Control of crown rot of banana using Carica papaya latex

Abstract

Crown rot, incited by a complex of fungi, is a major cause of postharvest losses in banana. Fusarium semitectum, Colletotrichum musae and C. gloeosporioides were identified as the major crown rot causing fungi in Sri Lanka. In addition Verticillium theobromae and Botryodiplodia theobromae are also associated with the disease. Conidia of major crown rot pathogens, when exposed to the water soluble fraction (WSF) of Carica papaya (papaya) latex underwent complete digestion. A 50% preparation of WSF digested a dense suspension of C. gloeosporioides conidia within 1 minute. Application of the WSF of papaya latex onto the cut surface of banana crown pre-inoculated with F. semitectum, C. musae and C. gloeosporioides prevented the development of crown rot. The activity of enzymes in the WSF of latex, particularly the chitinase, could be implicated to the conidia digestion process. The latex is more effective when applied at least 60 minutes after dehanding, allowing sufficient time for crown exudates to dry out. This appears to be due to the coagulation of proteins in papaya latex in the presence of watery exudate of the freshly exposed banana crown. The latex treatment also hardened and induced a black colouration in the exposed crown surface forming a physical barrier to invading pathogens.