Assessments of Pea weevil (Bruchus pisorum L.) inWest Shewa and East Arsi Zones and its Management using some Insecticides on Field Pea (Pisum sativum L.)

Abstract

Field pea (Pisum sativumL.) is the second most important legume crop in Ethiopia after faba bean. Insect pests are one of the major constraints of field pea production, among which the pea weevil, Bruchus pisorumL., is an economically important pest. This study was conducted to assess B. pisorum distribution and damage level in West Shewa and East Arsi zones of Oromia region, Ethiopia and compare the effects of three insecticides with their respective times of application on B. pisorumunder field condition, at Holetta Agricultural Research Center. Three insecticides: Karate, Coragenand Sevin were applied at flowering, pod setting, and both flowering and pod setting stages of naturally infested field pea plots sown to susceptible variety ‘Burkitu’.The survey results revealed that 64% respondents in Cheliya, 60% in Liben Jawi, 50% in Munesa and 56.1% in Lemu Bilbillo districts were not aware about B. pisorum as field pea production constraint. Mean percentage grain damage caused by B. pisorumwere 0.01 ±0.07and0.09±0.24% in Cheliya and Liben Jawi districtsof west Shewa, respectively; whereas grain damage up to 2.11±2.65% was recorded in Munesa. However, the pest was absent in Lemu Bilbillo of East Arsi Zone. The mean grain weight loss caused by the insect was 0.1±0.08% and 0.01±0.05% in Cheliya and Liben Jawidistricts; whereas1.19 ± 1.52% grain weight losses recorded in Munesa district of East Arsi Zone. The results of field experiments revealed that there was no significant (P>0.05) difference among insecticide treatments and control plots. Similarly, insecticide application frequency and crop phenology had no effect on egg and larvae under field and adult emergence of B. pisorum in the storage conditions. This could be due the fact that B. pisorumattack and development occurred at specific crop phenology (usually young pod stage) and lack of fresh attacks on harvested grains either under the field or in the storage conditions. However, both the survey and field studies were conducted for a single season and further studies are needed to explore the effect of prolonged seasons; additionally, screening of more chemical insecticides against the pest both under controlled and field condition are necessary