Eco-friendly management of Phytophthora root rot and gummosis in mandarin

The oomycete Phytophthora nicotianae causes root rot, foot rot, crown rot, and gummosis in the mandarin crop throughout India. Most mandarin root stocks grown in country is susceptible, or at best moderately susceptible, and necessitates frequent fungicide applications to avoid heavy yield losses. Four years of field trials in three different locations (Akola, Ludhaina and Tinsukia) investigated the effect of different conventional and one non-conventional chemical integration with bio-agents on Phytophthora root rot and gummosis. The foliar spraying of potassium phosphonate (potassium salt of phosphonic acid) at 3 g/liter water was superior in terms of average reduction in lesion oozing (51.54%), minimum feeder root rot index (1.07), increase in canopy volume (7.93%), and higher fruit yield (17.84 t/ha). Potassium phosphonate is known to induce defense responses in mandarin as well as to have direct toxic effects on oomycetes, which in turn inhibits the development of root rot and gummosis. The use of potassium phosphonate in mandarin crops has been promoted as a feasible method as part of the integrated disease management strategy for Phytophthora root rot and gummosis management.