Evaluation of Selected Green Gram (Vigna Radiata) Varieties Against Insect Pests Infestation in The Field, Tharaka Sub-County, Kenya

Abstract

Background: Green grams farming plays a vital role in Tharaka and the country(Kenya) at large by ensuring food security, creating employment for rural households and greatly contributing to the national economy. However, the infestation of pests on the green grams has drastically affected its production in the country. This paper presents different types of insect pests attacking green grams in the field and the most resistant among the selected green gram crop varieties in Tharaka sub-county of Kenya. Materials and Methods: Insect pest infestation was monitored on the following green gram crop varieties; Uncle (KS20), Biashara (KAT 00308), Karembo (KAT 00309), Tosha (KAT 00301) and Nylon (N26). The level of resistance of the aforementioned green gram crop varieties against the field pests was also determined. The study was conducted in Mukothima and Gatunga wards of the Sub-County during one growing season (March-May, 2023), the period of long rains. The experiment was laid out in a Randomized Complete Block Design (RCBD) with four replications. The type and population of insect pest was determined by observation, setting up sticky traps and dissecting microscope analysis. The data was analyzed using Friedman's two-way nonparametric ANOVA. Results: White flies (Uncle-334.3, Biashara-446.33, Karembo-352.8, Tosha- 420, Nylon- 515.7) and aphids (Uncle-323.9, Biashara-459.6, Karembo-394.5, Tosha- 413.6, Nylon- 468.8) were the major pests recorded on green gram crops with population mean value per variety indicated in brackets. Other insect pests noted during the study season included African pod borers and leaf weevils. Nylon (severity of leaves damage-1991.0, incidence of pods damage- 0.328, number of holes poked in leaves- 3.11) proved to be the most resistant to whiteflies and aphids while Tosha (severity of leaves damage-2564.76, incidence of pods damage-0.599, number of holes poked in leaves-4.45) the least resistant to whiteflies and aphids. Conclusion: Whiteflies, aphids, African pod suck borers and leaf weevils were the insect pests infesting the growing green gram varieties during the planted season with whiteflies and aphids causing major damages. N26 variety was the most susceptible to attacks but also the most resistant to damage and loss.