Oil and Other Early Season Sprays for Apple and Pear Trees

Oil and Other Early Season Sprays for Apple and Pear Trees
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Reference: Ohio State University Extension

Early spring is the best time to apply sprays to control certain insects, mites, and diseases on apple and pear (domestic and oriental) trees. Gardeners who have had problems with certain pests and diseases in the past year should consider applying early season sprays to prevent or minimize pest damage to the leaves and fruit of apple and pear trees. Additional applications of fungicides or insecticides sprays during the growing season may be necessary to control specific pests that are not present during the dormant and early season. Applying the proper sprays early in the growing season should minimize the use of pesticides during the remainder of the growing season.

Oils defined and application suggestions Early spring brings warm temperatures and long sunny days. Certain pests overwinter on the trees. These include the eggs of the European red mite and scale insects such as San Jose scale and oystershell scale. These can be effectively controlled with oil. There are a variety of horticultural oil products on the market but their names can be confusing.

Oils called "dormant oils" are intended to be used before the leaf or fruit buds of apple and pear trees open in the spring. For central Ohio, the dormant biological stage, or bud swell of apples, occurs in late March to early April (Figure 1). Applying dormant oils at this time can effectively control scale insects, such as the San Jose and oystershell scales. Dormant spray oils have an emulsifer added to allow the oil to mix with water. Household or automative oils cannot be used because they will not mix with water and are not formulated for use on plants. These types of oils will not provide insect control and are harmful to plants.

The "delayed-dormant" sprays are applied at the green tip (Figure 2) through half-inch green (Figure 3) bud growth stages. This spray is most effective for controlling eggs of European red mite. The mite eggs are most susceptible to control by oil when they are close to hatching. After the half-inch green bud stage, dormant oils can injure the young leaves and are not recommended for use at this time.


Figure 1. Bud swell stage.	Figure 2. Green tip stage.	Figure 3. Half-inch green.

If oil is not applied by half-inch green, there are other options for controlling mites and scales. Scales can be controlled with an insecticide, such as diazinon, at the active crawler stage which occurs in June for San Jose scale and in late May for oystershell scale. Mites can be controlled anytime during the season with a miticide, such as dicofol (Kelthane). However, these insects or mites are more easily controlled in their immature stages in the early spring then they are most effectively controlled and before they increase into high populations later in the summer.

Most oils for delayed-dormant applications are called Superior, Supreme, or more precisely a "70-second viscosity" oil. These lighter oils can be applied as either dormant or delayed dormant sprays with higher rates for dormant and lower rates for delayed-dormant applications. Gardeners should make a 2% solution by mixing 2 fluid ounces (4 to 5 tablespoons) of dormant oil per gallon of water for the delayed dormant application. Never apply more than a 2% solution when green tissue is present. Apply the solution when temperatures are above 45 degrees F and when temperatures are not predicted to drop below 40 degrees F for 24 hours. Oil can cause leaf damage (phytotoxicity) under cool temperatures, high humidity, or wet conditions because the leaf does not have sufficient wax (cuticle) to protect itself. The oil also breaks down on the leaf when exposed to near freezing temperatures.

Oil applications at either dormant or delayed-dormant stages are most effective if they are applied in high volumes of water. Complete coverage of all bark is necessary to effectively control scale or eggs. Use the following as a guideline to determine and obtain complete coverage.

Complete Coverage
Tree Height	Gallons/tree*
8 to 12 feet	1 to 3
12 to 18 feet	3 to 5
18 feet or higher	4 to 6
*Use lower amounts on trees which have little or no leaf exposure.

Coverage of the entire tree is essential. Some mite or insect eggs can escape the suffocation by the spray because of poor coverage of the top of the tree where limbs are upright and oil does not reach (cover) the narrow crotches. Limb stubs left behind from pruning are also areas that may not be covered. Always thin out upright limbs and make cuts as close to limbs as possible. Planting dwarf apple and semi dwarf pear trees can aid in achieving maximum coverage and can reduce the amount of spray needed per tree.

Other Early Season Insecticide Sprays
Oil sprays are effective and efficient in reducing certain early season pests. However, other insect pests infest fruit trees after the half inch green bud stage of bud development. These stages of bud development are pink bud (before bloom) (Figure 4) and petal fall (after bloom) (Figure 5). An insecticide such as diazinon (25% concentrate 2 teaspoons/gallon of water) can be used at the pink bud stage if rosy apple aphid is present. This rosy-colored aphid causes severe distortions in the leaves and fruit and should not be confused with several green colored aphids that are much less serious. The spray at pink also helps control tarnished plant bug, which makes dimples in the fruit surface.


Figure 4. After bloom.	Figure 5. Pink bud.

An insecticide, such as phosmet (Imidan 12.5% wettable powder) 3 tablespoons (or 18 grams) per gallon of water; or Imidan 50% wettable powder, 2 teaspoons (4.5 grams per gallon of water) or a multipurpose malathion/methoxychlor (see label) spray can be effective at petal fall against other early pests, such as codling moth, plum curculio, and leafrollers. Reducing insects at this time will minimize the number of adults and offspring present during the summer. It will also reduce the injury to fruit as they begin to grow.

Codling moth, which is usually the most serious pest of home fruit plantings, may be partially controlled by the petal-fall spray but is most effectively controlled about 2 weeks after petal-fall. In mid-summer (July), another insecticide application can control the second generation of codling moth as well as apple maggot.

Summer oils, such as SunSpray Ultra-Fine Spray oil, have been developed for use on foliage during the summer without phytotoxicity problems. Oils and insecticidal soaps should never be mixed together for application. Gardeners should read the label for all types of oil sprays and closely follow all precautions.

Fungicide Sprays
Early season applications of a fungicide or a combination of fungicides is generally required to control apple scab on susceptible cultivars. On susceptible cultivars a fungicide is not required before half-inch green. At half inch green (as soon as green tissue is present) and at tight cluster, a fungicide such as Captan or Captan plus Benomyl should be applied to apple trees. Captan alone can be quite effective if applied at the proper stage (see label for rates). To assure high quality fruit a combination of an insecticide and fungicide(s) at tight cluster, pink, and petal fall. Fungicide may be applied during bloom but do not apply an insecticide at bloom to protect bees (Figure 6).


Figure 6. Full bloom.

The most effective means of controlling apple scale is to plant scab resistant apple cultivars. Many of these cultivars have resistance to other diseases as well and they may eliminate the need for early season fungicide applications in the home orchard. Removing scab infected leaves from the orchard can reduce apple scab infection.

For pear, apply dormant oil and apply a fungicide only at pink and a fungicide plus insecticide at petal fall.

Note: Pesticides vary in the per cent of active ingredients. Examples used in this fact sheet may not compare to your particular pesticide. Read your pesticide label and mix the proper amount.

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