Evaluation of plant resistance in field pea by host plant choice behaviour of pea weevil (Bruchus pisorum L.) : implications for pest management

Abstract: Field pea (Pisum sativum L.) is an important grain legume crop due to its nutritional value and role in improving soil fertility in cropping systems. Insect pests are one of the main production constraints for field pea, with pea weevil (PW), (Bruchus pisorum L.) being an economically important pest of field pea worldwide. Current PW control practices rely on chemical insecticides, which are unaffordable for most small-scale farmers in developing countries such as Ethiopia, where PW is established in northern and north-western regions, causing severe crop losses. Furthermore, pesticides have adverse effects on human health and the environment. This thesis investigated host plant resistance in field pea and mapped Ethiopian farmers’ knowledge and management practices to control PW. The farmers surveyed were aware of PW and able to identify damaged seeds based on common symptoms, but most considered PW a storage pest. To resolve this knowledge gap, it is important to provide training for these farmers. In addition, development of integrated pest management strategies for PW is vital for sustainable production of field pea. Most Ethiopian field pea accessions that were screened for resistance to PW were found to lack resistance and only a few accessions showed moderate levels of resistance based on percentage seed damage (PSD). Gene bank accessions and newly collected populations performed better than released varieties. Some of the accessions formed neoplasm in the greenhouse due to neoplastic gene (Np) and these genotypes had less PSD than non-Np genotypes. Ultraviolet light suppressed neoplasm formation in Np genotypes, while intercropping of Np genotypes with sorghum enhanced neoplasm formation. Female PW use flower volatiles to locate host plants, but no discrimination between genotypes based on flower volatiles was found. However, oviposition patterns reflected the resistance pattern found in field screening. Adet was an attractive genotype for oviposition, while non-host plants (Pisum fulvum Sibth. et Sm. and Lathyrus sativus L.) were less preferred by female PW. Pod morphological traits such as pod wall thickness, trichomes and neoplasm may influence oviposition acceptance by female weevils. These results can be used in developing alternative pest management strategies for PW.