Control of wild rice in rice

The four main wild rice species are: Oryza rufipogon Griff, embracing a wide range of “red rice” types closely related to O. sativa L.; O. longistaminata Chev. & Roehr, a rhizomatous perennial; O. barthii Chev. the annual wild rice of West Africa; and O. punctata Kotschy ex Steud, a small seeded annual. The distribution and importance of these species are discussed in relation to the different systems of rice growing. Annual wild rice problems are favoured by dry sowing followed by flooding. For cultural control, soil puddling and direct sowing into water are recommended. In a series of pot experiments with O. punctata and rice, 18 herbicides were shown to be at least partially selective, including: alachlor, butachlor, S‐4‐chlorobenzyl diethyldithiocarbamate (B‐3015), 4‐(2,6‐dichlorobenzyloxymethyl)‐4‐ethyl‐2,2‐dimethyl‐1,3‐dioxolan (WL 29226), 3‐(α α‐dimethylbenzyl)‐1‐methyl‐1‐phenylurea (K 1441), isoproturon, metamitron, molinate and perfluidone. B‐3015 was the most selective of these but the selectivity of alachlor and molinate could be greatly increased and became comparable to B‐3015 when the crop seed was dressed with the protectant 1,8‐naphthalic anhydride (NA). Other herbicides for which NA provided a protective effect were: butachlor, metolachlor (CGA 24705), epronaz, ethofumesate, perfluidone and 4,4,4‐trichloro‐2‐phenylbut‐1‐ene (Dowco 221).