Grass seed head suppression process

Composition and method for preventing the formation of cobs in grass

This invention relates to a synergistic composition useful for reducing the formation of cobs in grass, which gives a surprisingly advantageous result at low levels of use, and to a method for preventing the formation of cobs by means of this composition.

Several compounds have been reported to be effective in inhibiting grass growth. Some of them are in fact commercially available for this purpose. However, a recurring difficulty with these compounds is that they are often so effective that the range of application between the amount of application that produces the desired effect and the amount at which the grass suffers from unpleasant discoloration or even destruction is often small. This means that there is a significant potential for destruction as a result of excessive or misuse.

Despite these difficulties, the use of compounds to impair grass growth has expanded on road sides and similar uses in large areas, as well as in pasture renewal.

This impairment may be a real reduction in the amount of vegetation growth and / or a reduction in the formation of grass spikes. This invention is particularly directed to a method of preventing the formation of cobs in grass by applying to it a synergistic mixture of two compounds which is particularly useful in small dosage amounts.

The composition of the invention contains A. 50-83% by weight of acetanilide of formula

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. 1 2 wherein R · * · and R independently represent a C 1 -C 4 alkyl group or a C 1 -C 4 -C₃alkoxy group, R³ on Cj_L-C₃an alkyl group and X is chlorine or bromine; and

B. 50-17% by weight of a triazole of formula

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R wherein R is hydrogen or methyl and X is chlorine or bromine, and all percentages are based on the combined weight of components A and B.

The invention further relates to a method of preventing the formation of cobs by applying to the herbs an effective amount of the composition of components A and B as defined above during a period beginning when the green growth of the herbs is at least 50% and ending about 6 weeks thereafter, but not later than started.

In a preferred method of preventing the formation of cobs, a composition is used in which R and R in the formulas of components A and B are both ethyl and R³ is a methyl group. The preferred substituent is chlorine in both components A and B of the mixture.

Green growth is the transition from dormancy (winter phase) to active growth. Green growth is

7572 % when this step has occurred in about half.

With respect to component B of the mixture, each of the groups R is preferably methyl.

The weight ratios of components A and B are preferably between 5: 1 and 1: 1, and most preferably this ratio is about 2: 1.

The effective application rate may vary depending on the current and future growing conditions of the grass and pasture.

However, it has been found that the synergistic effect decreases with increasing application rate. Thus, when more than about 1.4 kg / ha of component A is used, the synergistic effect is not significant and if the amount of component A is less than about 0.84 kg / ha, its effect alone or with component B is not sufficient. Thus, in the preferred method, up to about 1.12 kg / ha of component A is used together with 0.224-0.672 kg / ha of component B. In general, an application rate of less than about 2.24 kg / ha of the combined weight of components A and B is preferred in the case of cool season grasses. However, for warm season grasses, higher application rates may be appropriate, perhaps as high as 3.36 or even 4.48 kg / ha.

The mixture can be applied to the grass for a period of 4-45 days before the formation of cobs can be expected without treatment. This usually occurs about 30 days after 100% green growth, and application 5-20 days before the formation of the cotyledons is particularly preferred.

The preparation of ingredient A is disclosed, for example, in U.S. Patent 3,829,306 and the preparation of ingredient B in U.S. Patent 4,205,075. Both ingredients are known to have a plant growth regulating effect independently. However, the finding that together they may have an unexpectedly beneficial cob growth-reducing effect on grasses was very surprising, especially considering that component B alone actually appears to improve cob formation.

The unexpected nature of this synergistic effect can be clearly seen by looking at the following examples, which are given for illustrative purposes only and are not intended to limit the scope of the invention.