Fungicide for plum trees

Plum Tree Fruit Spray: When To Spray Plum Trees For Insects

Plum trees, like other fruiting trees, benefit from a regular maintenance program of pruning, fertilizing and preventive spraying to foster the healthiest most bountiful crops. Plum trees are susceptible to several diseases and pests that not only damage the tree and fruit, but act as vectors to disease, so spraying plum trees on a regular schedule is paramount to their health. The big question is, when and what to spray on plum trees. Read on to find out.

When to Spray Plum Trees for Insects

Creating a schedule for when to spray plum trees for insects is helpful if you are as absentminded as I am. You can do this by specific dates or, more importantly, maintain your schedule by the stage of the tree. For instance, is it in a dormant phase, is it actively growing or is it fruiting? Whichever works for you, the important thing is to stick to the annual spray maintenance schedule for when and what to spray on your plum trees.

Giving an exact date or even a gist of one is difficult here since plum trees grow in different climates and microclimates, meaning

that your tree might not need to be sprayed at the same time as my tree.

Also, before you spray for the first time during a growing year, prune out last season’s new growth by 20% when the tree is in its dormant stage, as well as any broken or diseased branches.

What to Spray on My Plum Trees?

What to spray on your plum trees is as important as when to spray. The first application of plum tree fruit spray will be during the dormant period with, you guessed it, dormant oil for trees. This application will prevent aphid and mite egg production, and scale. It is applied BEFORE buds appear. The dormant oil should contain endosufan or malathion.

Keep in mind that dormant oil cannot be applied when a freeze is expected. If the temps dip below freezing, the oil can harm the tree.

The second time you’ll use plum tree fruit sprays is when the tree begins to bud but shows no color in the spring. Spray with a fungicide to prevent things like:

  • Brown rot
  • Plum pockets
  • Leaf curl
  • Scab

This is also a good time to apply Bacillius thuringiensis to the plum tree to keep oriental fruit moth and twig borer at bay.

Once petals have fallen from the plum tree, check for aphids. If you see aphids, spray either with neem oil, zinc sulfate, or add some dishwashing liquid to malathion and spray the tree concentrating on getting any curled leaves. At this time, spray a second time with Bacillius thuringiensis and fungicide.

Once the fruit begins to develop and the husks are pulling back from the fruit, spray plums with spinosad, esfenvalerate or permethrin to control the twig borers. Spray again with a mix of fungicide, malathion and sulfur to control leaf curl, plum pocket, scab and brown rot and aphids. Spray every 10 days during fruit development. STOP spraying a week or so prior to harvesting.

Your local extension office or a good nursery can help you further to create a schedule for spraying plum trees and offer advice on products and/or non-chemical options for controlling disease and pests on your plum tree.

If you have a fruit tree, you know that gardeners are not the only ones who enjoy the bounty of the harvest. There are many pests — such as scales, aphids and mites –that feast on the tender plant parts and these same pests overwinter on the fruit trees. Dormant oils help control these annoying pests and are safe for use on fruit trees. Peach Leaf Curl

Dormant sprays or delayed dormant sprays are a generic term for an application of pesticides—including fungicides, highly refined horticultural oils and oils in combination with a pesticide– that are applied to leafless deciduous trees during fall, winter, and early spring. All fruit and nut trees and many landscape trees and roses are susceptible to aphids, mites, scale and specific insect and disease problems affecting fruit quality and tree health

Some dormant sprays are applied to control over-wintering insects, while others are used to prevent disease infection. While dormant sprays are commonly used on fruit trees, they can also benefit roses and other ornamental shrubs that might develop insect or fungal disease problems as the warmer weather arrives in the spring. Dormant sprays should only be used in conjunction with good garden sanitation. Be sure to rake up and dispose of all fallen leaves and debris that may harbor fungus spores and overwintering insects.

Dormant oil is a refined petroleum product formulated for fruit tree use. It has been in use for well over a century in commercial orchards, and is still regularly used today. It is classified as an insecticide, and acts by coating over-wintering insects hiding in tree trunk and limb bark with a suffocating layer of oil. Oils used at this time of year include insecticidal oils, narrow range, supreme and superior oils. Dormant disease control applications use materials such as copper, lime sulfur, Bordeaux, and synthetic fungicides.

Dormant sprays provide efficient and economical treatment for a number of over-wintering pests and diseases such as: scale, peach twig borer, aphid eggs, leaf curl, powdery mildew and shot hole.

Here is a partial list for fruit trees:

• Apple and pear – dormant oil helps control scale, overwintering aphids, mite eggs and pear phyla.

• Apricot – dormant oil helps control scale, mite and aphid eggs and peach tree borer. Never use sulfur on apricots.

• Cherry – is susceptible to oozing from gummosis (Bacterial canker) and may respond to dormant sprays containing fixed copper.

• Peach and nectarine – require repeated applications of fixed copper spray to control peach leaf curl. In December or January, prune off half to two thirds of last season’s growth to stimulate new fruiting wood. Spray the ground after removing leaves and branches. Use dormant oil if scale is present.

• Plum and prune -dormant oil helps control scale and overwintering aphid and mite eggs. Apply copper for shot hole fungus. Heavy pruning may be needed to help control tree size. Spray ground after clean up. Shothole disease on apricots

• Nut trees- remove any nuts still hanging on the tree. Spray with dormant oil to control scale. Oil sprays also help control peach tree borers and mite eggs.

Applying dormant or delayed dormant treatments

A dormant spray may not be required every year in the backyard orchard. For some insect pests and diseases, one dormant application may be adequate with good spray coverage. For other problems, up to 3 applications may be necessary for good control. Decide if you need to apply by noting the amount of insect and disease pressure during the previous growing season. If you decide to spray always read the label and follow the directions, more is not better. Make sure you dress in protective clothing, including long pants, a long-sleeved shirt, chemical-proof gloves, and safety goggles.

Treat at the beginning of dormancy in late November and again just before the buds begin to open in February or early March. One way to remember when to consider dormant spraying is to do so around Thanksgiving, Christmas and Valentine’s Day. Once flower buds begin to open you may damage fruit and kill pollinating bees if spraying is done at this time. Therefore, it is important to spray at the proposed times before “bud break”. Spraying after pruning allows maximum coverage since there are no leaves to block the spray. A good time to spray is right after a period of rain or foggy weather but not during fog, rain or right before a freeze. Avoid spraying trees that are showing signs of drought stress.

Sprays can be applied with a pump sprayer or hose-end sprayer that is sized appropriately for the number of plants you need to spray. The sprayer should be clean, in good working order and not been used for any herbicides. Spray the entire dormant plant taking care to saturate every branch, stem or cane as insects and the tiny dust-like spores of fungal diseases hide in the smallest nooks and crevices. Don’t use a dormant spray on any plant that has any leaves or is actively growing. Leaves, especially tender new growth, may be damaged by the spray from the impurities in the oils or the reflection of the sun off the oil.

Dormant oils generally won’t harm beneficial insects since they are applied at a time when beneficial insects aren’t present on fruit trees and have a low toxicity level to humans and mammals. Furthermore, dormant oils won’t leave harsh residue behind. It loses its ability to control pests once dried.

If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website: ucanr.edu/sjmg

New Users

Homeowners who grow fruit in backyards or small orchards find that disease and insect pests often ruin the crop and in some instances damage the tree itself. In some years it may be possible to grow acceptable fruit without the use of pesticides, but in most years a few well-timed insecticide and fungicide sprays are needed. The effects of many pest problems can be reduced if several things are considered prior to buying and planting fruit trees.

One of the most important factors for producing fruit is selection of an area suitable for growing fruit trees. Fruit trees perform best in full sunlight and moist but well-drained soil having a pH of 6.0-6.5. If environmental conditions are not suitable for growing fruits, pest and disease problems are more difficult to manage and in some instances cannot be controlled. Additionally, fruit quality likely will be poor.

Second only to having a good location, is the selection of fruits and fruit cultivars that are adapted to your area of North Carolina. Your county extension agent can usually tell you what fruits and which cultivars of these fruits are best suited for your area. It is important to buy only quality trees that are disease and insect free. Also check the roots to be sure they have not been allowed to become dry. Large is not always better; a tree 3-4 feet in height is much easier to establish than a taller tree. Furthermore, most fruit trees should be cut-back to a 2-3 foot height when planted, and the new growth trained. Planting a smaller tree reduces stress on the root system allowing the tree to become better established during the first year after planting.

Once trees are planted, they require regular maintenance. Fruit trees need to be properly trained and annually pruned so that sunlight can penetrate through the tree (). Pruning should also be done to remove damaged and diseased wood and to stimulate new growth. Pruning out dead wood and removal of mummied fruit is the most important cultural practice that can be done to reduce disease losses.
Fertilization and lime application to maintain proper tree growth and soil pH are usually necessary yearly. The goal of fertilization is to produce adequate tree growth to support a quality fruit crop, not to produce excessive tree growth. Trees that have been established for several years and growing in heavy-textured soil may require little or no yearly fertilization. Apply the fertilizer in a circle around the tree at the drip line (outer edges of the branch canopy). A grass and weed-free area around the tree should be maintained particularly during the first few years of tree establishment. Heavy mulching may lead to problems such as retaining excess water resulting in root rots and an environment conducive for destructive insects and other pests such as small rodents that can damage the tree trunk and root system.

Although the extent of pest injury can vary from year to year depending on environmental conditions, certain fruit are more likely to have problems than are others. Stone fruits (Prunus spp., eg., peach) generally require more care than pome fruits (eg. apples and pears). Tree fruits requiring the most care to those requiring the least are nectarine, peach, cherry, plum, pear and apple.

Conditions favoring disease development or insect occurrence vary depending on the particular disease or insect. Generally, warm, rainy or damp conditions are very conducive for the development of tree fruit diseases. For best control of diseases, fungicides and bactericides should be applied before rainfall but allowing 2-3 hours for spray material to dry. There are specific times of the year when certain pests can most easily be controlled. Also during the growing season, at certain stages of tree growth, fruit are more susceptible to particular diseases and insects and damage is likely to be greater than during other times of the growing season. Knowledge of these conditions can greatly reduce the number of sprays and fruit losses.

All fruit should be picked before becoming over-ripe. No fruit should be allowed to remain on the trees after ripening. All fruit should be picked and if not consumed, removed from the fruit-growing area. This helps reduce many disease and insect problems for later-ripening fruit. Rake and remove all dropped fruit and leaves after leaf fall which will reduce the likelihood of many diseases and insects the following year. Use of rigorous cultural and sanitation practices can usually reduce the number of sprays needed.

The pesticides selected for use in this information note were chosen because they are relatively safe to the user and the environment near the home, effective against a wide range of fruit diseases and insects and are usually available at many garden centers. For individuals with only a few trees, the combination fruit sprays available at garden centers may be most convenient. Some fungicides for use on fruit trees contain copper which is an effective fungicide but the foliage and some fruit of most fruit trees is quite sensitive to copper which can cause leaf and fruit spots and defoliation. Remember, pesticides are designed to kill pests and as such they should be used, stored, and disposed of only as instructed on the container label. Always read and follow the directions on the container label before using the pesticide.

Apples

DISEASES: During the early part of the growing season (initiation of new leaf and flowers through fruit set), apple scab, powdery mildew and fire blight are the primary disease problems. Apple scab affects both the foliage and fruit and infections can result in defoliation and malformed fruit. Powdery mildew primarily affects the foliage and is characterized by white fungal growth on the surface of affected leaves. Fire blight, a bacterial disease, can be particularly destructive during the bloom period, causing blossom blight and shoot and branch dieback as the bacteria grow from the blossoms into the shoots. In the Piedmont and Coastal Plain, cedar apple rust can be destructive on susceptible cultivars when they are grown in close proximity to the Eastern red cedar (the alternate host of the fungus on which cedar galls develop). Infections are characterized by yellow spots on the leaves and fruit. During the summer, bitter rot, black rot and white rot, can be destructive as fruit ripen, particularly in poorly pruned trees with dead wood within the tree. One of the most common disease complexs during the summer period is sooty blotch and flyspeck. The fungi that cause these diseases grow on the cuticle of the fruit, but do not cause any damage to the fruit themselves. For more information on apple diseases see “A Growers Guide to Apple Insects and Diseases in the Southeast” (http://ipm.ncsu.edu/apple/contents.html).

For control of fungal diseases, apply captan + sulfur when the first green tissue is visible and repeat at 7-day intervals until blossoms begin to open. Captan is more effective than sulfur against most apple diseases but acceptable apples can be produced with sulfur, although sprays will need to be applied more frequently than the combination of captan + sulfur. DO NOT spray an insecticide during bloom because the insecticides can kill bees and other pollinating insects. However, spraying with streptomycin (several brand names available) just before any rainfall during bloom at the rate of 1 teaspoon per gallon of water (0.8 oz per 10 gallons) will aid in the control of fire blight.

When flower petals begin to drop, make a fungicide and insecticide application and repeat at 2 to 3 week intervals until 3 weeks before harvest. Use a 2-week spray interval if weather conditions are wet or there have been disease or insect problems in past years. You do not need to include sulfur in sprays with captan, beginning about 1 month after petal fall. Where cedar apple rust is a problem, include myclobutanil (sold under various trade names) in the sprays beginning at tight cluster and continuing for one month after bloom. If myclobutanil is used, you do not need to include sulfur in the spray program.

INSECTS: San Jose scale is a common home orchard pest that can kill trees within a few years if not controlled. The use of a horticultural oil (applied at 3% solution), just before or when buds begin to shown green in the spring is highly effective against scales. The plum curculio and oriental fruit moth are also common insect pests that often require control at petal fall. Both insects lay eggs directly in small fruitlets, with plum curculio damage causing a scarring of the fruit and oriental fruit moth larvae boring into the apple. Other insect pests that can directly injure fruit during the season include the codling moth, which is present in May and June, and the apple maggot that can be present from mid-July through mid-August. Indirect pests (i.e., those that feed on the leaves) that may occur include a number of different aphid species, which are common during the first 6 wks after bloom but are a concern on small, newly planted trees. The European red mite can cause bronzing of leaves and is most common during June and July.

Insecticide active ingredients (sold under various brand names) available for the home orchard are shown in the table at the end of this document. When choosing an insecticide to apply, be sure to match the correct product with the target pest to be controlled.

Pears

DISEASES: Pears are affected with many of the same diseases as apples with the exception of cedar apple rust, which does not occur on pears. Pear scab has not been reported in North Carolina. Fire blight tends to be more severe on pears than apples and can kill large limbs and even entire trees of susceptible cultivars; Bartlett is highly susceptible. Pear leaf spot (also called fabraea leaf spot) can be important on some cultivars.

Captan is not registered for use on pears. Use thiophanate methyl (Thiomyl Systemic Fungicide, other brands) at 2 teaspoons per gallon of water (6 2/3 tablespoons per 10 gallons). Use the same fungicide spray schedule for pears as described above for apples, excluding captan.

INSECTS: Pears have a few additional insect pests beyond those mentioned for apple, most notably the pear psylla. The most opportune time to control psylla on pear is before bloom with an oil application, both as a dormant and delayed dormant (when green buds begin to appear) application. Pear leaves are highly susceptible to damage by mites, including twospotted spider mite, and the pear blister and pear rust mites. The use of horticultural oils after bloom at 1% solution can help to suppress mite populations. The codling moth and oriental fruit moth can both be serious pests of pears.

Peaches and Nectarines

DISEASES: The most common diseases encountered on peaches and nectarines are leaf curl, peach scab, and brown rot of fruit (the same fungus also causes blossom blight). Bacterial spot can cause significant fruit loss on some varieties in some locations. For a detailed description of and information about peach diseases (same diseases also occur on nectarines) see “Southeastern Peach Growers’ Handbook” (http://www.ent.uga.edu/peach/peachhbk/toc.htm).

A bacterial disease, bacterial spot, affects both leaves and fruit. First symptoms on fruit may be confused with peach scab or chemical spray injury. Bacterial spot is best managed by planting tolerant varieties. It is more of a problem in the eastern third of North Carolina where peaches and nectarines are planted in light, sandy soils. A copper material applied in late autumn (late October – mid-November) and in early spring at budswell and again just before blossoms open may reduce bacterial spot as well as control leaf curl.

Leaf curl can be controlled with a single application of Bordeaux mixture, fixed coppers or lime-sulfur (use rates recommended on product label). The spray for leaf curl must be applied during the dormant season before buds swell in late winter (usually February-March). This spray may be applied in the autumn once most of the leaves have dropped. Some cultivars of peaches and nectarines are less susceptible to leaf curl than are other cultivars. Peach and nectarine foliage is very sensitive to copper and can be injured and defoliation may occur, thus copper should not be sprayed in late spring and summer when leaves are present.

To control peach scab, captan or sulfur sprays should be started at late petal fall and repeated every 7-10 days for approximately 4 weeks. Chlorothalanil also is very effective against peach scab. Once scab lesions are observed, sprays will not be effective because the infections occurred during the 4-week period after petal fall. Chlorothalanil is best used in the place of captan + sulfur in the first 1 or 2 sprays of the season as injury to leaves may occur when used later and should not be used after fruit set. Peaches and nectarines that ripen mid-July or later should continue to be sprayed every 3-4 weeks. These fungicides can be applied in combination with the post-bloom insecticides.

If weather conditions are wet and brown rot has been a problem previously, 2 to 3 applications of captan or sulfur should be used starting 3 weeks prior to anticipated harvest. Use a formulation labeled for bearing fruit trees that does NOT contain insecticide. If sulfur is used for brown rot control, spray every 5 to 7 days starting 3 weeks before anticipated harvest when weather conditions are wet. Captan is a more effective fungicide than sulfur. Also, it does not need to be applied as frequently as sulfur. Not allowing fruit to become overripe on the tree and removing any rotten fruit from the tree area can aid in reducing fruit rots.

INSECTS: Scales can be serious pests of peaches and nectarines and a dormant oil application is important to manage them. The most serious insect pests of nectarines and peaches occur immediately after bloom, when a complex of stink bugs and plant bugs feed on small developing fruits and cause what is known as “catfacing” damage. The plum curculio and oriental fruit moth are also major pests that occur at this time. A 3-week period beginning at petal fall is a critical time for insect control, and two applications at 10-14 day intervals with a pyrethroid insecticide is often required to control the pest complex. As the crop approaches harvest, Japanese beetles and June bugs can feed on ripened fruit.

Peachtree borer is a clear-wing moth that lays eggs on tree trunks and the larvae bore into the base of the tree near the soil-line. This usually results in a dark yellow gum that contains saw dust-like wood particles called frass. A pyrethroid insecticide applied to the trunk of the tree (from the first scaffold limb to the ground) during the first week of September, will help to control this insect borer.

Cherries and Plums

The fungal disease, black knot, can occur on branches of cherries and especially plums. This is most common when these fruit trees are grown near wooded areas that contain wild cherry. Black knot can be reduced by pruning out the knots as soon as observed and spraying a fungicide such as chlorothalonil just as new growth starts in the spring, with two additional sprays 7 to 10 days apart. The fruit disease most commonly encountered on cherries and plums is brown rot, the same disease that affects peaches and nectarines. Apply the first fungicide spray for brown rot 3 weeks before anticipated harvest. If frequent periods of precipitation occur, apply 1 to 2 additional sprays at 5-7 day intervals as recommended for peaches.

Cherries and plums are susceptible to attack by many of the same insect pests previously mentioned for peaches, including scales, plum curculio and peachtree borer, and precautions should be take to control these insects. The cherry fruit fly and black cherry fruit fly can also be common pests, and are similar in appearance and damage to the apple maggot. Cherries and plums are susceptible to damage by these fruit flies from late May through July. Most insecticides recommended for tree fruits are effective against cherry fruit fly, including carbaryl, malathion and the pyrethroids.

Pesticide use in the home orchard

Pesticides are designed to kill pests such as insects and disease-causing organisms like fungi and bacteria. By law, they must be used, stored, and disposed of only as instructed on the container label. Always read and follow the directions on the container label before using a pesticide. Before purchasing a pesticide, be sure that it is approved for use on the fruit crop to which you plan to apply it. The approved crops are stated on the pesticide label. Also, when preparing to spray fruit during the 3-week period before anticipated harvest, check the label to be sure that the pesticide can be applied within that time frame. Store all pesticides and containers (example sprayers, measuring instruments) used for application away from children and pets and do not use these containers for any other purpose.

For management of the most common diseases that affect fruit trees grown in the home orchard, the fungicides found in various brands of tree fruit sprays contain captan, sulfur, chlorothalonil, or copper. These materials generally are safe for use on most fruit trees, however, some plants are sensitive to copper and injury to fruit and leaves may occur when copper-containing materials are applied after the bloom period. Some products may also contain the fungicides myclobutanil (very effective for powdery mildew and rust diseases of apples and brown rot of peaches) or tebuconazole (effective for brown rot of stone fruits). Only copper and Agri-mycin (streptomycin) have activity against bacterial diseases such as fire bight. Agri-mycin does not control fungal diseases. Captan and sulfur often can be purchased individually and prepared as indicated in the table. Where one or just a few trees are involved, ready-to-use mixtures may be the best to purchase. Read and follow the directions on the container label. Pesticides for homeowner use and available at many garden centers are sold under the brand names such as Bonide(http://www.bonideproducts.com/), Spectracide (http://www.spectracide.com/), and Bayer Advanced (http://www.bayeradvanced.com/). A list of products, product labels and material safety data sheets (MSDS) can be found at their websites.

Additional Tips

  1. Use personal protective equipment such as clothing, gloves, and a respirator as recommended on the product label.
  2. Mix fresh spray for each application. Do not save spray mixture for the next application. This is not only unsafe, but the pesticide loses its activity and also can damage the sprayer. Carefully calculate the amount of spray needed so that excess does not result and create a disposal problem.
  3. Most fungicides and insecticides can be mixed together in the same tank unless the pesticide label prohibits mixing them. DO NOT spray an insecticide during bloom because it is likely to kill pollinating insects such as honeybees.
  4. Spray carefully and thoroughly to cover all parts of flowers, leaves, and fruit until a noticeable amount of water begins to drip from the foliage. Shake the sprayer often while spraying so that the chemicals do not settle out.
  5. In most cases for disease control, apply the pesticide prior to rainfall; however, sprays should not be applied closer than 2-3 hours before rainfall to allow for sufficient drying.
  6. Pesticides should be stored in a safe location that is cool and dry. Liquids should not be stored where the temperature will drop below 32F.
  7. ALWAYS Read and observe the instructions on the container label for the time interval between the last pesticide application and reentry into orchard or for harvest. This interval may vary depending on the pesticide.

Fungicides for Disease Control in the Home Orchard

Pesticide

Rate (per 1 or 10 gallons of water)

Fungicide

1 gal

10 gal

A mix of captan and sulfur will control most tree fruit diseases. However, there are certain times that a substitute or an additional fungicide is recommended for control of a particular disease. These have been mentioned for the specific fruit crop.

DO NOT mix captan and or sulfur with oil.

Captan 50% WP Plus

1 tablespoon

5 oz

Sulfur 80-90% WP *

3 tablespoons

10 oz

*Sulfur applied when temperatures are high (>85 F) may cause phytotoxicity.

There are several organic-approved fungicides available for disease control in the home orchard. These include sulfur, various formulations of copper, neem oil, phosphorus acid fungicides and biologicals. Biologicals are generally more effective in suppressing some diseases when disease pressure is light and use should be initiated before disease symptoms are observed or disease pressure (eg, wet weather) becomes high. Disease control results with biologicals can be variable depending on the disease, weather conditions, and how they are used. Organic disease control products can often be found at garden centers or can be purchased online from various sources.

Insecticides for Disease Control in the Home Orchard

Only common names of active ingredients are listed, because insecticides are available under many different names and formulations. Consult the label for rates and preharvest intervals.

Insecticide

Class

Uses

Oils

Mostly petroleum based

Often referred to as horticulture oils or dormant oils. Oils have been used for >100 years to control scales and other pests of fruit trees. Applied as a dormant application it should be used at a 3% solution. Some highly refined or light weight formulations can be used after bloom, but should only be used at a 1% solution. Do not use in combination with or at least 10 days before or after a fungicide that contains sulfur or captan is applied, or severe leaf burn will occur.

Carbaryl

Carbamate

An old insecticide that controls a broad spectrum of pests, but is not effective against aphids or scales, and can flare mite populations. Also acts as a fruit thinning agent when applied to apples within about 2 weeks after bloom

Malathion

Organophospate

Another old insecticide that also has broad spectrum activity. Effective against insects with sucking mouthparts such as aphids.

Spinosad

Spinosins

A fermentation product of a soil-dwelling organism. It is effective against thrips and leafminers, and leafrollers. Certain formulations are approved for organic use.

Azadirachtin (Neem)

Botanical

Extracted from the seed of the neem tree, formulations of this are approved for organic use. It is most effective against insects with sucking mouthparts such as aphids and leafhoppers, but also has some activity against plum curculio.

Insecticidal soap

Potassium salts of fatty acids

Insecticidal soap can help control soft bodied insects such as aphids and mites, but it has no residual activity.

Acetamiprid

Neonicotinoids

This relatively new insecticide has broad spectrum activity and provides good control of many major pests, including aphids, beetles, and oriental fruit moth. It can also flare mite populations.

Pyrethrin

Botanical

This botanical insecticide has rapid knockdown activity against many pests, but insects often recover. Piperonyl butoxide (PBO) is often mixed with pyrethrin to act as a synergist. It has very short residual activity, which limits its effectiveness.

Permethrin

Cyhalothrin

Bifenthrin

Pyrethroids

These three different pyrethroid insecticides are synthetic analogs of pyrethrins, but they have enhanced activity and much longer residual activity. They provide excellent control of many key pests, but they can also flare mite populations.

Recommendations of specific chemicals are based upon information on the manufacturer’s label and performance in a limited number of trials because environmental conditions and methods of application may vary widely, performance of the chemical may not always conform to the safety and pest control standards indicated by experimental data. All recommendations for pesticide use were legal at the time of publication, but the status of registration and use patterns are subject to change by actions of state and federal regulatory agencies.

Last Update: October 2012

When to spray plum trees.

Growing fruit can be a challenge in Kentucky and plums are no exception. It may be too late for a few pests such as aphids, mites or scale but bloom time is the most important time to control pests. Disease and insect problems can occur at different times of the year so a spray schedule should be followed if possible. Various insecticides can be used so read and follow all label instructions for safe and effective use of pesticides.

This is a simplified spray schedule for peach, cherry and plums. This publication has a variety of pesticides recommended for your convienence:

The detailed schedule that follows has information on sprayers, how to spray, and has a pictorial (at the end) on what the differing stages of bloom look like by plant. Organic options are available here as well :

Feel free to contact our office if you have other questions.

Let me know if I can help you further!
Carol Wilder
Horticulture Technician
Jefferson County Cooperative Extension Service
502-569-2344
810 Barret Ave
Louisville KY 40204

Home Fruit Spray Schedule [fact sheet]

Introduction

Disease and insect control measures suggested in this guide are recommended only for home fruit production. When this program is followed, trees and small fruit plants should be reasonably free from insect and disease injury. This spray schedule is developed for the average conditions existing in New Hampshire.

The weather is the greatest variable related to pest control. Warm, wet weather in spring favors the development of apple scab, cedar apple rust, fire blight, mildew, rots, and many other diseases. Under such conditions, it may be necessary to spray more often to prevent infection. Dry, hot weather is often more favorable for insect population buildup, so it may be more difficult to control insects during hot, dry weather. If surface blemishes on fruit do not bother you, you may follow a less intensive schedule. One such minimal spray schedule for apples is indicated in the chart.

General Purpose Spray Mixtures

General purpose spray mixtures are useful for the control of common pathogens and insects that attack fruit, except plum curculio, peach tree borers, and pathogens that cause black knot of plum, cedar apple rust, fire blight, and peach leaf curl. Some mixes are labeled for tree fruit only. Check the label before you buy. The ingredients usually include one or more insecticides (such as carbaryl, permethrin, malathion) and one or more fungicides, usually captan, sometimes sulfur. Captan is generally considered a good choice for management of many fruit diseases. Sulfur is particularly good for powdery mildew, and is somewhat effective for scab, rust, and brown rot.

Reliance on a mixture simplifies spraying fruit. Since all pests do not always threaten your crop in combination, use of the mixture results in some unnecessary spraying. The choice is yours – total reliance on general-purpose mixtures is simple and convenient but can be wasteful at times, may harm non-target species and may increase the risk of pests and pathogens developing resistance to pesticides. Combining insecticides and fungicides in your sprayer tank as needed is more complex, but uses only what is required, when it is required.

Garden supply stores sell general purpose mixtures under a variety of names. The ingredient pesticides can also be purchased separately and mixed when used. Refer to the labels for precautions before mixing any pesticides.


Apple scab.

The weather is the greatest variable related to pest control. Warm, wet weather in the spring favors the development of apple scab, cedar apple rust, fire blight, mildew, rots, and many other diseases.


Black knot.


Black rot of grape: fruit rot. Credit: APS Press, Photograph courtesy R.C. Pearson.


Brown rot on nectarine.

Supplemental Spray Materials

The proper use of supplementary spray materials can increase the yield of usable fruit. Bacillus thuringiensis (Biobit, Dipel, Javelin, Sok-BT, B.t.) is effective on foliage-feeding caterpillars. Sevin is registered for all of the listed crops. It is effective for many pests, including apple and blueberry maggots, Japanese beetles, spittlebugs and tent caterpillars. Some backyard products contain permethrin. It can be somewhat effective on plum curculio (a major, serious tree fruit pest), but not in the low concentrations available to backyard growers. To really control plum curculio, adding a supplemental spray (like carbaryl) is necessary. Spray oil can help control certain aphids, mites, scales, and pear psyllas on fruit trees (oils can also suppress some diseases). Copper soap (copper octanoate) is effective for cedar apple rust, fire blight and peach leaf curl. Myclobutanil is effective against brown rot and cedar apple rust. Propiconazole is effective for brown rot, and chlorothalonil is also labeled for brown rot. Bacillus subtilis (Serenade) is registered for fire blight and gray mold, Streptomyces lydicus (Actinovate) is labeled for small fruits for gray mold and powdery mildew, and potassium bicarbonate is effective for powdery mildew. The following sections will give examples and situations where supplementary sprays or sanitation may be helpful.


Leaf spot symptom. Credit: APS Press, Photograph courtesy C. A. Smith.

Diseases

Apple Scab — When growing scab resistant varieties, fungicides are rarely needed. Examples of resistant varieties are: Freedom, Jonafree, Liberty, MacFree, Nova Easygro, Prima, Pristine, and Redfree. If susceptible varieties are grown, rake and destroy fallen apple leaves in autumn.

Black Knot of Plum and Cherry — This disease causes black knots/ growths on twigs and spurs. It is controlled by cutting out and burning the diseased twigs in the fall, winter, or very early spring. All infected wild trees adjacent to the orchard should be destroyed, if possible, to prevent spread of the disease. Select resistant varieties of plum.

Black Rot of Grapes — The fungus causing this disease overwinters on all parts of the plant, but mummified berries on the ground or clinging to the vines are the major infection source in the spring. Removal of mummified fruit is important for management. Captan, copper soap, and myclobutanil are effective for control.


Cedar apple rust: fruiting body on cedar. Credits: J.OBrien, USDA FS


leaf spot on apple leaf and juniper gall (bottom). Credits: J.OBrien, USDA FS

Brown Rot of Cherry, Peach and Plum — The fungus that causes this disease overwinters on mummified fruits hanging on the tree or on the ground. Clean up fallen fruit before, during, and after harvest. Remove and destroy all unharvested fruits and mummified fruits from trees after harvest. Captan, propiconazole, chlorothalonil, or myclobutanil (Immunox – Do not use Immunox Plus, it is not labeled for use on fruit) are registered.

Cedar Apple Rust — The fungus causing this disease overwinters on red cedar trees or junipers growing nearby. These trees should be removed, where practical, or remove galls in late winter to reduce infection on apple leaves and fruit. Rust can be controlled by applying copper soap (copper octanoate) prior to pink bud, or myclobutanil from half-inch green through pink.

Cherry Leaf Spot — The fungus causing this disease overwinters in infected leaves from the previous season. Raking fallen leaves in the autumn is essential for control. Myclobutanil and Captan are effective for control.

Fire Blight on Apple and Pear — This disease primarily affects spurs and twigs. It is controlled by cutting out and burning blighted branches as soon as they are seen. Cut at least 6-12 inches below any sign or symptom of the disease. After each cut, disinfect the pruning tools with a mixture of 1-part chlorine bleach and 9 parts water or 70% isopropyl alcohol. If there is a history of fire blight, copper soap can be applied as a late dormant spray (do not apply copper after green tip or fruit injury may occur).

Fire blight.

Gray Mold of Strawberry and Raspberry— This disease is also called Botrytis fruit rot. Cultural practices that promote air circulation can reduce infections. A 3-spray program (just before bloom, full bloom, petal fall) may eliminate the need for fungicides during harvest. Botrytis also causes blossom blight on blueberries. Captan, Bacillus subtilis, and Streptomyces lydicus are registered.

Gray mold.

Peach Leaf Curl — Leaves become curled, crinkled, thickened, and red, pink or purple. The disease is controlled by applying copper soap after leaf drop in autumn (best) or before buds swell in spring.

Peach leaf curl.

Powdery Mildew — Various formulations of wettable sulfur or potassium bicarbonate can aid in management of powdery mildew problems. Usually not a serious problem in New Hampshire, except on grapes. Some varieties of grapes are sensitive to sulfur.

Mummyberry of Blueberry — Fruit turn grayish, dry and drop off before ripening. Removing affected fruit before they fall, adding 2” of mulch and spring cultivation will help reduce infections.

Mummyberry of blueberry.

Insect Pests

Aphids — Insecticidal soap or malathion may help in aphid outbreaks, but most fruit-attacking aphids are held in check by predators.

Green apple aphids with one of their predators, the orange maggot.

Apple Maggot (Rhagoletis pomonella) — The larvae tunnel in apples in July & Aug. There are traps to guide if/when spraying is needed.

Adult apple maggot.

Codling Moth (Cydia pomonella) — The larvae tunnel in apple flesh, and feed on the seeds. They are usually controlled by sprays for curculio and apple maggot.

Adult codling moth. Credits: W. Cranshaw, CSU, Bugwood.org.

Leaf-Feeding Caterpillars— Gypsy moth (Lymantria dispar), tent caterpillars (Malacosoma spp.), fall webworms (Hyphantria cunea) and others may be controlled by applying a spray with Bacillus thuringiensis. Trade names include Dipel, Xentari, Javelin, Biobit, and others. The material must be eaten by caterpillars in order to work. Read the label before buying! Some strains of B.t. (Example: israelensis) do not work on caterpillars. The label will clearly indicate what pests are affected.

Japanese Beetle (Popillia japonica) — This insect is sometimes a problem; add carbaryl (Sevin) to the spray mixture or use carbaryl alone.

Adult Japanese beetle. Credit: D. Cappaert, Bugwood.org.

Pear Psylla (Cacopsylla pyricola) — Psyllas suck plant juices, and can stunt pears. Blackened leaves and twigs are signs of psyllas. High rates of nitrogen fertilizer often create psylla problems. Insecticidal soap may help with psyllas.

Pear psylla nymph covered with honeydew. Credit: W. Cranshaw, CSU, Bugwood.org.

Peach Tree Borer (Synanthedon exitiosa) — These insects attack the trunk and main limbs of trees and are best controlled by spraying the lower trunk and the crotches thoroughly during July and August with an insecticide that lists peach tree borers on the label. None are now available for backyard use, so the best defense is to avoid mechanical injury to the trunks. Trunk injury greatly increases attractiveness to peach tree borers, to lay eggs.

Peach tree borer evidence: gum mixed with “sawdust”.

Plum Curculio (Conotrachelus nenuphar)— This insect attacks very young apples, causing most of them to drop in June. Most all-purpose spray mixtures have too-low a concentration of permethrin to control curculios. Adding a spray of carbaryl when the fruit reach ¼ inch diameter will control this insect for seven days. But new labels require that a second application cannot be applied until 14 days later. Surround is a non-toxic alternative, but is very tricky to apply correctly.

Scale Insects — These are sometimes troublesome on backyard fruit plants. If they are a problem, apply a “superior” oil spray, 5-6 tbs. per gallon of water or 2 1/2 cups per 5 gallons of water, when buds begin to swell in the spring. Be sure to thoroughly wet the entire surface of all limbs and twigs, especially the top of plants and trees.

Scales: Eggs exposed from under adult scale cover. Credits: W. Cranshaw, CSU, Bugwood.org.
Scales: Nymphs next to a shell. Credits: W. Cranshaw, CSU, Bugwood.org.

Soil Pests — Several soil insect pests such as white grubs may be troublesome in strawberry beds. To avoid such problems, eliminate grass from your beds and don’t locate the beds in areas where grass grew the previous year.

Spotted Wing Drosophila (Drosophila suzukii) — Spotted wing drosophila attacks ripe raspberries and blackberries, blueberries, plums, currants, some grapes (especially dark varieties with thin skins), some peaches and August-October maturing strawberries. Late-maturing varieties are the most heavily hit. Early maturing varieties of brambles and blueberries may escape significant attack. Attacked fruit turn sour and quickly rot. The most severe problems are in Rockingham & Hillsborough counties. Coös, Grafton and Carroll counties have the lowest problems. Effective insecticides include Entrust, Malathion (high rate), Exirel and others.

Adult spotted wing drosophila adult.

***Additional note, added by A. Wallingford May 2019: Cabaryl may now be more difficult for home owners to acquire.

It is unclear whether or not products containing the pyrethroid, zeta-cypermethrin, will offer equivalent control as carbaryl. However, these products will certainly have activity on common apple insect pests and offer an alternative to carbaryl.

Spray Schedule for Tree and Small Tree Fruits

Tables 1-4 summarize spray schedules for fruit trees and small tree fruits. Use appropriate materials for the pests indicated (consult pesticide labels). Watch for supplementary materials (time of application) and pests to be controlled.

***Additional note, added by A. Wallingford May 2019: Cabaryl may now be more difficult for home owners to acquire.

It is unclear whether or not products containing the pyrethroid, zeta-cypermethrin, will offer equivalent control as carbaryl. However, these products will certainly have activity on common apple insect pests and offer an alternative to carbaryl.

For more related fact sheets, go to extension.unh.edu/resources/category/Agriculture.

Stop! Read the label on every pesticide container each time before using the material. Pesticides must be applied only as directed on the label to be in compliance with the law. All pesticides listed in this publication are contingent upon continued registration. Contact the Division of Pesticide Control at (603) 271-3550 to check registration status. Dispose of empty containers safely, according to New Hampshire regulations.

Download the Resource for the complete fact sheet and a printable version.

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