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.

How Pests, Diseases, and Hosts Fit Together (with links to UC IPM)
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.

Orchard Pests by Season: *Dormant*
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

Orchard Pests by Season: *Petal Fall to Harvest*
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

Orchard Pests by Season: *Summer*
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

Orchard Pests by Season: *Green Tip – Petal Fall*
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] Control Options for Major North Coast Stone Fruit Diseases in Home Orchards, Rachel Elkins

[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:

Root and Crown Diseases
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.

Leaf and Fruit Infections
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.

Shoot Infections
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.