Control of Eutypa Dieback of Grapes

The objective of this research is to find an effective control for Eutypa dieback, caused by the fungus Eutypa lata. Specific objectives this year were:

  1. Continue testing efficacy of fungicides.
  2. Study colonization of wounds by applied fungi.
  3. Determine how the biological control agents inhibit infection.
  4. Test the combination of fungicide and biological control treatment.
  5. Monitor the natural flora of pruning wounds of grapevines.
  6. Determine the relationship between vine training system and disease susceptibility.
  7. Determine the susceptibility differences between cultivars.

Fusarium, Cladosporium, Aureobasidium and Trichoderma were tested for their Eutypa control effectiveness relative to benomyl and for their ability to colonize the grape wound surface. The biologicals were often as effective as benomyl with Fusarium lateritium being the most successful wound colonizer. A dual treatment of F. lateritium and benomyl is being investigated as a control measure. The natural rate at which F. lateritium is benomyl resistant was determined to be 1 ppm. Screening for F. lateritium mutants which grow at higher benomyl concentrations is taking place. The total wound area of vines of different training systems was assessed and the nonspur wounds, those made directly on the cordon, accounted for over half of the total wound area. If nonspur growth was removed in the summer, the total wound surface area could be diminished in half and this would make the vine less susceptible to Eutypa infection.