Solarization as a method for producing fungal-free container soil and controlling wilt and root-rot diseases on cucumber plants under greenhouse conditions

Abstract

The effect of solar heating on mulched or un-mulched soil on Fusarium wilt or Rhizoctonia root-rot diseases under greenhouse conditions was studied. Isolation and pathogencity tests proved that the most pathogenic fungi of wilt and root-rot were Fusarium oxysporium f.sp. cucumerinmum (isolate No 2) and R. solani (isolate No. 2), respectively. It caused wilt and root-rot diseases by 26.4, 67.7% and 41.0 and 71.0% at pre- and post-emergence stages of cucumber, respectively. Nylon bags containing soil artificially infested with the inoculum of F. oxysporium f.sp. cucumerinum or Rhizoctoia solani were buried 10–20 cm below the soil surface in either mulched or un-mulched soil for 4, 6, or 8 weeks and were evaluated for mulching effects on reduction of fungal population density and disease incidence. Results indicated that the reduction of fungal population increases as the period of soil mulching was prolonged. The large reduction in F. oxysporium f.sp. cucumerinum and R. solani population (99%) was obtained in soil mulching for eight weeks and decreased gradually to reach its minimum (55%) after four weeks of mulching soil. Cucumber plants were transplanted in pots containing previously buried soil under mulching or un-mulching conditions. The effectiveness of soil solarization on wilt or root-rot incidence of cucumber was evaluated under greenhouse conditions. The highest reduction in Fusarium wilt or Rhizoctonia root-rot was obtained in mulched soil for eight weeks. It reduced the pre- and post-emergence more than 88.5 and 95.2%, respectively, compared with untreated control. On the other hand, un-mulched soil reduced the wilt or root-rot diseases by more than 46.2 and 49.1% for pre- and post-emergence, respectively. The results obtained indicate that the fungus remained active for four weeks in un-mulched soil. It could be suggested that soil-solarization for eight weeks proved highly efficacious for reducing wilt and root-rot pathogens of cucumber plants, and might be considered as applicable treatment for controlling such soil-borne plant pathogens.