Assessment of economic injury levels of cotton seed bug, Oxycarenus gossypinus Dist. (Hemiptera: Lygaeidae) on cotton in Samaru Zaria, Nigeria

Abstract

Field trials were carried out during 2021 and 2022 cropping seasons at Samaru, Zaria to study the economic injury levels (EIL) of Oxycarenus gossypinus on cotton. Nymphal instar at levels 0 (control), 10, 20, 30, 40 and 50 per meter row of (SAMCOT- 9) cotton variety were released at boll forming stage into caged cotton. The treatments were arranged in a randomized complete block design (RCBD) replicated four times. Parameters assessed included, number of bolls produced; healthy and damaged, their weight and the rate of association between nymph density, weight of lint and lint staining rate. There was a decrease in yield of cotton with an increase in number of nymphs of O. gossypinus in the caged cotton. Weight of stained lint increased from 0.17 kg ha-1 to 4.69 kg ha-1 when cotton seed bug was infested with zero (where no nymph released) to 50 nymphs per caged plant, respectively. The cotton seed also decreased from 24.17 kg ha-1 to 15.38 kg ha-1. The ratio of the value of yield saved to the cost of insecticide application at ten nymphs per meter row in 2021 was 0.69 and in 2022, was 0.78. The mean EIL value for O. gossypinus nymph was determined as 1.30 nymphs per meter row. Hence, appropriate control measures should be adopted to check regular increase in the cotton seed bug population to avoid cotton lint quality losses in the study area, this would ensure judicious and sound use of insecticides.