The present invention concerns a fungicide which is characterized in that as active component it contains a mixture of a triazole compound and a boric acid ester selected from trihexyleneglycol biborate and compounds having the general formula

B-(0-R) ₃ I

or the general formula

in which formulae R is an aliphatic group having 1-18 C- atoms or an aromatic group, the triazole compound and the boric acid ester forming a mixing ratio between 1:1 and 1:20, preferably between 1:2 and 1:10. The fungicide according to the invention exhibits a surprising synergistic effect.

Preferably the fungicide according to the invention contains as active component a mixture consisting of propiconazole (1-[[2-(2,4-dichlorophenyl)-4-propyl-l,3- dioxolan-2-yl]methyl]-lH-l,2,4-triazole) and a boric acid ester, preferably Borester-7 (trihexyleneglycol biborate). Such a mixture has a wood-preserving effect which is far better than the expected, purely additive effect.

Propiconazole, which has the structural formula

is a clear, pale or vivid yellow, very viscous liquid, which during recent years has gained a footing as wood preservative. The compound is a systemic fungicide with a broad activity spectrum. It is i.a. used within agricul¬ ture for controlling diseases in grain varieties caused by Erysiphe graminis, Leptosphaeria norodum, Pseudocero- sporella herpotrichoides, Pyrenophora teres and Rhyncho- sporium secalis, and it is also used in certain localities for combating Uncinula necator on grapes.

Within the field of wood preservation the compound has partly been used per se (cf. Alex Valc e: "Suitability of Propiconazole (R 49362) as a new-generation wood-preserv¬ ing fungicide", The International Research Group on Wood Preservation", presented March 1989 at the annual meeting in Lappeenrauta, Finland), and partly been used in mix¬ tures with other fungicides. The compound in pure form for protection of wood and coatings against microorganisms has been described in DK published application No. 163 805. Mixtures of propiconazole with other fungicidally and insecticidally active compounds are i.a. known from EP published specifications No. 413 909 and No. 458 060 which concern fungicidal mixtures of propiconazole with pyrethroides and carbamates, respectively.

As mentioned propiconazole is the preferred triazole- constituent in the fungicide according to the invention,

but it is quite feasible to replace propiconazole wholly or partly by other triazoles which are effective against wood destroying fungi. An example of such a triazole compound is tebucanozole (α-[2-(4-chlorophenyl)ethyl]-a- (1,1-dimethylethyl)-lH-l,2,4-triazole-l-yl-ethanol).

Boron compounds have for many years been used as active component in agents for all sorts or wood preservation. Boric acid was put to use as early as in 1937 and is still used, but also borates and various boric acid derivatives have found use as fungicides.

Boron containing formulations have good diffusion properties and are consequently often the only usable possibility when it comes to treatment of hard to impregnate types of wood.

Glycol esters of boron, which are soluble in organic solvents, e.g. trihexyleneglycol biborate, and boron dissolved in co-solvents, such as monoethylene glycol, have made it possible to utilize borates in a number of different formulations, the effect of which is due to the hydrolysis of the boron compound to boric acid in the wood.

Agents or concentrates for wood preservation which contain organic boron acid esters in combination with various bio- cides are described in DE published specification No. 3 617 250.

It has not previously been tried to use propiconazole and boric acid esters together.

It has, however, now surprisingly been found that by mixing the two fungicides a mixture is obtained which has an effect which is clearly better than the expected,

purely additive effect. The synergism appears from the following table:

Table 1

External tests with Coniophora puteana performed in accordance with European standard EN113.

The table is to be interpreted as follows:

Propiconazole, which in pure form has a threshold value

(biological reference value as defined in European

₃ standard EN599-1) of 0.19-0.37 kg/m , exhibits a threshold

3 value which is below 0.054 kg/m in mixture with 10 parts of boric acid ester. The concentration of the boric acid ester in the wood in the experiment at issue was 0.54

₃ kg/m , and this level is far below the limit at which the

3 boric acid ester alone has an effect (above 2.09 kg/m ).

The mixture is thus significantly more effective than the individual components.

Furthermore, internal tests with Coniophora puteana have been performed in accordance with the so-called Sobeto-

test. In this test small wooden blocks (length 3.0 cm, width 1.0 cm, and thickness 0.5 cm) are treated with impregnating agent and tested against fungi (Coniophora puteana) in a soil medium. The mass loss of the wooden blocks is an expression of the decomposition of the fungus and the wood, and the weight of the wooden blocks is consequently recorded before and after the fungal exposure. The results appear from the table below:

Table 2

This table is to be interpreted in the same way as table 1 above.

In the fungicidal formulations according to the invention it is preferred to use solvent mixtures of hydrocarbons and for example glycol ethers. Use can be made of a mixing ratio of as much as 1:1, the mixing ratio preferably being between 1:20 and 1:1.

The following example illustrates the invention.

EXAMPLE

The formulation used in the tests described above was prepared according to the following recipe:

Propiconazole 0.6%

Trihexyleneglycol biborate 6.0% Dipropyleneglycol monomethylether 8.4% Dearomatized hydrocarbon solvent 85.0%

The ratio between propiconazole and trihexyleneglycol biborate is 1:10, but according to the invention it may vary from 1:2 to 1:20. Also the ratio between the solvents may be varied.