POSTHARVEST HEAT-TREATMENT OF APPLES TO CONTROL SAN-JOSE SCALE (QUADRASPIDIOTUS-PERNICIOSUS COMSTOCK) AND BLUE MOLD (PENICILLIUM-EXPANSUM LINK) AND MAINTAIN FRUIT FIRMNESS

Postharvest heat treatments were applied to three apple (Malus domesti ca Borkh.) cultivars: 'Anna', 'Golden Delicious', and 'Jonathan'. The temperatures ranged from 38 to 50 degrees C and from 5 to 96 hours. Th e temperatures of 50 degrees C for 5 or 10 hours and 46 degrees C for 10 hours controlled all developmental stages of San Jose scale on 'Gol den Delicious' and 'Jonathan' fruit. Blue mold germination was prevent ed by 36, 32, and 38 degrees C after 28, 33, and 32 hours, respectivel y. The time needed to control the fungus was longer than that required to kill the insect. Apples were damaged by a 50 degrees C treatment b ut could withstand at least 12 hours at 36 degrees C and at least 24 h ours at 42 degrees C. At 38 degrees C no damage was found on preclimac teric apples even after 96 hours, but if postclimacteric fruit were he ated at 38 degrees C heat damage occurred. The treatments that did not cause damage maintained the fruit firmness during post storage ripeni ng. The results are discussed in the context of developing integrated postharvest heat treatments.