2-(poly-substituted aryl)-6-amino-5-halo-4-pyrimidinecarboxylic acids and their use as herbicides

A method of selectively controlling undesirable vegetation in rice which comprises contacting the undesirable vegetation or locus thereof with or applying to the soil to prevent the emergence of undesirable vegetation an herbicidally effective amount of a compound of formula I

• wherein
• Q represents a halogen;
• R1 and R2 independently represent H, C1-C6 alkyl, C3-C6 alkenyl, C3-C6 alkynyl, hydroxy, C1-C6 alkoxy, amino, C1-C6 acyl, C1-C6 carboalkoxy, C1-C6 alkylcarbamyl, C1-C6 alkylsulfonyl, C1-C6 trialkylsilyl or C1-C6 dialkyl phosphonyl or R1 and R2 taken together with N represent a 5- or 6-membered saturated ring;
• and
• X represents halogen, C1-C4 alkyl, C1-C4 haloalkyl, C1-C4 alkoxy, C1-C4 haloalkoxy, C1-C4 alkylthio, C1-C4 haloalkylthio or —NR3R4;
• R3 and R4 independently represent H or C1-C4 alkyl;
• and
• agriculturally acceptable derivatives of the carboxylic acid.