It won’t be long before spring is here, pushing dormant leaf and flower buds into action. Some important orchard chores need to be accomplished before these sleeping buds begin to swell. This includes treating peach trees for scale with a dormant oil spray and the annual pruning of peaches.
Dormant Oil Sprays
Winter time is prime time to apply a dormant oil spray to deciduous fruit, nut and certain landscape trees and shrubs to control scale and other insect pests. Horticultural oils are highly refined petroleum products for controlling scale, mites and other overwintering insects and their eggs on plants. Horticultural oils work mainly by coating pests with a suffocating film of fine oil. Their toxic action is more physical than chemical and is short-lived.
Horticultural oils for controlling insect pests have been around for many decades. Initially, their only use was as a dormant spray on deciduous trees since early formulations could injure plants when applied during the growing season. Great advances in formulations have been made and horticultural oils are now safely used, when manufacturer’s directions are followed, during both the growing and dormant season.
Horticultural oils have several advantages over conventional pesticides. They have a wide range of activity against scale, mites, and other insects and their eggs. There is little or no resistance to oils by pests. A major advantage is that oils are usually less harmful to beneficial insects and predatory mites than other insecticides with longer residual activity. Oils are safe to handle and relatively harmless to humans, animals and birds, leave little or no residue on crops, and some formulations can be used by organic farmers in the TDA Organic Certification Program, if they are OMRI listed.
Some potential disadvantages of horticultural oils include injury to weakened or stressed plants when used during the growing season. Therefore, time applications during the growing season to avoid high temperatures, drought conditions, and prolonged wind, and don’t spray plants severely weakened by insect or disease. Always read and follow labels carefully to avoid problems.
Scales are the most serious pest to control in the winter time. Scales are tiny, sucking insects that attach themselves to tree limbs and branches with thin, smooth, tender bark. They suck sap from the plant and a heavy infestation of scale insects can weaken and kill branches or entire trees. Each scale insect covers itself with a waxy, protective material. This waxy armor makes scale difficult to control with most insecticides.
Scale is often overlooked because they often blend in to branch and bark color. Look for the presence of small bumps that can be flicked off with a fingernail.
Most fruit trees including peaches, plums, apricots, apples and pears can have scale infestations. Pecans also benefit from an oil spray, although phylloxera are more of a problem than scale on pecan trees. If pecan leaves and leaf stalks had galls or large bumps on them last year – an indication of phylloxera infestation – then an oil horticultural oil application can help reduce the reoccurrence.
Late January or February, shortly before bloom or leafing, is the best time to apply oil. Scale insects grow weaker through the winter and are more vulnerable to the suffocating oil film if it is applied late in the dormant season. Do not apply dormant oil after trees have begun to bloom or leaf out.
Mix oil according to label directions. Dormant oil works best if applied when the temperature is above 55 degrees although it can be applied when the temperature is between 40 and 70 degrees F.
Good spray coverage on the upper and lower sides of branches is critical for effective control. Use sufficient volume of solution to thoroughly wet limbs and bark.
Trees with a really severe scale infestation may need two oil sprays. If a second application is needed, wait at least 3 weeks between sprays. It can be difficult to tell if scales are dead since they don’t move around, and dead scales don’t fall of the bark or leaves. Take a knife blade or your finger nail and press on a scale. If a bit of “juice” comes out, it is alive. If the scales are flaky and dry, then they are dead. Scales with tiny holes have been parasitized by small wasps.
For more on using oils as pesticides, click here to go to an online publication by that title.
Proper pruning of peach trees, starting from the day they are planted, helps keep trees to a manageable harvest height and maintains the productivity of trees.
Newly planted peach trees should immediately be cut back to about two to three feet tall. Several branches will develop near the cut during the spring. During the summer, select three or four well-spaced, wide-angled branches to form a bowl-shaped framework of scaffold branches. Cut these back about 18 to 24 inches from the main trunk to force side shoots. These new shoots will become the secondary main branches from which most fruit wood will be produced. Remove all suckers sprouting from the base of the tree.
The ideal shape for training a peach tree is an open center like a bowl with three or four major branches radiating out from the trunk like spokes on a wheel. Plums can a have a central, main trunk.
Training during the next few years after planting depends on the tree’s rate of growth.
Remove vigorous, upright shoots and larger branches that grow into the open, bowl-shaped center of the peach tree. Leave enough short, leafy growth and fruiting branches on the interior to prevent sun scald of the main scaffold branches.
On bearing trees, clip the secondary main branches and other branches to maintain a practical tree height, about 7 to 8 feet tall. Fruit are produced on 1-year-old shoots, so there must be plenty of new growth every year. The 2012 peach and plum crop will be produced on wood that is produced this year. Yearly pruning helps stimulate this new growth. Thin out crowded shoots that will receive little sunlight. Remove low shoots that are in the way and which might sag to the ground under a heavy crop load.
Yearly pruning is needed to keep the center of the peach tree free of excessive growth. Light is critical for development of fruit wood and flower buds, and good air circulation helps reduce disease problems.