Seasonal Pest Intensity of Spodoptera litura (Fabricius) and Its Effect on Fruit Yield in Six Tomato (Solanum lycopersicum L.) Varieties under Unprotected Field Conditions
Ankita Awasthi *
Department of Zoology, A.N.D.N.N.M. Mahavidyalaya, Kanpur, Uttar Pradesh, India.
*Author to whom correspondence should be addressed.
Abstract
Tomato (Solanum lycopersicum L.) is one of the most widely grown and economically important vegetable crops in India, but its yield is consistently constrained by lepidopteran fruit borers, particularly Spodoptera litura (Fabricius). A field investigation was carried out during 2016–17 to record the pest intensity of S. litura on six tomato varieties — Pusa Gaurav, Ratna, Arka Saurabh, Pant Bahar, Arka Abha and an untreated Control — left unprotected from pest attack, and to relate this intensity to fruit yield. A field plot measuring 35x22 m was arranged with three replications in a randomised block design (R.B.D.) and a 1.0 m block border. The plots measured 6.0*3.0 m and were separated by a 0.5 m border. The distance between rows and plants was 75x75 cm. A completely randomised design (C.R.D.) for laboratory experiments and a randomised block design (R.B.D.) was employed for field experiments. Larval counts per plant were recorded at weekly intervals from the third week of January to the first week of April and subjected to square-root transformation before analysis. Pest intensity varied appreciably among varieties and across the observation period, with population build-up generally peaking between mid-February and early March. Arka Saurabh recorded the lowest mean pest intensity (0.37–0.39 larvae/plant) but also a comparatively low yield (15.40 kg), whereas Pant Bahar combined a low pest load (0.28–0.54 larvae/plant) with the highest yield (18.95 kg), suggesting a favourable tolerance response. Ratna and Pusa Gaurav carried the heaviest pest burden and showed correspondingly greater within-season yield variability. The untreated Control recorded the lowest overall yield (13.40 kg), underscoring the yield penalty associated with unmanaged S. litura infestation. These findings indicate that varietal choice can meaningfully influence S. litura pressure and support the inclusion of Pant Bahar and Arka Saurabh in integrated pest management and future breeding programmes targeting fruit-borer tolerance.
Keywords: Spodoptera litura, tomato, Solanum lycopersicum, pest intensity, varietal resistance, yield