Pest and Diseases

Yields can be halved due to pests, disease and weed competition. Diseases are the greatest threat – most common are black pod and witches’ broom. Black Pod also known as Pod Rot – due to the fungus Phytophthora spp – causes global yield loss of 20-30% and annual tree deaths of 10%. Infected pods develop a brown patch which spreads over the pods and cankers spread to trees that have no genetic resistance to the disease. 

Witches’ Broom caused by the fungi Marasmius and Moniliophthora perniciosa has in the past devastated production throughout all of South America, Panama and the Caribbean. The main symptoms are thick ‘brooms’ – lateral shoots - which grow from infected buds leading to malformed pods which usually die young.

Resistant new varieties are the key to long term sustainability against these diseases, but fungicide use also helps minimize disease loss, particularly when used alongside appropriate fertilizer programmes.

Swollen shoot is a viral disease spread by insects which is increasing in West Africa and causing significant production losses. In young trees, shoots are noticeably swollen and in older trees the swelling prevents the movement of water and nutrients leading to leaf loss.

While the current recommendation is to remove and burn infected trees, there are indications from CIRAD research in Ghana and Ivory Coast that YaraLiva Nitrabor can reduce the impact of swollen shoot disease. Vascular Streak Dieback (VSD) is a major fungal problem in Indonesia. Currently, control is to cut the infected branch 30cm below the last visibly infected tissue and then fertilize to encourage new growth.

In young plants, balanced nutrition and an adequate supply of potassium and boron in particular, have been shown to increase cocoa resistance to VSD.