Drechslera sp. (Pyrenophora chaetomioides (Speg.)), a potential biocontrolagent for Bromus sterilis and other Bromus spp.

Infection by a Drechslera sp. (perfect stage, Pyrenophora chaetomioides (Sp eg.)), isolated from Bromus sterilis, killed B. sterilis, B. commutatus and B. secalinus. B. diandrus and B, hordeaceus were both infected but not kil led Successful infection required a 24-h dew period. Reduction of the dew p eriod to 8 h significantly reduced the infection of all Bromus spp. tested as determined by leaf necrosis. Inoculation with a low inoculum concentrati on (2 x 10(4) conidia/ml) produced little dry weight reduction, but at 2 x 10(5) conidia/ml with an 8-h dew period the dry weights of B. commutatus, B . diandrus, B. secalinus and B. sterilis were reduced by 11-25%. Extending the dew period to 24 h resulted in 77% mortality of B. sterilis and 93% mor tality of B. commutatus and B. secalinus.