HOT WATER DIPPING AS A DISINFESTATION TREATMENT AGAINST THE FRUIT FLY DACUS AQUILONIS (MAY) (DIPTERA : TEPHRITIDAE) IN MANGOES

Preliminary experiments on five varieties of mangoes showed that, depending on size, fruit may need immersion in 48°C water for up to 90 minutes to obtain the necessary heating profile. However, infested fruit placed in water at this temperature for > 30 minutes achieved 100% mortality of all fruit fly stages.

The effect of fruit injury from exposure to this treatment was also examined. All treated fruit was held at 25°C and scored for 15 physiological characters, fungal rots and marketability. Criteria for acceptance of the dipping treatment included weight losses of < 10% between dipping and maturity and > 75% marketability of treated fruit. A strong relationship existed between weight loss and marketability of fruit.

Fruit treated on the day of harvest often exhibited severe surface scalding within 5 – 6 days even when exposure was as brief as 30 minutes. Damage was greatly reduced when fruit was dipped 24 or 48 hours post-harvest. Scald damage was most noticeable on sap burns or immature areas of the fruit surface. The varieties Kensington Pride and Haden were the most severely affected with Irwin exhibiting least heat damage.

Dipped fruit were unmarketable if stored at 13°C between harvest and treatment but, when held at ambient temperatures, injury levels were acceptable. There appeared to be no difference in the characters measured between marketable treated and control fruits.

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