Project Number: 3611-22000-018-00
Project Type: Appropriated

Start Date: Apr 06, 2005
End Date: Apr 05, 2010

Objective:
1) Gain knowledge of the ecology of important weeds in vegetable and agronomic crops to understand fundamental principles affecting weed emergence, growth, interference, seed production, and crop yield and quality; 2) Investigate biotic and abiotic factors linked to seed predation and microbiological activities regulating weed seed and seedling survival in soil ecosystems; and 3) Identify effective combinations of weed management components through application of new and existing knowledge and technology that exploit useful plants, natural enemies, and environmental interactions. The objectives will address the need to develop new strategies that include more efficient use of herbicides combined with increased use of alternative, biologically based weed management for agroecosystems.

Approach:
Processes that regulate weed population density will be investigated, with particular focus on spatiotemporal variation in demographic parameters and population growth rates at multiple levels of scale. As a means of unifying observations, whole life cycles of weeds will be the unit of study whenever possible. Important microbial seed bank relationships will be identified along with the underlying mechanisms of interactions between microbes and weed seeds. Factors that control these interactions and natural plant defenses will be examined. Long-term rates of weed seed loss due to predation will be measured and used to validate mathematical models that predict long-term predation rates from point measurements of seed predation. Attention will be paid to cropping system effects on seed predation rates, with the goal of understanding how crop habitat affects the seed-feeding activity of different seed predator taxa. Mechanisms underlying synergistic effects of combinations of weed management tactics on weeds will be examined within the context of both vegetable and agronomic production systems. Options for managing weeds in vegetables are limited, thus focused efforts using sweet corn as a model, along with application of the larger knowledge base gained from field corn and soybean studies, will be beneficial for minor crop systems. A long-term goal of this work is to develop practical guidelines, supported by ecological understanding, for creating multi-tactic weed management systems that are effective, perform consistently, and use herbicides to tune, rather than drive the system. Initially, the weed species of focus are giant ragweed, velvetleaf, giant foxtail, and wild proso millet. This research will improve our understanding of fundamental factors associated with multi-trophic processes and interactions regulating weeds throughout their life cycles. These data will contribute to systematic prediction of the impact of weeds on agronomic and vegetable crops, leading to more effective synergistic combinations of weed management tactics.