Influence of abiotic factors on seasonal incidence of spotted pod borer, Maruca vitrata (Geyer), in black gram

Introduction

Black gram (Vigna mungo (L.) Hepper), commonly referred to as urd bean. is an important pulse crop belonging to the family Fabaceae. It is broadly cultivated in India and consumed in diverse manners, including whole or split dal, both husked and unhusked, along with roasted grains. Besides its value as a nutritious food crop, black gram is also used as highquality fodder for dairy animals and serves as an effective green manure crop, contributing to soil fertility and sustainable farming systems Varieties of black gram grown in India were analyzed for their physical attributes and cooking qualities The proximate composition showed that the three cultivars had protein levels ranging from 24.5 to 26.7 percent, fat content between 1.1 and 1.3 percent, ash content of 2.8 to 3.7 percent, and carbohydrates comprising 60.4 to 63.3 percent. The seeds exhibited measurements ranging from 4.66 mm to 5.11 mm in length, 3.71 mm to 3.79 mm in breadth, and 3.20 mm to 3.29 mm in thickness. True density fluctuated between 1.25 and 1.29 g mL-1, with porosity spanning from 33.43 to 36.09 percent. The seeds exhibited hydration and swelling capacities between 0.036 and 0.041 g per seed, as well as 0.037 to 0.042 mL per seed, respectively. The time required to cook unsoaked seeds ranged markedly from 35.3 to 42.7 minutes. The cooked seeds exhibited hardness values between 2.12 and 2.55 kg, while their adhesiveness ranged from 0.02 to 0.99 kg. The cultivars of black gram are high in protein, and the soaking treatment augmented their cooking attributes. (Wani et al., 2013) [1] The yield of black gram in India is around 598 kg per hectare. In 2025-26, India's black gram total production was 17.14 lakh tonnes.

India's total black gram production is 17.14 lakh tonnes for 2025, a decrease from 22.42 lakh tonnes in the previous year. Black gram occupies the third place after chickpea and pigeon pea.

Department of Agriculture and Farmers welfare 2025

The Spotted pod borer, M. vitrata (Geyer), Gram pod borer, H. armigera (Hubner), Bihar hairy caterpillar, Spilosoma obliqua (Walker) and Leafhopper Empoasca kerri (Pruthi) were recorded as most prominent pests. Whereas, remaining all other insect-pests like Whitefly, Bemisia tabaci (Gennadius), Surface grasshopper, Chrotogonus trachypterous (Blanchard), Stem fly, Ophiomyia phaseoli (Tryon), Black aphid, Aphis craccivora (Koch), Tobacco caterpillar, Spodoptera litura (Fabricus), semilooper, Plusia orichalcea (Fabricus), Blue butterfly, Lampides boeticus (Linn.) and Blister beetle, Mylabris pustulata (Thunberg) were observed as minor pests throughout the crop growing season i.e. Kharif, 2018 and 2019 in black gram. (Yadav et al., 2020) [2] . Across India, 60 insect species are known to attack black gram at various phases of crop growth (Lal and Sachan, 1987) [3] . Among these insects-pests pod borers i.e. spotted pod borer, Maruca vitrata (Geyer) and gram pod borer, Helicoverpa armigera (Hubner) are the serious insect pests of grain legumes causing seed and pod damage. Black gram production is significantly reduced by roughly twelve insect species, which are pests (Soundararajan and Chitra, 2012) [4] . Pod borer complex include H. armigera (Hubner), M. vitrata (Geyer), Etiella zinckenella (Treitschke), Apion ampulum (Faust) and Lampides boeticus (Linnaeus). Among the pod borers, M. vitrata is a major constraint for the production of black gram at critical stages such as reproductive and pod development. Therefore, the current study was carried out to know the seasonal incidence of borers on black gram in kharif, seasons and their relationship with meteorological parameters. The spotted pod borer represents a major pest affecting tropical food legumes, causing harm to soft leaf axils, flower buds, flowers, and pods through webbing and boring into flower or pod clusters during the cooler seasons on around 39 different hosts. Pigeon peas and cowpeas characterized by short maturation times and dense clusters are more prone to susceptibility. The extent of damage in cowpea was approximately 25-40 percent, whereas in pigeon pea, it fluctuated between 9 and 84 percent globally. Female moths placed around 200 flat, scaly eggs on flower buds, flowers, leaves, leaf axils, terminal shoots, and soft pods. The larvae are negatively responsive to light, with the larval phase spanning from 8 to 21 days on differing hosts. (Ganapathy, N. 2010) [5] M. vitrata is a major insect-pest of black gram, which appears attacks the crop throughout its growth period, from vegetative development to reproductive maturity, resulting in significant damage to flowers and pods by web formation and larval feeding

Materials and Methods Experimental Site

The experiment was conducted at the Crop Research Centre (CRC) of Sardar Vallabhbhai Patel University of Agriculture & Technology, Meerut, Uttar Pradesh. The research farm is situated 10 km from Meerut city on the Delhi-Dehradun National Highway (NH-58), at 29°17′ N latitude and 77°42′ E longitude, with an altitude of 237 m above mean sea level. The location represents the Western Plain Zone of Uttar Pradesh under the Upper Gangetic Plain agro-ecological region.

Meteorological data

The weekly average values of temperature, relative humidity, and cumulative rainfall observed throughout the crop growing period. i.e. Kharif, 2025 from meteorological observatory located at Department of Soil Science, SVPUA&T, Meerut and obtained for the seasonal occurrence and influence of climatic factors on population dynamics of spotted pod borers, M.vitrata in black gram.

Observation

Assessment of the occurrence of major pod borer pests were recorded at weekly intervals from 50% flowering stage until crop harvest. Larval population was assessed from 5 randomly selected plants in the untreated control plots and the mean value of larvae per 5 plants was computed to examine the population build-up trend. The relationship between pod borer incidence and prevailing weather parameters was analysed using simple correlation analysis as per the methodology outlined by (Gomez and Gomez, 1984) [6] .

Statistical Analysis

Where, r = Simple correlation coefficient Sx 2 = Correlated sum of squares for meteorological parameter. Sy 2 = Correlated sum of squares for pest incidence. Sxy = Correlated sum of cross products

Pest Identification

The larval stage possesses a transparent and lustrous body marked with six rows of prominent black spots arranged along the thorax and abdomen. These characteristic markings give rise to the common name 'spotted caterpillar'. Larvae are agile in nature and, upon slight disturbance, escape by falling from infested flowers and pods while hanging through a silk thread. The insect completes its developmental cycle in approximately 18 to 35 days.

Result

The findings related to the population dynamics of Maruca vitrata in relation to weather variables, along with their correlation analysis, are presented in Table 2 for the Kharif season of 2025.

Population dynamics

Table 1 and Fig. 1 illustrate the seasonal incidence of spotted pod borer, Maruca vitrata (Fabricius), on black gram. The occurence of M. vitrata was first observed during the 35 th SMW at the flowering stage of the crop, with a abundance of 1.00 larva per 5 plants. Thereafter, The larval abundance showed a gradual increase with the progression of crop growth and flowering. The population attained its maximum level during the 41 st SMW, recorded 6.40 larvae/5 plants. Subsequently, the population revealed a declining trend and decreased to 1.20 larvae/5 plants by the 43 rd SMW (20-26 October). The current findings are in agreement with. conformity with the observations of Yadav and Singh (2015) [7] , who noted that the incidence of Maruca vitrata commenced throughout the 35 th SMW and reached maximum abundance during the subsequent weeks of crop growth. Comparable results were documented by Rathod et al. (2017), who observed the initiation of spotted pod borer incidence during the later vegetative to flowering phase of the crop. Further, Berani et al. (2017) [9] also concluded that the occurrence of M. vitrata persisted from September to October, which is in agreement with the present observations of peak larval activity during the flowering stage followed followed by a gradual decrease as the crop approached maturity

Correlation

Correlation analysis between the data on larval abundance of M. vitata in relation to weather variables, as presented in Table 2, indicated that maximum temperature showed a positive and significant association (r = 0.667*) indicating that an enhancement in maximum temperature conditions were conducive to the build-up of population of larvae. Conversely, the minimum temperature (r = 0.287) revealed a positive but non-significant relationship, while relative humidity at morning hours (r = -0.586) relative humidity during evening hours (r = -0.328) and rainfall (r = -0.592) exhibited negative associations with larval incidence. The observations of the present study are corroborated by the observations of Manjunath (2014) [10] , who reported a significant positive association between maximum temperature and larval incidence of Maruca vitrata. Similar results were also documented by Sravani et al. (2015) [11] , who recorded a significant positive association between highest temperature and M. vitrata population. Kapoor and Shankar et al. (2019) [12] further reported that minimum temperature exhibited a positive influence on pest incidence which is consistent with the findings of the present study The inverse relationship between rainfall and larval abundance recorded in the present study is in agreement with the observations of Sravani et al. (2015) [11] , who reported a Negative association between rainfall and M. vitrata incidence. Comparable observations were recorded by Kapoor and Shankar et al. (2019) [12] , who recorded a negative association of rainfall with pest population buildup. However, the present findings regarding relative humidity during morning hours are in contrast with the observations of Sravani et al. (2015) [11] , who reported a positive relationship between morning relative humidity and larval population. The differences observed in the results may be attributed to differences in agro-climatic conditions, crop season, and prevailing environmental factors during the course of investigation.

Conclusion

The present investigation revealed that the incidence of Maruca vitrata commenced during the 35 th SMW at the flowering phase of the crop and attained peak population during the 41 st SMW. Similarly, the larval abundance showed a gradual reduction as the crop approached maturity. Correlation studies indicated that maximum temperature exhibited a significant positive effect on larval abundance build-up, whereas rainfall and relative humidity exhibited negative association with pest incidence. The study clearly demonstrated that warm and comparatively dry weather conditions favoured the multiplication and seasonal occurrence of M. vitrata. Therefore, timely monitoring of pest occurrence in association with to prevailing weather parameters may be useful for forecasting pest outbreaks and adopting suitable management practices at the Flowering phase of the crop for effective suppression of M.vitrata infestation.

References

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