Defoliation and Die-back an Emerging Threat to Cashew Cultivation in the Konkan Region of Maharashtra, India

Abstract

Cashew is a million-dollar crop, and it is the second most important cash crop in the Konkan region of Maharashtra after mango. Till 2019, the cashew plantations in the Konkan region were free from destructive diseases leading to economic losses. But in July and August 2019, the total monthly rainfall was 1711 and 1312 mm respectively, supported by cloudy weather and high humidity above 93% which led to the sudden outbreak of defoliation followed by dieback of the new vegetative flush of the plants, throughout the region. To combat this unexpected natural calamity thorough investigations were conducted. Extensive surveys conducted during the season revealed that in the primary phase of the disease, new as well as old cashew plants suffered from severe defoliation. On the establishment of the pathogen, the infection progressed to the newly emerged main and lateral branches which consequently lost vigour, turned brown, and then black. The colonization of pathogens within the tissues of the host leads to the formation of small white encrustations on the upper surface of the dead twigs. The pathogen was isolated and identified as Cylindrocladium spp.