​Screening of Pigeonpea Varieties through Nylon Bag No-choice Bioassay for Host Plant Resistance to Helicoverpa armigera

Background: The legume pod borer, Helicoverpa armigera (Hübner), is one of the most damaging crop pests, including pigeonpea. Host plant resistance is a component of pest management and therefore, we standardize a nylon bag No-Choice Bioassay technique to screen for resistance to H. armigera under field conditions. Methods: Pigeonpea plants were infested with 24 h old 1, 2, 3, 4 and 5 larvae per plant inside the nylon bag. Observations were recorded on pod damage, larval survival, larval weight, pupation, adult emergence, and fecundity after 10 days. Result: Pigeonpea varieties AL-201, H03-41 and PAU-881 exhibited lower pod damage (15.89 to 19.77%) and larval weight (12.02 to 13.82 mg). The expression of resistance to H. armigera was associated with trichome density, pod wall thickness and higher amount of phenolic compounds and condensed tannins. Lower trichome density and thin pod walls and higher amounts of sugars rendered the varieties Paras, Manak and Pussa-992 more susceptible to H. armigera. Nylon bag assay can be used to screen and select pigeonpea cultivars for resistance to H. armigera.

Influence of Weather Parameters on the Seasonal Abundance of Legume Pod Borer Maruca vitrata (Crambidae: Lepidoptera) on Dolichos Bean (Lablab purpureus var. typicus)

Background: Legume pod borer, Maruca vitrata (Fabricius), infests the Dolichos bean throughout the cropping season. However, there is no information on the seasonal abundance of M. vitrata over different seasons on Dolichos bean, which is an essential tool for forecasting and developing integrated pest management strategies. Methods: The seasonal abundance of M. vitrata on Dolichos bean were studied during three consecutive cropping seasons of 2019 Summer, Kharif and Rabi. The larval population in flowers and pods and the number of larval webbings and weather parameters were recorded and subjected to correlation and multiple linear regression analysis. Result: The overall larval abundance was observed to be higher in flowers than in pods. The highest larval abundance in flowers and pods was 14.60 and 13.40 during the 48th and 50th standard meteorological week (SMW) of Rabi 2019 respectively, which corresponds to 8 to 10 weeks after sowing (WAS) in flowers and 10 to 12 WAS in the case of pods. The number of larval webbings was higher, with 18.76 during the 49th SMW of Rabi 2019. The maximum temperature had a significant negative correlation with the larval abundance in flowers (r= -0.570), pods (r= -0.523) and the number of active webbings (r= -0.477). At the same time, the regression coefficient shows that rainfall had a significant negative influence on the larval abundance in pods (B= -1.26).

Functional characteristics of a novel odorant binding protein in the legume pod borer, Maruca vitrata

Insect olfaction system plays a key role in the foraging food, pollination, mating, oviposition, reproduction and other insect physiological behavior. Odorant binding protein are widely found in the various olfactory sensilla of different insect antennae and involved in chemical signals discrimination from natural environment. In this study, a novel OBP gene, MvitOBP3 is identified from the legume pod borer, Maruca vitrata, which it mainly harms important legume vegetables including cowpea, soybean and lablab bean. Real-time PCR results demonstrated that MvitOBP3 gene was abundantly expressed in the antennal tissue of M. vitrata, while low levels were distributed in the head, thorax, abdomen, leg and wing of adult moths. The recombinant OBP3 protein was purified using the prokaryotic expression and affinity chromatography system. Fluorescence competitive binding experiments indicated that that MvitOBP3 protein exhibited greater binding affinities with host-plant flower volatiles including Butanoic acid butyl ester, Limonene, 1H-indol-4-ol and 2-methyl-3-phenylpropanal, highlighting they may have attractant activities for the oviposition of female moths on the legume vegetables. Moreover, protein homology modeling and molecular docking analysis revealed that there are six amino acid sites of MvitOBP3 involved in the binding of the host-plant volatiles. These findings will further promote to understand the key role of odorant binding protein during host perception and oviposition of M. vitrata moths, which improve the efficiency of semiochemical-based prevention and monitoring for this pest in the legume vegetables field.

NEEM, Azadirachta indica L. (A. Juss): AN ECO-FRIENDLY BOTANICAL INSECTICIDE FOR MANAGING FARMERS’ INSECTS PEST PROBLEMS - A REVIEW

The search for reducing risks associated with the use of chemicals has necessitated use of pest control using plant products. Neem is perhaps one of the most useful medicinal plant in the tropics. Each part of the tree has huge insecticidal property. Apart from the chemistry of the neem compounds, considerable progress has been achieved regarding the biological activity and insecticidal uses of neem. It is now considered as a valuable source of unique natural product for botanical insecticides against various pests. Farmers in tropical countries commonly used its leaves, seed kernels and its oil in various forms. Neem is utilized in form of powders, extracts or as an emulsifiable oil. Researches had shown that neem consists of pesticidal ingredients called triterpenes (limonoids). Trials conducted on the effect of neem products revealed secondary metabolites affect metabolic processes that include feeding and oviposition deterrence; metamorphosis inhibition, protein synthesis, changes in biological fitness, impaired sexual communication and chitin synthesis. Azadirachtin in particular interferes with chemoreception and exerts direct negative effects on many insect tissues such as muscles and digestive epithelial cells as well as insect mortality. Neem derived biopesticides are cheap, available in all ecological zone, posed no hazard to applicator and the environment as it is biodegradable. Insects such as Aphids, African migratory locust, legume pod-borer, coreid bugs and storage insect pests such as cowpea seed bruchid were controlled using neem. Sustainable insect pest control can be achieved with the use of neem based biopesticides.

Functional characteristics of a novel odorant binding protein in the legume pod borer, Maruca vitrata (Lepidoptera: Crambidae)

Insect olfaction system plays a key role in the foraging food, pollination, mating, oviposition, reproduction and other insect physiological behavior. Odorant binding protein are widely found in the various olfactory sensilla of different insect antennae and involved in chemical signals discrimination from natural environment. In this study, a novel OBP gene, MvitOBP3 is identified from the legume pod borer, Maruca vitrata, which it mainly harms important legume vegetables including cowpea, soybean and lablab bean. Real-time PCR results demonstrated that MvitOBP3 gene was abundantly expressed in the antennal tissue of M. vitrata, while low levels were distributed in the head, thorax, abdomen, leg and wing of adult moths. The recombinant OBP3 protein was purified using the prokaryotic expression and affinity chromatography system. Fluorescence competitive binding experiments indicated that that MvitOBP3 protein exhibited greater binding affinities with host-plant flower volatiles including Butanoic acid butyl ester, Limonene, 1H-indol-4-ol and 2-methyl-3-phenylpropanal, highlighting they may have attractant activities for the oviposition of female moths on the legume vegetables. Moreover, protein homology modeling and molecular docking analysis revealed that there are six amino acid sites of MvitOBP3 involved in the binding of the host-plant volatiles. These findings will further promote to understand the key role of odorant binding protein during host perception and oviposition of M. vitrata moths, which improve the efficiency of semiochemical-based prevention and monitoring for this pest in the legume vegetables field.

Emergence of Maruca vitrata as a Major Pest of Food Legumes and Evolution of Management Practices in Asia and Africa

Legume pod borer, Maruca vitrata, has emerged as a major pest on food legumes in Asia and Africa. It is an oligophagous pest, feeding on over 70 species in Fabaceae. We examine the species complex in Asia, Africa, Oceania, and the Americas, with an emphasis on molecular taxonomy. Studies on pheromone production and perception suggest the existence of pheromone polymorphism, especially in Asia and Africa. No Maruca-resistant varieties are available in the major food legumes including cowpea, pigeonpea, mungbean, and yard-long bean. Legume growers use chemical pesticides indiscriminately, leading to the development of pesticide resistance. However recent developments in habitat management, classical biocontrol with more efficient parasitoids, biopesticides, and judicious use of insecticides pave the way for sustainable management of M. vitrata, which can reduce the pesticide misuse. Active engagement of the private sector and policy makers can increase the adoption of integrated pest management approaches in food legumes.

Infectivity of entomopathogenic nematodes against the legume pod-borer, Maruca vitrata Fabricius, infesting pigeon pea

The legume pod-borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae) (LPB), is an important insect pest of pigeon pea. Chemical pesticides are generally employed to manage this pest, but because of the soil residue issues and other environmental hazards associated with their use, biopesticides are also in demand. Another benign alternative is to use entomopathogenic nematodes (EPNs) to manage this vital pest. In the present study, the infectivity of ten native EPNs was evaluated against LPB by assessing their penetration and production in the LPB. The effectiveness of the promising EPNs against second-, third- and fourth-instar LPB larvae was also studied. Heterorhabditis sp. (Indian Agricultural Research Institute-Entomopathogenic Nematodes Rashid Pervez (IARI-EPN RP) 06) and Oscheius sp. (IARI-EPN RP 08) were found to be most pathogenic to LPB, resulting in about 100% mortality within 72 h, followed by Steinernema sp. (IARI-EPN RP 03 and 09). Oscheius sp. (IARI-EPN RP 04) was found to be the least pathogenic to LPB larva with 67% mortality. Maximum penetration was exhibited by Heterorhabditis sp. (IARI-EPN RP 06) followed by Oscheius sp. (IARI-EPN RP 08), whereas the lowest rate of penetration was exhibited by Oscheius sp. (IARI-EPN RP 01). The highest rate of production was observed with Oscheius sp. (IARI-EPN RP 08), followed by Oscheius sp. (IARI-EPN RP 04 and 10). Among the tested instars of the LPB larvae, second-instar larvae were more susceptible to EPNs, followed by third- and fourth-instar larvae. The results indicate that Heterorhabditis sp. (IARI-EPN RP 06) and Oscheius sp. (IARI-EPN RP 08) have a good potential to the manage LPB.

WEATHER PARAMETERS AFFECTING THE POPULATION DYNAMICS OF LEAF FOLDER AND POD BORERS ON MUNGBEAN

The experiment was conducted to know the abundance of major insect pests on 15 mungbean varieties viz., BARI Mung-1, BARI Mung-2, BARI Mung-3, BARI Mung-4, BARI Mung-5, BARI Mung-6, BINA Moog-4, BINA Moog-5, BINA Moog-6, BINA Moog-7, BINA Moog-8, BU Mug-1, BU Mug-2, BU Mug-4 and Patuakhali local Mung and the role of weather parameters on the population mobility of insects at the farmer’s field of sadar upazila of Patuakhali district, Bangladesh during late Robi season 2016. Variety BARI Mung-4 had the lowest number of leaf folder while variety BARI Mung-6 had the highest number of leaf folder indicating higher susceptibility to leaf folder. Variety BARI Mung-4 had the lowest number of gram pod borer and BARI Mung- 6 had the highest abundance of gram pod borer followed by BINA Moog-7. Variety BINA Moog-4 had the lowest number of legume pod borer and BARI Mung-6 had the highest abundance of legume pod borer followed by BINA Moog-7. Population of leaf folder showed a negative correlation (R2= -0.020) with temperature. Similarly, gram pod borer (R2= -0.317) and legume pod borer (R2= -0.014) showed a negative correlation with temperature. In case of relative humidity, population of leaf folder (R2= -0.175) showed a negative correlation while gram pod borer showed a positive correlation (R2= 0.031) but legume pod borer (R2= -0.086) showed a negative correlation.

Effect of Planting Dates on Incidence of Legume Pod Borer (Maruca vitrata Geyer) on Cowpea (Vigna unguiculata (L.) Walp.) Varieties in Samaru Kataf, Kaduna State

Field experiment was carried out during 2018 cropping season to evaluate the effect of planting dates on incidence of legume pod borer Maruca vitrata on cowpea (Vigna unguiculata) varieties. The treatments consist of five varieties of cowpea (local variety, SAMPEA 6, SAMPEA 7, SAMPEA 8 and SAMPEA 10) which were sown at three different dates, 7th (early), 24th (Mid) August and 7th (early) September, 2018. The experiment was laid out in a Randomized Complete Block Design (RCBD) replicated three times. The number of M. vitrata larva on flowers, damaged pods and weight of grains were determined. The result showed that first sowing nearly August had less infestation by M. vitrata than those in mid August and differs significantly (P≤0.05) from those sown in September. All varieties sown in early and mid August had less M. vitrata infestation and produced higher grain yield of 533.33kg and 395.06 kg on SAMPEA 7 and SAMPEA 8, respectively compared to those sown in early September: 256.79 and 197.53 on SAMPEA 7 and SAMPEA 10, respectively. Local variety and SAMPEA 6 were the varieties with higher mean number of M. vitrata, higher pod damage and low grain yield. Therefore, SAMPEA 7 can be utilized in breeding program for the management of pod borer.