Studies of cocoa tree genetic resistance to attack by Scihlbergella singularis (Haglund.) (Hemiptera: Miridae), have so far been based on field observations of cultivar performance. Although this approach was useful in guiding breeding programmes, observations on tree crops are time-consuming (3–4 years) and labour-intensive. Thus a standard laboratory microassay method based on a study of the mirids’ dietary preferences was developed to quantify the attractiveness of cocoa trees to mirids under controlled conditions, with reproducible results.

A dual approach was taken to establish relations between laboratory data and field observations: preliminary cultivar sorting of both clones and hybrids in the laboratory, by microassays was combined with an eight-year observation programme in two different ecological zones in Ivory Coast: on the shores of a lagoon (Bingerville) and under thinned forest in Basse Côte (Divo). In Cameroun only clones from IRA field station at Nkoemvone were tested by microassays.

After three successive sets of field observations, a comparative analysis of the results revealed close correlations between cultivar responses in microassays and those observed in the field.

Cultivar responses to mirids revealed that there are two performance groups within the planting material selected, viz., in increasing order of attractiveness, Forasteros (upper and lower Amazon cultivars) and Trinitarios.

In Cameroon, microassays revealed behavioural polymorphism amongst the cultivars tested: plants of the same origin can react very differently to mirids as it was the case for the local trinitarios SNK group.

The microassay technique is quick and easy to use, and is effective for the early selection of mirid-tolerant plant material.