Site Visit Highlights – Shawnee Hills AVA

Shawnee Hills American Viticultural Area

Recently I was invited to visit 3 vineyards in the Shawnee Hills AVA of Illinois. This was my third trip to Southern Illinois as a guest speaker and vineyard advisor. Each visit I learn more about the challenges these growers face and how they are dealing with them. The Shawnee Hills AVA grows a mixture of European (Vitis vinifera) winegrapes and French-American hybrid wine grapes. The most commonly planted in the vineyards I visited on this trip included Cabernet Franc, Chardonnay, Chardonel, Chambourcin, Vidal Blanc, and Vignoles. Having worked with both hybrid and vinifera grapes all across the southeastern United States, I always find similarities in the difficulties each region faces. In this summary I will discuss the most common issues and some solutions that growers may consider.

 

 Young Vine Training 101

Getting back to the basic of proper young vine training will have lasting effects for a vineyard. Proper training can establish a good root system, strong trunks, and permanent wood structure that will improve vine health, yields and reduce costs for management. If growers could focus more attention on this topic, it will have a positive long -term impact.  The three most common mistakes and their correction are listed below:

 1. Retain proper wood size when pruning

Smaller than pencil size wood should be cut back during dormant pruning; only allow pencil size wood or greater for producing trunks and cordons.

One of the most common mistakes of the dormant grapevine pruner is to retain small diameter wood. The ideal range of acceptable, fruitful wood for spurs, canes, trunks or cordons is from 5/16 to 1/2 inch diameter, or about pencil to sharpie size wood. Wood smaller than this range is often weak, producing smaller shoots and weak spur positions in succeeding years. It is also a poor choice for developing trunks or cordons on young vines (in which case the larger end of the range is preferred). There can also be some disadvantages for wood larger than this range. Large caliper wood, often referred to as “bull wood” does not push buds as reliably and can often have long internodes, leading to problems with shoot distribution uniformity. Likewise, there can be many gaps in the canopy from non-push buds if bull wood is used for cane pruning or cordon development. My two favorite mantras for dormant grapevine pruning are “no wimpy wood” and “when in doubt, cut it out!”

 

2. Laying long canes for cordon development

This grower properly laid down only 15 inches of cane per season to develop the cordon in a stepwise fashion. All shoots have good vigor and no blank spots are present.

In general, there are two reasons to lay down canes to renew your cordons; 1) you are training a young vine and you do not yet have a cordon and 2) you are experiencing cordon dieback due to fungal diseases in the wood, poor vine training, or both. Grapevines are well known to express apical dominance in bud positions most distal from the base of one-year-old wood.  When developing cordons in either the renewal or the initial development stage it is best to do so in a stepwise fashion, allowing no more than about 5-7 buds or 15” of cane laid down per season. Leaving shorter canes promotes more even bud break, hence less blank spots on the fruiting wire. As little as 6 inches of blank fruiting wire per vine can result in 0.5 tons per acre of yield loss. When cane pruning, this rule is often disregarded because the cane is removed each year.

 

 

3. Choose the proper vine tying material 

Regardless of the training system or age of the vine, some form of tying material is needed to keep the vine on the trellis system. The main reason I bring this up here is because many new growers forget to upgrade tying materials after the first few years of vine training. There are plenty of options for tying materials on young and mature vines. It is easier to start with what not to use. Anything that is not flexible has the potential to girdle vines and thus should be avoided. The leading culprits for vine girdle include, zip ties, hard plastic ag-lock ties, and wire. Do not let these items in the vineyard unless used to tie training stakes. No one will go back and “loosen” them later as the vine grows, so it is best to avoid them in the first place. I prefer using temporary material when training vines, and upgrading to a stretchable tie once permanent structures are selected for tying down. For example, thin green tape stapled with a tapner gun works well for training green growing shoots. A grower can then switch to a stretchable tubular tie or even twine for the next few years of vine development. Keep in mind that even flexible ties can girdle vines if tied on too tightly. If you aim to have a crop in years 2 or 3, then plan to have stronger support than is offered by a one-year tie.

Improving pest and disease control

Each year we see the occasional outbreak of a fungal disease on fruit or foliage. Understanding how fungicides work, which ones are used for forward protection (before a rain) and reach back protection (after a rain) will surely reduce the number of infections in vineyards. I will focus the rest of the visit highlights on some of the chronic, long term problems that are in need of further investigation.

Galls produced by foliar Phylloxera may have some impact on vine health if significant leaf area is affected.

Foliar or “Aerial” Phylloxera was observed in vineyards across all sites.  Some level of foliar phylloxera is tolerable and no economic losses or vine decline was observed due to this pest.  It is generally observed that foliar phylloxera infestations will build over time when not controlled, therefore I am recommending that vineyard managers record the incidence and severity of these infestations and be open to options for knocking back populations before economic damage is realized.  If shoot growth is not stunted to the degree that it is slowing ripening of fruit, then control may not be needed. Timing of foliar insecticides is tricky with foliar phylloxera, and it is best to spray when crawlers first appear in galls from the first generation to control the second, more damaging generation.  I encourage the group to work with local extension viticulturists to develop degree-day models to assist with spray timing. Link to work on foliar phylloxera by the University of Arkansas: http://www.uaex.edu/Other_Areas/publications/PDF/FSA-7074.pdf

Canker disease can cause significant dieback of trunks & cordons. There are preventative measures growers should be using.

Fungal diseases of grapevine trunks and cordons were observed throughout the mature vineyard blocks visited. There is a sizeable body of research from the University of California and some nationwide projects that are addressing the prevention and long-term economic impacts of these complex wood rotting fungi. Some of the diseases most likely to occur in vineyards include Esca, Eutapa, and Bot Canker. Each of these diseases expresses symptoms differently.  There are some fungicide products available for use on pruning wounds in some states. Cultural practices can also be a big help. The main preventative measures for most canker diseases include delaying pruning as late as possible (pruning wounds heal faster later in winter), not pruning during or just before rain (disease spores are spread by rain), and application of registered fungicides such as Rally 40WSP and Topsin M (check for registration for dormant application in your state).  Sealants may also prevent fungal infection, but do not contain fungicidal qualities.

Summary

Shawnee Hills AVA Growers

Growers have made significant improvements in southern Illinois vineyards since my previous visits. Canopy management is improving, and pest and disease management is on par with most regions I have visited East of the Rockies. If new and experienced growers (expanding acreage) would consider the advice above and revisit some of the basics of vine development I am confident the results will have long term impacts on vine health and yield. Vine canker disease prevention should begin at minimum when vines are in their 3rd leaf and should continue every year onward. New fungicide products and better degree day models would also help if implemented in the region, in collaboration with expert viticulturists including extension and outreach professionals. The wine potential is outstanding in the Shawnee Hills AVA. I encourage the growers to raise the bar another notch in the vineyard and those wines will only improve.

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