Pruning fruit trees is an important horticultural practice that promotes proper tree vigor and canopy architecture for optimal fruit production. Generally the best time for dormant pruning pome fruit in the northeast is January through early March. Stone fruit, with the exception of sweet cherry, may be safely pruned as late as the delayed dormant and early bloom periods.
Apple and pear diseases that form overwintering cankers are fire blight, white rot, and nectria twig blight. Stone fruit diseases that form overwintering cankers are cytospora canker on peach, plum and cherry, and bacterial canker on sweet cherry. Sweet cherry should not be dormant pruned. The time to prune Sweet Cherry is after harvest to disrupt the disease cycle of bacterial canker. In general winter cuts should be made at least few inches below the infection site to remove any infected wood that is not visible. Many of these cankers can be easily removed from the canopy while pruning, however removal is generally not practicable if the infection occurs on the trunk or base of the scaffold.
Scale infestations should also be noted while pruning. Scale infestations often start in a small area of the orchard from which they build rapidly and spread. Dormant pruning offers an excellent opportunity for the grower or orchard worker to take note of new or building scale infestations that might otherwise go unnoticed until they cause significant damage. Scale insects that attack tree fruit are san jose scale and rarely, oyster shell scale in pome fruit. In addition to san jose scale, white peach scale can often be found infesting peach orchards in the south and mid-atlantic regions, especially after a string of mild winters. San jose scale can be difficult to spot if the populations aren’t large. Look for wood that looks weak or dead and has a dark grey, blackish, or ashy appearance. White peach scale is very easy to spot in the orchard. Look for bright cottony white spots that look like splashed paint. Removal of infested wood has little if any value for controlling scale populations, however it is important to note where they exist so that dormant oils and spring applications of effective materials can be planned and prioritized.
