SUMMARY
The preemergence herbicides benefin, bensulide, DCPA, and siduron were evaluated for their influence on conidial germination, germ-tube growth, primary branching of germ tubes, and conidial production by Drechslera sorokiniana at molar concentrations of 10-12, 10-9, 10-6. All herbicides at all concentrations inhibited conidial germination and either had no effect on or inhibited germ-tube growth. Concentrations of DCPA and siduron at 10-9 and 10-6M stimulated germ-tube branching, but other concentrations of these herbicides and all concentrations of benefin and bensulide had no effect. Bensulide, except at 10-12M, and siduron inhibited mycelial growth. DCPA stimulated mycelial growth at 10-12M, had no effect at 10-9 M, and inhibited growth at 10-6M. All concentrations of benefin stimulated mycelial growth. DCPA, except at 10-12M, benefin and bensulide inhibited conidial production. All concentrations of siduron stimulated conidial production. Benefin, DCPA, and siduron induced germination from intercalary cells of a small number of conidia. Bensulide and DCPA induced bulbous, appressorium-like apices on germ tubes of some germinating conidia.