When do you have to spray vines?
Even though this is often the colloquial expression: It is not the wine as a beverage that is sprayed (except in Austria, it means mixing the wine with mineral water), but the plant - i.e. the vine in the vineyard.
The "spraying" of the vineyards serves the Plant protection. The vines and the grapes have a lot of natural enemies, such as bacteria and viruses, fungi, insects, birds and wild animals. There are chemical and biological (organic) plant protection products against such diseases and pests, which are usually applied in liquid form. A distinction is made between "spraying" and spraying: spraying means that the pesticide is applied mixed with water in the vineyard, spraying means that the mixture of pesticide and water is applied with the help of a blast of air; spraying requires about 50 to 70 percent less water than spraying.
The following explanations refer to both application with a sprayer and spraying. Very important: These are only general instructions that can by no means stand alone. Before using any crop protection product, it is imperative to read and observe the hazard labels (environmentally hazardous, harmful, toxic) and the instructions for use under all circumstances!
Effects of plant protection products
Plant protection products (Pesticides) can be divided into Fungicides (which are effective against fungi and may contain, among other things, sulphur and copper ), Bactericides (which are effective against bacteria), Insecticides (which are effective against insects) and Herbicides (which act against weeds ). Since all these agents kill life(micro-organisms, animals and/or plants) and affect the ecosystem in the vineyard, responsible use is essential. The prerequisite for this is knowledge of the mode of action and application of the plant protection product, as well as the proper equipment and operation of the equipment for application. In addition to the correct dosage of the agent - exclusively in accordance with the respective approved application rate (kg/ha or l/ha) - proper storage and disposal, the respective prescribed distance from water bodies and the necessary user protection must also be observed. This is because chemical plant protection products in particular can also have a toxic effect on beneficial insects and crops as well as on groundwater and thus on humans and animals in general - apart from the health hazards that may exist for the user during application.
The effectiveness of crop protection depends on a variety of factors. These include the weather, the time of day, the spraying technique (nozzle, pressure, blower type, arrangement and setting), the stage of development of the vine (and the associated foliage density), the mode of action of the agent and the risk of disease or pest infestation (infestation pressure). The quantity used and the pH value of the water as well as the droplet size also determine the success.
Timing and frequency of spraying
To give an idea of the proportions: All "green" (i.e. worthy of protection) parts of the vine - leaves, shoots and grapes - reach, depending on growth vigour, grape variety and vine training a surface area of 30,000 to 40,000 square metres per hectare. The leaf area, which can be extrapolated from the shoot length growth, is decisive for the dosage of the plant protection product: In years with normal weather conditions for the growing region, the leaf area per shoot grows by about 400 square centimetres within ten days. After this period, according to a rough rule of thumb, a new treatment is necessary to protect the newly grown plant parts. However, leaf area growth is also strongly dependent on the weather during the vegetation period between the end of May and the beginning of August, so that the plant protection work must be adapted to the respective conditions each year.
The timing of the plant protection application is based on relevant forecasts of how likely it is that diseases and pests will occur in the year in question. For this purpose, it is necessary to constantly check the vineyards for corresponding symptoms. It is also crucial to continuously monitor the relevant weather factors that increase disease pressure (see below); this is possible, for example, with the help of local weather stations. In addition, the development of certain animal pests, such as the grape berry moth, can be monitored by means of egg laying in small cages and/or pheromone traps.
The use of plant protection also depends on whether the winegrower works conventionally, integrated or organically:
- In conventional viticulture, plant protection is prophylactic and rather undirected with (at least predominantly) chemical agents: According to precise calendrical plans, which are often prescribed by the agricultural industry (the manufacturers of the agents), pesticides are regularly applied as a preventive measure, without monitoring the development of diseases or infestation by pests. Negative effects on the ecosystem in the vineyard are not taken into account. However, this form of viticulture is becoming less and less common.
- Integrated Pest Management relies on a combination of mechanical, physical, biological, biotechnical and chemical methods, with chemical plant protection having only a supplementary effect. The measures depend, among other things, on the weather, the stage of development of the vine and the previous year's infestation. Constant observation of the vineyard and the weather is of particular importance here.
- At organic or ecological viticulture only organic plant protection products are used. Herbicides are generally prohibited here, and other means of protection against insects, animals and microorganisms are preferred. However, certain fungal diseases can be controlled or prevented most effectively by applying fungicides containing sulphur or copper. Fungi thrive particularly well in warm and humid atmospheres, and with the help of modern meteorological methods, weather developments can now be predicted quite reliably. More and more winegrowers therefore only use plant protection products when there is a real risk of disease (in technical terms: when fungal pressure increases).
The application of active substances, i.e. "spraying", makes most sense in the early morning hours or in the evening during the warmer season. In order for the droplets of the active ingredient-water mixture to reach the plant surface and adhere to it, the air humidity must be sufficiently high, otherwise the water in which the active ingredient is dissolved can evaporate at least partially in the air, so that the protection is then insufficient. Furthermore, the active ingredient needs time to penetrate (approx. 15 minutes).
The duration of effect of the agent - usually between 6 and 21 days - therefore depends on the weather(rain washes off the active ingredient again), the time of spraying (see above), the effectiveness of the wetting (application quality) and the residual amount of active ingredient from the previous treatment. Now that integrated and organic viticulture are becoming more and more widespread, organic plant protection products are also increasingly being used. However, as these are less aggressive than chemical pesticides, they have to be applied more frequently: The agents are more environmentally friendly, but the frequency of their use is higher.
Examples of fungal diseases: Powdery and downy mildew
The greatest danger to vines and grapes comes from fungal diseases such as powdery and downy mildew. These are therefore examined here as examples with a view to plant protection.
Powdery mildew (Oidium)
- reddish-brown to brownish-purple, irregularly branched spots on one-year-old wood
- infected buds(eyes) sprout with a white fungal coating
- grey-white, mealy coating on all green parts of the vine
- musty smell in the vineyard
- warm weather with high humidity
- Temperature of 21 to 26 °C
- Humidity of 50 to 95
preventive cultural measures:
- airy training of the vines
- conscientious foliage work
- regular control for symptoms
- at budbreak: treatment with two-percent net sulphur (guideline 3 kg/ha)
- most important treatment period: 10 days before flowering (usually end of May), beginning of flowering (usually beginning/middle of June) and end of flowering (when approx. 80 % of the flower caps are open)
- at the beginning and during flowering: every 7 to 10 days spraying of oidium treatment, if necessary with net sulphur additive
- at the end of flowering (usually July/August): careful foliage work and application of Oidium treatment agent with net sulphur additive (guideline 2-3 kg/ha)
- from mid-August onwards, no more use of wetting sulphur, as this can impair the taste of the winelater on(buckwheat)
Treatment in case of infestation:
- Washing with 1.5 percent soft soap solution
- Application of oidium treatment agent with the addition of net sulphur, as described above
Downy mildew (Peronospora)
- on the upper side of the leaf round, 2-3 cm large, light-coloured, oily spots
- white fungal lawn on the underside of the leaf
- white to yellowish fungal lawn on inflorescences and young berries
- persistent warm and humid weather
- heavy rain (5-10 mm in 2-3 days)
- 4-6 hours of leaf wetness at at least 10 °C over 24 hours
preventive cultural measures:
- high and wide-ranging training of the vines
- conscientious foliage work
- moderate nitrogen fertilisation
- most important treatment period: during flowering
- use peronospora treatment every 7 to 10 days
Karl Bauer: Viticulture, Agrarverlag