Issue link: http://read.dmtmag.com/i/350705
www.goodfruit.com Good Fruit Grower AUGUST 2014 43 Developmental processes vary by cultivar and govern fruit growth potential during any period of time, he said. For the first month after bloom, fruit development (that drives growth potential) is strongly influ- enced by heat accumulation. Higher temperatures within one month after bloom increase the rate of fruit development. Fruit growth potential is determined by genetics, he said. Fruit growth at any given time can be compared to the growth of money invested at compound interest. "Fruit growth potential that is lost early in the sea- son cannot be made up later," he said. "To optimize fruit size and yield, crop load adjustments need to be made as early as economically feasible, especially in years of heavy fruit set." Interest in blossom thinning is increasing not only because it reduces labor costs, but also because it avoids setting fruit that will be lost in the fruit thinning process. "Thin the tree early enough so that the tree can supply enough resources to remaining fruit to pay their potential interest rate. Optimal timing and amount of thinning can increase both fruit size and yield." Temperature accumulations in the first month after bloom have a very large effect on fruit development. In California, the growing degree-hour accumulation during this period can vary by 100 percent (from 4500 to 9000 growing degree- hours), and this can cause the time for fruit development (time from bloom to fruit maturity) to vary from year to year by as much as 30 days for a given cultivar. Warm springs speed up fruit development, which increases demand on the tree's resources. Thus, counterintuitively, warm springs lead to a tendency for fruit to be smaller because it is more difficult for the tree to keep pace with potential fruit growth demands. "This is also a likely explanation for why large fruit sizes in some warm locations are hard to achieve," he said. For more information on DeJong's research, go to http://ucanr.edu/ sites/fruitreport/. • PEACHES AND PRUNES are his forte D r. Theodore M. DeJong (pronounced "DeYoung") joined the faculty at the University of California, Davis, in 1981 after earning his doctorate there in 1977. Much of his intellectual stimulation for tree fruit physiology research came from his goal of developing integrated understanding of fruit tree carbon budgets and growth through crop modeling. In addition to his work with peaches, he has been the principal investigator on a prune-breeding project since 1985. The goal is to develop new prune (dried plum) cultivars that will increase orchard efficiency, spread the harvest season, and maintain or increase dried product quality. The industry currently depends on one cultivar, French, but new cultivars seeking a place include Muir Beauty and Tulare Giant, which are earlier, and Sutter, which is later. California produces 99 percent of prunes grown in the United States. Last year, DeJong received the title of Distinguished Professor at UC Davis. This year, he received the Outstanding Research Career Award from the Environmental Physiology of Fruit Crops Working Group of the International Society of Horticultural Sciences. —R. Lehnert Ted DeJong