Submitted to: Journal of Fruit and Ornamental Plant Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 14, 2006
Publication Date: July 1, 2006
Citation: Brown, M.W., Tworkoski, T. 2006. Enhancing biological control in orchards by increasing food web biodiversity. J. Fruit and Ornamental Plant Research. Vol. 14 (Suppl. 3) 2006., 19-27. Interpretive Summary: Synthetic herbicides often are used to control weeds that cause yield loss and contribute to insect pests and diseases in orchards. Alternative weed management may be required due to negative public perception and possible regulatory restriction of some synthetic herbicides and to minimize the negative effects on beneficial insect populations. Organic wastes, such as sawdust, may be available locally and could be used as mulches to suppress weeds in orchards. Additional weed control with a natural product herbicide, eugenol, was used in conjunction with the mulch. Mulch can be effective for annual weed control and increases the abundance of biological control insects but, mulch provided only partial control of perennial weeds. Eugenol provided additional control of weeds that grew through the mulch. The use of mulches and other alternative weed control methods that have less impact on beneficial insects will increase the sustainability of insect and weed management in orchards.
Technical Abstract: High biodiversity is a key to sustainable biological control in orchard systems. A diverse biological control community is needed to provide control of the large number of pests from many taxonomic groups in orchards. Orchard floor management practices range from partial to complete removal of ground cover (e.g. grasses, legumes, weeds) with techniques that include synthetic herbicides, tillage, mulch, and flaming. Such practices are designed to reduce below-ground competition with the crop but they also alter abiotic and biotic components of the soil and impact orchard food webs. We have investigated increasing biodiversity in the orchard with the addition of compost mulch under the trees. In addition to providing nutrients and organic matter to the soil, the compost also provided weed and insect control. Food web analysis of the soil-based food web revealed that the predator: herbivore ratio in the compost treated apple orchard was 0.85 but without mulch or with mulch and herbicide the ratio ranged from 0.15 to 0.32. It is proposed that the predator: herbivore ratio could be used as a measure of the sustainability of biological control. The use of eugenol as a natural herbicide is proposed as one tool for managing weeds that may be less disruptive to biological control.