Ethephon (ethrel) sprayed once on to pineapple inflorescences at the onset of flowering, at rates of 400, 800 and 1200 ppm, suppressed anthesis, with the highest suppression from the latter concentration. Suppression was associated with failure of flowers to open; where flowers did open they were usually short, shrivelled and devoid of nectar. One application was sufficient to affect anthesis for the following 16 days. Ethephon-treated plots had a significantly lower incidence of ‘fruit collapse’ (a disease caused by Erwinia chrysanthemi entering via the open flowers). Highest control (2·3% incidence) was achieved with ethephon at 1200 ppm compared with 7·0% in the control (P < 0·01). A highly significant correlation was established between disease incidence and the mean number of open flowers.