2013 ASHS Annual Conference

Regulatory constraints on the use of soil fumigants for soil disinfestation, and continued lack of new herbicide tools for vegetables suggests that physical pest control tools may be the best options available for specialty crops. Strawberry is susceptible to soilborne pathogens such as Verticillium dahliae, and thus most strawberries are grown on previously fumigated soils. Steam has been used since the 1880s to disinfest greenhouse soils. However, steam application methods used in greenhouses are not appropriate for field use. Soils are disinfested with steam by maintaining the soil temperatures above 70 °C for 20 minutes. We have evaluated an automatic steam applicator prototype that rapidly blends steam with soil, thus raising soil temperatures from ambient to 70 °C in about 90 seconds. Field results from 2011 to 2013 indicate that steam controls weeds and soilborne diseases and produces strawberry fruit yields comparable to chloropicrin. The main deficiency with this approach is lack of commercial-scale machinery to apply steam. However, if we commit to developing a cost-effective commercial steam applicator this obstacle can be overcome.
A commercial intra-row cultivator was tested for weed removal effectiveness in transplanted celery, lettuce, and radicchio and as a crop thinner and cultivator in direct-seeded lettuce. The intra-row cultivator utilized machine-vision guidance to align a rotating cultivator disk with the crop plant to be protected and to remove weeds elsewhere in the plant line. The intra-row cultivator was compared to a standard inter-row cultivator that could not remove weeds from within the plant line. Weed densities, hand weeding times, crop stand, and yields were monitored. Economic analysis was performed on the data. The intra-row cultivator generally removed more weeds and had shorter weeding times than the standard inter-row cultivator. However, the rotating cultivator reduced lettuce stands more than standard hand thinning practices and as a result, lettuce yields were lower with the rotating cultivator than with the standard cultivator. In transplanted celery, lettuce and radicchio, the rotating cultivator removed more weeds than the standard cultivator, but without reducing transplanted crop stand or yields as was the case in seeded lettuce. The economic analysis does not indicate any advantage to the use of the rotating cultivator tested here and significant increases in speed and accuracy will be needed to improve upon the current standard practices in California vegetables.