The present invention relates to a composition for controlling plant growth in viticulture, as well as to a method of using such a composition.

A considerable part of the total work involved in viticulture consists of leaf work. This work includes the pinching off of undesired vine shoots and the fastening and pruning or thinning out of the vines. These tasks constitute a considerable amount of work since they must be carried out within a relatively short specific period of time.

Previous attempts to mechanize this work have not yet been successful. (See D. Maul: "Moglichkeiten zur Mechanisierung der Laubarbeiten" in "Der Deutsche Weinbau", No. 18, 1977). Also chemical methods for carrying out this work have not previously been known. In accordance with the present state of the art, therefore, this leaf work is carried out by hand. The shortage of workers and the cost of labor impose a considerable burden on the vine grower.

The basis of the vine is the "stem", which consists of perennial wood, so-called "old wood". The fruit-bearing shoots develop at the upper end of the stem from the buds of annual shoots. Shoots, however, can be formed not only from annual wood but also directly from the perennial old wood of the stem. Such shoots, also known as "wild shoots", bear no fruit and must be removed by hand. This work is referred to as "pinching off the stem shoots."

It is known from West German Provisional Pat. No. 1,642,343 that cyanamide can be used to kill ground sideshoots of hop plants. In this case, however, there are concerned vegetative shoots which develop from the underground portion of the stem of the hop plant. After breaking through the surface of the earth, the side shoots are treated with cyanamide but the underground stem itself does not come directly into contact with cyanamide.

The object of the present invention is to reduce the amount of manual leaf work in viticulture by using an agent for controlling undesired plant growth. This purpose is achieved by using an agent for the chemical "pinching-off" of undesired stem shoots in viticulture, i.e., a chemical composition containing an agent for suppressing the growth of undesired stem shoots, which agent is cyanamide. We were surprised to find that the active substance, cyanamide, can be used for killing stem shoots of grape vines without adversely affecting the other vegetative and generative developments of the vine. There are fundamental phytomorphological differences between the stem shoots of vines and the ground shoots of hop plants. The shoots of grape vines develop on the part of the plant which is above the ground while the ground shoots of the hop plant, on the other hand, develop from the underground part of the stem. Furthermore, when cyanamide is used for killing the shoots of vines it is not possible to prevent the stem also being contacted by the cyanamide. The active substance, cyanamide, completely destroys those shoots which are directly contacted. It has been found that the stem which is also contacted by the cyanamide at the same time is not damaged. The further development of the stem, the vegetative growth, the grape blossoms, and the development of the grapes are not adversely affected. It is known, and of particular advantage for the use of cyanamide for controlling undesired plant growth, that the active substance decomposes rapidly and completely on the plant and in the earth so that no undesired residues remain either in the ground or in the grapes.

The active substance, cyanamide, is desirably applied in a growth-suppressing amount and in the form of a dilute aqueous 50% solution by spraying. The concentration of cyanamide in the dilute spray solution may be 1-5% by weight, preferably 1.5 to 3% by weight. This means that with about 1000 liters of spray mixture per hectare, 10 to 50 and preferably 15 to 30 kg of cyanamide are applied per hectare. The shoots to be removed must be thoroughly wetted with this spray solution, each stem requiring about 100 to 150 ml of spray mixture. By this method the undesired shoots of all common kinds of graphs can be killed. In the following Examples 1-5, this action is shown on the two most important types of grapes, Riesling and Silvaner.

EXAMPLE 1

Place of experiment: Haardter Mandelring

Type of grape: Riesling/5 BB

Size of lot: 12 vines

Length of the shoots treated: about 4-8 cm

Number of shoots per vine: average 10-12

Height of vines sprayed: about 60 cm

The cyanamide was applied in aqueous solution containing 1.5, 2.0 and 2.5 weight % of cyanamide.

______________________________________Treatment   Burning of the treated New sprouting fromon      shoots in %            shoot residuesMay 29th   June 1         June 8  June 24______________________________________Untreated    0              0      --1.5 wt. %   85             90      none                          (shoot residues2.0 wt. %   90             95      completely re-                          moved)2.5 wt. %   95             100______________________________________

No damage to the shoots above the spray zone was noted. Further development of the vine, blossoms, and development of grapes were not adversely affected.

EXAMPLE 2

Place of experiment: Neustadt/LFA

Type of grape: Silvaner/5 BB, wide-spacing

Size of lot: 2 lots of 12 vines each

Length of shoots treated: 20-60 cm

Height of vines: 1.10-1.20 m

Aqueous solutions containing 1.5 wt. % and 2.0 wt. % of cyanamide were used.

______________________________________    Burning of the treated                       Number of newTreatment on    shoots             shoots per stemMay 25   May 27     June 1      July 28______________________________________Untreated    --         --          2.51.5 wt. %    shoot tips Shoot tips  2.0    completely and leaves of2.0 wt. %    killed     the shoots  1.0               completely               killed.               Shoot base               incipient               burning.______________________________________

No damage to the vine or above the spray zone was noted. No adverse effect on the further growth was observed.

EXAMPLE 3

Place of experiment: Geinsheim/Adam

Type of grape: Silvaner, normal planting

Lot size: 2 lots of 10 vines each

Length of shoots treated: 15-20 cm (max. 50 cm)

Height of stem of vine: 80 cm

A 2% by weight aqueous solution of cyanamide was used.

______________________________________Treatment on    Burning of the shoots                     Number of new shootsMay 27   June 3     June 7    July 2______________________________________                         per lot                                per vineUntreated    --         --        34     1.7Cyanamide    shoot tips all shoots                         16     0.8solution killed,    completely    leaves dis-               killed    colored    brown______________________________________

EXAMPLE 4

Place of experiment: Neustadt/Geinsheim

Type of grape: Silvaner

Size of lot: 2 lots of 10 vines each

Height of stem of vines: about 80-100 cm

A 2% by weight aqueous cyanamide was used.

______________________________________            Number of shoots remaining  Time of   (relative)Treatment    Treatment   May 30   June 7 June 21______________________________________Untreated    --          100      100    100Cyanamide    May 23 withsolution 5 cm length    of shoot    0        0      0    May 30 with    10 cm length    of shoot    --        50     5    June 7 with    15 cm length    of shoot    --       --      50______________________________________

EXAMPLE 5

Place of experiment: Geinsheim/Adam

Type of grape: Silvaner

Size of lot: 2 lots of 10 vines each

Height of stem of vines: about 80 cm

A 2% by weight aqueous cyanamide was used.

______________________________________                Number of vine                             Number of                shoots remaining                             new shoots    Time of     (relative)   (relative)Treatment    Treatment   June 23      August 8______________________________________Untreated    --          100          100Cyanamide    May 27 withsolution shoot length    of 5-8 cm   25           33    June 4 with    shoot length    of 10-15 cm 25           25______________________________________

From the foregoing Examples it is apparent that aqueous cyanamide solutions are selectively effective in suppressing the growth of "stem shoots" in viticulture.