Management of dry root rot disease of mandarin (Citrus reticulate Blanco) through biocomposted agricultural wastes

Abstract

The effects of soil drenching with biocomposted agricultural wastes (BCAW) , Trichoderma harzianum (spore suspension 5x10 6 cfu/ml ) and Topsin-M 70% were evaluated for controlling dry root rot caused by Fusarium solani of mandarin (Citrus reticulate Blanco) under green house and field conditions. Manipulation of soil with biocompost (composted of sugarcane bagasse, rice straw and soybean straw inoculated with spore suspension 5x10 6 cfu/ml of T. harzianum isolate NB10) , T. harzianum (spore suspension 5x10 6 cfu / ml ) and Topsin M 70% successfully controlled F. solani the main pathogen of dry root rot disease on mandarin. Complete reduction of the F. solani linear growth was recorded at 100 ppm of Topsin M and T. harzianum . In greenhouse, the highest reduction in Fusarium dry root rot disease on mandarin seedlings was obtained with biocompost (BCAW) at 10% (w/w) and Topsin-M (1 g/L) . Moreover, such treatments caused highest reduction in population density of Fusarium solani in rhizosphere soil of treated seedlings , but Trichoderma population were highly increased. Under Field condition which were amended soil around stems of diseased mandarin trees by biocompost (BCAW) and Topsin-M (1 g/L) treatments as twice applications per season resulted in recovering great number of diseased trees and decreased the disease severity on others. Population density of Fusarium spp. were highly decreased, where population density of Trichoderma spp were increased in rhizosphere soil of treated trees by biocompost (BCAW) . The highest increased in fruit yield was recorded on mandarin trees treated with bio-compost and Topsin M treatments as twice soil applications. It could be suggested that using soil amendments by biocompost (composed agricultural wastes colonized by T. harzianum ) alone or in combined with a reduced rates of Topsin M 70 % (fungicide) can be successfully used to replace traditional fungicides and avoid environmental pollution