Maruca Vitrata Research Articles

New artificial diet for continuous rearing of the bean pod borer, Maruca vitrata.

The bean pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), is a serious pantropical pest of grain legumes. A suitable artificial diet is desirable for producing uniform insects for commercial purposes or research. Three previously described artificial diets, 1 newly-developed artificial diet, and cowpea (Vigna unguiculata (L.) Walp. (Fabales: Fabaceae)), the natural hostplant of M. vitrata, were used for rearing M. vitrata, and the life parameters were examined. The results indicated that insects completed a full life cycle only when the larvae were fed cowpea or the diet reported by Onyango and Ochieng'-Odero (1993), called the “D-OO diet.” However, the rearing efficiency (i.e., larval and pupal survival, longevity of adults, and fecundity) on the D-OO diet was inferior to the rearing efficiency on cowpea. Subsequently, a new artificial diet was formulated based on soybean powder, Glycine max (L.) Merr. (Fabales: Fabaceae), and wheat germ, Triticum aestivum L. (Poales: Poaceae). The egg production, egg hatching, larval developmental duration, and pupal survival of the M. vitrata reared on the new artificial diet were found to be significantly improved relative to the D-OO diet, but were not significantly better than on the host-plant cowpea. The optimum rearing density was 15–25 larvae per box. There were no significant changes in reproductive potential after 8 successive generations of rearing on the new diet. These results indicated that the newly developed diet could serve as a viable alternative to cowpea plant for continuous rearing of M. vitrata.

Bionomics of the parasitoid Apanteles taragamae as influenced by different diets fed to its host, Maruca vitrata

The parasitoid Apanteles taragamae Viereck (Hymenoptera: Braconidae) has been introduced into Benin by the International Institute of Tropical Agriculture (IITA-Benin station) from Taiwan in an attempt to control the cowpea pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), a serious pest of flowers and pods of cowpea Vigna unguiculata Walp. (Leguminosae: Fabaceae). Both the pest and its parasitoid are currently mass-reared using a cowpea and maize flour-based meridic diet. In this study, the suitability of germinating seeds from three cowpea varieties, Kpodji-guegue, Tawa and TVX3236, as substrates, was tested for rearing A. taragamae under laboratory conditions. The seeds that were soaked for 48 h were the most suitable for M. vitrata larval rearing with up to 87 % survival. The highest parasitism rate of M. vitrata larvae by A. taragamae was observed on the local variety Tawa. Compared to meridic diet, the development cycle of the parasitoid was shorter on Tawa sprouts which also lead to the highest lifetime fecundity. The parasitoid sex ratio varied significantly between feeding substrates with a higher proportion of female wasps on the improved varieties TVX2336 and local variety Kpodji-guegue. Rearing M. vitrata larvae on germinating cowpea grains is 4.38 times cheaper than on meridic diet. The data are discussed with emphasis on the effects of feeding substrates quality on life history parameters of insect pests and their parasitoids.

Application of Cry1Ab/Ac Bt strip for screening of resistance for Maruca vitrata in cowpea

Maruca vitrata is a significant constraint to cowpea production in most cowpea growing areas of sub-Saharan Africa. Yield losses caused by M. vitrata in these regions are estimated in millions of tons annually and the prevalence of M. vitrata infestation is steadily increasing. Recombinant DNA technology have led to development of some cowpea lines with Maruca resistance as well as other important agronomic traits but it is time-consuming and difficult to screen for the resistant trait especially in the segregating populations using conventional screening techniques, which will lead to delay in the development of Maruca resistant cowpea varieties. The use of allele-based selection tool will make it easier to select plant traits and reduce the time needed to develop new Maruca resistant cowpea varieties. In this study, the efficacy of using Cry1Ab/Ac Bt strip for detecting Maruca resistant transgene in transgenic cowpea was systematically investigated for the first time through field derived progenies. The results show that the Cry1Ab/Ac Bt strip was effective for detecting the presence of the resistant gene in cowpea genome. Maruca resistant plants were successfully screened from the segregating cowpea plants and the genetics of the gene was monitored. The Cry1Ab/Ac Bt strip was found to be suitable for genetic analysis of the Maruca resistant transgene in cowpea. This study has demonstrated the precision of using Cry1Ab/Ac Bt strips as a screening tool of transgenic lines containing Cry1Ab gene, this has an importance in the hybridization programme where genotypes having cry gene can be distinguished at seedling stage at lesser time, with the potential of putting the breeding process on a fast track and increase the efficiency of breeding activities. Keywords: Bacillus thuriengiensis , Cry1Ab/Ac Bt strips, transgenic cowpea, Maruca vitrata . African Journal of Biotechnology Vol. 12(40), pp. 5869-5874

English

Maruca vitrata is a significant constraint to cowpea production in most cowpea growing areas of  sub-Saharan Africa. Yield losses caused by M. vitrata in these regions are estimated in millions of tons annually and the prevalence of M. vitratainfestation is steadily increasing. Recombinant DNA technology have led to development of some cowpea lines with Maruca resistance as well as other important agronomic traits but it is time-consuming and difficult to screen for the resistant trait especially in the segregating populations using conventional screening techniques, which will lead to delay in the development of Maruca resistant cowpea varieties. The use of allele-based selection tool will make it easier to select plant traits and reduce the time needed to develop new Maruca resistant cowpea varieties. In this study, theefficacy of using Cry1Ab/Ac Bt strip for detecting Maruca resistant transgene in transgenic cowpea was systematically investigated for the first time through field derived progenies. The results show that the Cry1Ab/Ac Bt strip was effective for detecting the presence of the resistant gene in cowpea genome. Maruca resistant plants were successfully screened from the segregating cowpea plants and the genetics of the gene was monitored.  The Cry1Ab/Ac Bt strip was found to be suitable for genetic analysis of the Maruca resistant transgene in cowpea. This study hasdemonstrated the precision of using Cry1Ab/Ac Bt strips as a screening tool of transgenic lines containing Cry1Ab gene, this has an importance in the hybridization programme where genotypes having cry gene can be distinguished at seedling stage at lesser time, with the potential of putting the breeding process on a fast track and increase the efficiency of breeding activities.   Key words: Bacillus thuriengiensis, Cry1Ab/Ac Bt strips, transgenic cowpea, Maruca vitrata.

Female Sex Pheromone Blends and Male Response of the Legume Pod Borer, Maruca vitrata (Lepidoptera: Crambidae), in Two Populations of Mainland China

The legume pod borer, Maruca vitrata (Lepidoptera: Crambidae; syn. M. testulalis), is a serious pantropical insect pest of grain legumes. Comparative studies of M. vitrata female sex pheromone components in two different geographic populations in China, Wuhan and Huazhou, confirmed that (E,E)-10,12-hexadecadienal (E10,E12-16:Ald) and (E)-10-hexadecenal (E10-16:Ald) were present in variable ratios in all pheromone gland extracts of both populations. (E,E)-10,12-hexadecadienol (E10,E12-16:OH) was always detected in minor amounts using polar DB-WAX columns, but was never detected using medium-polar DB-17 columns for the two populations. E10-16:OH was not found in any of the M. vitrata sex pheromone gland extracts. The average ratios of E10-16:Ald, E10,E12-16:Ald, and E10,E12-16:OH in the pheromone gland extracts of populations from Wuhan and Huazhou were 79.5:100:12.1 and 10.3:100:0.7, respectively. Electrophysiological testing suggested that E10,E12-16:Ald elicited the highest male electroantennography (EAG) response, followed by E10,E12-16:OH and E10-16:Ald. Field-trapping tests with single synthetic sex pheromone lures showed that E10,E12-16:OH alone could not attract males, whereas E10,E12-16:Ald or E10-16:Ald alone attracted few males. Wuhan and Huazhou males were most attracted by lures containing E10-16:Ald + E10,E12-16:Ald + E10,E12-16:OH in doses of (80 + 100 + 10) microg and (10 + 100 + 10) microg, respectively, per vial. Males could discriminate between the blends that were most attractive to their own geographic population and those that were most attractive to the reference population. Our findings suggest that geographic variation exists in the sex pheromone system of M. vitrata in China. The results are discussed with regard to the mechanisms underlying the sex pheromone variation.

Efficacy of Bacillus thuringiensis Against Maruca vitrata (Geyer) on Cowpea

Spotted pod borer, Maruca vitrata (Geyer) is a major constraint in the production of grain cowpea. The pest causes losses in grain yield of cowpea ranging from 20 to 60 per cent. In order to manage the pest, field experiments were conducted at four farmers fields during rabi 2010-2011. The study revealed that the pest can be managed effectively by spraying profenophos @ 1ml/litre at the time of flowering, Bacillus thuringiensis @ 1g/litre one at the time of flowering and next one was at 15 days later, Beauveria bassiana @ 20 g/litre at the time of flowering and other one was at 15 days interval and carbaryl @ 4 g/litre at the time of flowering. At harvest, the treatments recorded the per cent pod borer incidence of 6.99, 7.40, 7.86 and 8.96, respectively. Significantly higher grain yield was recorded in profenophos (817.18 kg/ha), Bacillus thuringiensis (754.89 kg/ha) and Beauveria bassiana (748.66 kg/ha) and carbaryl (669.31 kg/ha) treated plots.

Evaluation of bio-pesticides against legume pod borer, Maruca vitrata Fabricius (Lepidoptera: Pyralidae), in laboratory and field conditions in Thailand

The legume pod borer (Maruca vitrata) is a major destructive insect found on the yard-long bean, causing serious damage from the flowering stage. Because growers mostly rely on synthetic pesticides to control this insect, it has developed resistance to some pesticides. Information on the efficacy of bio-pesticides against this pest in Thailand is scarce. This study was conducted to evaluate the effects of selected bio-pesticides against M. vitrata. Among six commercially available bio-pesticides, only Bacillus thuringiensis subsp. kurstaki and B. thuringiensis subsp. aizawai were found to be more effective against M. vitrata under laboratory conditions, while neem was least effective. In a field trial undertaken between June and September 2011, both B. thuringiensis formulations significantly reduced pod damage compared with untreated plots of the yard-long bean. A similar efficacy pattern was observed during the second field trial between October 2011 and January 2012. These results suggest that B. thuringiensis formulations could become important components in an integrated pest management strategy for controlling M. vitrata on the yard-long bean in Thailand. However, the results of the current study imply the need for additional field trials with combinations of microbial, botanical, and chemical pesticides rather than a single bio-pesticide per treatment in the management of M. vitrata.

Feeding preferences of the legume pod borer Maruca vitrata (Lepidoptera: Crambidae) larvae and suitability of different flower parts for larval development

With the advent of transgenic Bacillus thuringiensis (Bt)-cowpea, there is a need to identify the feeding preferences of Maruca vitrata Fab. to determine in which component of the plant the expression of the toxin needs to be the highest to ensure the greatest efficacy of insecticidal Bt proteins. In the current study, we examined the feeding preferences of M. vitrata larvae in a naturally infested cowpea field. We also tested, in the laboratory, the suitability of different flower components for the larval development of M. vitrata. Our results indicate that in the field, all types of flowers, regardless of their age, were infested with M. vitrata larvae. The reproductive organs, in the flowers, were the preferred feeding diet for the larvae. Laboratory bioassays confirmed that the reproductive organs were the optimal tissues for M. vitrata larval development. The implications of these findings for transgenic Bt-cowpea are discussed.

Molecular-Phylogenetic Characterization of Arrestin-2 from Maruca vitrata (Lepidoptera: Crambidae)

Abstract Most physiological processes to external stimulants rely upon intracellular signal transduction mediated by ligand binding of G-protein-coupled receptors. The G-protein signaling pathway is deactivated by arrestin-2 binding, which is indispensable for receptor internalization and recycling. We identified the full-length cDNA encoding arrestin-2 in Maruca vitrata F. using rapid amplification of cDNA ends. The open reading frame of MaviArr2 is 1,221 bp in length, encoding 407 amino acids. The alignment of the known arrestin-2 amino acid sequences from other insects revealed that MaviArr2 has the highest similarity (98.8%) to the monarch butterfly, but shows low homology (53.9–60.7%) with ants and bees. A certain number of highly conserved protein-binding motifs were identified from the deduced MaviArr2 amino acids, demonstrating their function as receptor deactivators in signal transduction pathways in cells. The genomic DNA sequence of MaviArr2, amplified by polymerase chain reaction, is 1,779 bp in size and is composed of six exons. Real-time quantitative polymerase chain reaction assay demonstrated a relatively higher expression of MaviArr2 mRNA in the late pupal stages, suggesting multiple developmental functions. Phylogenetic analysis showed the lepidopteran arrestin-2 protein sequence is closely related to that of Diptera, but distant from Hymenoptera arrestin-2. Intraspecific genomic sequence comparisons of MaviArr2 show a greater conservation of the gene in M.vitrata from Africa than those from geographical locations in Asia. These findings are a significant step forward in our understanding of arrestin-2 gene architecture and functions, which may provide a possibility to manage M.vitrata through molecular and phylogenetic techniques.

Effect of plant secondary metabolites on legume pod borer, Helicoverpa armigera

The effect of various flavonoids, lectins and phenyl β-d-glucoside on larval survival, weights and the activities of digestive (total serine protease and trypsin) and detoxifying [esterase and glutathione-S-transferase] enzymes of Helicoverpa armigera larvae at 5 and 10 days after treatment (DAT) was studied through diet incorporation assay. Flavonoids (quercetin, cinnamic acid, caffeic acid, chlorogenic acid, catechin, trihydroxyflavone, gentisic acid, ferulic acid, protocatechuic acid and umbelliferone) were incorporated in artificial diet at 100, 500 and 1000 ppm, lectins: groundnut leaf lectin (GLL), concavalin (ConA) and phenyl β-d-glucoside at 2.5 and 5 μg mL−1. Flavonoids such as chlorogenic acid, caffeic acid and protocatechuic acid at 1,000 ppm were more toxic to H. armigera larvae at 10 DAT than quercetin, catechin, cinnamic acid, trihydroxyflavone, gentisic acid, ferulic acid and umbelliferone. Larval growth and development were significantly reduced in H. armigera larvae fed on a diet with GLL and ConA at 5 μg mL−1 compared to the larvae fed at 2.5 and 1.25 μg mL−1 concentrations. The enzyme activities of the larvae were significantly reduced in flavonoid-treated diets. The flavonoids such as chlorogenic acid, caffeic acid, gentisic acid, trihydroxyflavone, catechin and protocatechuic acid, and lectins, GLL and ConA can be utilized in insect control programs.

Record of Three Larval Parasitoids (Hymenoptera: Ichneumonoidea) of Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) from Southern India

Maruca vitrata (Fabricius) (Lepidoptera: Crambidae) commonly known as legume pod borer is known to infest many leguminous crops. In the recent rearing records of larval parasitoids from M. vitrata three species of wasps have been bred, Bassus relativus (Bhat and Gupta, 1977) (Hymenoptera: Braconidae: Agathidinae), Phanerotoma hendecasisella Cameron, 1905 (Braconidae: Cheloninae) and Trathala flavoorbital is (Cameron, 1907) (Ichneumonidae: Cremastinae). Amongst these three Indian species of wasps, B. relativus is recorded for the first time as a larval parasitoid of M. vitrat a. In the present study main diagnostic characters of all the three species of parasitic wasps along with their hosts and distribution details are provided.

Effect of Nine Plant Volatiles in the Field on the Sex Pheromones of Leguminivora glycinivorella

Attraction of the soybean pod borer, Leguminivora glycinivorella (Matsumura), an economically important pest of soybean, to nine plant volatiles, alone or combined with two kinds of synthetic sex pheromone, ((E,E)-8,10-dodecadienyl acetate (EE8,10-12:Ac), or a blend of EE8,10-12:Ac and (E)-10-dodecenyl acetate in a 10:1 ratio), was evaluated in field trapping experiments in a soybean field in Harbin, China. By themselves, the plant volatiles (dose) linalool (0.1 mg), (Z)-3-hexenyl acetate (0.1 mg), and geraniol (0.1 mg, 1.0 mg) were weakly attractive to L. glycinivorella males, but significantly reduced mean catches when higher doses were combined with pheromones. Conversely, (E)-2-hexenal, benzaldehyde, and phenylacetaldehyde were not attractive to L. glycinivorella males at any dose tested, but significantly increased mean catch when certain doses were combined with the binary pheromone blend. Other plant volatiles, such as (Z)-3-hexen-1-ol, (Z)-3-hexenyl acetate, and (E)-2-hexenyl acetate, were unattractive on their own, but significantly reduced mean catch of L. glycinivorella males when certain doses were combined with the pheromones. These results suggest that efficacy of pheromone-baited traps for survey and monitoring of L. glycinivorella male moths may be enhanced by the addition of specific plant volatiles and that the relative dose is critical.

Female Sex Pheromone Blends and Male Response of the Legume Pod Borer, Maruca vitrata (Lepidoptera: Crambidae), in Two Populations of Mainland China

The legume pod borer, Maruca vitrata (Lepidoptera: Crambidae; syn. M. testulalis), is a serious pantropical insect pest of grain legumes. Comparative studies of M. vitrata female sex pheromone components in two different geographic populations in China, Wuhan and Huazhou, confirmed that (E,E)-10,12-hexadecadienal (E10,E12-16:Ald) and (E)-10-hexadecenal (E10-16:Ald) were present in variable ratios in all pheromone gland extracts of both populations. (E,E)-10,12-hexadecadienol (E10,E12-16:OH) was always detected in minor amounts using polar DB-WAX columns, but was never detected using medium-polar DB-17 columns for the two populations. E10-16:OH was not found in any of the M. vitrata sex pheromone gland extracts. The average ratios of E10-16:Ald, E10,E12-16:Ald, and E10,E12-16:OH in the pheromone gland extracts of populations from Wuhan and Huazhou were 79.5:100:12.1 and 10.3:100:0.7, respectively. Electrophysiological testing suggested that E10,E12-16:Ald elicited the highest male electroantennography (EAG) response, followed by E10,E12-16:OH and E10-16:Ald. Field-trapping tests with single synthetic sex pheromone lures showed that E10,E12-16:OH alone could not attract males, whereas E10,E12-16:Ald or E10-16:Ald alone attracted few males. Wuhan and Huazhou males were most attracted by lures containing E10-16:Ald + E10,E12-16:Ald + E10,E12-16:OH in doses of (80 + 100 + 10) microg and (10 + 100 + 10) microg, respectively, per vial. Males could discriminate between the blends that were most attractive to their own geographic population and those that were most attractive to the reference population. Our findings suggest that geographic variation exists in the sex pheromone system of M. vitrata in China. The results are discussed with regard to the mechanisms underlying the sex pheromone variation.

Conventional and Molecular Approaches towards Genetic Improvement in Pigeonpea for Insects Resistance

Pigeonpea [Cajanus cajan (L.) Millspaugh] is an important food legume of the semi-arid tropics (SAT) sustaining livelihood of millions of people. Stagnant and unstable yield per hectare all over the world is the characteristic feature of this crop. This is primarily ascribed to its susceptibility/sensitivity to a number of biotic and abiotic factors. Among biotic factors, insects such as pod borer (Helicoverpa armigera), pod fly (Melanoagromyza obtusa) and spotted borer (Maruca vitrata) substantially damage the crop and result in significant economic losses. Management of these insects by genetic means has always been considered environment friendly approach. However, genetic improvement has always been impeded by limited genetic variability in the primary gene pool of pigeonpea. Wild species present in the secondary and tertiary gene pools have been reported to carry resistance for such insects. However, transfer of resistance through conventional backcrossing has not been much successful. It calls for gene introgression through marker assisted backcrossing (MABC) or advanced backcross breeding (AB breeding). In this review, we have attempted to assess the progress made through conventional and molecular breeding and suggested the ways to move further towards genetic enhancement for insects resistance in pigeonpea

Host plant resistance to insect pests of grain legumes -A review

Grain legumes are important source of dietary protein in tropical region and insect pests cause considerable damage to these crops. Development of resistant varieties in legume crops is an important component in integrated pest management strategies. Though insecticides are effective against sucking pests and pod borer complex, development of insecticide resistance, residues in short duration crop produces and environment hazards demand alternative eco safe method of management. The chapter reviews the development and studies on host plant resistance in major grain legumes against pod borer complex Maruca vitrata, Helicoverpa armigera, etc. and major sucking pests. The mechanisms of resistance, factors responsible for the resistance are discussed in this paper.

English

Insecticide spray offers the most effective control of insect pests where resistant varieties are not available as is the case with the legume pod borer and pod sucking bug complex. Field experiments were conducted in the northern Guinea and Sudan savannas (Samaru and Minjibir, respectively) zones of Nigeria during 2005 to 2007 rainy seasons to evaluate the efficacy of common and new insecticides in the Nigeria markets for field control of insect pests of cowpea. Post spray insect counts showed that the new insecticide combinations gave control of thrips, Megalurothrips sjostedti (Order: Thysanoptera, Family: Thripidae) statistically similar to Monocrophos. Maruca vitrata (Order: Lepidoptera, Family: Crambidae) population densities were significantly reduced by the application of the insecticide regime of Imidacloprid (first spray), Cypermethrin (second and third) which however was not different from Cypermethrin-Dimethoate. The no spray plots gave significantly higher fodder yield in Samaru. The highest mean grain yields at Minjibir were obtained from plots sprayed with Imidacloprid + Cypermethrin + Cypermethrin (1391 kg/ha) while highest mean grain yield (924 kg/ha) in Samaru was from Monocrophos applied three times. Considering safety issues and environmental concerns, Imidacloprid (first spray) and Cypermetrin (second and third sprays) is recommended in a three insecticide spray recommendation for cowpea cultivation, especially in the Sudan Savanna of Nigeria and three sprays of Cypermethrin-Dimethoate in the northern Guinea Savanna. Key words: Cowpea, Megalurothrips sjostedti, Maruca vitrata, tricel, courage, grain yield.

Developing Pheromone Traps and Lures for Maruca vitrata in Taiwan

The larvae of the legume pod borer, Maruca vitrata (Lepidoptera: Pyralidae), cause severe damage on economically important legume crops in the tropics. The female moth produces volatile components to attract males for mating. The so-called sex pheromones are species-specific multi-component blends and are used as lures in crop protection for pest monitoring. Their chemical identification and ratios is critical to design efficient lures. The following sex pheromone components for M. vitrata have been described: (E, E)-10,12-hexadecadienal (major compound), (E, E)-10,12-hexadecadienol and (E)-10-hexadecenal (minor components). The ratio of 100:5:5 of these components was the most attractive in trapping experiments in Benin, Africa. According to this ratio, a synthetic pheromone lure was developed for commercial use. But the commercially available blend was not attractive in field trapping experiments in other regions of sub-Saharan Africa and Southeast Asia. These findings lead to the conclusion that there is a possible polymorphism in the blend composition of the M. vitrata sex pheromone among populations from different geographical regions. In Taiwan, M. vitrata moths were never caught efficiently by the commercially available pheromone lures and traps. This paper reports trap and lure optimization experiments for effective trapping of Taiwanese M. vitrata moths in different leguminous crops.

Synthesis and Field Evaluation of the Sex Pheromone Analogues to Soybean Pod Borer Leguminivora glycinivorella

In order to develop efficient lures for soybean pod borer Leguminivora glycinivorella (Matsumura) in China, (E,E)-8,10-dodecadienyl acetate (EE-8,10-12:Ac), the main component of the pheromone of L. glycinivorella, and 12 structurally-related compounds were synthesised in good overall yields, regiospecificities, and stereo-selectivities via coupling reactions catalysed by Li2CuCl4. The effect of different synthetic compounds, alone or in combination with EE-8,10-12:Ac, on numbers of captured L. glycinivorella males was evaluated. EE-8,10-12:Ac, (E)-10-dodecenyl acetate(E-10-12:Ac), (E)-8-dodecenol (E-8-12:OH), tetradecyl acetate (14:Ac), and (Z)-9-tetradecenyl acetate (Z-9-14:Ac) alone displayed different attractiveness to L. glycinivorella males. 14:Ac, E-8-12:OH, E-10-12:Ac, (E,E)-8,10-dodecadienal (EE-8,10-12:Ald), (E)-8-dodecenal (E-8-12:Ald), (E)-10-dodecenal (E-10-12:Ald) and Z-9-14:Ac all showed a synergistic effect to EE-8,10-12:Ac at certain dosages. The binary mixtures of EE-8,10-12:Ac and E-10-12:Ald, Z-9-14:Ac,14:Ac, E-8-12:Ald, EE-8,10-12:Ald, E-8-12:OH, or E-10-12:Ac in suitable ratios give 17.00-, 10.98-, 10.67-, 6.73-, 5.54-, 4.30- and 4.50-fold increases in trap catch, respectively, over the standard pheromone lure, and as novel pheromone blends, demonstrated potential use in pheromone traps to monitor or control L. glycinivorella populations in China.

Modeling Evolution of Resistance byMaruca vitrata(Lepidoptera: Crambidae) to Transgenic Insecticidal Cowpea in Africa

We created a detailed model of the Maruca vitrata (F.) and cowpea [Vigna unguiculata (L.) Walp] system to study the possible evolution of resistance by the insect to transgenic insecticidal cowpea, which is under development. We focused on population dynamics and genetics in a region of west Africa. We simulated single-toxin and pyramided (two-toxin) cowpea and emphasized conservative, worst-case scenarios in our analysis. The results indicate that as long as a pyramided, transgenic cowpea can be developed, seed saving by farmers and reliance on natural refuge are not major problems for resistance management. Furthermore, it is possible that one or both toxins in the pyramid may not need to be high dose for evolution to be delayed significantly (>20 yr or 80 generations for resistance to become a concern if transgenic cowpea is deployed in areas where M. vitrata is endemic). If efforts are made to deploy transgenic cowpea only into the regions where M. vitrata is not endemic, then there is little to no concern with resistance emerging in the M. vitrata population.

EVALUATION OF NATIVE SOAP (BLACK SOAP) FOR THE CONTROL OF MAJOR INSECT PESTS AND YIELD OF COWPEA (VIGNA UNGUICULATA (L.) WALP) IN ABRAKA, DELTA STATE

The experiments were carried out during the early and late planting seasons on a public land adjacent to Campus 2, Delta State University, Abraka, Nigeria. The study evaluated native soap at 1, 2 and 3 percent concentrations for insecticidal property in the control of cowpea insect pests, namely cowpea aphid, Aphis craccivora Koch, legume bud thrips Megalurothrips sjostedti Tryb, legume pod borer, Maruca vitrata Fab. and pod sucking bugs. It also assessed influence of control on cowpea yield. The result showed that native soap at 3% concentrations significantly reduced (P<0.05) A. craccivora in the early season. M. sjostedti damage, thrip population, Maruca damage and pod sucking bug were generally low in this season. In the late season, colonies of A. craccivora were reduced at 1 and 2% concentrations. Similarly, all the tested concentrations checked flower thrips. Maruca damage was slightly suppressed at 1 and 2% native soap concentrations. The control plots had the highest population of sucking bugs suggesting that native soap had effect on bugs. Yields were 1,355.90kg ha-1, 1105.20kg ha-1 and 919.80kg ha-1 for 3%, 2% and 1% soap concentration respectively in the early season. Late season grain yield were 570.80kg ha-1, 510.10kg ha-1 and 358.90kg ha-1 for 3%, 1% and 2% respectively. Based on the high yields, particularly in the early season, the study suggests that native soap can be an effective insecticide against cowpea insect pests, and could form component of the integrated pest management. It was however, observed in the field that native soap caused delay and reduction in copious cowpea flowering. Eliminating this factor could be necessary to increase the efficacy of soap in the management of cowpea insect pests.