Guava Wilts a Multidimensional Malady: Role of Guava Stem Borer and Concomitant Fungi in Effecting the Pathogenic Process in India

Study involving surveys undertaken in guava cultivation belt of Uttar Pradesh comprising of Allahabad-Varanasi, Unnao- Kanpur in Eastern and Central region respectively as well as Badaun and Farrukhabad in Western region of the state indicate that the guava orchards in the former two regions are mainly afflicted by stem borer, Bactocera rufomaculata and bark eating caterpillar, Indarbela quandrinotata which seem to pave the way to infection of Fusarium oxysporum f. sp. psidii. Stem borer affected guava plants consistently yielded the colonies of Fusarium oxysporum f sp psidii from live worm, wood scrapings from the borer infested hole and soil/roots of guava orchards in Badaun and Farrukabad exhibited the fungal induced typical wilt. Analysis of the fungal distribution on dried/healthy branches from different set of plants comprising of healthy, 30%, 90% and 100% wilt revealed the prevalence of Fusarium oxysporum f. sp. psidii, in the lower/middle portions whereas Botrydiplodia theobromae and Pestalotiopsis psidii in peripheral branches. A positive correlation was noticed between of Fusarium oxysporum f. sp. psidii, in plants exhibiting 30% wilt as compared to negative correlation between B. theobromae and wilt (30%). However, in the plants displaying 100% wilt, role of B.theobromae and Pestalotiopsis psidii was more pronounced as compared to F. oxysporum f. sp. psidii. Our study sheds the light on varying degree of contribution made by the insects and fungi in effecting the wilt disease witnessed in guava and flagged the crucial issue that fungal centric approach has miserably led the failure of durable and reproducible management schedule(s) developed so far in different guava cultivation pocket(s) of the country.

Author(s): Rashid M Khan, Achal Singh and Om Prakash

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