Grapes

The brown marmorated stink bug (BMSB) has been a localized problem in Maryland thus far but that may be expected to change in the future. The full impact on vineyards and wine quality potential of this newly introduced pest is unclear. This Timely Viticulture was created to give growers some background on the pest. The next TimelyVit will address some potential management options. Regretfully, it must be stressed from the beginning that this is a new “introduced” pest and very little is currently known of its biology, but it is evident that it has the potential to be a very significant pest.

Over the past few years there have been quite few cases in Maryland of injury to grapevines from herbicides that were sprayed to control weeds before planting crops on adjacent or nearby fields. Damage has ranged from some minimal leaf distortion through severe damage, crop loss, and vine death.

Managing excessive vine vigor is one the greatest battles in Eastern viticulture and this problem is exacerbated in seasons with high rainfall and warm spring temperatures. Many vigorous varieties and variety/rootstock combinations are quickly beginning to increase in shoot length.

The annual goal in the established vineyard is to have the vines fill their allotted trellis space, top out vegetative growth just above the top wire at veraison, and produce a crop that is in balance with the vegetative vigor.

Spring frost is a significant production hazard in nearly all locations in the MidAtlantic however (luckily!) most areas of Maryland do no experience damage frequently compared to other areas. As with most issues in viticulture, prevention or avoidance through excellent attention to site selection is the best option to reduce risk. With that said, the following is some information on what to do when an event has occurred.

Phomopsis is the first disease on a grower's radar screen. Phomopsis cane lesions are common on spurs on cordons, therefore, as the buds from these spurs grow, the fungus can easily move from last year’s wood (spur) to this years new shoot and perpetuate the disease.

Difenoconazole is a sterol-inhibiting (SI) fungicide recently registered for use on grapes and other fruit. It belongs to FRAC Group 3, along with myclobutanil (Rally), tebuconazole (Elite, Tebuzol, Orius), and fenarimol (Vintage, formerly Rubigan). Difenoconazole protects vines and fruit from powdery mildew (PM), black rot (BR), and Phomopsis cane and leaf spot.

Fall is a critical time for vineyard weed management, especially for controlling pesky perennial weeds and pre-emergence of winter annuals. The following is some “timely” basic information on weeds and some specifics on management considerations in the fall.

It is critical to properly monitor and assess the fruit maturity and characteristics to make the appropriate management, harvest, and winemaking decisions to produce the best quality grapes and wine possible. Previous Timely Viticultures on Crop Development Sampling and Evaluating Samples described how to take a proper sample that best represents the actual ripeness stage of the cultivar in that vineyard.

It is critical to properly monitor and assess the fruit characteristics and maturity to make the appropriate management, harvesting, and winemaking decisions to produce the best quality grapes and wine possible from each specific vintage.