The Effect of Weather Factors on the Population Density of Oxycarenus spp. (Hemiptera: Lygaidae) on Roselle and Kenaf

Abstract

Roselle, Hibiscus sabdariffa and Kenaf, Hibiscus cannabinus are two important fibre crops in most parts of Africa. Insect pests are one of the major constraints in the production of these crops. The cotton seed bug Oxycarenus spp. attacks Roselle and Kenaf during the seed formation stage and cause reduction in seed viability. This study examined the effect of weather factors namely, relative humidity, temperature, sunshine and soil evaporation on the population density of Oxycarenus spp. on Roselle and Kenaf during the planting seasons 2012 and 2013. The treatments consisted of two types of Roselle (Green-calyxed and Redcalyxed) and Kenaf. The experiment was laid out in the field using Randomized Complete Block Design and the treatments were replicated four times. The results showed that the population of Oxycarenus spp. was significantly (p<0.05) higher on green-calyxed H. sabdariffa and red-calyxed H. sabdariffa than on Kenaf in 2012 and 2013. The differences in the density of the bug per fruit on green-calyxed H. sabdariffa and redcalyxed H. sabdariffa were significant in the two planting seasons. Relative humidity in the morning and maximum temperature correlated positively and negatively, respectively with the density of Oxycarenus spp. during the two planting seasons. Sunshine hours per day correlated positively, while soil temperature and soil evaporation had a negative correlation with the bug density. This information on the seasonal variation in the bug density and its relationship with weather factors could be used in pest forecasting for these fibre crops which is an important tool in formulating a successful pest management programme.

Keywords: Malvaceae, Fibre crops, weather factors, Oxycarenus spp., pest management, planting seasons, pest density.