Effect of Harvesting and Threshing Time and Grain Fumigation of Field Peas (Pisum sativum L.) on Pea Weevil (Bruchus pisorum (L.) (Coleoptera: Bruchidae) Development and Damage

Abstract

Experiments were conducted in the field and in the laboratory to investigate the effects of harvesting and threshing times and grain fumigation on pea weevil, Bruchus pisorum (L.), development, the damages they cause and the associated grain yield on field peas in Ethiopia. Pre-harvest data indicated that significantly more eggs were found on flat and swollen pods than on other stages of the pod. Egg and larval density significantly varied with season. Grain yield was significantly higher on plots harvested early; seasons, fumigation and threshing times did not affect yield. Delay in harvesting caused more infected seeds and seeds with infected black spots. Fumigation and threshing time did not affect the number of infested seeds and seeds with infected black spots. When data were recorded after four months of storage, all factors, i.e., season (year), harvesting and threshing time and fumigation significantly affected the number of adult weevil emergence windows. Therefore, the number of windows was significantly higher in 2004/05 than 2006/07, in non-fumigated seeds compared to fumigated ones, and in late harvested and threshed seeds compared to others. Apart from reducing the physical damage and reduction of seed weight loss of seeds in store, early harvesting, threshing, and fumigation immediately after harvest contributed to the reduction in the inoculum of the beetle in the future. It can; therefore, be concluded that growers should practice early harvesting and threshing and fumigate immediately after threshing to minimize the damage in an infested seed pea crop and also to reduce future inoculums.

Keywords: pea weevil, harvesting and threshing time, fumigation, field peas