Many plants that are candidates for refining into biofuels also possess qualities that make them potentially useful for managing soilborne pests, reclaiming polluted soils, supplementing animal feed and other purposes. Phytoremediation with these plants may provide a practical and economical method for managing the movement of trace elements into water tables, surface- and tail-water runoff, and drainage effluent. Mustards (Brassicaceae) are of particular interest for biodiesel, and grasses (Gramineae) for bioethanol production. These plants, as well as others such as certain members of the onion family (Alliaceae), also possess properties that could make them effective natural biofumigants for soil. Some of these crops have high allelopathic activity and must be employed carefully in rotations to avoid damaging subsequent crops.

We compared reflective plastic and wheat straw mulches with conventional bare soil for managing aphid-borne virus diseases and silverleaf whitefly in cantaloupe. The occurrence of aphid-borne virus diseases was significantly reduced with both mulches as opposed to bare soil, and reflective plastic performed better than wheat straw. Silverleaf whitefly numbers, both adults and nymphs, were reduced equally by plastic mulch and wheat straw, and were significantly lower than with bare soil. Reflective plastic produced mature melons sooner and more cartons per acre than the other production systems. The reflective plastic system also produced a greater number of large-size melons, which are favored in the late-season market. Plants grown over straw mulch produced higher overall yields, including large-size melons, than those grown over bare soil.

Grass cover crops can be harvested for biomass or used as a surface mulch to reduce erosion, improve soil structure, suppress weeds and conserve moisture. There is concern, however, that such plantings may affect subsequent crops. We studied the effects of sudex, a sorghum hybrid used as a cover crop, on subsequent crops of tomato, broccoli and lettuce started from transplants. Within 3 to 5 days of being transplanted into recently killed sudex, all three crops showed symptoms of phytotoxicity including leaf necrosis, stunting and color changes. There was 50% to 75% transplant mortality in all three species. Plant growth and development, as determined by biomass measurements, were also significantly affected. Yields of mature green tomato fruit and marketable broccoli and lettuce heads were reduced significantly. Tomato, broccoli and lettuce should not be transplanted into sudex residue for at least 6 to 8 weeks, or until the residue has been thoroughly leached.

Organic farmers and limited-resource growers in the San Joaquin Valley and other agricultural areas in California — many of whom are ethnic minorities — encounter limited options and environmental constraints when seeking economically viable pest management methods. Over the past 8 years, we have conducted weed research and implementation projects on soil solarization at the UC Kearney Research and Extension Center and on farms in the surrounding San Joaquin Valley. In the Kearney studies, small-scale solarization in parsley reduced weed biomass 94% to 99% over the untreated control. Furthermore, in an on-farm study, solarization provided effective weed control for strawberries at a much lower cost than methyl bromide, with comparable yields. This research has provided guidelines and technical support for growers wishing to implement solarization and related techniques for nonchemical soil disinfestation in a wide variety of specialty crops.