Diseases, parasitic plants and weeds of cultivated rice in West Africa.
AbstractIn case of a serious attack by Sclerotium oryzae[Magnaporthe salvinii] Catt. it is advisable to burn all the haulms affected, to cultivate the soil and to maintain sufficient moisture in order to facilitate the destructive action of the soil micro-organisms. On rice fields under cultivation for many years and which are now approaching exhaustion, the disease caused by Helminthosporium oryzae[Cochliobolus miyabeanus] is more serious: haulms and other crop residue should be burnt, a potassium fertilizer applied (an excess of nitrogen is dangerous), all infected parts left fallow or under pasture, and possibly the seeds disinfected. Several diseases of the ear and of the grain are indicated.
A number of species of Striga and Rhamphicarpa fistulosa are parasites of rice. The diffusion of these parasites takes place in conditions of deficiency in the crops, and methods for their control are the following: (a) to interrupt the cultural succession; (b) to maintain a cultivated fallow with manioc; (c) to grow for one year Cassia occidentalis L. ; (d) to leave the plots under pasture or to supply manure. Among the numerous weeds is Oryza barthii, a plant of the natural rice field which invades the cultivated fields. Oryza breviligulata (sego) has a similar action. Other weeds belonging to the Gramineae are: Digitana horizontalis, Saccolepis interrupta, Panicum laetum, Echinochloa stagnina, E. pyramidalis, and, among other families, Cyperus sp., Scirpius sp. Hibiscus asper, Octodon filifolium, ipomoea repens. For weeds, other than Gramineae, treatment with a hormonic herbicide, such as 2, 4-D at the start of vegetation (before the rice fields are submerged), is advised.-E.B.