Viticulture Practices for the Midwest
Disease/Pest Management
In the Midwest, the high humidity during growing season creates one of the
most troublesome problems growers face--fungus diseases such as powdery and
downy mildew. There are a number of ways to minimize infestations, with canopy
management and trellis systems being among the most important. Quite a lot
of the material we will be covering is based on my opinion
that living as closely with your vines as possible and being willing to do
more preventive maintenance will greatly decrease both the level of disease
pressure and the amount of reliance you must place on chemical disease/pest
control. However, there is virtually no way at this time one can grow
healthy, clean crops of grapes in our area without some use of chemical
control, especially for "the big four" of powdery, downy, black rot and
botrytis bunch rot.
Given that you need to use some chemical control, you need to consider what can
be done to make this as little as possible. These sprays are relatively expensive, can lead to
development of resistant populations of disease in the vineyard and can be both nasty to
handle and sometimes a health risk, depending on the chemical and whether it is handled
properly. The best way I know to learn about chemical controls is to obtain a copy of the
Illinois Commercial Small Fruit and Grape Spray Guide, which is updated annually and can be acquired by contacting the Cooperative Extension Service of the University of Illinois.
Although it is necessary to use chemical control to some degree, good site
selection, trellis design, cultivar selection and especially canopy
management by balanced pruning and close observation of vine development can
greatly reduce the level of use.
Another factor in disease/pest control is the concept of Integrated Pest
Management (IPM). This approach to vineyard management involves using the
positive local environmental factors such as beneficial insects,
compost-based fertilization, pheromone traps to determine infestation
levels, providing nesting and/or roost space for insectivorous birds and
raptors, and a variety of other approached which minimizes the necessity for
chemical intervention. Sprays for insects, for example, are only applied
based on reaching a certain level of population of the problem caterpillar,
beetle, moth or whatever. This will almost certainly result in less cost
than regularly spaced applications, "just in case". The spray guide
referred to earlier will give you the information about chemicals which are
effective, their application rate in pounds, gallons etc., per acre, and so
on, but IPM thinking will greatly improve your wise use of these control sprays.
This wise use is very important not only because of cost factors, but also
because there is an ever increasing chance of developing a strain of disease
such as powdery mildew which will become impossible to control with existing
types of antifungal sprays. This is already happening in other plant
types, such as with new resistant variety of potato blight (this blight, or
more correctly its ancestor, caused the great famine in Ireland in the
1840's). While it could be argued that loss of grapes is not as significant
as loss of food crops, it is still something to be concerned about. The
more you rely on chemicals to control disease pressure in your vineyard, the
sooner you will develop one of these resistant populations.
Winter maintenance in the vineyard is just as important to the longevity
and health of vines as any other season. It is also a good time to take
stock of how vines are doing, check trellis systems for any developing
problems and prepare for the reawakenings to come. Once the vines have gone
dormant and dropped all their leaves, it is a good idea to walk the vineyard
with some colored plastic ribbon, marking vines with canopy problems (bull
canes, for example), or vines which are showing stress, stunting, a lack of
healthy canes, as evidenced by gray, blotchy color instead of the typical
mahogany. This is also the time to do a post-harvest, dormant spray
determination. If you had a problem during the growing season with downy
mildew for instance, a dormant spray of Bordeaux mix can be applied to
destroy a significant portion of the inoculum retained on the canes and
trunks without having to be concerned with "burning" the growing tissue.
Another important part of maintaining a healthy, productive vineyard is to
encourage the nesting and brooding of various "vineyard friendly"
biologicals, from ladybugs and praying mantis populations to providing
nesting boxes for bluebirds. While many people try to discourage birds from
entering their plots, bluebirds should be encouraged as they consume
enormous quantities of insects and do not bother the fruit at all. Besides,
it is truly a wonderful sight in early spring to witness the arrival of
these beautiful birds with the lilting song! You can easily find
information on building houses and their appropriate placement and
maintenance from the library or the Department of Conservation.
When you are doing your winter vineyard inspection, you can also watch for
problems with potential erosion spots, wire tension problems, post
deterioration and check for early or over-wintering signs of pests. In the
context, let me mention another excellent resource book for the vineyard: "A
Compendium of Grape Diseases", which describes many pests and diseases,
their modus operandi and methods of detection and control. This manual also
includes color photos which are very helpful in distinguishing the problem
and it is readily available through Presque Isle Wine Cellars catalog, North
East, PA.
This brief overview of vineyard establishment and maintenance is intended only as a general guide and introduction. The bibliograpy below will provide more detailed and complete information. In addition, there are several institutions in our region which are devoted to
research and development of both viticulture and wine production. The Illinois Grape Growers and Vintners Association is actively pursuing legislative changes to improve the situation and would welcome anyone interested to join at a very reasonable cost (currently $25 to $50 annually). The secretary's address is listed in Bibliography/Sources or you can contact me at my business/home as listed.
Introduction
Site Selection
Planting/Trellis Systems
Erosion/Weed Control
Disease/Pest Management
Bibliography
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