ASSESSMENT OF THE ABILITY OF YEAST-DERIVED ELICITORS TO CONTROL BARLEY POWDERY MILDEW IN THE FIELD

Phytoalexin elicitor-active yeast cell wall extracts sprayed on to det ached barley leaves of cv. 'Golden Promise' gave good control of milde w when applied 2/4 h before inoculation. Extracts with the highest eli citor activity conferred the greatest protection against mildew infect ion with some extracts giving up to 95 % reduction in infection. Appli cation of these yeast extracts to both spring and winter barley in a s eries of field trials between 1989-91 increased resistance to mildew a nd reduced loss of grain yield. Yeast extracts were not as effective a s fungicide in terms of disease control and yield enhancement though i n some cases they increased yield to levels approaching those obtained using fungicide. No detrimental side effects of the yeast extracts to wards plants have been observed.