Insect injury and mortality of seedlings of field penny-cress (Thlaspi arvense L.).

Abstract

During 1997–1999 the injury caused by insect herbivors and mortality of plants of field penny-cress (Thlaspi arvense L.) was studied on an early fallow field at Prague-Ruzyně. The highest abundance of the weed (102 plants per m2) was recorded in 1999, the lowest (27 plants/m2) in 1998. Nearly all plants (100% in 1997 and 1998, 94% in 1999) were injured by flea beetles (Phyllotreta spp.). Injury was greatest (> 50%) in younger seedlings. Mortality was low in 1997 (17.1%) and 1999 (15.8%), but high in 1998 (94%) because of concurrent drought. Herbivory and drought may kill a large proportion of seedlings and thus change the composition of the weed community.