Studies on Bathycoelia thalassina (H.-S.) (Hemiptera; Pentatomidae), the cause of premature ripening of cocoa pods in Ghana

Abstract

Bathycoelia thalassina (H.-S.), of which the developmental stages and life history are described, is responsible for premature ripening of cocoa pods in Ghana. Experiments conducted at Tafo to determine the nature of the damage to pods showed that the insect feeds directly on the beans, and that beans so attacked turn brown and subsequently die: only the empty shell of the bean remains.The saliva of the insect kills any tissue of the pod that it penetrates and within four days the injured areas cease to grow and become yellow, then brown, and finally black.The symptom most characteristic of damage is the change in colour. The pod may become completely yellow, or yellow in the basal or distal half only (usually the latter) or yellow in spots, depending on the size of the pod, the site of attack, and the duration of feeding at each site.The insect usually attacks pods of the Amazon varieties, 10–17 cm. long. The incision made by the stylets is microscopic, and is covered by a jelly-like substance, and no evident lesions develop on the surface as in damage caused by cocoa mirids or coreids.Damage caused by B. thalassina on young pods resembles cherelle wilt of physiological origin, and the two can be distinguished only by slicing the pods, whereupon the former can be recognised by the presence of injured beans.According to the survey of damage caused by B. thalassina in Ghana, this species seems to be an economic pest on some Amazon and hybrid types of cocoa, whereas Amelonado cocoa usually suffers little.