Summer in the Vineyard - 2019
A Carl’s Corner about similar issues was posted in June, 2018, and a version with photos was also posted on the TexasWineLover.com website.
This has been an unusual spring and early summer for the Texas Hill Country. The much greater than normal amount of rainfall has certainly been different, and made for one of the most abundant, colorful, and longest lasting wildflower displays folks can remember. The temperatures have also been moderate, typically below 90 degrees until just this past week. The rain and moderately warm temperatures not only inspired the Texas wildflowers as Hill Country vineyards have also seen a burst of growth, not only on the vines, but with the weeds, insects, and fungal diseases that tend to plague grapevines during humid conditions. The grapevines have flowered, set the fruit, and are now showing clusters of hard green grapes that will race forward to veraison (color change) in just a few weeks. It is an exciting time in the vineyard, but also one filled with lots of work.
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 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 the most common trellising system, VSP or vertical shoot position, 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 another important task. The goal is to pull less productive leaves, particularly 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, adequate leaf cover over the fruit is needed 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, like we are experiencing in the Texas Hill Country in 2019, a lot of spray may be needed. This can consume a vineyard manager’s time, and 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 fellow 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. So far, because of all the rain in 2019, irrigation has not been a significant issue. Almost all vineyards in Texas are equipped with either drip or underground 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 both 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 just sit back and relax and avoid the summer heat while the vines do their thing. However, 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 typically 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, offer thanks to those vineyard workers who toil to provide fruit that’s used to make the Texas wines we all appreciate.