Pre-bud break grape management

By Terence Bradshaw

April 15, 2016

In these next few days and week(s) before buds start swelling on grapes in Vermont, there are a few activities that can be performed that may improve management in your vineyard for the 2016 growing season. First of course is wrapping up any pruning, including careful removal of any disease inoculum including diseased wood and mummy berries that may harbor black rot and phomopsis. Now is also a good time to consider a dormant lime sulfur spray to further reduce disease inoculum. Mark Longstroth from Michigan State University Extension outlined the principles of dormant lime sulfur application in vineyards in an April 16, 2011 posting:

“Lime sulfur is an effective dormant spray when applied early in the season as growth begins. When applied as a true dormant spray before growth begins, lime sulfur can be used with oil to increase the penetration of the caustic sulfur into the surface of the infected tissues. Once green tissue appears, [lime sulfur] should not be mixed with oil. Oil will carry sulfur into green plant tissue causing injury. It is generally recommended to not use oil within a week of a sulfur spray when green tissue is exposed. Lime sulfur rates should be reduced when green tissue is exposed. Recommended rates vary for different products with dormant rates in the 10 to 12 pounds per 100 gals of water to 5 or 6 pounds when green tissue is exposed. Lime sulfur (calcium polysulfide) is a caustic material and after application it breaks down, releasing sulfur. It is very effective against diseases that overwinter on the host. Lime sulfur is also effective against many insect pests that overwinter on the plant.”

Remember that lime sulfur is pretty ‘hot’ stuff and requires that applicators follow precautions to reduce contact with the material. Very good coverage is required for this material to work, and the target zone of the trunks and cordons small, so application with a handgun may be best. If using an airblast sprayer, consider shutting off the fan to reduce drift, although that will require application on a relatively windless day. Airblast or boom sprays are also difficult to target the trunks without substantial overspray to the open space between trunks.

Now is also a good time to consider chemical weed control applications if you will be using that method. I outlined the best practices in applying early spring herbicides in an April 24, 2014 post: “…It is important to avoid herbicide contact with green tissue. Grapes are especially sensitive to many herbicides, so early spring before bud break is a good window for application of materials if you will be using them in the vineyard. Young vines with thin bark on the lower trunk can also be damaged by herbicide contact, so shielded sprayers or waxed trunk guards should be used.

Specific herbicide materials and their use restrictions and guidelines ca be found in Chapter 6 of the New York and Pennsylvania Pest Management Guidelines for Grapes

In February 2013, a Northern Grapes Project Webinar on vineyard groundcover management was offered that can be viewed here:
http://youtu.be/pSNy08aEs4E
Also, slides from vineyard weed identification and management presentations made to growers at the Northwest Michigan Horticultural Research Center from April 17, 2014 are available here:
http://bit.ly/1kdeGWp

The window to best manage weeds with herbicide applications is short, so please consider getting out there in the next couple of weeks. Once weeds get established in the vineyard and vines start growing, under trellis groundcover management becomes very difficult without causing vine injury.

-Terry

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