Impact of harvesting time on field carry over infestation of Sitophilus oryzae (L.) (Coleoptera: Curculionidae) in different maize genotypes

Study was carried out to evaluate the effect of time of harvest on field carry over infestation of rice weevil Sitophilus oryzae L. in maize. The maize ears were harvested at three different stages namely early harvest- i.e. just before physiological maturity (stage 1), timely harvest i.e. at physiological maturity (stage 2) and late harvest i.e. around ten days after physiological maturity (stage 3). The harvested maize ears were dried, shelled and stored separately over a period of 150 days. The emergence of F1 progeny of S. oryzae were significantly higher in late harvest maize (37.51) while relatively lower number in timely (27.09) harvest and lowest number in early harvest maize (14.47) were observed. The interaction effects between different stages of harvest × genotype, genotype × storage duration, different stages of harvest × storage duration, different stages of harvest × storage duration × genotype on F1 progeny emergence were found significant. Similarly, maize ears harvested at early and timely period, showed significantly lower weight losses as compared to late harvest maize. The mean per cent weight loss recorded at 90 and 150 days after storage were 0.66 and 2.24; 1.21 and 5.19; 2.24 and 6.33 in early, timely and delayed harvest maize kernels, respectively. The F1 progeny emergence was significantly and positively correlated with stage of harvest (r=0.4435). Also significant and positive correlations were found between weight loss and storage duration (r=0.3280). The kernel hardness was found significant negative correlation with progeny emergence and weight loss. The results indicated that physical and biochemical traits are also responsible for varying levels of resistance to S. oryzae. Use of cultural practices such as timely harvest of maize is one of the most promising approaches for efficient in minimization of field carry- over infestation of S. oryzae.