zondag 23 oktober 2011

Cacao Diseases in Central America 2

The Tropical Agricultural Research and Higher Education Center (CATIE) is a regional center dedicated to research and graduate education in agriculture and the management, conservation and sustainable use of natural resources.
Its members include the Inter-American Institute for Cooperation on Agriculture (IICA), Belize, Bolivia, Colombia, Costa Rica, the Dominican Republic, El Salvador, Guatemala, Honduras, Mexico, Nicaragua, Panama, Paraguay, Venezuela and Spain.

Source:  Tropical Agricultural Research and Higher Education Center, CATIE, 2009.

Black pod or phytophthora

Caused by Phytophthora palmivora and also by P. capcisi in some countries of the region
This disease attacks several parts of the plant (see the following section) but the most severe damage occurs on the fruits, particularly on those that are nearly ripe. It produces a brown spot with a regular edge that spreads rapidly, covering the entire fruit within a few days. Internally it causes a brown rot.

How do we recognize the disease?
Brown spots usually begin to appear at the end of the fruit
The spot covers the fruit within a few days
Mycelia fungi form on the spots
Internal rotting partially or completely damages the seeds
Phytophthora palmivora: Brazil

How does the organism reproduce?
Minuscule interlaced threads appear on the brown spots, in the form of a initially sparce white mycelium.
This produces the spores and other reproductive structures that act like the seeds of the organism.

How does the disease spread?
The most common route of infection is via spores that have the capacity to swim; these become active in very humid conditions and when a period of low temperature alternates with a warm period.
The spores are transported by splashing rain, water currents,
wind, ants, etc.
Direct contact between diseased and healthy fruits is another major source of infection.

The appearance of mycelia is the most contagious stage of black fruit and
we must avoid it by eliminating diseased fruits before they produce spores!

Phytophthora blight of papaya caused by Phytophthora palmivora.
Live cycle of moniliasis / black pod
Learning about the life cycle of the organisms that cause these diseases will help us to better understand when and how to control them. The duration of the life cycle depends on the cacao variety and environmental conditions: it is shorter in warm, moist climates and longer in cooler climates.

Life cycle of moniliasis (about 85 days)
1/ Young fruits are infected
2/ 30 days later the first symptoms appear
3/ 20-50 days later the brown spots appear and develop
4/ 8-12 days later, the mycelia appear and produce the first spores
5/ The spores are produced for up to seven months and are dispersed by wind, rain or animals

Life cycle of black pod (11 days)
1/ Fruits of different ages become infected
2/ Five days later, brown spots appear and develop
3/ After three days, brown spots cover the entire fruit
4/ After three days, mycelia cover the entire fruit
5/ Water, ants and other insects disperse the spores

next time:  Recommended practices for controlling cacao fruit diseases