Abstract:
From a detailed survey on the occurrence of leaf blight
disease of coconut in Thiruvananthapuram (Coconut Research
Station, Balaramapuram and Instructional Farm, Vellayani) and
Alappuzha Districts (Rice Research Station, Kayarnkulam) it was
revealed that Pestalotiopsis palmarum (Cooke) Stey was the
major pathogen causing grey leaf blight of coconut in both the
areas. Curvularia sp. were also found to be contribute to this
disease. Of the various media tested, best growth of P. palmarum
was seen in potato dextrose agar and broth. Among the various
carbon sources tested dextrose, starch and inositol were equally
effective for the growth of P. palmarum and for Curvularia sp.,
Sucrose, dextrose and starch were the best carbon sources.
A temperature of 25°C and 35°C was found to be optimum
for the growth of P. palmarum and Curvularia sp respectively.
Arecanut, cinnamon, clove, guava, mango, nutmeg and sapota
intercropped with coconut in the three locations were found to be
host of the pathogen P. palmarum. In vitro evaluation of
fungicides revealed that Bordeaux mixture (1000 ppm) and Bavistin
(2000 ppm) were superior in inhibiting the growth of P. palmarum
on the other hand Bordeaux mixture (1000 ppm) and Dithane M-45
(1000 ppm) effectively inhibited the growth of Curvularia sp.
Monitoring of the disease intensity over a period of 12
months has shown that grey leaf blight intensity was high in
palms planted at closer spacing and which received no
fertilizers. The disease intensity was minimum in palms with
wider spacing and with higher level of fertiliser (N2P2K2). In
general higher level of fertilizers and wider spacing may be
considered as a management practice for controlling the incidence
and intensity of the grey blight diseases in coconut palm in
South Kerala.
