As daily temperatures soar into the 90+ degree range, and sometimes violent thunderstorms appear without much warning, you definitely get the feeling that it is summertime here in Texas. Although many of us would like to stay inside to avoid the heat, at this point in the grape growing season, many tasks are required of the vineyard manager. Most vines are showing vigorous, bushy green growth, and, unfortunately, so are the grasses and weeds under the vines.
The vines are past the early spring budding stage, and with the heat there are certainly no more concerns about frost damage to those buds. The buds bloomed into flowers that by now have developed into grape clusters of pea-sized, hard green berries. There are other living species coming to life in the vineyard, such as most of the pests that can harm vines and grapes. Myriad fungal diseases stand ready to blossom on vine leaves and grape clusters, and insects of many types are making an appearance in the vineyard. In order to manage these issues to assure good development of fruit for this year’s harvest, frequent observation and diligent effort by the vineyard manager is required.
The term canopy management relates to a number of procedures designed to balance vine growth and provide the best possible opportunity for ripening a bountiful harvest of fruit. One canopy management task involves shoot tucking. As shoots grow, they can encroach on neighboring shoots and vines. Vertical shoot positioning (VSP) is the most common trellising system, and the goal is to keep the shoots in an orderly and vertical arrangement supported by catch wires above the fruiting zone. Shoot tucking most often involves physically handling the stems and placing them in an orderly and upright manner. This effort 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.
As vines put out vigorous growth, hedging, or trimming of the shoots becomes a large part of canopy management. Shoots that grow too long are not only unsightly in the vineyard, but they can overshade 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 are not necessarily better and should be controlled by hedging. Removing short or underdeveloped stems, especially those that have no grape clusters, is also part of this hedging process. For many vineyards, particularly smaller ones, most of this hedging work is done by hand. For larger vineyards, such as those often seen on the Texas High Plains, special hedging machines are used to maximize efficiency and minimize labor costs.
Once stems have been removed from the vines, the usual practice is to either pick up the trimmed material or convert it into mulch. If a vineyard has history with significant fungal diseases, removal of this trimmed material is the best option since fungal spores, ready to spread infection in the vineyard, may exist on the downed leaves and stems. Otherwise, the trimmed leaves and stems can be chopped into mulch with equipment such as flail mowers.
Leaf pulling is also key to canopy management. The goal here is to pull less productive leaves, specifically those on the shoot below the grape cluster(s), to open up the fruiting zone 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 particularly 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 winemaker friend here in Texas 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 is used to make the Texas wines we all appreciate.