Solved! The Best Time to Spray Fruit Trees
Here’s how to know when to spray fruit trees for a delicious backyard crop of apples, peaches, or pears.
Q: There are several fruit trees and vines in my garden that I would love to pick fruit from. Unfortunately, the fruit doesn’t grow very well and the leaves look bad. I probably need to spray but don’t know much about it. Can you tell me when to spray fruit trees?
A: Caring for fruit trees is a year-round job that includes pruning, fertilizing, removing diseased fruit, and spraying multiple applications at different times of the year. Timing is critical for each of these tasks. Pruning takes place in midwinter and late summer to stimulate vegetative growth and increase fruit production. Growers should fertilize trees during their growing season because it is during active growth that they absorb and use the nutrients.
To know when to spray fruit trees, you first need to know what threatens the tree and when the threat is active. An insect egg can lie dormant in the bark of an apple tree all winter, only to hatch and feed on the leaves in spring. Or a particular fungal spore might infect a peach tree only while the flowers are open. Knowing the timing and types of threats for each kind of fruit tree helps you to spray for maximum protection and minimal waste.
Dormant spray, insecticide, fungicide, or general-purpose spray? Know what to spray and when to spray it.
Spray applications are timed to control disease and insect pests. Timing coincides with plant and fruit development. Climate and weather play a huge role in the timing of fruit tree growth and development. Growth stages to watch for include dormancy, preblossom, blossom, petal fall, and fruit formation. Each stage has specific, observable characteristics.
Dormancy is the time before buds begin to swell in spring. Preblossom stage includes five distinct growth stages that are observed on the tree buds before the flowers open: silver buds, green tips, half-inch green, tight cluster (of flower buds), and pink (but not yet open) flower buds. Blossom is the stage from the time the first flower opens until the last petal drops. Petal fall is the time after blossom, before the first tiny fruits begin to develop. Fruit formation is the final stage, which lasts until harvest.
Avoid spraying while flowers are open, since insecticides sprayed at that time kill bees and other pollinators. Read and follow all safety precautions to minimize personal exposure to pesticides. Always follow pesticide mixing instructions. Increasing the concentration of the chemical in the spray solution does not kill insects faster. In fact, doing so kills more nontarget species and increases the likelihood of runoff contaminating local streams and groundwater.
- Dormant spray, or dormant oil, refers to the timing of an application of horticultural oil. When sprayed on dormant fruit trees, horticultural oil kills overwintering scale insects, mealybugs, mites, aphids, and other pests on the bark of the tree. Depending on the manufacturer, horticultural oil has either a mineral (petroleum) or plant base. One application per year, or less, is typical.
- Insecticidal sprays kill insect pests, especially those that feed on foliage, bore into trunks, or spoil developing fruit. Most fruit crops require multiple applications through the growing season for protection against different bugs. Avoid spraying insecticides while flowers are present, as these products also kill pollinators.
- Fungicidal sprays control the spread of fungal and bacterial diseases in fruit trees. You might need to apply fungicide several times throughout the growing season to protect against different diseases. Although fungicide is not rated for control of insects, many of these products can damage or kill pollinators, so avoid spraying fungicide while flowers are open.
- General-purpose sprays control most insect and disease pests of fruit trees. Simply spray a single product at defined intervals throughout the growing season. There is no need for specialized knowledge of plant diseases or insect life cycles. On the downside, using only general-purpose fruit tree spray increases unnecessary pesticide exposure. There are times when only a fungicide or an insecticide is required, but this product contains both. Further, general-purpose sprays might not control some problematic insects and diseases.
- Foliar fertilizer sprays of micronutrients like zinc, copper, magnesium, molybdenum, boron, and calcium can aid fruit development where these nutrients are lacking or unavailable due to soil alkalinity. These elements mix with water for applying directly to the leaves, which absorb the nutrients and efficiently move them to developing fruits. Strictly follow label instructions to avoid damaging trees. Major nutrients such as nitrogen, phosphorus, and calcium should be applied to the root zone.
Use general purpose fruit tree sprays during the growing season to protect against insects and diseases.
General-purpose fruit tree sprays conveniently cut spray application time in half. A powerful mix of broad-spectrum insecticide and fungicide is the key. Active ingredients might include organic products like pyrethrins and neem oil, or inorganic chemicals like malathion, carbaryl, and captan.
Apply general purpose fruit tree spray at one- to two-week intervals following key plant development observations. The first application is at green tip, followed by pre-bloom, full pink, petal fall, first cover (one week after petal fall), and second cover (two weeks after petal fall). Trees might require additional treatments. Consult the product label for detailed directions because some chemicals can go on a fruit tree up to the day of harvest, but others indicate “do not spray within __ days of harvest.” Each product varies.
Fertilize during early fruit development.
If your fruit trees show symptoms of deficiency in zinc, copper, magnesium, molybdenum, boron, or calcium, a foliar application of one or more of these micronutrients may help. Foliar spray of micronutrients aids fruit development where certain micronutrients are lacking in the soil or are unavailable due to soil alkalinity. Apply foliar sprays of micronutrients on a cool, overcast day at or near the petal drop stage. Be cautious with this approach as unnecessary or excessive application of these nutrients can damage fruit trees.
Foliar fertilizer cannot replace proper soil fertility. The major nutrients that trees need cannot be absorbed in sufficient quantities through foliage, and fertilizer applied to foliage does not travel throughout the body of the plant.
The best time to fertilize fruit trees is in early spring. Apply granular fertilizer across the root zone around the time the leaf buds open. This is the signal that the tree is ready to actively grow. The first flush of growth in spring comes from energy stored in the roots. By the time the fertilizer penetrates the soil into the root zone, the tree is ready to take up the nutrients for optimum growth and fruiting.
Avoid fertilizing after mid-spring. A spike in soil nutrients during fruit development can cause trees to abort fruit to produce more vegetative growth.
Use dormant sprays in late winter to kill overwintering insect pests on fruit trees.
Apply dormant oil in late winter or early spring if there was intense pest pressure during the previous growing season. This treatment normally goes on every three to five years. Unless pest populations spike, it is not necessary to spray dormant oil every year.
You must complete dormant spraying before buds begin to swell. Air temperature is critical during application to ensure complete coverage and avoid damaging the trees. The temperature must be above 40 degrees Fahrenheit during application. While spraying, be sure to fully coat all surfaces of the tree, paying close attention to undersides of branches and branch crotches.
Use fungicidal sprays during the growing season to protect fruit trees against diseases.
Targeted, stand-alone fungicide treatments significantly improve fruit quality when applied at the proper time. Fruit disease spores infect their hosts when environmental conditions are ideal. Some fungal spores activate during cool, wet spring weather. Other diseases spread in hot, humid summer conditions. It is important to anticipate plant diseases and begin treating them just before they arrive.
Each kind of fruit tree has its own ideal fungicide spray schedule based on the diseases that threaten it. Fungicide applications are most critical during the green tip through petal fall stages of apple and pear trees. Peach trees and plum trees require spring, summer, and fall disease control treatments for best results. Find application timing on the product label for the prevention of specific diseases.
Use insecticidal sprays during the growing season to protect fruit trees against insects.
Apply insecticidal sprays at 2-week intervals from green tip until bloom, and from petal drop until harvest for general insect control. It is possible for insects to build up tolerance to even the best insecticide if it is used repeatedly. The solution is to alternate applying insecticides with different active ingredients. If you primarily use a general-purpose spray to kill insects and diseases, alternate the scheduled treatments using a different kind of insecticide to eliminate the risk of pests building up tolerance to either chemical. Read the active ingredients on the label to be sure.
Use combination sprays during the growing season to target both insects and diseases.
Combination sprays are two different pesticides sold individually, normally an insecticide and a fungicide, mixed into the same sprayer and applied at the same time. Like mixing your own general-purpose fruit tree spray, this practice is a way to customize an application and save time. Combination spraying is a way to do an all-in-one spray with a single application if your normal procedure is to alternate pesticides.
Not all products are compatible, and some mixtures can be dangerous. Read both product labels before mixing to ensure that mixing the two is safe and allowable.