Evaluation of Pest and Disease Resistance in Winter Squash Varieties Under Organic Management in the Southeast

View the project final report

Commodities

• Vegetables: cucurbits

Practices

• Pest Management: genetic resistance

The hot and humid climate of the Southeast is a challenge for the successful production of squash due to numerous disease and insect pressures. Economically important pests and diseases of squash in the Southeastern United States include downy mildew (Pseudoperonospora cubensis), powdery mildew (Podosphaera xanthii), cucurbit yellow vine disease (Serratia marcescens), squash bugs (Anasa tristis), vine borers (Melittia cucurbitae), and pickleworm (Diaphani nitidalis). The organic market growers in the Southeast face additional challenges due to the lack of efficacious pesticides. Plant host resistance, if available, is the first line of defense when using organic methods of production. In previous studies, C. moschata cultivars have shown better adaptation to Southeastern conditions, and in this study, promising cultivars of C. moshcata as well as selected cultivars from C. pepo and C. maxima were tested in field trials at the University of Georgia for resistance to diseases and pests, as well as fruit quality and yield.

Another option for management is the use of bio control organisms to target pathogens and insect pests.

The first objective of this project was to determine appropriate varieties of winter squash for organic production in the Southeast using multi-year replicated field trials in which varieties were evaluated for disease resistance, insect feeding preferences and fruit quality parameters.

The second objective examines the use of bio control to reduce the impacts of plant diseases. Cucurbit yellow vine disease is a recently introduced bacterial disease transmitted by squash bugs. The disease results in plant death. Other strains of S. marcescens are known to be effective bio control and plant growth promoting organisms in other systems. This research looked at whether non-pathogenic endophytic strains of S. marcescens have disease-controlling abilities by optimizing the use of the squash bug vector to introduce not only the pathogen but also the bio control agents into young squash plants. Plants were then evaluated in the field for the development of downy and powdery mildew, and cucurbit yellow vine disease.

1. Evaluation of varieties of winter squash for disease resistance, yield, fruit quality, and insect pest feeding preference.
2. Development of a squash bug inoculation method to introduce potential bio-control organisms into squash plants.