Effects of cover crops, weeds and plant debris on development ofMycocentrospora acerinain caraway

Abstract

SummaryThis paper reports on the search for inoculum sources ofMycocentrospora acerinaon caraway (Carum carviL.). Obvious suspects are cover crops of biennial caraway and preceding crops of annual caraway. Other suspects are weeds in or alongside the field. Finally, survival structures of the fungus, chlamydospore chains, packed in plant debris or naked, are suspected.M. acerinais able to infect many plant species, including cover crops of caraway such as spinach for seed production and peas. However, the agronomical suitability of a crop to serve as a cover crop of biennial caraway proved to be a more important factor in determining caraway yield than the susceptibility of the cover crop toM. acerina.This finding was corroborated by the fact that spinach and peas as preceding crops had no significant effects onM. acerinadevelopment in spring caraway sown the next year. Dill, barley and four weed species were found as new hosts ofM. acerina.The role of weed hosts, susceptible crops and plant debris in the survival of the fungus in years without caraway is discussed. Caraway sown on soil containing infested caraway straw, infested debris of other plant species or chlamydospores grown in pure culture, became infected byM. acerina.Only high inoculum densities of chlamydospores in the soil caused severe damping‐off of caraway seedlings. The opportunity for disease management by agronomical means is quite limited.