Biological control of Phytophthora root-rot of coorg mandarin (Citrus reticulata) by Trichoderma species grown on coffee waste

A study was conducted during 1989-1992 to find out the potential of biological control of root-rot of  coorg mandarin (Citrus reticulata Blanco) caused by Phytophthora nicotianae Breda de Haan var parasitica (Dastur) Waterhouse and P. colocasiae Racib. Trichoderma harzianum Rifai,  virde Pers. ex S F Gray and Gliocladium virens Miller, Giddens & Foster, were found widely distributed in Citrus orchards, with population of 200-2000 colony-forming units/g soil. Seventeen isolates were found highly antagonistic to both Phyphthora spp under in-vitro condition. For large-scale multiplication of these fungi, local waste (coffee-cherry husk, fruit skin and berry mucilage; poultry manure and mushroom-grown waste) was found suitable, giving 20-30 million colony-forming units/g substrate. Pot trials amended with coffee-cherry husk and poultry manure in 1 : 2 decreased feeder root-rot and increased the growth of coorg mandarin seedlings. It was on a par with best fungicide treatments like Akomin 0.3%, metalaxyl + mancozeb (Ridomil MZ) (0.25%) spray, or drenching of chlorothalonil (0.2%). Isolates E, T3, 3HR and D of T. harzianum and isolate B of T viride grown on cofee-cherry husk decreased the feeder root-rot and increased the plant growth when applied @ 1 % inoculum in soil. Thus native Trichoderma spp can be multiplied on large scale on easily available coffee waste and applied in the root zone of coorg mandarin plants either alone or with fungicide sprays tor effective management of root-rot.