Alfalfa, soybeans, maize, turnips and wheat crops established by conse
rvation tillage, and that had been subjected to no slugs, medium or hi
gh densities of slugs Deroceras reticulatum (Muller) at sowing, were h
arvested. The crop yields were inversely related to slug density, and
seedling damage and mortality during crop establishment. Alfalfa and w
heat suffered high levels of seedling mortality and their yields were
reduced by up to 80%. Soybean yields were reduced by 25-46% at the med
ium and high slug densities, which parallel plant survival after slug
attack during establishment. Maize grain yield was reduced by similar
to 32% at medium and high slug densities in 1989, but drought conditio
ns in 1988 precluded a grain harvest and there was no reduction in tot
al plant yields where slugs were present at establishment. Turnips, wh
ich suffered only minor losses from slugs during establishment, conseq
uently showed no yield reductions at maturity.