Studies on Bioligy and Control of Eupatorium Odoratum Linn

Abstract

Attached

E.Odoratum which is one of the most important weeds in the wet low country areas offers serious competition to coconut palms. Its characteristics have been studied in relation to its importance as a weed. The change in the population density of the weed under coconut cultivation, the reproductive capacity of the plant and viability of the seed under various environmental conditions have been studied, as they form the principle medium of distribution. The cardinal temperatures for germination of E. odoratum seed in the presence of light, air and 70%-80% MHC are 18 ̊ c minimum, 28 ̊ c ± 2 ̊ optimum and 36 ̊ c maximum. The weed can be controlled by uprooting at intervals of 5 months. The nutrient content and C/N ratio at the time of flowering and its importance as a green manure have also been discussed. Attempts to develop a method of biological control of the weed with the aid of pests or fungal diseases proved unsuccessful. Contact, pre emergence and systemic herbicides were tested for control of E. odoratum and it was found that effective control could be achieved by spraying a mixture of 2,4-D and 2,4,5-T to the regenerated growth after slashing, at the rate of 2 pints in 40 - 60 gallons of water per acre. The cost of this treatment has been compared with that of manual weeding. It should be noted however that the mixture at this concentration is harmful to coconut seedlings and young nuts, if the spray comes into direct contact with the palm. The weeds that grow in succession when E. odoratum is controlled has been studied, and their significance discussed.