Reduction of anthracnose on ripened mango fruits by chemicals, fruit bagging, and postharvest treatments

Abstract

We evaluated the ability of fungicides to eradicate latent anthracnose infections and to protect young mango fruit from new infections in laboratory and field experiments in Thailand. Naturally inoculated developing fruits on the trees, 60 days after fruit set, were sprayed with 125 mg a.i./L. azoxystrobin, 125 mg a.i./L. difenoconazole, 500 mg a.i./L. carbendazim, 750 mg a.i./L. prochloraz, or 1050 mg a.i./L. propineb. All fungicides reduced the severity of subsequent postharvest anthracnose, although none of the treatments reduced disease incidence. Prochloraz was the most effective, reducing disease severity from 18.2 to 9.8% of the fruit surface area affected. Prochloraz also significantly reduced the development of postharvest symptoms on artificially inoculated developing fruit. Disease incidence on harvested fruits was further reduced if fungicide sprays were followed by fruit bagging, whether with new or once-used kraft paper bags with black-lined paper. Sprays of 300 mg a.i./L. of the defence primer Bion to sixty day-old developing fruit immediately before bagging also reduced subsequent anthracnose incidence to 47.5% and severity to 1.8% of fruit surface area, equivalent to prochloraz spray. Comparing postharvest dipping in prochloraz (250 mg a.i./L), azoxystrobin (250 mg a.i./L) or hot water (55 °C for 3 min), before storage at 15 °C for 10 days showed that hot water was the most effective postharvest treatment for mango fruits. From these results, the most effective management of anthracnose on mango fruit includes spraying developing fruit with prochloraz or Bion, followed by fruit bagging until harvest, and hot water dips of harvested fruit.