Reducing postharvest decay in cactus pears by dip treatment with imazalil or azoxystrobin

Abstract

Postharvest decay in cactus pear is a minor problem in fruit marketed directly after harvest, while it may represent a major cause of losses when fruit are cold stored or subjected to cold quarantine treatments. Unfortunately, to date, no postharvest fungicide has been registered to control postharvest decay of cactus pears. Thus, the objective of this study was to evaluate the efficacy of two globally known fungicides, imazalil (IMZ) and azoxystrobin (AZO), registered for postharvest treatment of various fresh produce species, to control decay on cactus pears. Second-crop cactus pears ‘Gialla’ fruits were dipped in 500 mg L-1 IMZ or AZO and stored at 1 or 8°C and 90-95% RH for 2 or 3 weeks, respectively, plus 1 additional week at 20°C and 55-60% RH to simulate retail conditions. At the end of storage, decay incidence ranged between 16 and 23% in control fruit, while the percentage of losses in treated fruit ranged between 3% (IMZ) and 5% (AZO). Although no significant difference was detected between the two fungicides in terms of percentage of rotten fruit, IMZ seemed to be more active than AZO in controlling Penicillium decay. Both chemicals ameliorated fruit responses to chilling injury, but a slightly higher decline in freshness, associated with faster transpiration activity, occurred in AZO-treated fruit. Based on these results, considering the complexity of the registration process of new chemicals and the easier procedure required for manufacturers to apply for extension of use of already registered pesticides, both chemicals could be good candidates as potential fungicides to control postharvest disease of cactus pears.