Management of weeds, apple sawfly (Hoplocampa testudinea Klug) and plum curcuclio (Conotrachelus nenuphar Herbst) with cellulose sheeting

A study was conducted to evaluate the efficacy of cellulose sheets as a barrier to prevent weed establishment under apple trees, to reduce the accumulation of weed seeds in the soil, and to prevent the completion of the developmental cycle of the apple sawfly (Hoplocampa testudinea Klug Hymenoptera: Tenthredinidae) and the plum curculio (Conotrachelus nenuphar Herbst Coleoptera: Curculionidae) in the soil. Replicated experiments were conducted over a 4-year period in two apple orchards of Southern Québec, Canada. Weed communities were monitored within quadrats and soil samples were collected to estimate the soil weed seed bank. Emergence cages and sticky traps were used in each plot to monitor emerging plum curculio or apple sawfly adults. Newly installed cellulose sheets provided adequate weed control throughout the summer and fall. However, weeds present on the cellulose sheets the following spring were attributed to the germination and establishment of weed seedlings in depressions in the sheets where organic matter had accumulated. The use of cellulose sheets reduced the accumulation of weed seeds in the soil. Cellulose sheets significantly reduced plum curculio and apple sawfly populations, but not consistently. The cellulose sheets under investigation biodegraded within 1 year of use, and accumulated debris and water in depressions on their surface. Loss of integrity of the cellulose barrier and variable suitability of fruit debris as an overwintering refuge may explain the variation in control success of cellulose sheets for both insect species.