FARMER'S NOTES
Managing fruit rot disease of areca nut
Infected palm showing characteristic symptoms of bud and crown rot diseases (Right). An affected nut with leslons.
FRUIT ROT of areca nut, caused by the fungus Phytophthora meadii, is a serious disease that could lead to great economic losses. Also known as "mahali" in Malayalam and "koleroga" in Kannada, the disease may cause fruit drop of 50 to 100 per cent in individual palms.
Scientists at the Central Plantation Crops Research Institute's (CPCRI's) Regional Station at Vittal, Karnataka, have come out with suitable package of practices to effectively manage the disease and make areca nut cultivation more remunerative to the growers.
Disease symptoms
"This disease occurs during South West monsoon. Its symptoms are invariably noticed as dark green water-soaked lesions near the perianth (calyx).
The infected fruits loose their natural green colour. The lesions on the fruits gradually spread covering the whole surface before or after shedding. The disease leads to heavy shedding of fruits,"explains Dr. N. Saraswathy, Senior Scientist at CPCRI's Regional Station at Vittal.
The infection of heartleaf results in bud rot and the outermost leaf sheath leads to crown rot. Both bud rot and crown rot are noticed during the South West monsoon season and continue in the cooler month falling in between October and February.
Favourable climate
The severity, persistence and spread of fruit rot are related to the pattern of rain. The disease appears usually 15 to 20 days after the onset of regular monsoon rains and may continue up to the end of the rainy season.
Continuous heavy rainfall coupled with low temperature (20 to 23 degree Celsius), high relative humidity and intermittent rain and sunshine hours are factors that favour the occurrence of fruit rot.
Disease spread is through heavy wind, rain splashes and flies. The fruit bunches infected towards the end of rainy season may remain mummified on the palm and such nuts provide inoculums for bud rot or crown rot or the recurrence of fruit rot in the next season, according to Dr. Saraswathy. Prophylactic spraying with one per cent Bordeaux mixture on the bunches is needed to prevent the incidence of the disease.
The initial spray is to be done immediately after the onset of monsoon showers, and the second spray after an interval of 40 to 45 days.
The spraying should be taken up when there is no rain. Care should be taken to prepare the mixture to get the right quality as other wise an acidic mixture will lead to copper injury and subsequent heavy shedding of nuts, according to the scientist.
A fine spray will be needed for effective spread of spray fluid over the surface of the nuts.
Control measures
As mechanical control measure, the areca bunches can be covered with polythene covers before the start of the heavy monsoon showers. Phyto-sanitary measures such as removal of all dried and infected bunch attached to the palm and collection and destruction of all shed nuts will prove to be rewarding.
It is essential to reduce the inoculums of the fungus and also check the incidence of other Phytophthora diseases like bud and crown rots, according to the scientist.
By Our Agriculture Correspondent
Printer friendly
page
Send this article to Friends by
E-Mail
Sci Tech
