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Resistance of cashew (Anacardium occidentale) genotypes to powdery mildew (Oidium anacardii) was assessed on detached leaves, seedlings and flower panicles. Leaves were more susceptible before the development of a waxy cuticle, which confers a dull appearance. Differences in susceptibility/resistance were observed on detached leaves inoculated in the laboratory. Some genotypes supported dense growth of mildew, whereas on others only slight infection was observed under comparable conditions. Mature leaves were immune to colonization. In the field the rate of mildew infection, as estimated from disease progress curves on both seedlings and flower panicles, varied significantly between genotypes allowing their categorization into susceptible and partially resistant clones. A similar rank order for degree of susceptibility/resistance was determined from studies on detached leaves, seedlings and flower panicles. Brazilian introductions of A. occidentale and the AZA2 and AC6 genotypes proved to be partially resistant, while AM6, ATA19 and AIN62 were highly susceptible. The relationship between leaf and flower mildew infection showed positive and highly significant correlations. It is concluded that each of the three approaches to the assessment of disease susceptibility can be used to screen genotypes against mildew attack. Screening in the laboratory provides a rapid indication of potential resistance providing that leaves are compared at the same stages of maturity.

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Cropping and disease patterns were observed over a period of 4 years in individual cocoa trees at three contrasting sites near Quevedo, Ecuador, with the aim of evaluating the importance of dry season production and the consequent avoidance of pod disease caused by Crinipellis perniciosa and Moniliophthora roreri. Distinction of the diseases on necrotic pods was aided by splitting open pods after removal from the tree. The year was divided into wet season (April to September) and dry season (October to March) harvest periods. The 3‐month lag between the actual wet and dry seasons and these harvest periods allowed time for symptom development. Combined disease losses ranged from 19·0% to 62·1 % at the various sites. At all sites and in each year, more ripe healthy pods were harvested in the dry season harvest period than in the wet season harvest period. In general, pod losses caused by C, perniciosa were curtailed more sharply by the dry season than those caused by M. roreri, which at one site caused as much damage in the dry season as in the wet season. The proportion of the annual production falling in the dry season harvest period varied among sites and between years at a given site. A comparison of trees from two progenies growing side by side showed consistent differences in cropping patterns, and identified certain trees that were productive, yielded consistently in the dry season harvest period, and were little affected by M, roreri. Analysis of long‐term rainfall data for the Quevedo region indicated that years which lack a normal dry season do occur, but only once every 10 years on average. Further exploitation of disease escape through selection and breeding appears to be both feasible and appropriate.