Tools for managing sour rot in grapes

Sour rot has been a challenge in some vineyards this fall.  It is critical to manage not just the causal organisms but also the Drosophila flies (spotted wing Drosophila as well as Drosophila melanogaster, the common “fruit fly) that can carry them.

Optimizing drying conditions and minimizing fruit injury are critical.  Research in Ontario and New York has shown that applications of antimicrobials such as potassium meta bisulphate (KMS at 5 kg/1,000 L) or peroxide (Oxidate) in combination with insecticides were the most effective way to manage the disease.

Information on insecticides registered for SWD control is available at: http://www.omafra.gov.on.ca/english/crops/facts/swd-registrations.htm.  The Delegate label was recently expanded to include SWD in grape.  The following is an excerpt from the new recommendations for SWD (and other Drosophila species) in grapevines:

Spotted wing drosophila has not been confirmed to be a major pest of grapes in Ontario.  However, all Drosophila species can vector the organisms that cause sour rot so controlling this insect may help reduce sour rot. Apply products with sufficient water to ensure complete coverage.

Yellow jackets are also active now and can damage berries and allow sour rot pathogens to enter.  Mako is the only product registered for yellow jacket control.  It is registered for SWD in other crops so would have activity in grapes if applied for yellow jackets.

Confirm with your winery regarding product acceptability and pre-harvest intervals.