Occurrence, severity and association of fungal pathogen, Botrydiplodia theobromae with sudden death or decline of tree bean (Parkia timoriana, (DC.) Merr) in North Eastern India

Abstract

Tree bean, Parkia timoriana is one of the most important perennial tree legume vegetable crops in north eastern region (NER) of India. Recently, sudden death or decline is emerging as a major constraint in the production of tree bean. The prevalence, intensity and etiology of this disease have not been extensively studied. The present work was aimed at studying the symptomology, severity and etiology of sudden death or decline of tree bean in the north eastern region of India. Typical symptoms of tree bean decline were initiated with wilting of half portion of the tree, excessive shedding of leaves, gradual drying up leading to death, and secondary infestation by insects on dead trees. The highest disease severity of 68.5% was observed in warmer regions like Kolasib, Mizoram. During survey, small bark borer was recorded in all districts and levels of infestation rate (holes/ft2 of log) reached maximum up to 25.49 in Hnanthial of Lunglei district. Young trees in the range 1–10 years with 57.32% (917 trees) of total trees (1600) infected were most susceptible to the disease compared to 12.58% (201 trees) infection in old trees in the range 21–30 years. The frequently associated pathogen with sudden death or decline of tree bean was identified as Botrydiplodia theobromae at the Indian Type Culture Collection, ICAR-IARI, New Delhi. It was the most aggressive species and proven to be pathogenic to tree bean following artificial inoculation.