Effect of plant condition on oviposition by ragwort flea beetle

Abstract

The impact of grazing animals on oviposition behaviour of ragwort flea beetle (RFB) (Longitarsus jacobaeae) was investigated in two field experiments In the first trial manually damaged ragwort plants were exposed for 5 days to RFB In the second trial ragwort plants grown in sheep and cattlegrazed pasture were collected both in April and May 1997 for the counting of eggs on plants and in the surrounding soil Removal of the majority of ragwort leaves reduced egg numbers/plant whereas damage to leaves did not Similarly ragwort from sheepgrazed pastures which was smaller than ragwort from cattlegrazed pastures had fewer eggs/plant but a similar number/g fresh weight of ragwort High local humidity under rosette ragwort plants is suggested as the critical factor determining oviposition behaviour of RFB