Pests & Diseases
Integrated Pest Management (IPM) is a method of encouraging natural predators to control pests in your garden or orchard. Nature provides a balance between plant pests and the beneficial insects that control these pests. The less we do to tamper with that balance, the more likely it is to work successfully. How does it differ from organic gardening? Proponents of IPM are not opposed to the use of chemical controls, but use them only when necessary and only in amounts and with proper timing to minimize a negative effect on the beneficial bugs in the garden.
- Learn to recognize the beneficials. Knowing the good bugs is important in assessing the situation in your garden.
- Use preventive sprays. “Managing Pests and Disease in Your Home Orchard” is a valuable publication to help you know when and what to spray.
- Use no spray before its time. Using the safest spray at the right time, only if necessary, is the essence of IPM.
- Plan ahead. Planting the right plant at the right time in the right location will help you minimize problems.
Natural predators such as lacewings, leatherwing beetles, ladybird beetles, ground beetles, wasps, praying mantis and pirate bugs will control or contain most pest populations at an acceptable level, especially if trees are kept vigorous, orchard areas are kept clean of trash and weeds, and trees are well pruned to facilitate good air movement. Home orchardists have little need to completely eradicate pests.
Most insect and mite pests of fruit trees are controlled by many beneficial species of insects and mites found in the orchard. Do not spray pests unless you are certain they are present in damaging numbers or this publication suggests you do so. Unnecessary sprays reduce control provided by beneficial species and may result in added damage from pests freed from their natural controls.
Several of the most common fruit tree diseases may be controlled by using the proper fixed copper spray during the dormant season. These diseases include: bacterial canker, brown rot, coryneum blight and peach leaf curl. See individual fruit tree pages for descriptions. Be certain to follow directions on the package exactly whenever sprays are used.
Beware: some fungicide brands recommend inadequate amounts of copper for peach leaf curl. There are numerous fixed copper materials. We recommend one that contains 50% actual copper. Do not store Bordeaux from one year to the next.
How Pests, Diseases, and Hosts Fit Together
The tables, below, are brief formats designed only as guides to be used with Integrated Pest Management (IPM) and other research-based references. If one or more of these pest and disease problems are not present, do not apply preventatives. Many do not become problems until trees begin to bear.
| Pest/Disease | Hosts(s) |
|---|---|
| Codling Moth | Apple, pear, sometimes walnut, plum |
| Peach Twig Borer (PTB) | Peach & nectarine, almond, apricot, plum & prune |
| Brown Rot Fungus | Peach & nectarine, cherry, plum & prune, almond |
| Fireblight | Pear, apple, quince |
| Scab | Apple, pear |
| Bacterial Canker | Peach & nectarine, cherry, plum & prune, pear (blast) |
| Peach Leaf Curl | Peach & nectarine |
Pests
[PDF] Fruittree Leafroller on Ornamental and Fruit Trees, UC IPM
[PDF] Ferrisia gilli: A Mealybug Pest of Pistachios and Other Decidious Crops, David Haviland, Robert Beede, Kris Godfrey, Kent Daane
Goals for reducing insect and mite damage in home orchards are to:
- Protect trees and crops from substantial damage
- Make it simple and easy
- Make it safe
- Use methods that enhance natural control factors
Dormant season treatments are most important since they will not kill beneficial insects. One spray controls many orchard pests. The following tables of Orchard Pests by Season list several common home orchard pests and include information on damage, description, life cycle, and control options. More importantly, it provides information on the seasons when these pests should be addressed if they are problems in the home orchard. When damage becomes obvious, it is often too late to treat with successful results for that year.
| San Jose Scale | |
|---|---|
| Hosts | Most deciduous fruit and nut trees. |
| Damage | Gets on fruit, kills shoots. |
| Description | Gray scale with yellow body. |
| Life Cycle | Three generations, overwinters as immature black cap stage. |
| Controls | Natural: limit tree size; lady beetles and parasitic wasps (avoid summer sprays).
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Leaf Curling Aphids | |
| Hosts | Apple, plum, cherry, and others. |
| Damage | Rolled, stunted leaves; stunted and distorted fruit; honeydew drip. |
| Description | Apple aphid (rosy purple); green apple aphid (small and green); mealy plum aphid (pale, green, waxy); black cherry aphid (shiny, black); leaf curl plum aphid (yellow green, shiny). |
| Life Cycle | Overwinters as eggs on tree. Eggs hatch as tree leafs. |
| Controls | Natural: Control may not be sufficient. Aphids develop before natural enemies build up.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Pear Psylla | |
| Hosts | Pears. |
| Damage | Honeydew with sooty mold, leaf burn, pear decline, leaf curl. |
| Description | Adult looks like miniature cicada, one-tenth inch; nymph yellow to brown at 5th nymph stage. |
| Life Cycle | About five generations a year; overwinter as adults. |
| Controls | Natural: Predators and parasites (avoid summer sprays).
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Blister or Rust Mites | |
| Hosts | Pears for pear blister, pear rust; peach and nectarine for peach silver. |
| Damage | Pear blister/rust russet fruit surface, blister, and damage leaves. Peach silver damages leaves. |
| Description | Mite: need hand lens to see, white to tan. |
| Life Cycle | Overwinters under bud scales and adjacent to leaf buds; many generations. |
| Controls | Natural: Predaceous mites (avoid summer chemical sprays).
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Peach Twig Borer (PTB) | |
| Hosts | Peach, nectarine, almond, apricot, plum, prune. |
| Damage | Invades fruit and kills new shoots. Fruit feeding usually superficial, not deep. |
| Description | Mature larva with chocolate brown bands, dark head. |
| Life Cycle | Several generations overwinter as larva in hibernaculum on tree. |
| Controls | Natural: not reliable.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Coddling Moth (key pest in apples and pears) | |
|---|---|
| Hosts | Apple, pear. |
| Damage | Worms invade fruit of apple, pear, sometimes walnut, and plum. |
| Description | Grayish brown moth, about ½ inch, copper tipped wings, larva white with black head, later larva pinkish with brown head. |
| Life Cycle | Overwinter as larva in cocoons, pupate in spring, emerges as adult early May. Two or three generations possible in Foothills. |
| Controls | Natural: Difficult pest.
Cultural: Sanitation, banding trunks, bagging fruit. Use temperatures to predict egg hatch and pheromone traps to monitor flights and estimate adult population. Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Mites | |
|---|---|
| Hosts | Many fruit and nut trees. |
| Damage | Pale stippling sometimes webbing on leaves; can distort leaves, fruit, blossoms, high numbers cause leaf drop. |
| Description | Minute true spiders, need hand lens to see: Spider mite, two spotted mite, European red mite, and brown mite. |
| Life Cycle | Ten days for two-spotted in hot weather. |
| Controls | Natural: Predaceous mites, many natural enemies; avoid chemicals.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Aphids | |
| Hosts | Many hosts. |
| Damage | Honeydew, foliage feeding, shoot distortion. |
| Description | Wooly apple aphid covered with white cottony wax. |
| Life Cycle | Many generations. Wooly apple migrates from roots. |
| Controls | Natural: predators (green lacewing, minute pirate bug, syrphid fly, damsel bugs, and many others); parasitic wasps (look for mummies).
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Redhumped Caterpillar | |
| Hosts | Deciduous trees, especially plum, prune, walnut. |
| Damage | Skeletonizes and strips all foliage on a branch. Young trees especially vulnerable. |
| Description | Older larvae with yellow body, black stripes, red hump on back and red head. |
| Life Cycle | |
| Controls | Natural: Many natural enemies; pick off, remove clusters by hand.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Fruit Worms | |
|---|---|
| Hosts | Fruittree Leafroller and Obliquebanded Leafroller: apple, pear, stone fruit, almond, citrus.
Green Fruitworm: apple, pear, plum, prune, cherry, apricot. |
| Damage | Feeding on young fruit and leaf some foliage loss, rolling and webbing. |
| Description | Fruittree leafroller: black with black-headed larva drops on spun thread.
Green fruitworm: green larva, large when mature, 1½ inches long. |
| Life Cycle | One generation, early season only; overwinters as eggs. |
| Controls | Natural: Some predators when larva are small, birds later on.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Thrips | |
| Hosts | Many hosts. |
| Damage | Spot on apples and pear, catfacing on nectarines, plums and peaches, cause depressed cavities on apples, distort fruit on pears. |
| Description | Flower thrips, madrone thrips, pear thirps. 1/20 inch when adult, long and slender. |
| Life Cycle | Flower thrips have many generations, heavy numbers after warm winters, low after very wet winters. |
| Controls | Natural: Modify habitat (avoid adjacent weedy or grassland area that dry up), encourage parasites, remove host plants, sanitation.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Plant Bugs | |
| Hosts | Apple, pear, stone fruit, and other hosts. |
| Damage | Fruit dimpled and pithy. |
| Description | Consperse stinkbugs most damaging, gray-brown to green black speckled legs, shield shaped, ½-inch. Conchuela, red shouldered and a number of other stinkbugs; Lygus, false chinch, leaf-footed box elder and others. |
| Life Cycle | Two generations for consperse, overwinters as adult. Same for other bugs. |
| Controls | Natural: Encourage parasites, remove host plants (ground covers and weedy areas), sanitation.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
| Pacific Flatheaded Borer | |
| Hosts | Many deciduous fruit and nut trees. |
| Damage | Mine and girdle trunks of young trees and limbs of older trees. |
| Description | Larva with large flat head and white body, ½- to ¾-inch long. |
| Life Cycle | Overwinter in xylem as pupae; adults emerge in early summer and lay eggs on sunburned or damaged tissue. |
| Controls | Cultural: Whitewash trunks to prevent sunburn; prune to shade larger branches.
Spray: See [PDF] Calendar of Backyard Gardening Operations |
Weeds
Please read [PDF] Home Orchard Weed Control by Paul Voosen, Farm Advisor UCCE Marin-Sonoma Co.
Weeds can have a dramatic effect on tree growth by competing for soil moisture, physical space, and nutrients. Some weeds might even have an antagonistic or allopathic effect on trees. Experiments comparing various weed control methods have demonstrated that young trees can be reduced in their growth by 1/3 to 1/2 in the first few years if weeds are allowed to compete with trees compared to treatments with no weeds.
One of the best ways to maintain the area under home orchard trees is completely weed free with an organic mulch. The mulch keeps the soil moist, reduces evaporation, and as it breaks down, it releases nutrients to the tree. It must be at least 3 inches deep to adequately control weeds and will need to be reapplied periodically to maintain that depth. Other mulches such as heavy-duty weed cloth is an alternative to organic mulches, which eliminates the need for frequent reapplication. The best weed cloth barriers will block all the light, control all the weed growth, allow water to pass through, and last 5–10 years. Another advantage is that it can be easily cleaned off of fallen leaves and fruit to prevent the spread of diseases. Mechanical cultivation with a tiller or hand hoe also works; the important thing is to keep the area free of weeds from the beginning of growth in the spring until leaf fall.
In the dormant period, it is not critical to maintain a weed free area under the trees, so cover crops or ornamentals can be grown to improve the soil or just to look nice. Mature trees can tolerate more weeds or turf or cover crops growing within their drip-line since they already have an established root system, are full sized, and don’t need to grow as much.
Diseases
[PDF] Navel Orange Split, Pamela M. Geisel, Carolyn L. Unruh, Patricia M. Lawson
[PDF] Apple Scab, UC IPM
[PDF] Cherry Crinkle Leaf, Stephen M.
Southwick
Conditions that favor fruit tree diseases are wetness and lack of sanitation. The Tables of Home Orchard Diseases, below, list diseases by the area of the tree that is affected by disease and includes conditions favoring the disease, name of the disease, symptoms that might be observed, and prevention tips:
| Crown Rot | |
|---|---|
| Hosts | Many hosts. |
| Causes | Caused by species of Phytophtora fungus when tree is too wet around crown. |
| Symptoms | Distress in tree top, reduced growth. |
| Prevention | Good drainage, mound soil at planting, don’t over-irrigate. |
| Oak Root Fungus | |
| Hosts | Many hosts. |
| Causes | Caused by Armillaria mellea fungus (while fans of mycelium under bark) when tree is too wet around crown. |
| Symptoms | Distress in tree top, reduced growth. |
| Prevention | Use resistant stock, don’t over-irrigate. |
| Peach Leaf Curl | |
|---|---|
| Hosts | Peach, nectarine. |
| Causes | Fungus, wet weather. |
| Symptoms | Irregular reddish lesions are sometimes seen on fruit. |
| Prevention | |
| Apple and Pear Scab | |
| Hosts | Apple, pear. |
| Causes | Fungus infects when wet from green tip stage through bloom period. |
| Symptoms | Fungus infects flowers, leaves, or fruit; causes dark scabby areas on fruit, damages leaves. |
| Prevention | |
| Blossom Blast / Fruit Brown Rot | |
| Hosts | Blossom Blast: Stone fruit, pear; Fruit Brown Rot: Stone fruit, almond. |
| Causes | Caused by brown rot fungus or by Pseudomonas syringae bacteria; brown rot produces gray spores. |
| Symptoms | Pseudomonas attacks only when freezing temperatures occur. Blights or “blasts” buds, blossoms, leaves, green fruit. Cankers. Brown rot fungus blights blossoms, leaves and twigs shrivel; brown or tan spots spread over fruit. |
| Prevention | Remove mummied fruit; cut off blighted wood. |
| Fireblight | |
|---|---|
| Hosts | Pear, apple, quince. |
| Causes | Bacteria, Erwinia amylovora, attacks flowers when wet and mean temperatures are over 60°F. |
| Symptoms | Bacteria moves into shoots and kills tissue causing blackened leaves and stems. |
| Prevention | Cut out infections well ahead of visible injury. |
| Bacterial Canker | |
| Hosts | Stone fruit, almond. |
| Causes | Caused by Pseudomonas syringae. |
| Symptoms | Foliage collapses and dies after leafing in spring due to girdling of branches. A canker develops at the point of infection and dark gum usually is extruded through the bark. |
| Prevention | Disease dies out in hot, dry weather. Keep trees vigorous by good cultural practice. |
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general-pests.html last updated October 27, 2008