In this project, researchers targeted all the causal organisms associated with sour rot with various chemical treatments to determine the most efficient control strategy.
Previously, reliable management practices for sour rot was hard to establish since there was uncertainty regarding the etiology and epidemiology of sour rot. It is now known that yeast, acetic acid bacteria (AAB) and Drosophila spp. (fruit flies) act together to cause sour rot.
The project consisted of replicate field trials conducted over three years in upstate New York, Finger Lakes.
- The causal organisms were targeted by pre-harvest applications of various antimicrobial agents (potassium metabisulfite, copper hydroxide, BLAD polypeptide and/or a mixture of hydrogen dioxide and peroxyacetic acid, depending on the year) and insecticides. Each on their own as well as in combination.
- Researchers also considered disease development in a commercial vineyard where two different trellis systems were used – High wire cordon (HW) and vertical shoot positioned (VSP).
64% control (compared to controls) was achieved when applications of an antimicrobial agent plus insecticide started preventatively at 15 Brix, before the onset of any symptoms, and were applied on a weekly basis until harvest.
- Control levels decreased when applications started once symptoms were observed.
- Application of only an insecticide, preventatively, provided considerable control in two years of the study.
- Antimicrobials were only effective when applied with an insecticide.
- The severity of sour rot, in all three years of the trial, was always significantly higher on vines trained on a high wire system, compared to VSP trained vines.
SIGNIFICANCE OF THE STUDY:
Managing sour rot, requires an integrated approach. A better understanding of how a disease develops and what the causal organisms are, is crucial information that is required to develop effective control and management practices against a disease. The results from this study can help growers who farm with wine grapes in areas where the climate is conducive to sour rot, to better manage their vineyards to reduce crop loss.
Image source: https://www.canr.msu.edu/ipm/diseases/sour_bunch_rot