ii) There are discrepancies among farmers and experts regarding management practices and the development of CPaD issues of the previous years. (iii) Field observations comparing CPaD in different altitudes and production systems indicate ambiguity of the role of shade trees. According to the locality-specific variability in CPaD pressure as well as in FPK, the importance of developing spatially variable and relevant CPaD control practices is proposed.

Manipulation of Frankliniella occidentalis (Thysanoptera: Thripidae) by Tomato Spotted Wilt Virus (Tospovirus) Via the Host Plant Nutrients to Enhance Its Transmission and Spread.

Earlier studies have shown that Tomato spotted wilt virus (TSWV) influences the biology, performance, and behavioral patterns of its vector Frankliniella occidentalis Pergande. In this study, using Capsicum annuum L. as the host plant, we aimed to determine the manipulation of F. occidentalis by TSWV through switching of the diet (+ or -TSWV) during vector's development. Behavioral patterns, fitness, as well as vector performance were evaluated. The specific parameters investigated included longevity/survival, fecundity, development time, feeding, and preferential behavior. F. occidentalis were reared on either TSWV-infected (exposed) or healthy leaves (non-exposed) throughout their larval stages. The emerging adults were then individually transferred to either healthy or TSWV-infected leaf disks. This resulted into four treatments, consisting of exposed or non-exposed thrips reared on either infected or healthy leaf disks as adults. All F. occidentalis exposed to TSWV in their larval stages had shorter development time regardless of the adults' diet. Whereas, the ones that were later reared on healthy leaf disks as adults recorded the highest longevity and reproduction rate. Furthermore, adults of F. occidentalis that were exposed to TSWV in their larval stages showed preference toward healthy leaf disks (-TSWV), whereas the non-exposed significantly preferred the infected leaf disks (+TSWV). These are further indications that TSWV modifies the nutritional content of its host plants, which influences vector's biology and preferential behavior, in favor of its multiplication and dispersal. The findings offer additional explanation to the often aggressive spread of the virus in crop stands.

Predictive Models for Tomato Spotted Wilt Virus Spread Dynamics, Considering Frankliniella occidentalis Specific Life Processes as Influenced by the Virus.

Several models have been studied on predictive epidemics of arthropod vectored plant viruses in an attempt to bring understanding to the complex but specific relationship between the three cornered pathosystem (virus, vector and host plant), as well as their interactions with the environment. A large body of studies mainly focuses on weather based models as management tool for monitoring pests and diseases, with very few incorporating the contribution of vector's life processes in the disease dynamics, which is an essential aspect when mitigating virus incidences in a crop stand. In this study, we hypothesized that the multiplication and spread of tomato spotted wilt virus (TSWV) in a crop stand is strongly related to its influences on Frankliniella occidentalis preferential behavior and life expectancy. Model dynamics of important aspects in disease development within TSWV-F. occidentalis-host plant interactions were developed, focusing on F. occidentalis' life processes as influenced by TSWV. The results show that the influence of TSWV on F. occidentalis preferential behaviour leads to an estimated increase in relative acquisition rate of the virus, and up to 33% increase in transmission rate to healthy plants. Also, increased life expectancy; which relates to improved fitness, is dependent on the virus induced preferential behaviour, consequently promoting multiplication and spread of the virus in a crop stand. The development of vector-based models could further help in elucidating the role of tri-trophic interactions in agricultural disease systems. Use of the model to examine the components of the disease process could also boost our understanding on how specific epidemiological characteristics interact to cause diseases in crops. With this level of understanding we can efficiently develop more precise control strategies for the virus and the vector.

Inheritance genetics of the trait vector competence in Frankliniella occidentalis (Western flower thrips) in the transmission of Tomato spotted wilt virus.

The complexity of tospovirus-vector-host plant interaction is linked to a range of factors influencing vector's efficacy in virus transmission, leading to high variability in the transmission efficiency within vector populations. Main shortcomings of most studies are the missing information on the intrinsic potential of individual insects to serve as efficient vectors, both at phenotypic and at genotypic levels. Moreover, detailed analysis of vector competence heredity and monitoring the splitting of both genotypes and phenotypes in filial generations has not been reported. In this study, using the model system Frankliniella occidentalis and Tomato spotted wilt virus, we evaluated the inheritance and stability of the trait vector competence in a population through basic crossings of individually characterized partners, as well as virgin reproduction. We hypothesized that the trait is heritable in F. occidentalis and is controlled by a recessive allele. From the results, 83% and 94% of competent and noncompetent males respectively, inherited their status from their mothers. The trait was only expressed when females were homozygous for the corresponding allele. Furthermore, the allele frequencies were different between males and females, and the competent allele had the highest frequency in the population. These suggest that the trait vector competence is inherited in single recessive gene in F. occidentalis, for which the phenotype is determined by the haplodiploid mechanism. These findings are fundamental for our understanding of the temporal and spatial variability within vector populations with respect to the trait vector competence and at the same time offer an essential basis for further molecular studies.

Optimizing Western Flower Thrips Management on French Beans by Combined Use of Beneficials and Imidacloprid.

Western flower thrips (WFT), Frankliniella occidentalis (Pergande), is an important pest of vegetable crops worldwide and has developed resistance to many insecticides. The predatory mites Neoseiulus (=Amblyseius) cucumeris (Oudemans), the entomopathogenic fungus Metarhizium anisopliae (Metsch.), and an insecticide (imidacloprid) were tested for their efficacy to reduce WFT population density and damage to French bean (Phaseolus vulgaris L.) pods under field conditions in two planting periods. Metarhizium anisopliae was applied as a foliar spray weekly at a rate of one litre spray volume per plot while imidacloprid was applied as a soil drench every two weeks at a rate of two litres of a mixture of water and imidacloprid per m². Neoseiulus cucumeris was released every two weeks on plant foliage at a rate of three mites per plant. Single and combined treatment applications reduced WFT population density by at least three times and WFT damage to French bean pods by at least 1.7 times compared with untreated plots. The benefit-cost ratios in management of WFT were profitable with highest returns realized on imidacloprid treated plots. The results indicate that M. anisopliae, N. cucumeris, and imidacloprid have the potential for use in developing an integrated pest management program against WFT on French beans.

Efficacy and Dose Response of Soil-Applied Neem Formulations in Substrates With Different Amounts of Organic Matter, in the Control of Whiteflies, Aleyrodes proletella and Trialeurodes vaporariorum (Hemiptera: Aleyrodidae).

Neem products have been used frequently as an alternative to synthetic pesticides, because of their insecticidal, insect antifeedant, and growth-regulating effects. Moreover, new formulations are continually being developed and therefore, they have to be evaluated for their efficacy and persistence. In this regard, two soil-applied products-a liquid-based drenching solution NeemAzal-T and NeemAzal granules-were evaluated against two whitefly species, Aleyrodes proletella L. and Trialeurodes vaporariorum (West) on Brussels sprout and tomatoes, respectively. The plants were grown in two substrates: one was a commercial substrate (CS) composed of 15% humus, 35% clay, and 50% peat, and the other was a commercial substrate and sand mixture in 1:1 ratio. The main objective of the study was to evaluate the efficacy, persistence, and dose response of the two soil-applied NeemAzal formulations in substrates with different amount of organic matter. The results show that the efficacy of neem formulations was dose dependent, with the highest doses of NeemAzal granules (300 mg/kg=21 mg azadirachtin [AZA]/kg of substrate) and NeemAzal T (2 ml/kg=20 mg AZA/kg of substrate) achieving up to 100% mortality of immature stages of whiteflies. NeemAzal caused significantly higher mortality in immature stages of both whitefly species with CS + sand mixture than with pure CS. Persistence of the NeemAzal formulations was not influenced by the substrate type but rather by time span between treatment application and infestation, with significant decrease in efficacy when whiteflies were exposed 10 d after treatments.

Spiroacetals in the colonization behaviour of the coffee berry borer: a 'push-pull' system.

Coffee berries are known to release several volatile organic compounds, among which is the spiroacetal, conophthorin, an attractant for the coffee berry borer Hypothenemus hampei. Elucidating the effects of other spiroacetals released by coffee berries is critical to understanding their chemo-ecological roles in the host discrimination and colonization process of the coffee berry borer, and also for their potential use in the management of this pest. Here, we show that the coffee berry spiroacetals frontalin and 1,6-dioxaspiro [4.5] decane (referred thereafter as brocain), are also used as semiochemicals by the coffee berry borer for host colonization. Bioassays and chemical analyses showed that crowding coffee berry borers from 2 to 6 females per berry, reduced borer fecundity, which appeared to correlate with a decrease in the emission rates of conophthorin and frontalin over time. In contrast, the level of brocain did not vary significantly between borer- uninfested and infested berries. Brocain was attractive at lower doses, but repellent at higher doses while frontalin alone or in a blend was critical for avoidance. Field assays with a commercial attractant comprising a mixture of ethanol and methanol (1 ∶ 1), combined with frontalin, confirmed the repellent effect of this compound by disrupting capture rates of H. hampei females by 77% in a coffee plantation. Overall, our results suggest that the levels of frontalin and conophthorin released by coffee berries determine the host colonization behaviour of H. hampei, possibly through a 'push-pull' system, whereby frontalin acts as the 'push' (repellent) and conophthorin acting as the 'pull' (attractant). Furthermore, our results reveal the potential use of frontalin as a repellent for management of this coffee pest.

Colonization of onions by endophytic fungi and their impacts on the biology of Thrips tabaci.

Endophytic fungi, which live within host plant tissues without causing any visible symptom of infection, are important mutualists that mediate plant-herbivore interactions. Thrips tabaci (Lindeman) is one of the key pests of onion, Allium cepa L., an economically important agricultural crop cultivated worldwide. However, information on endophyte colonization of onions, and their impacts on the biology of thrips feeding on them, is lacking. We tested the colonization of onion plants by selected fungal endophyte isolates using two inoculation methods. The effects of inoculated endophytes on T. tabaci infesting onion were also examined. Seven fungal endophytes used in our study were able to colonize onion plants either by the seed or seedling inoculation methods. Seed inoculation resulted in 1.47 times higher mean percentage post-inoculation recovery of all the endophytes tested as compared to seedling inoculation. Fewer thrips were observed on plants inoculated with Clonostachys rosea ICIPE 707, Trichoderma asperellum M2RT4, Trichoderma atroviride ICIPE 710, Trichoderma harzianum 709, Hypocrea lixii F3ST1 and Fusarium sp. ICIPE 712 isolates as compared to those inoculated with Fusarium sp. ICIPE 717 and the control treatments. Onion plants colonized by C. rosea ICIPE 707, T. asperellum M2RT4, T. atroviride ICIPE 710 and H. lixii F3ST1 had significantly lower feeding punctures as compared to the other treatments. Among the isolates tested, the lowest numbers of eggs were laid by T. tabaci on H. lixii F3ST1 and C. rosea ICIPE 707 inoculated plants. These results extend the knowledge on colonization of onions by fungal endophytes and their effects on Thrips tabaci.

Coffee berry borer joins bark beetles in coffee klatch.

Unanswered key questions in bark beetle-plant interactions concern host finding in species attacking angiosperms in tropical zones and whether management strategies based on chemical signaling used for their conifer-attacking temperate relatives may also be applied in the tropics. We hypothesized that there should be a common link in chemical signaling mediating host location by these Scolytids. Using laboratory behavioral assays and chemical analysis we demonstrate that the yellow-orange exocarp stage of coffee berries, which attracts the coffee berry borer, releases relatively high amounts of volatiles including conophthorin, chalcogran, frontalin and sulcatone that are typically associated with Scolytinae chemical ecology. The green stage of the berry produces a much less complex bouquet containing small amounts of conophthorin but no other compounds known as bark beetle semiochemicals. In behavioral assays, the coffee berry borer was attracted to the spiroacetals conophthorin and chalcogran, but avoided the monoterpenes verbenone and α-pinene, demonstrating that, as in their conifer-attacking relatives in temperate zones, the use of host and non-host volatiles is also critical in host finding by tropical species. We speculate that microorganisms formed a common basis for the establishment of crucial chemical signals comprising inter- and intraspecific communication systems in both temperate- and tropical-occurring bark beetles attacking gymnosperms and angiosperms.

In vitro effect of pesticides on the germination, vegetative growth, and conidial production of two strains of Metarhizium anisopliae.

Entomopathogenic fungi are widely used as biological control agents against a broad range of insect and arachnid pests. However, the control efficacy of entomopathogenic fungi is variable because of unfavourable and fluctuating environmental conditions and intrinsic factors. One strategy to enhance entomopathogenic fungi efficacy is a combined use of entomopathogenic fungi and low dosages of pesticides. These sub-lethal dosages of chemicals can increase the control efficiency of entomopathogenic fungi but only if they do not affect the fungi. Adverse effects could include the inhibition of germination and/or vegetative growth as well as conidiogenesis. The present study investigated the in vitro effects of different concentrations of fipronil, permethrin, imidacloprid, NeemAzal, and amitraz as potential candidates for combined applications on two strains of the entomopathogenic fungus Metarhizium anisopliae (MA). MA was inoculated on a medium amended with five different concentrations (0.32-200 ppm) of the abovementioned pesticides. The germination, vegetative growth, and sporulation were evaluated. The results showed, according to a physiology parameter compatibility classification, that all pesticides were compatible with both tested MA strains. Only fipronil in the higher dose rates of 40 and 200 ppm was close to moderately toxic to MA-7. Furthermore, only higher concentrations of the pesticides caused a slight inhibition (about 15%) of conidial germination and a reduction in colony size. Sporulation was reduced at most by approximately 50% by 40 or 200 ppm of fipronil or amitraz, respectively. Therefore, it is possible to use the tested pesticides in combination with either strain of MA for an integrated pest management approach. Studies on the effect of these combinations on target organisms are in progress.

Thermal tolerance of the coffee berry borer Hypothenemus hampei: predictions of climate change impact on a tropical insect pest.

Coffee is predicted to be severely affected by climate change. We determined the thermal tolerance of the coffee berry borer, Hypothenemus hampei, the most devastating pest of coffee worldwide, and make inferences on the possible effects of climate change using climatic data from Colombia, Kenya, Tanzania, and Ethiopia. For this, the effect of eight temperature regimes (15, 20, 23, 25, 27, 30, 33 and 35 degrees C) on the bionomics of H. hampei was studied. Successful egg to adult development occurred between 20-30 degrees C. Using linear regression and a modified Logan model, the lower and upper thresholds for development were estimated at 14.9 and 32 degrees C, respectively. In Kenya and Colombia, the number of pest generations per year was considerably and positively correlated with the warming tolerance. Analysing 32 years of climatic data from Jimma (Ethiopia) revealed that before 1984 it was too cold for H. hampei to complete even one generation per year, but thereafter, because of rising temperatures in the area, 1-2 generations per year/coffee season could be completed. Calculated data on warming tolerance and thermal safety margins of H. hampei for the three East African locations showed considerably high variability compared to the Colombian site. The model indicates that for every 1 degrees C rise in thermal optimum (T(opt.)), the maximum intrinsic rate of increase (r(max)) will increase by an average of 8.5%. The effects of climate change on the further range of H. hampei distribution and possible adaption strategies are discussed. Abstracts in Spanish and French are provided as supplementary material Abstract S1 and Abstract S2.

Soil application of azadirachtin and 3-tigloyl-azadirachtol to control western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae): translocation and persistence in bean plants.

To study the systemic effects of active neem ingredients, the substrate of bean plants was treated with a 170 g kg(-1) azadirachtin (NeemAzal-U; Trifolio-M GmbH, Lahnau, Germany, registration pending). This product was used at a dose rate of 10 mg AZA (azadirachtin a) and 1.2 mg 3-tigloyl-azadirachtol (azadirachtin b) per treated bean plant. Afterwards, the translocation and persistence of AZA and 3-tigloyl-azadirachtol and the effects on western flower thrips, Frankliniella occidentalis (Pergande), were studied. Residues of AZA and 3-tigloyl-azadirachtol from substrates with different contents of organic matter [pure culture substrate (CS), CS-sand mixture] and from various plant parts were quantified by high-performance liquid chromatography-mass spectrometry (HPLC-MS). The dissipation trends of AZA and 3-tigloyl-azadirachtol were similar within the same substrates. A slower decline of both active ingredients was measured with CS than with CS-sand mixture. Residue analysis of the bean plants showed that only small proportions of the initial amounts of AZA and 3-tigloyl-azadirachtol applied to the substrate were present in the plant (0.3-8.1%). Variable amounts of residues of the active components in relation to plant parts and time of analysis indicated a different translocation pattern for the two active ingredients. Higher residues of the active ingredients were found in roots and stems after neem application using CS, whereas higher residues were found in leaves after CS-sand mixture treatments. Mortality of F. occidentalis after NeemAzal-U soil applications reached up to 95% on CS-sand mixture, compared with 86% in CS.

Effect of imidacloprid on the reproduction of acaricide-resistant and susceptible strains of Tetranychus urticae Koch (Acari: Tetranychidae).

Occasional reports linking neonicotinoid insecticide applications to field population outbreaks of the two-spotted spider mite, Tetranychus urticae Koch, have been a topic of concern for integrated pest management (IPM) programmes, particularly in apples. In order to shed light on the factors which may contribute to the occasional field population increase of T. urticae following the application of neonicotinoid insecticides, greenhouse experiments have been set up. Four different T. urticae strains, namely GSS (acaricide-susceptible), WI (organophosphate-selected), USA (a largely uncharacterised strain) and Akita (METI (mitochondrial electron transport inhibitor) acaricide-resistant and cross-resistant to dicofol), were compared for their fecundity without insecticide treatment and for their ovipositional response to foliar and drench applications of the field-relevant dose of imidacloprid (100 mg litre(-1)). Without insecticide treatment, strain GSS laid significantly more eggs (162.50 (+/- 5.43)) than the multiple resistant strain Akita (139.90 (+/- 5.54)) during a 16 day oviposition period. With imidacloprid treatment the highest effect was observed with GSS, with a significantly reduced number of eggs in drench (143.40 (+/- 4.22)) and foliar (144.60 (+/- 5.85)) applications. For strains Akita and USA, no significant differences were observed in oviposition between imidacloprid treatments and controls. The proportion of F1 female offspring decreased significantly with drench application for GSS and WI, while no differences were observed among strains in the survival of F1 immature stages, except for strain USA. The viability of eggs was relatively high (from 82.9 (+/- 4.5)% for USA to 95.2 (+/- 1.2)% for GSS) and not affected by imidacloprid treatments.

Insecticide drift deposition on noncrop plant surfaces and its impact on two beneficial nontarget arthropods, Aphidius colemani Viereck (Hymenoptera, Braconidae) and Coccinella septempunctata L. (Coleoptera, Coccinellidae).

Drift of the pyrethroid insecticide lambda-cyhalothrin into field margins bordering wheat and its effect on nontarget arthropods was investigated under field conditions. Insecticide deposition on leaf surfaces of broad beans exposed within field margins at 1-, 2-, and 3-m distance from the field edge and directly within the crop was quantified using a fluorescent tracer. The toxicity of leaf deposits to the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Braconidae) and to larvae of the ladybird Coccinella septempunctata L. (Coleoptera: Coccinellidae) was estimated. Mean corrected mortalities of A. colemani were < 50% (1 m) and < 30% (2 and 3 m), and mortalities of C. septempunctata larvae were < or = 80% (1 m), < or = 67% (2 m), and < or = 52% (3 m) 12 and 24 h postexposure to drift deposits. High positive correlation coefficients proved the relationship between leaf deposits and mortalities of test organisms. The connection of drift deposit measurement and exposure bioassay provides a promising approach to determining effects of insecticide drift on nontarget arthropods. However, due to the patchiness of drift deposition on noncrop plant surfaces, risks to nontarget arthropods at defined distances from the sprayed crop are not highly predictable.

Effects of neem and spinosad on Ceratothripoides claratris (Thysanoptera: Thripidae), an important vegetable pest in Thailand, under laboratory and greenhouse conditions.

Toxicity of three biopesticides, i.e., two neem products and spinosad, was determined on foliage-dwelling life stages of Ceratothripoides claratris (Shumsher) (Thysanoptera: Thripidae), a major thrips pest on tomatoes, Lycopersicon spp., in central Thailand. Direct and residual contact toxicities of NeemAzal-TS (1% azadirachtin) and systemic activity of NeemAzal-MD 5 (5% azadirachtin) affected the survival of first larval stage (L1) in a concentration-dependent manner. However, neither second larval stage (L2) nor adult survival was influenced by both neem products. On the contrary, spinosad caused 100% mortality in both larval stages and adults of C. claratris regardless of the concentrations tested. No strong ovicidal effects were detected in three different age groups of eggs (i.e., 1, 2, and 3 d old) topically treated with both NeemAzal-TS and spinosad. Residual toxicity was highest with fresh residues of NeemAzal-TS compared with 1-, 3-, 5-, and 7-d-old residues and in general was higher under laboratory than greenhouse conditions. Irrespective of the age of the spray residues, spinosad always caused 100% mortality in larvae and adults. Strongest systemic effects were observed in L1 larvae 1 d after soil drenching with NeemAzal-MD 5 at the highest concentration tested. Foliar and soil applications of NeemAzal-TS and NeemAzal-MD 5, respectively, did not cause any oviposition deterrent effects.

Effects of neonicotinoid insecticides on the bionomics of twospotted spider mite (Acari: Tetranychidae).

Previous reports indicate that applications of imidacloprid, a neonicotinoid insecticide, can lead to population buildups of twospotted spider mite, Tetranychus urticae Koch, in the field. Moreover, laboratory studies showed enhanced fecundity of T. urticae after an imidacloprid treatment. In this study, experiments were conducted in the greenhouse to investigate the potential effects of imidacloprid and several other neonicotinoid insecticides on fecundity, egg viability, preimaginal survivorship, and sex ratio of T. urticae (German strain WI) on French beans, Phaseolus vulgaris L. Four insecticides, i.e., imidacloprid (Confidor 200SL), thiacloprid (Calypso 480 SC), acetamiprid (Mospilan 70 WP), and thiamethoxam (Actara 25 WG), were tested at field-relevant (100, 120, 125, and 95 ppm) and sublethal doses (10, 12, 12.5, and 9.5 ppm), respectively. Both spray and drench applications were tested. At field-relevant doses, fecundity of T. urticae decreased and was lower in the treatments compared with the untreated control, whereas preimaginal survivorship and proportion of female offspring (i.e., sex ratio) were lower compared with the control. At sublethal doses, no significant differences were found among the treatments. Data on egg viability, preimaginal survivorship, and sex ratio at sublethal doses followed the same trends as at field-relevant doses. In an additional experiment, the metabolism of imidacloprid into monohydroxy-imidacloprid, olefine, guanidine, and 6-chloronicotinic acid was compared with the oviposition pattern of T. urticae. These findings are discussed with regard to previous laboratory and field observations of imidacloprid-induced fertility increases in T. urticae.