PROTECTION OF CROPS AGAINST PARASITIC WEEDS

Parasitic plants have been the subject of intensive study over the past 20 years and there has been considerable progress in understanding their physiology and biochemistry. Progress in control methods, the main subject of this review, has been less impressive and problems from the agriculturally important parasitic weeds, especially the root parasites Striga and Orobanche species, are tending to increase. Potential control methods are reviewed under the main headings of resistant varieties, cultural and mechanical control, chemical control and biological control. Progress in resistant varieties includes the discovery of good resistance in cowpea to Striga gesnerioides and Alectra vogelii. Under cultural methods, the values of solarization for Orobanche and of mixed cropping for Striga are of particular interest. The use of glyphosate for Orobanche and Cuscuta and of dicamba and anti-transpirants for Striga are notable among developments in chemical control. In biological control there has been no major advance but perhaps some increased realization of the potential for use of fungi as myco-herbicides. Most problems require not only an integrated approach, but a sustained, long-term programme of integrated control measures.