Effect of Tree Size, Topography and Shoot age on Pest Infestation and Tree Growth of Palas (Butea monosperma)

Abstract

A bench mark survey was conducted in March, 2017 to generate information about health status of palas trees (Butea monosperma), the most important host tree of rangeeni lac insect (Kerria lacca Kerr.). The principal objective of the study was to identify factors responsible for poor growth of this important tree. Infestation of termite and trunk borer is perennial problem for palas trees. Therefore, information was generated under three different conditions (i) tree size i.e. small and big (mean trunk girth 74.3 cm and 151 cm) (ii) land topography i.e. upland/ lowland and (iii) tree with old/ new shoots i.e. trees having shoots of > 2 year or one year old. Land topography was found to have effect on termite infestation. In upland condition, termite galleries covered 50 per cent of the tree length, while the same value was merely 5.8 per cent in case of lowland. Smaller trees were 43 per cent less infested in comparison to big ones. Similarly, upland trees were 2.5 times more infested than lowland. Number of live shoot and additive shoot diameter per prune point were also found to be higher in case of relatively smaller trees. Number of live shoot per prune point was recorded to be 3.6 and 3.1 in small and big sized trees, respectively and additive live shoot diameter was 52.4 and 43.2 mm per prune point on small and big trees. But, in contrast, average number of dead shoots were found higher in big sized trees. Only variation was observed in case of trees with old and new shoots, where 19.2 per cent increase in average diameter was observed in newly emerged shoots i.e. pruned one year back. Better performance of smaller sized trees in terms of growth and pest resistance could be attributed to better rejuvenation power and vitality for being younger in age. Similarly, higher attack of pest in upland soils could be attributed to maintenance of poor health on relatively less fertile uplands.