Solar heating of the soil for the control of pink root and other soilborne diseases in onions

The effectiveness of solar heating of the soil by means of mulching with transparent polyethylene, against soilborne pathogens of onions, was tested in two field experiments: at Yotvata (hot region) and at Gefen (cooler one). In both experiments, solar heating significantly reduced the incidence and severity of the pink root disease caused by Pyrenochaeta terrestris by 73-100% during the 6-7 months of plant growth. Rhizoctonia solani, Fusarium infection, and weed populations (except for Melilotus) were also considerably reduced by this treatment. In addition, stand and plant growth were improved and yields were increased by 109-125% at Yotvata and by 59-62% at Gefen, as compared with the untreated control. Similar results were obtained when soil was moistened by sprinkler irrigation before applying the mulch or by sprinkler irrigation supplemented by drip irrigation under the mulch. Pentachloronitrobenzene did not control pink root disease.