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Many species of thrips (Thysanoptera) in the family Thripidae form mating aggregations, but the adaptive significance of these aggregations and the extent of male and female mate choice is poorly understood. We studied the mating behaviour of the bean flower thrips Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), which forms male aggregations and occurs across sub-Saharan Africa. We tested whether males choose mates by female age or mating status. No-choice mating bioassays with one male and one female were used to simulate the way males usually encounter only one female at a time in aggregations in the field. Virgin females violently resisted mating attempts by males, but we found no compelling evidence to establish whether this was indiscriminate or was screening suitable males. Younger males (1–2 days old) did not discriminate females by age (1–2 or 7–10 days old), but older males (7–10 days old) avoided mating with older females. Any male choice by female mating status (virgin or mated) was weak or absent. The mating behaviour of M. sjostedti shows broad similarities with that of other thrips species that form aggregations, but also shows some distinct and novel differences, which can help our understanding of the adaptive significance of aggregations.

The potential of semiochemicals to lure insect pests to a trap where they can be killed with biopesticides has been demonstrated as an eco-friendly pest management alternative. In this study, we tested two recently characterized male-produced aggregation pheromones of the bean flower thrips Megalurothrips sjostedti (Trybom), namely (R)-lavandulyl 3-methylbutanoate (major) and (R)-lavandulol (minor), for their field efficacy. Moreover, compatibility of these pheromones and two other thrips attractants, Lurem-TR and neryl (S)-2-methylbutanoate, with the entomopathogenic fungus (EPF) Metarhizium anisopliae ICIPE 69 has been determined. Our study revealed that the M. sjostedti aggregation pheromones have dose-dependent antifungal effects on the EPF viability, but showed no fungistatic effect at a field-realistic dose for attraction of thrips. (R)-lavandulyl 3-methylbutanoate had similar antifungal effects as neryl (S)-2-methylbutanoate 8 days after exposure, whereas, Lurem-TR had a stronger antifungal effect than other thrips attractants. In the semi-field experiments, all autoinoculation devices maintained at least 86% viability of M. anisopliae conidia after 12 days of exposure. Field trials demonstrated for the first time that (R)-lavandulyl 3-methylbutanoate increases trap catches. Our findings pave a way for designing a lure-and-kill thrips management strategy to control bean flower thrips using autoinoculation devices or spot spray application.

The efficacy of spot spray and cover spray applications of Metarhizium anisopliae (Metsch.) Sorok. in combination with the thrips attractant Lurem-TR (methyl-isonicotinate) was compared in field experiments for the management of bean flower thrips (BFT), Megalurothrips sjostedti (Trybom), on a cowpea crop in two seasons (June-December 2014). Treatments were applied five days after the placement of Lurem-TR in the field. During the first season, BFT densities per plant 5 days post-application were lower in spot spray (10.1 ± 4.3) and cover spray (11.5 ± 4.8) treatments than in the control treatment (41.8 ± 15.2). In the second season, 5 days post-application, the spot spray treatment recorded the lowest BFT density of 32.5 ± 6.0, followed by cover spray with 40.9 ± 7.0 thrips. The control treatment recorded the highest BFT density of 67.4 ± 10.3 5 days post-application. Conidial viability and thrips conidial acquisition did not differ between the two application methods. Grain yields of 1430.7 ± 114.2 kg and 1312.1 ± 87.7 kg were obtained in the cover and spot spray treatments, respectively, while 976.8 ± 105.2 kg in the control during the second season. The cost benefit analysis indicated profits with the spot spray than cover spray application due to the reduction in labor and the quantity of inoculum used. Spot spray application of biopesticides could therefore be a viable option for small-scale farmers for the management of BFT on cowpea.

The study was conducted to determine efficacy of insecticides against Thrips, Megalurothrips sjostedti Trybom on cowpea grown at field experiments were conducted at Breeder Seed Production Centre, Govind Ballabh Pant University of Agriculture and Technology, Pantnagar 2014.The most effective treatment for the control of thrips Megalurothrips sjostedti Trybom was seed treatment with fipronil @ 3 ml/kg + spray with fipronil @ 5 ml/lt with maximum reduction (70.06%) in the thrips population of cowpea while lowest effective treatment for the control of thrips Megalurothrips sjostedti Trybom was seed treatment with imidacloprid 17.8SL @ 10ml/kg + spray with monocrotophos 36SL @ 2ml/lt with minimum reduction (16.02%) in the thrips, Megalurothrips sjostedti Trybom population of cowpea crop.

In sub-Saharan Africa, Megalurothrips sjostedti Trybom are the most destructive insect pest of cowpea. It causes approximately 100% reduction in cowpea yield. Synthetic insecticides are widely used in controlling this pest, however, health and environmental hazards are another challenge. This study sought to evaluate 25 cowpea genotypes from Ghana, Mali, Nigeria, Niger, Burkina Faso, Togo and South-Sudan for resistance to this pest under field screening using a 5 by 5 alpha lattice design with 2 checks at University of Ghana farms. The results revealed Laduni 1B as resistant, 20 moderately resistant and 4 susceptible genotypes were also identified in this study. In the determination of correlated and non-correlated variables, ten traits were reported important to the resistance of cowpea genotypes to flower bud thrips. The genotypes with resistance could be used to introgress the resistant trait into other preferred but susceptible cowpea varieties.

Cowpea is an important grain legume in sub Saharan Africa where its protein rich grains are consumed. However, its production is hampered by some major constraints including flower bud thrips (Megalurothrips sjostedti) that can cause 60% to total crop yield loss. Therefore, the development of resistant varieties becomes necessary. Thus, the present study was designed to determine the inheritance and elucidate the genetic control of cowpea resistance to thrips. Generation mean analysis model was exploited to assess the mode of inheritance of the resistance to flower bud thrips in cowpea using six generations (P1, P2, F1, F2, BC1P1 and BC1P2) derived from cross of Komcalle and Sanzi. Parameters such as number of flowers abortion per plant, number of pods per plant, thrips damage, number of thrips per plant and 100 seeds weight were exploited for progenies evaluation. Generation mean analysis revealed the existence of additive (a), additive x dominance (ad) and dominance x dominance (dd) effects as the mode of gene action predominantly involved into cowpea for thrips resistance control. Number of effective factors for thrips damage control varied from 3 (number of aborted flowers per plant) to 6 (weight of 100 seeds). Estimated Broad and narrow sense heritabilities for flower bud thrips resistance were low indicating large effect of the environment on the trait.

Aggregation of the bean flower thrips, Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), has been observed on cowpea, Vigna unguiculata (L.) Walp. To understand the mechanism underpinning this behavior, we studied the responses of M. sjostedti to headspace volatiles from conspecifics in a four-arm olfactometer. Both male and female M. sjostedti were attracted to male, but not to female odor. Gas chromatography/mass spectrometry (GC/MS) analyses revealed the presence of two distinct compounds in male M. sjostedti headspace, namely (R)-lavandulyl 3-methylbutanoate (major compound) and (R)-lavandulol (minor compound); by contrast, both compounds were only present in trace amounts in female headspace collections. A behavioral assay using synthetic compounds showed that male M. sjostedti was attracted to both (R)-lavandulyl 3-methylbutanoate and (R)-lavandulol, while females responded only to (R)-lavandulyl 3-methylbutanoate. This is the first report of a male-produced aggregation pheromone in the genus Megalurothrips. The bean flower thrips is the primary pest of cowpea, which is widely grown in sub-Saharan Africa. The attraction of male and female M. sjostedti to these compounds offers an opportunity to develop ecologically sustainable management methods for M. sjostedti in Africa.

Male sexual aggregations are a common territorial, mating-related or resource-based, behaviour observed in diverse organisms, including insects such as thrips. The influence of factors such as plant substrate, time of day, and geographic location on aggregation of thrips is uncertain, therefore we monitored the dispersion of male and female bean flower thrips (BFT), Megalurothrips sjostedti (Trybom) (Thysanoptera: Thripidae), on cowpea, Vigna unguiculata (L.) Walp. (Fabaceae), over three cowpea growth stages and across three cowpea-growing areas of Kenya. Our results indicated that for all the crop growth stages, the density of BFTs varied over the time of day, with higher densities at 10:00, 13:00, and 16:00 hours than at 07:00 hours. Thrips densities did not differ among blocks at the budding stage, but they did at peak flowering and podding stages. Dispersion indices suggested that both male and female BFTs were aggregated. Active male aggregation occurred only on green plant parts and it varied across blocks, crop stages, and locations. Similarly, active female aggregation was observed in peak flowering and podding stages. Such active aggregation indicates a semiochemical or behaviour-mediated aggregation. Identification of such a semiochemical may offer new opportunities for refining monitoring and management strategies for BFT on cowpea, the most important grain legume in sub-Saharan Africa.

Les biopesticides sont de plus en plus recommandes dans la production du niebe comme alternative a l‟utilisation des insecticides chimiques de synthese. La presente etude a pour objectif de determiner la periode d‟epandage des huiles de neem qui reduit le niveau des populations des thrips et de Maruca vitrata Fabricius en culture de niebe. La variete amelioree de niebe „tiligre‟ a ete semee dans six parcelles elementaires de 48 m2 chacune et correspondant aux traitements suivants : un temoin sans insecticide, un temoin de reference utilisant l‟insecticide de synthese le Pacha 25 EC (Acetamipride 10g/l + Lambda-Cyhalothrine 15g/l) et deux periodes d‟epandage dont une precoce (stade boutons floraux) et une tardive (stade 25% floraison) pour les deux huiles. Le nombre de larves et adultes de thrips, de larves de M. vitrata et les rendements gousse et graine ont ete les parametres mesures. Les resultats ont montre que lorsque l‟huile locale de neem et le TopBio sont epandus de facon precoce en culture de niebe, ils ont reduit de facon significative le nombre des thrips comme l‟insecticide chimique. L‟huile locale de neem, le TopBio n‟ont pas reduit le nombre de larves de M. vitrata comparativement aux deux temoins. Lorsque l‟huile locale et TopBio ont ete appliques de facon precoce, il y a eu une augmentation significative des rendements grains, respectivement de 1647,4 kg/ha et 1554 Kg/ha contre des rendements de 550 Kg/ha et de 600 Kg/ha pour les applications tardives. Au regard de ces resultats, l‟huile locale de neem en application precoce peut etre recommandee comme biopesticide dans la production familiale du niebe. Mots cles : Biopesticide, traitements precoce et tardif, insectes ravageurs. English Title: Effects of neem (Azadirachta indica L.) oils spraying periods on the populations of Megalurothrips sjostedti Trybom and Maruca vitrata Fabricius in the cowpea field Biopesticides are increasingly use in cowpea production as alternative to the use of synthetic chemical pesticides. The current study was aims to determine the period on which the application of neem oils significantly reduces trips and Maruca vitrata Fabricius populations level in the field. Cowpea variety « tiligre » was planted in six plots of 48 m2 each corresponding to the following treatments: a control without insecticide spray, a control using chemical insecticide Pacha 25 EC (Acetamiprid 10g/l + Lambda-Cyhalothrin 15g/l) and two spraying periods of two types of neem oils both at early (budding stage) and late (25% of flowering) stages. The number of larvae and adults trips, larvae of M. vitrata and pod and seed were the measured parameters. The results obtained showed that when local neem oil and TopBio were applied early in the cowpea field, they significantly reduced trips populations to the similar level to those of the chemicals insecticide. Local neem oil and TopBio didn‟t reduce the number of the larvae of M. vitrata compare to both controls. When local neem oil and TopBio were early applied, there led to a significant yield increasing of 1647.4 kg/ha and 1554 Kg/ha, respectively versus the yields of 550 Kg/ha and de 600 Kg/ha for late application. Considering this result, local neem oil, early applied, can be recommended as biopesticide for family cowpea production. Keywords : Biopesticide, early spray, late spray, insect pests.

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.

PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2016 Grain legumes are among the key economical crops widely grown in western and eastern Africa as important sources of food and animal fodder. However, the production of grain legumes in Kenya is seriously affected by a complex of insect pests particularly thrips. Yield losses of 20 to 100% have often been reported in some areas. The bean flower thrips (BFT), Megalurothrips sjostedti is considered to be the most important thrips pest of grain legumes. Chemical control is still the main management strategy, with detrimental consequences on the environment, users and consumers. Entomopathogenic fungi (EPF) are among the most promising alternatives to chemical pesticides. Inundative sprays are the most common application techniques for EPF. Although efficient and environmentally safe, the performance of entomopathogenic fungi is affected by several environmental parameters such as UV light, temperature, drought and rain. In order to improve the efficacy of EPF, an autodissemination system has been developed for the management of thrips in greenhouses. In this system, thrips are attracted to an autoinoculator where they are infected with an EPF before returning to the environment to disseminate the EPF to conspecifics. It therefore provides promising prospects, but for effective control, the conidial persistence and thrips attraction need to be optimized, while the EPF and the semiochemical should be compatible. The objective of this study was therefore to optimize the autodissemination system for thrips management on grain legumes in Kenya. The semiochemical Lurem-TR, has been found to inhibit conidia of EPF when put together in an autoinoculation device. The effect of spatial separation of Lurem-TR on the persistence of conidia of EPF, Metarhizium brunneum and Metarhizium anisopliae was therefore evaluated to develop an autodissemination strategy for the management of M. sjostedti. Influence of spatial separation of the semiochemical on thrips attraction and conidial acquisition by thrips from the autoinoculation device was also investigated in the field. This study showed that conidia persistence of both fungal species increased with distance of separation from Lurem-TR. Attraction of thrips to the device also varied significantly according to distance between the device and semiochemical. More thrips were attracted when Lurem-TR was placed in a container below the device and at 10 cm distance from the device. Conidial acquisition by thrips was not significantly different between spatial separation treatments of conidia and Lurem-TR. Seven alternative thrips attractants, namely 4-anisaldehyde, ethyl benzoate, cis-jasmone, linalool, methyl anthranilate, trans-caryophyllene and phenylethanol were also screened for their compatibility with M. anisopliae ICIPE 69 in autodissemination devices and for their attraction to M. sjostedti in the field. Methyl anthranilate (MA) was found to be the attractant most compatible with M. anisopliae and its attractiveness to M. sjostedti was similar to that of Lurem- TR. The performance of the attractant, methyl anthranilate, was compared to the commercial attractant Lurem-TR in autoinoculation devices treated with M. anisopliae under field conditions for two seasons. Densities of M. sjostedti in plots with the two semiochemical-baited autoinoculation devices were less than in the control plots during both experimental seasons. Plots with MA-baited and Lurem-TR-baited devices had similar densities of M. sjostedti during both seasons. However in the second season thrips densities in plots with the Lurem-TR-baited devices did not differ significantly from the control plots. Conidial viability of M. anisopliae was significantly higher in semiochemical-free baited devices (control) than in semiochemical-baited devices in both seasons. Conidial germination decreased over time in all the treatments but remained above 45%, 12-15 days post-exposure. The average number of conidia acquired by a single M. sjostedti ranged between 2.0 and 10.0 x 103 conidia in both semiochemical-baited device treatments during both seasons. Significantly more conidia were acquired by single thrips in MA-baited devices compared to Lurem-TR baited devices during the podding stage of the crop during the second season. Significantly higher mortality of M. sjostedti was caused in field plots by Lurem-TR baited and MA-baited autoinoculation devices compared to mortality of M. sjostedti collected from the control plots in both seasons. Cowpea yield also differed significantly between the treatment plots. The highest yield was recorded in plots where MAbaited devices were placed. From this study, it could therefore be recommended that methyl anthranilate be used in autoinoculation devices for the management of M. sjostedti on grain legumes. The success achieved with MA in these trials resulted in the evaluation of this EPF for possible use in a spot spray strategy. The efficacy of spot spray and cover spray applications of M. anisopliae in combination with the thrips attractant Lurem-TR was compared in field experiments for the management of M. sjostedti on a cowpea crop in two seasons. Plants in the treatment plots where a spot spray application of M. anisopliae was done five days after the placement of Lurem-TR recorded the lowest densities of M. sjostedti. Fungal viability and thrips conidial acquisition did not differ between the two application methods. Compared to the control treatment plots, both application strategies resulted in yield increases of 34.1 and 46.2% with spot and cover spray treatments, respectively. The cost benefit analysis suggests that the spot spray application was more profitable due to the reduction in labour and the quantity of inoculum used. Doctoral

Grain legumes play an important role in community livelihood and in the national economy in Kenya. Unfortunately, in many African countries, production doesn't satisfy the demand in grains due to various constrains. Understanding farmers practices and behavior in the management of grain legume pests is a crucial step in the development of sustainable management strategies. A total of 216 farmers were surveyed in eight districts of eastern Kenya to evaluate farmers' knowledge and perceptions of grain legume pests; to examine current pest management practices, and to identify other production constraints. Grain legumes are grown by a wide age-group of farmers, with both genders equally represented. Chemical control remains the main pest management strategy, and, to ensure pesticide effectiveness, farmers also use increased application rates, chemical alternation, frequent application and mixtures of chemicals. While farmers used other control measures, they showed only limited interest in biological control. The majority of the farmers had experience in grain legume farming and were able to identify the major pests, which were the legume flower thrips Megalurothrips sjostedti Trybom, the cowpea aphid Aphis craccivora Koch and the legume pod borer Maruca vitrata Fabricius. Our survey revealed that education and proximity to extension services contributed significantly to farmers' knowledge of grain legume pests, suggesting the need to provide continuous training and capacity building on integrated pest management in grain legume farming. The study also suggests integration of other pest management strategies such as the use of early maturing varieties, biopesticides and biofertilizer to reduce the use of chemical for sustainable pest management.

The field study was conducted during the planting season of cowpea to evaluate the natural toxicant from Tephrosia vogelii and Petiveria alliacea and their mixture against Megalurothrips sjostedti and Apion varium at three different concentrations (5, 10, and 20% v/v). The experiment was set up in randomized complete block design. The field observations showed that the two insect pests were effectively controlled by the botanical insecticides compared with untreated plants. Also, the plant extracts at 20% and 10% v/v significantly protected cowpea pods and grains from the damage. However, higher grain yield was obtained from the plant treated with 20% v/v compared to those treated with 10%, 5% v/v and untreated plants. Combination of the two plant extracts at 20% v/v had the same efficacy with synthetic insecticide (Decis). Thus, these plant extracts can be used in organic farming. DOI: http://dx.doi.org/10.3329/bjar.v36i4.11745 Bangladesh J. Agril. Res. 36(4): 575-582, December 2011

Losses caused by flower thrips in cowpea are important. These pests can cause from 60% to total crop yield loss. There is, therefore , an urgent need to address this issue. This work has been undertaken to identify sources of resistance to thrips in cowpea. Twenty cowpea genotypes were screened at Kamboinsé research station under improve netting in pots. The number of aborted flowers per line, the percentage of damage to flowers and stipules, and the number of thrips per genotype were evaluated. The results revealed the existence of six genotype of cowpea resistant to thrips. Among these genotypes three are already known thrips resistant lines (TVU1509, TVx3236 and Sanzi). Moreover, Sanzi showed interesting potentialities that maybe exploited. The new identified lines are Nafi, variety popularized in 2012 and variety KVx780-3 which is being popularized. The KVx165-14-1 (old popular variety) showed sources of tolerances while the KN1 genotype was susceptible to thrips. In another hand, all the wild genotypes showed high susceptibility to thrips.

The effect of crude aqueous extracts of orange, Citrus sinensis L., peel and chilli pepper, Capsicum annum L. in mixtures with extracts of other plant species on Megalurothrips sjostedti (Thysanoptera: Thripidae) in cowpea flowers and pod setting ability of the treated plants was evaluated in two years of field studies. Compared with the other treatments, crude extract mixtures of chilli pepper with neem leaf, orange peel with African curry (Ocimum gratissimum L.) leaf and orange peel with Gmelina arborea L. leaf (in that order) were superior in reducing the numbers of thrips (

This thesis was elaborated within the framework of the European Erasmus Mundus Programme “Agricultural Transformation by Innovation (AGTRAIN)”; L’objectif principal de cette thèse a été de rechercher une technique alternative de protection du niébé Vigna unguiculata (L.) contre le thrips des fleurs Megalurothrips sjostedti Trybom en se basant d’une part sur les pratiques actuelles des petits producteurs au Kenya et d’autre part sur le comportement et l’écologie de cette espèce à l’égard des signaux olfactifs qui seraient susceptibles de les repousser. Plus spécifiquement les buts à atteindre étaient les suivants: (1) Identifier et recenser les dégâts et l’impact sur la production occasionnés par les ravageurs du niébé dans différents agrosystèmes du Kenya et les méthodes utilisées par les petits producteurs pour les éviter ou les limiter; (2) Estimer l’impact des changements climatiques attendus dans les différentes régions d’Afrique sub-Saharienne sur la distribution du thrips des fleurs du niébé; (3) Etudier l’effet répulsif et insecticide de plusieurs huiles essentielles et de leurs composants majeurs sur les thrips pour proposer des associations avec des plantes potentiellement répulsives dans le cadre de stratégies de protection intégrées. L’idée de départ a été de recenser les pratiques des petits producteurs en matière de protection des cultures de niébé mais aussi identifier leur connaissance et leur perception des différentes techniques utilisées qui pourraient servir au développement d’une stratégie de protection intégrée en alternative à la lutte chimique. Afin de recenser le statut des différents ravageurs et d’identifier les pratiques de lutte utilisées, j’ai réalisé une enquête auprès des familles de petits producteurs, basée sur un questionnaire semi-structuré et ce dans plusieurs districts représentatifs de la région Est du Kenya principale zone de production du niébé. D’après les producteurs, les principaux ravageurs du niébé sont le thrips des fleurs M. sjostedti, le puceron Aphis craccivora et le foreur des gousses Maruca vitrata. La lutte chimique serait la principale, si ce n’est la seule, technique utilisée par les petits producteurs pour la protection du niébé avec une augmentation des fréquences d’application et des doses de pesticides chimiques utilisés en mélange qu’ils doivent pulvériser pour conserver leur efficacité. Ce résultat suggère la sélection de populations de ravageurs devenues résistantes aux pesticides qui ne peut qu’accentuer la baisse d’efficacité de cette lutte chimique sans parler de son impact croissant sur la santé et l’environnement. Ce problème viendrait s’ajouter, toujours aux dires des producteurs, à un régime pluviométrique irrégulier qui constitue avec les dégâts des ravageurs les principales contraintes de cette culture. Ces résultats nous ont permis de confirmer et compléter ceux de la littérature concernant en particulier les ravageurs et le niveau de connaissances des petits producteurs en matière de protection de la culture du niébé et de montrer la nécessité de développer des méthodes de lutte alternatives à la lutte chimique qui pourraient être adaptées aux conditions de cultures et adoptées par les producteurs. Nos résultats d’enquête ayant montré que les aléas climatiques étaient aussi un facteur important de perte de production pour 93% des producteurs, j’ai tenté d’estimer l’impact des changements climatiques potentiels en Afrique sub-Saharienne sur la distribution géographique du thrips M. sjostedti en me basant sur sa répartition actuelle (166 références) et la répartition du niébé (350 références). J’ai utilisé pour cela les outils MAXENT (Maximum Entropy) et AFRICLIM pour prédire les effets des changements climatiques en 2055. La pluviométrie et la température ont été les variables environnementales retenues en utilisant une méthode de ré-échantillonnage de type ‘jacknife’. J’ai aussi étudié l’effet répulsif et insecticide de 24 huiles essentielles et de leurs composés majeurs sur des adultes de thrips M. sjostedti en utilisant un olfactomètre à colonnes placées verticalement sous une hotte. Les résultats ont mis en évidence un fort effet répulsif de 7 extraits de plantes. J’ai effectué des analyses chimiques par hromatographie en phase gazeuse couplée à un spectrophotomètre de masse (GCMS) pour identifier les composés hydro-carbonés de ces 7 extraits. J’ai pu montrer l’effet répulsif mais pas insecticide de 16 de ces composés sur larves et adultes de M. sjostedti en utilisant différents bioessais. Les résultats de mes études ont montré le potentiel de l’utilisation d’extraits de plantes pour repousser les thrips. L’utilisation d’extraits de plantes répulsives pourrait être intégrée à une nouvelle stratégie de protection du niébé. Cependant aucun des composants testés n’a montré de propriété insecticide. Des plantes productrices de certains de ces composés volatiles répulsifs pourraient aussi être utilisées en association pour mieux protéger les cultures de niébé dans le cadre d’une stratégie de lutte intégrée de type push-pull. Mais ces plantes potentiellement répulsives devront avant tout être validés en laboratoire puis dans des expérimentations en plein champ.

International audience; Megalurothrips sjostedti Trybom is an important pest of cowpea (Vigna unguiculata L.) in Africa. To propose an alternative to chemical control, the repellency of 24 plant extracts was evaluated against adult female thrips of M. sjostedti in the laboratory. Plant extracts in ethanol were separately applied on a filter paper disk in a still air visual cue olfactometer. The results showed highly significant differences in repellency among extract type, concentration and their interactions. We classified the level of repellency into four categories as strong, good, moderate and weak or non- repellent based on hierarchical ascendant classification. We identified Piper nigrum, Cinnamomum zeylanicum, Cinnamomum cassia as strong repellents. Five extracts were classified as good, eight as moderate and the remaining eight extracts were weak or non-repellent. Repellency of the extracts increased with the concentration suggesting that the behavioral response of M. sjostedti was dose-dependent. Mono- and sesquiterpene hydrocarbon compounds from seven highly repellent extracts were identified by gas chromatography-mass spectrometry (GC/MS). The use of repellent extracts could be useful in developing integrated pest management strategies for thrips on legume crops. In this regard, the specific modes of action of the identified compounds need to be investigated to incorporate them into the existing crop protection strategies.

The efficacy of aqueous neem and Eucalyptus leaf extracts in mixtures containing extracts of other plant species was investigated for the management of the legume flower bud thrips, a major post-flowering insect pest of cowpea in the Research Farm of the Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria. The extracts mixtures were applied at 10:10% w/v in equal ratio and sprayed four times at weekly intervals. The results showed that thrips pressure on cowpea flowers was significantly (P < 0.05) less (< 1.0/flower) on plants sprayed with leaf extract mixtures of Neem + Eucalyptus, Neem + lemon grass, Neem + bitter leaf, Neem + tomato, and Eucalyptus + African curry (in that order) than on unsprayed plants. These extract mixtures also increased pod density per plant compared with the unsprayed plants in the two years of investigation. The synergistic attributes of some plant extracts in mixtures with those of other plant species could form the basis of biopesticides form...

Megalurothrips sjostedti (Trybom) This is a common species on Fabaceae across the entire Afrotropical Region (Zur Strassen 2003). Adults have been intercepted incidentally in the Netherlands on different species of plants from Africa, such as cut flowers. From Ethiopia it was found once only, a single female on Rosa��� cut flower at the flower auction in Aalsmeer, 2.vi. 2005 (P. Rozenboom)., Published as part of Vierbergen, Gijsbertus, 2014, Thysanoptera intercepted in the Netherlands on plant products from Ethiopia, with description of two new species of the genus Thrips, pp. 269-278 in Zootaxa 3765 (3) on page 272, DOI: 10.11646/zootaxa.3765.3.3, http://zenodo.org/record/225825, {"references":["Zur Strassen, R. (2003) Die terebranten Thysanopteren Europas. Die Tierwelt Deutschlands 74, 1 - 277."]}

The effect of host plant resistance on growth and developmental parameters of the bean flower thrips Megalurothrips sjostedti Trybom was determined on nine cowpea ( Vigna unguiculata {L.}Walp.) cultivars under laboratory conditions. Newly emerged adults M. sjostedti were confined on peduncles with floral buds of the different cowpea cultivars. M. sjostedti suffered 100% pre-imaginal mortality on cowpea lines Moussa local, TVu1509, TVx3236, Sewe and Sanzibanili. Antibiosis is believed to be the mechanism of resistance operating in these cultivars. On KVx404-8-1, M. sjostedti had a prolonged developmental period though not significantly different from Vita 7, the susceptible check at P M. sjostedti with the suitability index (growth index) not significantly different from the susceptible check (Vita 7) at P

Studies were carried out in eastern Uganda to assess the effect of legume flower thrips ( Megalurothrips sjostedti ) injury on cowpea grain yields and to establish economic injury levels (EILs) and action thresholds for thrips on cowpea. The studies relied on various insecticide spray regimes to obtain different thrips densities per experimental unit and use of exclusion cages in the field to confine defined numbers of thrips populations. A significant negative relationship ( y =−0.011 x +1.77; r =0.87; P =0.003) was observed in the field studies between thrips densities and cowpea grain yields. The EIL was established at seven thrips per inflorescence. The study also revealed that three well timed (i.e., applied after bud initiation to minimize flower bud abortion) insecticide sprays are effective in the control of thrips. The three sprays are regarded effective in that thrips densities were kept below the established thresholds. More than three sprays also reduced thrips populations to less than seven per inflorescence but these were not economical.