Researchers find short-term insect problems, long-term weed problems
Published source details
Lanini W.T., Zalom F., Marois J. & Ferris H. (1994) Researchers find short-term insect problems, long-term weed problems. California Agriculture, 48, 27-33.
Published source details Lanini W.T., Zalom F., Marois J. & Ferris H. (1994) Researchers find short-term insect problems, long-term weed problems. California Agriculture, 48, 27-33.
This study is summarised as evidence for the following.
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A randomised, replicated, controlled study in 1989-1993 in northern California, USA (Lanini et al. 1994) (part of the study by Poudel et al. 2001) found 32% of tomato fruitworm Helicoverpa zea eggs were parasitised in organic plots compared to 25-37% in conventional plots of tomato Solanum lycopersicum in 1989. In organic plots, parasitism occurred on 0-9% of leaves with potato aphids Macrosiphum euphorbiae compared to 0-5% in conventional plots, across all years. Weeds were more widespread in organic than conventional plots for some years and crops, for example in maize Zea mays in 1991 (3.5% vs. 0.5-1.8% ground cover). Plant-parasitic nematodes decreased in organic but increased in conventional plots in 1989-1992. Occurrence of disease and mobile pests was similar between treatments, and the authors suggest that pests may have migrated between the small plots. Organic tomato plots had more tomato fruitworm damage in 1989 and more stink bug (Pentatomoidea) damage in 1992 (1.5% and 11% of fruits damaged, respectively) than in conventional plots (0.0-0.5% and 6-7%), but damage was similar in other years. Organic plots were tilled to control weeds and conventional plots were treated with herbicides, insecticides, acaricides, fungicides and tilled. Treatments were replicated four times in 0.12 ha plots.