Impact of planting and harvest dates on yam infestation by white grubs

Abstract

The white grub, Diaprepes abbreviatus L. (Coleoptera: Curculionidae), is a significant pest of yam tubers and the second cause of tuber rot in Haiti. Larval feeding inflicts severe damage to tubers, leading to notable losses due to decreased tuber quality, reduced marketability and increased susceptibility to secondary parasites and pathogens. This study examined the influence of planting and harvesting dates on the vulnerability of yam tubers to white grub infestation and the resulting tuber quality across 24 farmers' fields. At harvest, we assessed the level of tuber infestation, white grub density and the tuber quality index. The results indicated that 85% of grub populations were found in fields planted on the traditional date. In addition, 69.5% of tuber damage occurred in early‐planted fields with fewer tubers damaged (30%) when harvested early. In contrast, in fields planted 30 days after the traditional date, the harvest date did not affect tuber infestation and damage by the pest. Overall, both planting and harvest dates impacted the quality grade of yam tubers. Delayed planting by 30 days and early harvesting (34th–38th week after planting) improved the marketability of yams. These findings highlight the importance of optimising planting and harvest schedules to better manage white grub infestation and enhance the marketability of yam tubers.