Bean Flower Thrips Research Articles

Scientific validation of plant extracts used by farmers in the management of bean flower thrips on French beans in Kenya

AbstractBean flower thrips (Megalurothrips usitatus) is a major French bean (Phaseolus vulgaris L.) pest. Small‐scale farmers manage the pest using mixed plant extracts although their efficacy has not been scientifically validated. We evaluated the efficacy of mixed plant extracts comprising; Capsicum frutescens, Allium sativum, Lantana camara, Tagetes minuta and Azadirachta indica, against M. usitatus under laboratory and screenhouse. We identified and quantified the secondary metabolites associated with insecticidal activity using spectrophotometry and liquid chromatography–mass spectrometry (LC–MS). The plant combinations included PE1 (C. frutescens + A. sativum + L. camara + T. minuta extracts infused for 14 days), PE2 (same as PE1 but infused for 24 h) and PE + N (the five plant extracts infused for 24 h) in distilled water. We used an organic commercial botanical (Pyneem) as a positive control and distilled water as a negative control. Pyneem and PE + N induced the highest mortality at 88% and 77%, respectively, in the laboratory, and 68% and 71%, respectively, in the screenhouse. Phenolics, terpenoids and organosulfur compounds were identified in PE + N and individual plant extracts in varied quantities. These compounds were significantly higher (p < 0.001) in PE + N compared to individual plant extracts. The study showed that PE + N efficiently manages bean flower thrips, and mixing different plant extracts amplifies the secondary metabolites' abundance. The use of mixed plant extracts could be incorporated into integrated pest management strategies for thrips management in legumes. The specific compounds identified in PE + N should be investigated further to understand their modes of action against the pest.

Comparison of Coloured Sticky Traps against Bean Flower Thrips (Karny) (Thysanoptera: Megalurothrips distalis Thripidae) in Summer Mung Bean

Comparison of Coloured Sticky Traps against Bean Flower Thrips (Karny) (Thysanoptera: Megalurothrips distalis Thripidae) in Summer Mung Bean

Chromosome-level genome assembly of bean flower thrips Megalurothrips usitatus (Thysanoptera: Thripidae)

Bean flower thrips Megalurothrips usitatus is a staple pest of cowpea and other legumes and causes dramatic economic losses. Its small size allows for easy concealment, and large reproductive capacity easily leads to infestations. Despite the importance of a genome in developing novel management strategies, genetic studies on M. usitatus remain limited. Thus, we generated a chromosome-level M. usitatus genome using a combination of PacBio long read and Hi-C technologies. The assembled genome was 238.14 Mb with a scaffold N50 of 13.85 Mb. The final genome was anchored into 16 pseudo-chromosomes containing 14,000 genes, of which 91.74% were functionally annotated. Comparative genomic analyses revealed that expanded gene families were enriched in fatty acid metabolism and detoxification metabolism (ABC transporters), and contracted gene families were strongly associated with chitin-based cuticle development and sensory perception of taste. In conclusion, this high-quality genome provides an invaluable resource for us to understand the thrips’ ecology and genetics, contributing to pest management.

FIRST REPORT OF COMMON BEAN FLOWER THRIPS Megalurothrips usitatus Bagnall IN COSTA RICA

<p><strong>Background: </strong>The species <em>Megalurothrips usitatus</em> is a thrips insect that has been recorded in Asia, Oceania, Australia and recently in America, attacking legume crops.<strong> Objective: </strong>to report <em>Megalurothrips usitatus</em> as species associated with flowers of common bean plants in Costa Rica.<strong> Methodology: </strong>the thrips from three growing bean locations were sampled and characterized through light microscopy in Costa Rica. Furthermore, a phylogenetic analysis of the COI gene compared with the databases of the National Center for Biotechnology Information (NCBI) was performed.<strong> Results: </strong>The species was recorded in three bean growing areas (Sardinal of Guanacaste, Estación Experimental Agrícola Fabio Baudrit Moreno in Alajuela and La Managua in Quepos).<strong> Implications:</strong> the new report of the insect in flowers of <em>Phaseolus vulgaris</em> implies future monitoring actions and respective integrated management; ignoring thrips populations could cause losses in the bean's regional production.<strong> Conclusion: </strong>the bean flower thrips is reported for the first time in Costa Rica. <strong></strong></p>

Synergism of Adjuvants Mixed With Spinetoram for the Management of Bean Flower Thrips, Megalurothrips usitatus (Thysanoptera: Thripidae) in Cowpeas.

The bean flower thrips, Megalurothrips usitatus (Bagnall) is an economically important insect pest of cowpea, Vigna unguiculata (L.) Walp in south China. Spinetoram is a newly available commercial active ingredient in the spinosyn mode of action group of insecticides that has been recommended for thrips management in China. In this study, the toxicity and efficacy of spinetoram for controlling M. usitatus were evaluated and compared to six other conventional insecticides. In addition, the synergistic effects of adjuvants (Silwet 806, Silwet 618, AgroSpred 910, and AgroSpred Prime) mixed with spinetoram for thrips control on cowpea were evaluated in both the laboratory and the field. Results of this study showed that spinetoram had higher toxicity and field efficacy of M. usitatus than other tested insecticides. A significant increase in efficacy was observed when spinetoram was applied at a recommended rate of 0.67 ml/L, mixed with Silwets (806 and 618) at the rate of 0.5 ml/L. Reductions of 50% and 40% in thrips infestation in the field over treatments without adjuvants were observed 3- and 7-days posttreatments, respectively. However, no significant reduction of M. usitatus was recorded when spinetoram was mixed with AgroSpreds (910 and Prime). Furthermore, no significant differences were found in thrips infestation between spinetoram sprayed alone at the rate of 0.67 ml/L and a reduced rate of spinetoram (0.45 ml/L) mixed with Silwets (806 and 618). The current research shows that Silwets mixed with spinetoram has a synergistic effect in the management of thrips.

Screening of Beauveria bassiana (Bals.) (Hypocreales: Cordycipitaceae) strains against Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) and conditions for large-scale production

BackgroundBeauveria bassiana (Bals.) (Hypocreales: Cordycipitaceae) is an entomopathogenic fungus that has potential as a biological control agent against many insect pests. This study was conducted to optimize the conditions for large-scale production on rice of B. bassiana and evaluate its virulence against the bean flower thrips Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae).ResultsThe optimal substrate quantity for conidia production was 200 g of rice per container (2.1 l), with substrate having a 52% moisture content, being supplemented with 2% cooking oil. In stage production of a batch, 150 ml of conidia suspension (at 24.33 × 107 spores/ml) was incubated for 10 days in SDA liquid medium amended with 4% glucose and 1.5% yeast extract. The SDA medium was then used to inoculate one container of the rice substrate. The optimum ratio of conidial suspension to substrate (v/v) was 20–25%. Virulence of the spore powder harvested from the rice substrate was same as that of produced on the SDA solid media against thrips. The level of control from an application of spore powder of the thrips M. usitatus was similar to that from chemical the pesticide spinetoram when applied in a cowpea (Vigna sinensis Endl) field.ConclusionsThe optimized rice substrate system can be used for a large-scale production of B. bassiana spores, which can be used for field control of thrips.

BIOLOGICAL TRAITS OF BEAN FLOWER THRIPS, Megalurothrips usitatus (THYSANOPTERA: THRIPIDAE) REARED ON MUNG BEAN

The bean flower thrips, Megalurothrips usitatus is a major pest of mung bean that causes flower dropping and significant yield loss of the crop. M. usitatus demonstrated to have variable lifespan when reared on different leguminous hosts but on mung bean, an important pulse crop in Bangladesh, is unknown. The experiment was conducted to determine the biological attributes of M. usitatus on mung bean in a climate control chamber at 26 ± 1°C, 75 ± 3% RH, and 16:8 hours L:D in the laboratory. The results revealed that the incubation period, first instar larva, second instar larva, prepupa, and pupal period of M. usitatus were 3.13 ± 0.06, 1.48 ± 0.05, 2.30 ± 0.08, 1.30 ± 0.07, and 2.26 ± 0.13 days, respectively. The combined developmental period from egg to adult was 10.54 ± 0.15 (mean ± SE) days. The larvae of M. usitatus were similar in appearance to the adults, but they lacked wings and were smaller and different in color. The first instar was pale yellow, while the second instar was darker and larger, ranging from deep yellow to orange-red. The wing pads of the prepupae were shorter than that of the pupae. The antennae of the prepupa were straight, but they were bent in the pupa. In the case of pre-adult mortality of M. usitatus, the mortality of the first instar larva was 14.41%, second instar larva 22.77%, prepupa 14.10%, and pupa 65.67%. The pre-adult mortality was 80.51% overall. Adult males had lower longevity (6.42 ± 0.44 days) than females (12.07± 1.56 days). The developmental period of M. usitatus on mung bean indicated the suitability of the leguminous crop as a potential host, as well as the need for information on the pest’s various growth stages in order to design effective management strategies.

Bean Flower Thrips Megalurothrips usitatus (Bagnall) (Insecta: Thysanoptera: Thripidae)

The Featured Creatures collection provides in-depth profiles of insects, nematodes, arachnids and other organisms relevant to Florida. These profiles are intended for the use of interested laypersons with some knowledge of biology as well as academic audiences. Megalurothrips usitatus (Bagnall, 1913) is a small sized (3-4 mm) insect in the order Thysanoptera and family Thripidae, commonly known as bean flower thrips, oriental bean thrips, and Asian bean thrips. It is an important economic pest of legumes. Megalurothrips usitatus was first reported in the USA in Florida in 2020 (Soto-Adames, F. N. 2020).

Mating behaviour, mate choice and female resistance in the bean flower thrips (Megalurothrips sjostedti)

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.

Exploiting Thrips Aggregation Pheromones to Develop a Lure-and-Kill Strategy for the Management of the Bean Flower Thrips

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.

Molecular characterization and virulence of fungal isolates against the bean flower thrips, Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae)

The bean flower thrips, Megalurothrips usitatus Bagnall (Thysanoptera: Thripidae) is a major pest of leguminous crops grown in Southern China. This study reports the isolation, identification (through molecular characterization) and pathogenic potential of 6 fungal isolates belonging to different fungal species. The fungi were isolated from soil samples collected from different areas of Southern China and were identified as Beauveria bassiana (3 isolates; SB010, SB009, SP016), Cordyceps fumosorosea (one isolate; SP535), Akanthomyces attenuatus (one isolate; SCAUDCL-53), and Aspergillus nomius (one isolate; SCAUN-1). Conidial suspension (1 × 108 conidia ml−1), and the crude extract (0.4 mg ml−1) of all the 6 fungal isolates were tested for their pathogenicity against M. usitatus adults. The results showed that A. attenuatus (SCAUDCL-53) and B. bassiana (SB010) were the most effective fungal isolates against M. usitatus out of all the isolates used in this study. At 5 days post-inoculation, conidial suspension of A. attenuatus (SCAUDCL-53) and B. bassiana (isolate SB010) caused 100 and 90% mortality rates, respectively. The median lethal time (LT50) values of fungal isolates SCAUDCL-53, SB010, SB009, SP016, SP535, and SCAUN-1against M. usitatus adults were 1.36, 3.79, 6.51, 8.49, 17.36, and 5.01 days, respectively. The application of crude fungal extracts of SCAUDCL-53, SB010, SB009, SP016, SP535, and SCAUN-1 against the pest resulted in 85, 93.3, 56.7, 33.3, 41.7, and 53.75% mortality rates, respectively after 5 days of application. Respective LT50 values of the crude fungal extracts against M. usitatus were 3.37, 2.85, 4.87, 7.13, 6.43, and 4.64 days. The fungal isolates used in this study showed considerable bioactivity against the M. usitatus and can be used as potential natural pest control agent for the ecofriendly management of M. usitatus.

The male-produced aggregation pheromone of the bean flower thrips Megalurothrips usitatus in China: identification and attraction of conspecifics in the laboratory and field.

Thrips, Megalurothrips usitatus, usually display aggregation behavior, which is probably mediated by a male-produced aggregation pheromone. Aggregation pheromones are species-specific, and can be used to develop commercial lures for monitoring and mass-trapping of pests. The active components of the aggregation pheromone for four thrips species have been identified. However, the components of M. usitatus-produced aggregation pheromone are still not clear. Y-tube olfactometer assays showed that both male and virgin female M. usitatus were significantly attracted to male but not female volatiles. This was additionally supported by electroantennogram (EAG) assays. Coupled gas chromatography-electroantennogram detection (GC-EAD) showed that one component of male-specific odors elicited a significant electrophysiological response. This compound was characterized as (2E,6E)-farnesyl acetate, which is structurally different from the active components of the aggregation pheromones of other reported thrips species. Electroantennal responses of M. usitatus increased with increasing doses of synthetic (2E,6E)-farnesyl acetate. Additionally, this compound significantly attracted adults in laboratory behavioral bioassays. Under field conditions, sticky traps with synthetic (2E,6E)-farnesyl acetate caught 1.5-7-fold more M. usitatus than controls, and this effect of the compound at a dose of 60 μg lasted at least 6 days. (2E,6E)-Farnesyl acetate was identified as the male-produced aggregation pheromone of M. usitatus. It could attract this thrips species under laboratory and field conditions, suggesting considerable potential as a commercial application to control M. usitatus populations. © 2020 Society of Chemical Industry.

Repellent activity of Cymbopogon citratus and Tagetes minuta and their specific volatiles against Megalurothrips sjostedti

AbstractCowpea is an important source of protein for people in Africa. However, the crop suffers major damage and yield losses due to bean flower thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae). Although companion plants are known to reduce the damage caused by insect pests, the role of their volatiles in repelling pests from target plants has been the subject of few investigations. Here, we used the Y‐tube olfactometer experiments and chemical analyses to investigate the effect of volatiles from cowpea flowers and two companion plants; lemongrass, Cymbopogon citratus and Mexican marigold, Tagetes minuta on the olfactory responses of M. sjostedti. The results revealed that M. sjostedti males and females were repelled by the volatiles from freshly cut leaves of C. citratus. The combination of freshly cut leaves of C. citratus and cowpea flower was repellent to females but not to males. The female thrips, but not males, were repelled by the volatiles from the vegetative stage of T. minuta. Fifty‐four compounds were identified in the volatiles from two herbal plants. Among the major compounds, citral and a 4‐component blend comprised of dihydrotagetone, (Z)‐3‐hexenyl acetate, limonene and (Z)‐β‐ocimene repelled females but dihydrotagetone alone attracted females. While myrcene combined with cowpea flower volatiles enhanced the attraction of females M. sjostedti, when tested alone was not attractive. These results highlight the potential of volatiles from C. citratus and T. minuta to repel M. sjostedti females. The use of these plants as companion plants in a cowpea cropping system could reduce M. sjostedti infestation.

Behavioural responses of bean flower thrips (Megalurothrips sjostedti) to vegetative and floral volatiles from different cowpea cultivars

Bean flower thrips (Megalurothrips sjostedti) is a key pest of cowpea (Vigna unguicalata) in Africa. To better understand the interaction of M. sjostedti to cowpea cultivars to improve management efforts, we investigated the repellent properties of volatiles of four cowpea cultivars, namely Ex-Luanda, Machakos, Ken Kunde 1 and Katumani 80 at different phenological stages. Bioassays were conducted to study host preference and gas chromatography–mass spectrometry for chemical analysis of volatiles. Our results showed no significant preference of females M. sjostedti for any cowpea cultivars tested in preference assays. However, in olfactometer, the volatiles emitted during the vegetative stage of only Ex-Luanda, Machakos and Katumani 80 cultivars were repellent to females, while only Ken Kunde 1 was repellent to males. Volatiles from flowers of Ken Kunde 1 were attractive to females, whereas volatiles from the flowers of Katumani 80 were repellent, respectively. Ex-Luanda and Machakos elicited neutral response. Flowers of Machakos 66 and Ex-Luanda cultivars were repellent to males, while Katumani 80 and Ken Kunde 1 were neutral. The volatile analysis showed that (E)-β-ocimene and 1-octen-3-ol were unique to the volatile profile of Katumani 80 flowers. Previous study showed that (E)-2-hexenal and hexanal were only abundant in the vegetative stage of Katumani 80. (E)-2-hexenal was repellent to the females at a concentration of 0.01% but not at 1%. Hexanal, (E)-β-ocimene and 1-octen-3-ol elicited a neutral response from females at 0.01% and 1%. Our study indicates that (E)-2-hexenal could be useful in the development of semiochemical-based repellent tools for M. sjostedti management.

Characterization of Male-Produced Aggregation Pheromone of the Bean Flower Thrips Megalurothrips sjostedti (Thysanoptera: Thripidae)

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.

Predation Functional Response and Life Table Parameters ofOrius sauteri(Hemiptera: Anthocoridae) Feeding onMegalurothrips usitatus(Thysanoptera: Thripidae)

Bean flower thrips, Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae), is a serious pest of cowpea in Hainan province, China. In this study, the predation functional response and life table parameters of the minute pirate bug, Orius sauteri (Poppius) (Hemiptera: Anthocoridae), feeding on M. usitatus were measured in the laboratory. The functional response of O. sauteri to increasing M. usitatus density was described by Holling's disc equation, and the maximum predation rate was 45.3 over 24 h. The intraspecific interference of O. sauteri was significant with increasing O. sauteri density. Orius sauteri was able to complete its life cycle feeding on M. usitatus, with an intrinsic rate of increase (r) of 0.16 and fecundity of 95.4 eggs per female. Female and male minute pirate bugs consumed an average of 304.7 and 104.0 thrips over their lifetimes, respectively. These results show O. sauteri to be a potential biological control agent in the integrated pest management of M. usitatus.

The Relation of the bean flower thrips, Megalurothrips usitatus Bagnall (Thripidae) abundance with the existence of thrips predators on the legume plant (Fabaceae) in Jambi region, Sumatera, Indonesia

The purpose of this research was to explore, identify and analyze, the abundance relationship of Bean Flower Thrips, Megalurothrips usitatus Bagnall (Thripidae) with existence of predator thrips at legume cultivation (Fabaceae) in Jambi region. The results showed the presence of M. usitatus in all the legume plants surveyed in the lowlands and highlands of Jambi Province. The abundance of M. usitatus in the lowlands was higher than in the highlands. The abundance of M. usitatus was significantly more in peanuts, long beans, and beans. The least abundance was in green beans and peas. M. usitatus was dominant species than other thrips. There were 4 families of predator thrips present in legume crops in the lowlands and highlands of Jambi Province. They were Coccinellidae, Oxyopidae, Theridiidae, and Chrysopidae. The abundance of predator thrips in the lowlands was higher than in the highlands. There were 8 species of predator thrips in legume crops in the Jambi region, Coelophora inaequalis of the family Coccinellidae being the most abundant.

Effectiveness and profitability of insecticide formulations used for managing snap bean pests

Snap bean ( Phaseolus vulgaris L.) farmers rely mostly on insecticides to manage pests and to satisfy the stringent market requirements for insect and blemish-free pods. However, the cost of these pesticides lowers farm incomes. In addition, heavy and wrong use of pesticides could result in residue accumulation, which reduces market access by the farmers. To identify optimal pest control with lower economic risks to farmers, we investigated the effectiveness and profitability of different insecticides and insecticide formulations against bean fly ( Ophiomyia spp.) and bean flower thrips ( Megalurothrips sjostedtii ). Two separate experiments were conducted during 2009 to 2012. The first experiment targeted bean fly and bean flower thrips, comprising the treatments: seed dressings, soil drenches, foliar sprays and an untreated control. We used randomised complete block design, with four replicates. All the seed dressing and soil drenching insecticides, except Apron, significantly lowered bean fly infestation by two to 60 fold when compared with control. These insecticides, however, did not control flower thrips. Confidor ® resulted in a marginal returns of 0.89 and Actara ® -0.11 compared to seed dressings, which ranged from 0.47 to 1.82. The second experiment laid in a randomised complete block design involved the foliar application of Roket ® under different spray regimes. Application of Roket ® reduced infestation of thrips, and resulted in positive MRR in all the seasons. Keywords: Frankliniella occidentalis , marginal rate of returns, Megalurothrips sjostedtii , Neonicotinoids, Ophiomyia phaseoli

Lure and infect strategy for application of entomopathogenic fungus for the control of bean flower thrips in cowpea

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 5days 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, 5days 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 5days post-application. Conidial viability and thrips conidial acquisition did not differ between the two application methods. Grain yields of 1430.7±114.2kg and 1312.1±87.7kg were obtained in the cover and spot spray treatments, respectively, while 976.8±105.2kg 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.

Active aggregation among sexes in bean flower thrips (Megalurothrips sjostedti) on cowpea (Vigna unguiculata).

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.