Effect of Grain Breakage and Relative Humidity on The Development of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) Infesting Stored Maize in Lafia, Nigeria

The effect of five levels of grain breakage at 20, 40, 60, 80 and 100% of 10g grain with control (unbroken grains) were studied on the development of Cryptolestes ferrugineus (Stephens) (Coleoptera: Laemophloeidae) under ambient laboratory conditions in Lafia, (08.330N and 08.320E) Nasarawa State Nigeria. In another set up of experiment, different levels of relative humidity generated from boxes measuring 20 x 20 x 20 cm fitted with electric light bulbs with range of 100, 60, 45, 25 watts with Control (no light bulb) were studied to determine the effect of relative humidity on the development of C. ferrugineus. These studies were laid out in a complete randomized design and replicated three times. Data was collected on number of adult mortality and progeny emergence for 20 and 56 days, respectively for both studies following date of infestation. Results of the different levels of grain breakage showed that there was significant difference in the level of grain breakage and the control treatment (P≤0.05). Results showed that maize grains broken at 80 and 100%/10 g of grain had more significantly adult emergence of C. ferrugineus when compared to other levels of grain breakage. The effect of relative humidity on progeny emergence showed that there was significant effect of relative humidity on the population and emergence (development) of C. ferrugineus. Different exposures to RH on C. ferrugineus increased insect mortality as relative humidity decreased. Mortality of up to 100% of C. ferrugineus was recorded at lower relative humidity when compared with the mortality in treatments having lower levels of RH as no emergence was recorded at RH of 18 and 24%. Treatments with high RH recorded high number of emergence as observed at 41 and 47% R.H. while 35% R.H. had the lowest adult emergence. The results of correlation among RH, temperature and mortality of adult C. ferrugineus showed that there were highly significant (P≤0.01) but negative correlations among relative humidity and temperature and mortality of adult C. ferrugineus. The potential of storing grains in low relative humidity environment coupled with low grain breakage is advocated for the management of C. ferrugineus.