There are two kinds of frosts: advective and radiating. Advective frosts result from horizontal moving of air with temperature below 0 degrees of Celsius usually in the beginning of spring and in the late autumn. Radiating frosts result from sharp fall of daily average temperatures and intensive radiation on clear, silent nights when the temperature on surface of the ground falls below 0 degrees.
The damage rate of plants because of radiating frosts in many respects depends on the landscape; bushes more severely and more often are damaged on the lowered places of concave forms of the relief, in hollows. Radiating frosts are most dangerous in full moon when bio-fields of plants are especially sensitive to the moonlight, and also in the new moon when their ability to live is at the lowest level.
The spring frosts of -(3-4) degrees of Celsius bring to ruining and opening buds and green sprouts can be damaged at the temperature of -0,2 degrees.
Because of autumn frosts to -2 degrees leaves and tops of trunks are damaged, and at temperature -(3-4) degrees damage and falling of berries at the grade ripening after September, 20-25 occur. In the autumn, in process of attenuation of growth processes and ripening of rod, frost resistance of grapevines grows.
Frosts from -4 to -10 degrees open buds, tops of sprouts, inflorescences, and in the autumn leaves, buds and tissue of vine in the spring are damaged. Berries are softened, lose turgor, their pulp becomes aqueous, quality of taste sharply goes down or absolutely vanishes, muscat aroma vanishes. As a result of autumn frosts photosynthesis in leaves is interrupted, putting off in fabrics of rod and roots of spare nutrients is stoped, and in winter bushes leaves are weakened, with the separate lost buds on trunks. Effect of frosts is especially negative and results in cancer, ticks, and also virus diseases.
Under the influence of frosts in the beginning of vegetation and especially before flowering plants are exposed to powerful stress, their resistance not only to diseases, but also to effect of adverse factors of environment is sharply reduced. The stress itself createdes background on which negative influence of pesticides and acid rains is amplified.
Scientific researches show, and experience of vine makers confirms, that it is possible to use a number of measures for increase of stability of grapevines to frosts. Among them are:
1. Maintenance of high agricultural conditions on vineyard (optimum feed, loading of bush of crop, duly carrying out of green operations, reliable shelter of bushes in winter and protection against diseases and pests).
2. Selection of grades with good ripening trunks by the end of vegetation (on 80-100 % of length) and application of measures for acceleration of ripening of vine. The best ripening of rod is promoted by duly carrying out of green operations, correct formation of bushes, reduction of irrigation and the termination of entering of nitric fertilizers during the second half of vegetation.
3. Avoiding early opening of bushes in the spring. Open bushes when danger of temperature fall to critical level -(10-12) degrees disappeared. Opening of bushes in our area can be carried out during the period from April, 15 till April, 25, however it is impossible to postpone opening, as the further delay can bring to the destroy uds and can lead to dying off of bark of the stem because of condensation.
4. Some amateur winemakers after opening bushes leave vine on the ground and pull a film above them at height 20-30 cm and remove it later when danger of spring frosts disappears. Attaching the stems to the wire demands extra care; by this time buds are 10-15 cm.
5. Carrying out late cutting of bushes in spring, in the beginning of swelling of buds, which allows to detain their blooming for some time.
6. The experience shows whitewashing of trunks and fruit parts after opening and cutting of bushes, delays buds opening and the beginning of vegetation of the bush approximately for a week.
7. Removing their stepsons it is recommended not to break them out, and to cut them off with secateurs, leaving one bud: there are wounds on the buds which reduce frost resistance not only of buds, but also of the trunk.
8. Fumigation is effective only at weak -(1-2) degrees frost, and spring frost in windless weather, but with stronger frosts with winds more than 5-7 m/s it is inefficient.
9. Fighting weeds between rows and around the bushes. Weeds, among other things, increase radiation at night at radiating frosts, intensifying cooling of plants.
10. A plentiful watering of soil around bushes and in interrow areas before frost, when air temperature falls to +(1-0) degrees, antifreeze watering, especially by sprinkler irrigation is the very effective means for late and early frost resistance. The effect of fighting frosts by watering is based on overhead irrigation that each drop of water at freezes warms environment (80 calories for 1 degree). Watering overhead irrigation allows to neutralize action of frost of -(3-5) degrees. The same effect has the installation of container with water (basins, pails, barrals), put under vineyards before expected frosts, along the row, one on each side of the bush. If at frosty night ice is formed in day-time it should be removed and the basin should be filled with water again.
11. Cultivation of grapes under the screen (45-50 cm wide zinc plated iron or duralumin cover above the row of a bush with ways for water flow on the edges and apertures above the head of the bushes for drain or rain water) reduces harmful influence of radiating frosts and extends the vegetative period of bushes in central Black sea area for 10-15 days. Leaves under the screen are not infected with the first autumn frosts, which in Russia usually are at the end of September. Besides, under the screen bushes are less suspectable to fungal diseases, first of all mildew.
12. Application of salts of humine acids (lignitic sodium, gibbersib, etc.) raises not only productivity, but also resistance of plants to adverse conditions of environment. Gummat sodium is applied for watering of plants with solution of 2 grammes per 10 liters of water in the first half of summer and 4 grammes per 10 litters of water in the second half. 3-4 times for season of vegetation it is recommended to spray adult bushes: after blooming of buds, after flowering, in phase of seeing of floral buds (2-nd decade of July) and during intensive maturing of berries.
At application of salts humine acids, and also other biostimulators in plants all exchange processes become more active, comprehensibility of basic elements of a feed improves, breath amplifies, the chlorophyll is more intensively formed, maturing of berries is accelerated, their quality raises, plants resist better to lack of moisture and low temperatures.
13. The increase of frost resistance of grapevines is improved with 3 applications of vitamins per the vegetation season with one-month intervals: solution of nicotinic acid (vitamin PP) in concentration of 0,02% and solution of vitamin A2 (ergocalciferol). Frost resistance of the small plants rises also with their softening before planting in a solution of nicotinic acid with concentration 0,05%.
14. In areas with frequent spring frosts the special attention should be payed on selection of the grapevine varieties tested in local research establishments and at experienced vineyards, and also possessing not only complex or group resistance to diseases, pests and frost, but also late blooming of buds and ability to fructify from spare (replacing) buds when the basic bud was lost. To the varieties, capable to fructify from replacing buds, are: The Alma-Ata early one, Ginu vagaas, Penalty koz, Crimean pearl, Muscat wax, the Muscat derbentsky, Muscat Susanna, Mertsisior, Novoukrainsky early, Autumn pink, Gift of Magaradjha, Saperavi northern, Suruchensky white, Violet early, Shasla northern, Anniversary-70.
It is necessary to emphasize, that last years many amateur vine makers began to grow complex-stable varietes and stopped to spray vineyard against fungal diseases. Aspiration to receive organic grapes, business creditable, however, according to scientists vine makers, these varietes are immune basically to mildew and rottening, and without processing with fungicides in some years they are affected by anthracosis, which is not less harmful, than mildew. For this reason it is recommended to spray complex-immune varieties and varieties with group immunity against fungal diseases two times per the vegetation season: 1-st (preventive, obligatory) when trunks have 5-6 leaves, 2-nd approximately in two weeks after flowering when ovary achieves the size of grain of millet or a fine pea.
Nikolay Andreyev «House, Garden, Kitchen-garden» #13/2001