Phytotoxicity of fungicide coated sugar beet seed depends on growth condition.

Fungicide-coated seed protects sugar beet plants from soilborne diseases, but seedlings coming from coated seeds often encounter phytotoxicity under field conditions. To understand the phytotoxic impact, fungicide-coated seed and the uncoated seed of two cultivars were sown with holes or no holes in plastic trays in greenhouse conditions. Our study demonstrated without fungicide coat on sugar beet seed and holes in plastic trays resulted in just above 90% germination. While fungicide-coated seed and no hole's underneath trays- showed the lowest germination (>20%). Fungicide-coated seed, having holes in plastic trays showed 90% germination. No fungicide coat on seed, having no hole's underneath trays showed 70% germination. We further estimated the percentage of stunted seedlings in both cultivars. Fungicide-coated seed with holes underneath plastic trays showed above 5% stunted seedlings while fungicide-coated seed, having no hole's underneath trays- showed the highest percentage of stunted seedlings (>10%) in both cultivars. In summary, our data demonstrated that the phytotoxicity of fungicide-coated sugar beet seed depends on growth conditions.

Spectral and thermal responses of peanut to infection and colonization with Athelia rolfsii

Soilborne fungal diseases, including southern stem rot (SSR, causal agent Athelia rolfsii), are major constraints to peanut production worldwide. Scouting for disease via visual observation is time and labor-intensive, but sensor technologies are a promising tool for plant disease detection. Prior research has focused on foliar diseases, and few studies have applied sensor-based tools for early detection of soilborne diseases. This study characterized the temporal progress of spectral and thermal responses of peanut plants during infection and colonization with A. rolfsii under controlled environment. In greenhouse experiments, A. rolfsii-inoculated and mock-inoculated lateral stems of peanut were inspected daily for symptoms, and leaf spectral reflectance and temperature were measured using a handheld spectrometer and thermal camera, respectively. Following onset of visual disease symptoms, leaflets on inoculated stems had greater spectral reflectance in the visible region compared to those on mock-inoculated stems. Leaflets on the inoculated stems also had greater normalized leaf temperatures as compared to leaflets on mock-inoculated stems. Overall, results indicate that signatures of disease development can be detected during peanut infection and colonization with A. rolfsii using spectral reflectance and thermal imaging technologies, and spectral signatures of disease are more consistent and specific compared to thermal ones. Though only one peanut variety, one pathogen isolate, and one single measurement were assessed per evaluation date, temporal progress of spectral and thermal responses on a daily basis characterized in this study can be used to develop sensor-based methods to detect southern stem rot and other soilborne diseases ultimately in the field.

Strategies to Improve Biological Control of Soilborne Plant Diseases

Biological control of plant soilborne diseases has appeared as an attractive alternative to other control methods. For the biological control of plant soilborne diseases, microorganisms mainly bacteria and fungi are used, which suppress growth and virulence traits or even kill pathogens and induce plant systemic acquired resistance. In recent years, the demand for organic food increased the use of biological control agents; however, complete control of plant diseases has not been achieved yet. The beneficial microbes used for biological control of plant diseases perform admirably under controlled greenhouse conditions but are not always successful under field conditions, which highly discourages the biological control methods. Hence, complete removal of chemicals from agricultural systems may not be impossible but a logical reduction in their application is feasible. Therefore, systematic integrated methods including both chemical and biological control and other control methods like cultural practices, resistant varieties and crop rotation are highly recommended.

Strategies to Improve Biological Control of Soilborne Plant Diseases

Biological control of plant soilborne diseases has appeared as an attractive alternative to other control methods. For the biological control of plant soilborne diseases, microorganisms mainly bacteria and fungi are used, which suppress growth and virulence traits or even kill pathogens and induce plant systemic acquired resistance. In recent years, the demand for organic food increased the use of biological control agents; however, complete control of plant diseases has not been achieved yet. The beneficial microbes used for biological control of plant diseases perform admirably under controlled greenhouse conditions but are not always successful under field conditions, which highly discourages the biological control methods. Hence, complete removal of chemicals from agricultural systems may not be impossible but a logical reduction in their application is feasible. Therefore, systematic integrated methods including both chemical and biological control and other control methods like cultural practices, resistant varieties and crop rotation are highly recommended.

Strawberries at the Crossroads: Management of Soilborne Diseases in California Without Methyl Bromide

Strawberry production has historically been affected by soilborne diseases such as Verticillium wilt. This disease was a major limiting factor in strawberry production in California in the 1950s and was the main reason that preplant soil fumigation with methyl bromide (MB) was developed in the late 1950s. MB fumigation was so successful that over 90% of the commercial strawberry fruit production in California utilized this technique. However, MB was subsequently linked to ozone depletion, and its use was phased out in 2005. The California strawberry industry was awarded exemption to the full phase-out until 2016, when all MB use in strawberry fruit production was prohibited. MB use continues in strawberry nurseries under an exemption to prevent spread of nematodes and diseases on planting stock. This review examines the impact of the MB phase-out on the California strawberry industry and evaluates the outlook for the industry in the absence of one of the most effective tools for managing soilborne diseases. New soilborne diseases have emerged, and historically important soilborne diseases have reemerged. Registration of new fumigants has been difficult and replacement of MB with a new and effective alternative is unlikely in the foreseeable future. Thus, crop losses due to soilborne diseases are likely to increase. Host plant resistance to soilborne diseases has become a top priority for strawberry breeding programs, and cultivars are increasingly selected for their resistance to soilborne diseases. The intelligent integration of a variety of management tactics is necessary to sustain strawberry production in California.