- Agronomic: corn, soybeans, wheat
- Animal Products: dairy
- Education and Training: extension, workshop
- Pest Management: biological control, field monitoring/scouting
[Note to online version: The report for this project includes figures and appendices that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact North Central SARE at (402) 472-7081 or firstname.lastname@example.org.]
Studies were completed to determine the impact of agricultural landscape structure on the biological regulation of pest insects and weeds. Overall goals were to determine the impact that factors such as field size, shape, type of crop, field border composition, distance to alternative habitats etc. have on the biological control of crop pests. These studies tested the hypothesis that landscape structure plays a pivotal role in determining the effectiveness of many species of predators and parasites in agricultural systems by fostering or inhibiting their populations over time.
An analysis of landscape structure conducted on two areas of Ingham Co. MI. in 1992 quantified significant differences in physical structure between an area of high structural complexity vs. an identically sized area two miles to the north of low structural complexity. The area of high heterogeneity had significantly more and smaller fields with smaller perimeters and shorter distances to an edge from field center. Crop-hedgerow edges were significantly more abundant in the high heterogeneity area while crop-crop interfaces were more abundant in the low heterogeneity area.
Previous studies by Landis et al. (1992) have shown that wooded field edges benefit Eriborus terebrans, currently the most important parasite of the European corn borer in the Midwest. In the current study it was found that Eriborus wasps require both a source of adult food (sugar) and a moderated microclimate for optimum survival. Corn fields do not provide these resources (during the first generation of the wasp) and wasps are forced to seek these resources in alternate habitats. Our studies have shown that nectar from flowering plants or the secretions of aphids feeding on weeds in field-edge habitats provide a suitable source of adult food. Fencerows and woods surrounding corn fields also provide a cooler, more humid microclimate than a corn field and wasps in these habitats live significantly longer. These studies demonstrate that landscape structure can play an important role in determining the effectiveness of natural enemies.
Studies of weed seed predation showed that during the winter of 1991-92 showed that, vertebrates removed 6-12% of the seeds on the soil surface of crop fields in a six day period. In the spring, insects and vertebrates removed 48.5% of the seeds within 5 meters of hedgerow and 35% at 100 meters from a hedgerow in a six week period. Carabid beetles were the most abundant insect seed predator and rodents and birds the primary vertebrate seed feeders. In 1992-93, up to 40% of large weed seeds were removed over the winter and up to 66% of the small weed seeds in the spring.