Early Summer Vineyard Tasks
It is definitely summertime here in Texas as temperatures soar into the 90+ degree range and sometimes violent thunderstorms appear without much warning. At this point in the grape growing season, many tasks are required of the vineyard manager. Vines are showing vigorous, bushy green growth, and, unfortunately, so are the weeds under the vines. The buds from early spring have bloomed into flowers only to be replaced by grape clusters of pea-sized, hard green berries. By now most of the pests that can harm vines and grapes, like fungal diseases and insects, have made an initial appearance in the vineyard. Diligent effort is required to manage these issues to assure good development of fruit for this year’s harvest.
As the vines put out vigorous growth, hedging, or trimming of the shoots is required as part of canopy management. Shoots that grow too long are not only unsightly in the vineyard, but they can over shade grape clusters and actually waste the vines’ energy. It usually takes about 12-15 leaves on a stem to ripen a cluster of grapes, so longer stems with more leaves don’t actually do much good and should be controlled by hedging.
Another part of canopy management involves shoot tucking. As shoots grow, they can encroach on neighboring shoots and vines. For VSP, vertical shoot position, the most common trellising system, the goal is to keep the shoots in an orderly and vertical arrangement supported by catch wires above the fruiting zone. Handling these stems and placing them in an orderly manner sort of reminds me of the childhood game of pick-up-sticks as one sorts through all the growth on each vine and tucks the shoots into proper position.
Leaf pulling is also key to canopy management. The goal here is to pull less productive leaves, those on the shoot below the grape cluster(s), to open up the fruiting area for better ventilation (faster drying) and greater access when spraying fungicide or insecticide. It is important to focus leaf pulling efforts to the north or east side of the rows that see more limited morning sun exposure. On the west or south side of the rows with more direct sun exposure, it is important to keep adequate leaf cover over the fruit to minimize sunburn on the grapes.
Unfortunately, grapevines are susceptible to a number of fungal diseases that can slow growth, damage fruit, and even kill a plant. These diseases can be as scary as their names: downy mildew, powdery mildew, grey rot, black rot, phomopsis, etc. These fungal infections most often appear under moist conditions (higher humidity, after rains, and when morning dew is slow to dry), especially when temperatures are warm-to-hot. Approved fungicide sprays are required to control fungal and mildew infections, and the vineyard manager must keep a close eye on the vines to identify and manage fungal disease with a timely and appropriate spray program. The amount of effort and expense required to manage fungal disease can vary significantly depending on the weather. During a rainy warm period, a lot of spray may be needed. This can consume a lot of the vineyard manager’s time, but also a lot of money as these fungicides are not inexpensive. In drier conditions, especially with gentle, drying winds, far less spray will be needed. Properly managing an effective spray program is an absolute necessity for a successful grape harvest.
As vines grow vigorously, so do weeds and grasses in the vineyard, especially those under the vines. These weeds and grasses can usurp moisture and nutrients needed by the vines. They can also grow tall into the fruiting zone making more difficult the tasks of canopy management and effective spraying. If left uncontrolled, tall weeds and grasses can eventually complicate harvest efforts. There are a number of weed control strategies available, and every vineyard manager needs to have one (or more). Old-fashioned hoeing or pulling can be done in smaller vineyards, but that involves back-breaking work. Herbicide sprays, if handled safely and carefully, can also help with weed and grass control. It is important to apply any herbicide below the level of fruit and leaves on the vines. Special cultivator attachments for tractors that can till the soil, effectively removing weeds and grasses, have been developed and are often used in larger vineyards.
A Texas winemaker reminded me to mention a problem related to weeds that can certainly happen here in the Lone Star State – rattlesnakes! If weeds build up around and under the vines, rattlesnakes can take residence and remain well-hidden. Until, of course, a vineyard worker disturbs the snake and creates what could become an ugly confrontation. Controlling weed growth and remaining vigilant when working in the vineyard are certainly important.
At this time in the growing season, insects can become a problem, especially sucking insects that can damage grapes and/or carry infectious diseases to vines, like the dreaded Pierce’s Disease. Approved surface and systemic insecticides are available to manage insect infestations, if needed. Most vineyard managers adopt an integrated pest management program to minimize the amount of insecticide needed, and to incorporate treatments that are specific for the type of insect currently causing problems. It is important to recognize that some insects are beneficial, and it helps to keep them around. So, insecticides that target specific harmful insects are best. One such material widely used in Texas is imidacloprid, a systemic insecticide that helps control sharpshooters and other sucking insects that can deposit Pierce’s Disease bacteria into vine leaves. This low toxicity material is generally applied in solution through the vineyard irrigation system rather than being sprayed onto the vines.
And, when thinking about insects, don’t forget fire ants that seem to love making mounds in vineyards. Probably everybody who has spent much time in a vineyard has had an uncomfortable experience with fire ants. Wasps represent another insect pest that can inhabit a vineyard and make life more difficult for workers. It is not pleasant to encounter and disturb a wasp nest while leaf pulling, tucking, or hedging the vines. A vineyard manager needs to be diligent in observing conditions in the vines and be prepared to take action as necessary.
With soaring temperatures and lots of Texas sun, keeping vines properly irrigated is very important to assure a successful harvest later in the season. Almost all vineyards in Texas are equipped with drip irrigation systems. This is an effective way to water vines that minimizes evaporative loss of valuable water and helps keep moisture away from fruit and leaves minimizing the potential for fungal infections. Vines don’t necessarily need a lot of water, but if conditions become too dry, they can shut down, retarding growth and fruit development. Many vineyards are now equipped with computerized water monitoring sensors that help manage both the timing and amount of water application. If a sophisticated water monitoring system is not available, it becomes necessary for someone to carefully monitor and manage conditions in the vineyard.
This is just a brief summary of tasks required by vineyard managers in early summer. It would be nice to be able to sit back and relax, avoiding the summer heat, while the vines do their thing, but vines need help in order to develop the healthy, ripe fruit expected by winemakers. Often people express to me an interest in either purchasing or starting a vineyard. I wonder how excited they would be if the amount of effort, hard work and sweat equity involved was fully understood. So, the next time you visit a Texas tasting room, winery, or vineyard, please take a moment to think about, and if possible, thank those vineyard workers who toil to provide fruit that’s used to make the Texas wines we all appreciate.