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Diseases
Leaf rust (Hemileia vastatrix)
This is an important disease causing economic loss particularly in Arabica coffee.
On the lower surface of the infected leaves, small pale yellowish spots appear early
after the first rains in the season. These spots soon increase in size and number,
and many such spots coalesce at severity causing premature defoliation. Severe defoliation
leads to debilitation of the bushes and results in poor cropping in the succeeding
seasons.
Control
Systemic fungicides, triadimefon (Bayleton 25 WP) at 160 g/200
litre of water, Hexaconazole (Contaf 5% EC) at 400 ml per 200 litre
of water are recommended as alternatives to Bordeaux spray.
Spray susceptible coffee with 0.5% Bordeaux mixture or 0.03% ai Oxycarboxin 20 EC 3-4
times a year: Bordeaux mixture 0.5% in February-March as pre- or post-blossom spray,
Oxycarboxin 20 EC 0.03% ai in May-June as pre-monsoon spray, Oxycarboxin 20 EC 0.03% ai
or Bordeaux mixture 0.5% in July-August in mid-monsoon spray (if incidence of leaf
rust is severe), Oxycarboxin 20 EC 0.03% ai or Bordeaux mixture 0.5% in September-October
as post-monsoon spray.
Black rot (Koleroga noxia)
A disease more in occurrence in endemic areas with heavy rainfall, saturated atmosphere
with 95-100% RH, thick overhead shade, low over-hanging branches, sheltered from
sunlight and wind in valleys or continuous mist during monsoon. The affected bushes
have blackening and rotting of leaves, twigs and developing berries. There will
be defoliation and berry drop in the affected branches. The entire block affected
looks totally debilitated with heavy damage to crop.Spray Carbendazim 0.03% (Bavistin) 120 g/200
litre of water in affected areas during break in the monsoon.
Control
Centering and handling of the bushes prior to the onset of monsoon and protecting
endemic patches with spraying Bordeaux mixture 1%. If incidence is observed during
the monsoon, remove the affected twigs and burn them. Spray with Bordeaux mixture
1% during break in the monsoon.
Coffee Berry Disease
This disease is caused by the fungus Colletotrichum coffeanum and affects
green or immature coffee berries and the coffee flower at any stage in its development.
Infected berries often show dark sunken spots that spread and coalesce to cover
the whole berry. As the fungus sporulates, a pale pink crust of conidia appears
on the lesion. Depending upon the timing of the infection, the bean can also become
infected.
In some cases, a milder scab-like disease occurs.
Losses of up to 75% of a crop have been reported.
Overhead spraying of fungicides can protect the flowers and berries without necessarily
protecting the rest of the plant. Effective fungicides include benomyl, captafol,
chlorothalonil, copper formulations, dithianon, thiabendazole, and thiophanate methyl.
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