Grapes

Botrytis is a major disease threat as harvest approaches. Botrytis cinerea is a fungus that affects many plant species, especially wine grapes, where it is commonly known as Botrytis bunch rot or gray mold.

The Spotted Lanternfly (SLF) is now confirmed in Cecil and Harford Counties in Maryland, and populations in Pennsylvania, New Jersey, Delaware and Virginia have been growing. The pest has been impacting vineyards in Pennsylvania. What is clear at this junction is that (1) grapevines are a favorite host of this pest and, (2) its feeding damage coupled with winter cold stress can cause vine death. At ground zero in Pennsylvania, feeding from this pest, combined with the moderately cold winters of 2017/18 and 2018/19 has done significant damage to multiple commercial vineyards.

Downy mildew is now a year-long challenge for grape growers in the East. Downy mildew is often difficult to manage because it requires specific weather conditions to become a serious threat, but it can develop into an epidemic very quickly in favorable weather.

At 3 to 4 weeks after bloom, the risks of black rot (BR), Phomopsis (Ph; including cane and leaf spot, and fruit rot), and powdery mildew (PM) are decreasing. Downy mildew (DM) will be the main threat. While most Botrytis bunch rot infections occur around bloom and fruit set, bunch closing and veraison may also be critical points for protection when weather conditions are favorable for infection, especially on susceptible varieties.

Some early cultivars in many vineyards are just starting to bloom. This is a critical time for taking tissue/petiole samples to assess the nutritional status of your vines. Remember all vineyards with income of >$2500 per year MUST have an approved nutrient management plan and MDA conducts regular monitoring to be sure you are in compliance. Recent analyzed tissue samples are at the core of the plan. The following are some timely considerations.

The growth period from 2 weeks pre-bloom until 3 to 4 weeks post-bloom is the most critical for protecting foliage, and especially flowers and newly set fruit from black rot (BR), Phomopsis (Ph), powdery mildew (PM), Downy mildew (DM), and Botrytis bunch rot infections.

This general term applies to the larvae (caterpillars) of a large number of butterfly/moth species (Lepidoptera) in the noctuid family that feed on buds, young shoots and leaves. Cutworm damage most commonly occurs in vineyards with weeds under the trellis or mulch, and in sandy or light colored soils.

Grape Flea beetles, Altica spp. (Coleoptera: Chrysomelidae), are small (4-5 mm), oval shaped, metallic blue-purple beetles that jump when disturbed.

Spring frost is a significant production hazard in nearly all locations in the Mid-Atlantic however (luckily!) most areas of Maryland do not 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.

Damage from low temperatures in early spring when grapevines are initiating their growth is a risk to sustainable/profitable wine grape production in the Eastern US. The majority of Maryland vineyards do not experienced a significant amount of freeze damage annually, in a major part due to proper site selection. However with the extremes of weather experienced over recent years, Maryland vineyards are at increased risk. This “TimelyVit” will give an overview of how timing and conditions of frosts/freezes during early growth can influence the level of damage.