Variation in ‘Sharwil’ Avocado Maturity during the Harvest Season and Resistance to Fruit Fly Infestation

Abstract

Avocados cannot be exported from Hawaii to the continental United States without a quarantine treatment to prevent the spread of fruit flies. Research was conducted on the maturity and infestation potential of ‘Sharwil’ avocados to assist in development of a multicomponent systems approach for quarantine security. Changes in fruit dry matter content and oil content were determined throughout the harvest season for ‘Sharwil’ avocados grown at three orchard elevations over two production seasons. Also, the ability to infest fruit with Mediterranean fruit fly and oriental fruit fly was measured throughout the harvest season and during fruit ripening. Fruit quality was consistent from one year to the next, regardless of orchard elevation, however, the time of harvest within a production season impacted avocado quality. Late season fruit had higher dry matter and oil contents, were smaller in size, and had a shorter shelf life than early and midseason fruit, but fruit flavor and texture did not change throughout the season. Mean dry matter content ranged from 32% (30 Jan.) to 38% (24 Apr.) in 2007 and from 29% (8 Jan.) to 40% (29 Apr.) in 2008. Percentage of oil content ranged from 21% to 25% in 2007 and from 18% to 28% in 2008. ‘Sharwil’ fruit with a minimum mean oil content of 18% had 29% dry matter and acceptable sensory quality. The dry matter and oil contents of individual avocados were highly correlated (r = 0.97). Avocado was a poor fruit fly host immediately after harvest but became an increasingly favorable host as fruit ripened. Fruit fly infestation rates were similar among early, mid- and late season fruit. The results could be used to develop a maturity standard for ‘Sharwil’ avocados based on dry matter content at harvest, and to develop guidelines for postharvest practices of a systems approach for quarantine security.