Recognize the problem
small black water-soaked spots on mango fruits and leaves can be caused by bacteria.
This is the so-called bacterial black spot disease. Spots appear on the
leaves, stems and fruits. On the leaves the spots are black and water-soaked.
They tend to be angular because they are restrained by the veins. Note, that
larger flat and black patches on leaves are usually non-problematic leaf
surface fungi and not bacteria. Bacteria-infected branches look black and
cracked. The infected fruits develop black dirty spots mostly with star
shaped cracks within them.
bacteria hide in stem wounds, on seedlings and on the shoot which acts as a
store tank from which the disease can move to leaves and fruits. The bacterium
is not easily spread. Therefore, it is important to use clean healthy
planting material. However, the bacteria might be spread by rain or pruning
are no curative chemicals available to control this disease. Copper-based
products of different types can partly protect uninfected trees from infection.
There are copper-oxychlorides, copper-hydroxides or copper-sulphates. Such
chemicals are toxic to you (WHO toxicity class II, moderately hazardous), and
are very toxic to aquatic organisms, so don’t spray near water sources. When
used too much in orchards, copper can accumulate in soil and water. It can
burn leaves. Therefore, never spray more than 6 kg copper per hectare per season!
Prune off diseased twigs
and destroy. But sterilize harvesting and pruning tools regularly during use.
Otherwise, you spread the disease.
- Spray copper oxychloride –based
products when the disease is first observed in your area, and has not yet
infected your trees. Such products can partly prevent disease spread, but
cannot cure it.
not spray during fruit set.
not enter the orchard until 1 day after spray. The pre-harvest interval is at
least 7 days.
- Also consider preventively spraying copper
after harvest flush and after the end of the rainy season to reduce disease
attack in the next season.
When using a pesticide, always wear protective clothing and follow the instructions on the product label, such as dosage, timing of application, and pre-harvest interval.