The loss of leaves, branches and flowers along with bark scuffing and root exposure that can occur during mechanical harvesting (MH) has not reduced long term yields of healthy trees. Nonetheless, such visible injuries have limited the widespread adoption of mechanical harvesting in Florida's citrus industry. There was little measurable physiological stress from MH in healthy, well-managed trees as leaf water relations, CO 2 assimilation and final yield were not affected. The abscission compound CMNP, can effectively reduce fruit detachment force and result in fewer visible injuries. Late season MH of 'Valencia' sweet orange remains a major problem when young fruitlets for next crop become large enough to be harvested prematurely. We determined if winter drought stress from January to March could delay flowering and fruitlet development so they would be too small to be susceptible mechanical harvesting. Drought stress during winter delayed flowering 2-3 weeks, reduced flowering and vegetative growth but did not reduce new fruit set relative to irrigated trees. Fruit growth after the delayed bloom caught up with the irrigated treatments so final yield and fruit quality were not affected. During mechanical harvesting, previously drought stressed trees had a higher fruit removal efficiency and less loss of the smaller young fruit than continuously irrigated trees for up to three months. Thus, winter time drought stress can be an effective practice to delay flowering and to avoid young fruit loss during late season mechanical harvesting of 'Valencia' oranges. Fruitlet oleocellosis in late season mechanical harvested trees did not increase fruitlet drop nor alter internal fruit quality.
