Process for the herbicidal treatment of sorghum using 2,4-diamino-6-chloro-5-methylthio-pyrimidine

A process for destroying weeds in sorghum crops which comprises applying to the area of the growing crop or to the crop area before the crop emerges, 2,4-diamino-6-chloro-5-methylthio-pyrimidine or a mixture of the two isomeric compounds 2,4-diamino-6-chloro-5-methylthio-pyrimidine and 4,6-diamino-2-chloro-5-methylthio-pyrimidine in which 2,4-diamino-6-chloro-5-methylthio-pyrimidine is preponderant, the rate of application of the above compound or mixture being from 300 g/ha to 4,500 g/ha. Herbicides may be simultaneously applied.

The present invention relates to a process for destroying weeds in sorghum 
crops, in which the herbicidal agent used is 
2,4-diamino-6-chloro-5-methylthio-pyrimidine (compound hereinafter 
referred to as A) or a mixture of the two isomeric compounds 
2,4-diamino-6-chloro-5-methylthio-pyrimidine (compound A) and 
4,6-diamino-2-chloro-5-methylthio-pyrimidine (compound B) in which 
compound A is preponderant, that is to say the percentage by weight of A 
in the mixture is at least 50% and preferably at least 80%. 
Compounds A and B and their mixtures are known products which are described 
in European patent application No. 78400062.2 (publication No. 681) and in 
Japanese patent application No. 77/6,335 (publication No. 78/92,789). None 
of these documents decribes the use of said products in a process for the 
herbicidal treatment of sorghum. 
The process according to the invention comprises applying to the area of 
the growing crop (post-emergence application ) or to the crop area before 
the crop emerges (pre-emergence application ) compound A or a mixture of 
compounds A and B wherein compound A is preponderant, the dose of compound 
A or of the mixture of A and B used ranging from 300 g/ha to 4,500 g/ha, 
preferably from 600 g/ha to 3,000 g/ha. In the pre-emergence application 
there may simultaneously be applied a herbicide belonging to the triazine 
family (atrazine, cyanazine, simazine, terbutryne, etc.), the dose of such 
herbicide used ranging from 500 g/ha to 5,000 g/ha. In the post-emergence 
application there may simultaneously be applied a herbicide chosen from 
atrazine, simazine and the family of acetanilides, in particular alachlor 
and propachlor, the dose of such herbicide used ranging from 500 g/ha to 
5,000 g/ha. 
The herbicidal compounds used in the process of the invention are 
preferably applied in the form of a composition which contains, in 
addition to the active material (that is, compound A or the mixture of 
compounds A and B, and possibly one of the herbicides indicated above), 
inert additives normally used in agriculture to dilute the active 
materials and to facilitate putting in aqueous suspension, adherence to 
foliage and resistance to atmospheric agents and to biological 
degradations. Such inert additives are well known by one of ordinary skill 
in the art. As such may be mentioned solid diluents (talc, silica, 
kieselguhr, chalk, diatomaceous earth, clay, etc.), liquid diluents 
(water, mineral oils, organic solvents), anionic or non-ionic 
surface-active substances, dispersants, adjuvants, and wetting agents. 
The compositions in which the active material is incorporated are prepared 
by intimately mixing suitable amounts of the various constituents. Such 
compositions may be particularly in the form of wettable powders or in the 
form of stable aqueous suspensions. These suspensions are applied by 
spraying on the area of the growing sorghum crops or on the crops area, 
before the crops emerge. 
The process according to the present invention enables a large number of 
undesirable plants to be destroyed belonging to the monocotyledon or 
dicotyledon classes, especially panicum milliaceum, and this without 
disturbing the development of the cultivated plant.

The following examples illustrate the invention without it being restricted 
thereto. In the examples and throughout the specification and claims, all 
parts and percentages are by weight unless otherwise specified. 
EXAMPLE 1 
The object of this test is to demonstrate the absence of phytotoxicity of 
the active material towards sorghum. 
The active material is a mixture containing approximately 89% by weight of 
compound A and 11% by weight of compound B. It is incorporated in a 
wettable powder having the following composition (the percentages are by 
weight): 
80% of active material 
10% of talc 
6% of silica 
3% of sodium methylnaphthalenesulfonate (dispersant) 
1% of the polyethoxyether of fatty alcohol known by the trademark REMCO 
L02B (non-ionic adhesive agent). 
The wettable powder is diluted in water before use and the suspenson thus 
obtained is sprayed, at the rate of 1,000 l/ha, on sorghum plants (NK 121 
variety) at the three leaves stage, which are grown in a greenhouse. The 
dilutions are calculated to give the doses of active material indicated in 
the following Table 1. 
15 days, then 30 days after the application of the suspensions, the degree 
of phytotoxicity towards the cultivated plant is evaluated. This degree of 
phytotoxicity is expressed by a value from 0 to 10. 0 corresponds to an 
undamaged plant and 10 to a destroyed plant. The results obtained are 
summarized in the following Table 1: 
TABLE 1 
______________________________________ 
Degree of 
Dose of phytotoxicity 
active material 
towards 
Active applied the sorghum 
material (g/ha) 15 days 30 days 
______________________________________ 
Mixture 89% of A 
625 0 0 
+ 11% of B 
Mixture 89% of A 
1,250 0.5 0 
+ 11% of B 
Mixture 89% of A 
2,500 1 0 
+ 11% of B 
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EXAMPLE 2 
Herbicidal Treatment of Sorghum (Post-emergence Application) 
The active material (mixture A+B of Example 1) is formulated as indicated 
in Example 1. The wettable powder is diluted in water before use and the 
suspension obtained is sprayed, at the rate of 1,000 liters/ha, on sorghum 
plants (NK 121 variety) in small plots, at the six leaves stage, which are 
infested with various gramineous or dicotyledonous adventitious plants 
(panicum milliaceum, setaria sp., chenopodium sp., etc.). The dilutions 
are calculated to give the doses of active material indicated in the 
following Tables 2 and 3. 
30 days, 60 days and 90 days after the application of the suspensions, the 
herbicidal efficiency towards the adventitious plants is evaluated on the 
one hand and on the other hand the degree of phytotoxicity towards the 
cultivated plant is estimated. The herbicidal efficiency is expressed by 
the percentage of destruction of the adventitious plants, the index 0 
being assigned by convention to the untreated control and the index 100 
corresponding to a total destruction of the adventitious plants. The 
degree of phytotoxicity towards the cultivated plant is expressed by a 
value from 0 to 10, 0 corresponding to an undamaged plant and 10 to a 
destroyed plant. 
The results obtained are summarized in the following Tables 2 and 3. 
TABLE 2 
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Dose of active 
Degree of phytotoxicity 
material applied 
towards the sorghum 
Active material 
(g/ha) 30 days 60 days 
90 days 
______________________________________ 
Mixture of A + B 
1,200 0 0 0 
of Example 1 
Mixture of A + B 
2,400 1 0 0 
of Example 1 
Mixture of A + B 
3,600 1.5 0 0 
of Example 1 
______________________________________ 
TABLE 3 
______________________________________ 
Herbicidal efficiency 
Dose of active 
towards the 
material applied 
adventitious plants 
Active material 
(g/ha) 30 days 60 days 
90 days 
______________________________________ 
Mixture of A + B 
1,200 80 75 65 
of Example 1 
Mixture of A + B 
2,400 100 100 100 
of Example 1 
Mixture of A + B 
3,600 100 100 100 
of Example 1 
______________________________________ 
Other suitable herbicides belonging to the family of acetanilides which may 
be used include metolachlor.