Changes in crop canopy architecture on the incidence of major foliar diseases of betelvine (Piper betle L.)

Betelvine (Piper betle L.) is a perennial dioecious creeper-belonging to the family Piperaceae usually grown under artificially erected structurals known as baroj that provides high moist and humid conditions favouring several diseases that in turn are major deterrents to good harvest. Betelvine suffers from many root and aerial diseases of which leaf rot caused by Phytophthora parasitica (Dastur) and leaf spot caused by Colletotrichum capsici Syd. (Butler and Bisby) are most important and are included in these studies for assessment. The extent of losses may vary from 20-40% for leaf rot and 10-20% for leaf spot, leading to almost total crop failure (Dasgupta and Sen, 1999). As the betel leaf is directly chewed immediately after harvest, it is not feasible to apply any pesticides that may cause toxic hazards to human being. An experiment was conducted for two consecutive years to study the effect of different crop canopy by maintaining three different plant to plant spacing (viz., 11.1, 9.53 and 8.3 cm.) on leaf yield, disease incidence and keeping quality (days to 50% rotting) of betelvine. With the above plant to plant spacing and standard row to row spacing (60cm), the plant population was maintained as 1.50, 1.75 and 2.00 lakh ha-1. The results revealed that when crop canopy was increased by reducing the plant to plant spacing from 11.1 cm to 8.3 cm there were significant increases in both the diseases under investigation (rot disease 19.76 to 22.30%; leaf spot disease 22.68 to 25.42%). Significant increase in yield (26.29 to 33.63 lakh ha-1year -1), decrease in fresh weight of 100 leaves (460.85 to 432.35g) and decrease in keeping quality of leaves (13.14 days to 10.28 days) were recorded when crop canopy was increased by reduction in plant to plant spacing from 11.1 cm to 8.3 cm. From these results it can be concluded that shifts in microclimate resulting from increase in canopy by reducing the plant spacing aggravated the spread and infection of disease.