Resistance of Theobroma cacao to Sahlbergella spp. on the Gold Coast

Extract

The damage done to cacao (Theobroma) in West Africa by certain species of Capsidae has been described by Dudgeon (1910), Cotterell (1926) and Voelcker and West (1940). At the start of a selection programme aimed at developing strains of cacao resistant or tolerant to such damage, it was considered necessary to develop a laboratory technique for testing the palatability of selections. It is noticeable in the field that certain trees appear consistently to escape attack ; this might be due to some form of unattractiveness to the Capsids. One of the most obvious forms of preference which seems to be shown by these bugs is that of Sahlbergella theobroma for seedlings and young trees up to about six years old and that of S. singularis for mature trees. Indeed until very recently there was no field record of S. singularis attacking seedlings in the Gold Coast. Conversely, attacks by S. theobroma on mature trees are confined almost entirely to pods, while the other species causes severe damage to shoots. Dudgeon (loc. cit.) reports old trees “ exhibiting damaged bark and dead branches ” in the presence of S. theobroma, but these may have been feeding on pods.