SYNERGISTIC HERBICIDAL COMPOSITION CONTAINING A SUBSTITUTED PHENOXY ALKANOIC ACID DERIVATIVE AND A GLYPHOSATE DERIVATIVE

1 . An herbicidal mixture comprising an herbicidally effective amount of (a) a substituted phenoxy alkanoic acid derivative of the formula

wherein

X represents C 1 or CH 3 ;

R independently represents H or CH 3 ; and

n is an integer from 1-3;

and (b) a glyphosate derivative.

2 . The herbicidal mixture of claim 1 in which the substituted phenoxy alkanoic acid derivative is a 2,4-D or dichlorprop derivative.

3 . The mixture of claim 2 in which the 2,4-D or dichlorprop derivative is a 2,4-D salt.

4 . The mixture of claim 3 in which the 2,4-D salt is the 2,4-D dimethylamine salt.

5 . The mixture of claim 2 in which the 2,4-D or dichlorprop derivative is a dichlorprop salt.

6 . The mixture of claim 5 in which the dichlorprop salt is the dichlorprop potassium salt.

7 . The mixture of claim 1 in which the glyphosate derivative is a glyphosate salt.

8 . The mixture of claim 7 in which the glyphosate salt is the glyphosate isopropylamine salt.

9 . The mixture of claim 1 in which the weight ratio on an acid equivalent basis of the substituted phenoxy alkanoic acid derivative component to the glyphosate component is between about 5:1 and about 1:48.

10 . The mixture of claim 2 in which the weight ratio on an acid equivalent basis of the 2,4-D or dichlorprop component to the glyphosate component is between about 3:1 and about 1:12.

11 . An herbicidal composition comprising an herbicidally effective amount of the herbicidal mixture of claim 1 and an agriculturally acceptable adjuvant or carrier.

12 . A method of controlling undesirable vegetation which comprises contacting the vegetation or the locus thereof with or applying to the soil to prevent the emergence of vegetation an herbicidally effective amount the herbicidal mixture of claim 1 .

13 . The method of claim 12 in which the undesirable vegetation is glyphosate-resistant horseweed.