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Preventing Fruit Tree Diseases – What Are Common Fruit Tree Diseases

Preventing Fruit Tree Diseases – What Are Common Fruit Tree Diseases


By: Liz Baessler

Fruit trees are a great asset to any garden or landscape. Keep reading to learn more about the identification of fruit tree diseases and fruit tree disease treatments.

Common Fruit Tree Diseases

Fruit trees are very diverse, but there are some common fruit tree diseases that can be found in many of them. The best thing you can do when preventing fruit tree diseases is to prune the tree(s) to allow sun and air through the branches, as disease spreads easily in dark, damp environments.

Peach scab and leaf curl

Peaches, nectarines, and plums often fall victim to the same problems, like peach scab and peach leaf curl.

  • With peach scab, the fruit and new twigs are covered in round, black spots surrounded by a yellow halo. Remove the affected parts of the tree.
  • With leaf curl, the leaves dry and curl up on themselves. Apply a fungicide before the period of bud swell.

Brown rot

Brown rot is an especially common fruit tree disease. Some of the many trees it can affect include:

  • Peaches
  • Nectarines
  • Plums
  • Cherries
  • Apples
  • Pears
  • Apricots
  • Quince

With brown rot, the stems, flowers and fruit are all covered in a brown fungus that eventually mummifies the fruit. Remove the affected parts of the tree and fruit, and prune to allow for more sunlight and air circulation among the branches.

Bacterial canker

Bacterial canker is another disease that can be found in virtually every fruit tree. The particular disease symptoms in fruit trees include holes in the leaves, as well as new shoots, and even whole branches dying off. It is mostly found in stone fruit trees and trees that have suffered frost damage. Cut off the affected branches several inches below the disease and apply a fungicide.

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Common Diseases of Stone Fruit Trees and Their Control

Trees that bear fruit with a hard woody pit, or “stone,” are commonly called “stone fruit” trees. Peaches, plums, apricots, nectarines, almonds, and cherries are in this group. Of the stone fruits, only peaches and nectarines are grown commercially in Oklahoma. However, many homeowners have at least one stone fruit tree in their yard. A number of serious fungal, bacterial, nematode, and viral diseases are common to stone fruits and should be of concern to all growers. Symptoms of several common diseases and their control measures are discussed.


Main diseases

Bacteriosis:

Fire blight produced by Erwinia amylovora

It is a very dangerous disease, that can destroy the whole orchard. The appearance of this disease is favored by high atmospheric humidity, wind, rain and temperatures between 10 and 30 degrees Celsius. The attacked trees look like were burned by the fire. The sprouts wilt and will have a brown color, the fruits become black or are stained. On wet weather, on the attacked tissue appears the bacterial exudate.

Prevention and control measures:

  • Cutting and burning the affected branches
  • Treatments, after each rain with Dithane M 45, Aliette WG 80, Champ 77 WG, Melody Compact 49 WG, Funguran OH 50 WP.

Crown-gall produced by Agrobacterium radiobacter pv. Tumefaciens

On the roots and on the stem develop tumors, at the start small and soft, and after a while becomes like a wood. The tumors are having different sizes and forms. This tumors generate formations like leaves, buds or sprouts. The cells that compose this tumors are big and deformed. This bacteria penetrates into the tree through the wounds produced by the nematodes, hail etc. The appearance of this disease is favored by the temperatures between 22 and 30 degrees Celsius and atmospheric humidity of 80%.

Prevention and control measures:

  • Sorting seedlings before planting
  • The orchard will be founded on the lands that were prepared properly
  • Disinfection of scissors and tools, before passing from a tree to another
  • Cutting the affected branches up to the healthy area, appliance of a treatments with Bouillie Bordelaise 4-5% and covering the wounds with cicatrisant mastic resin
  • The seedling roots will be bathed in a solution of Bouillie Bordelaise 1% or Topas 100 EC 0.025%
  • Treatments in the vegetation period with products based on copper.

Quince leaf blight produced by Diplocarpon maculatum

This fungus parasitize the quince and pear orchards, rarely the apple orchards. The first form of attack manifests on the leaves. The symptoms are represented by circular, yellow, later red, spots. In their center will appear black dots that represent the fungus fructifications. The spots can unify and produce tree defoliation. The disease can attack the sprouts and fruits. The sprouts brunify and dry. On the fruits appear spots like those on the leaves. They unite, and the pulp cracks. On those cracks can develop diseases that produce the rot of the fruits.

Prevention and control measures:

  • Gathering and burning of the fallen leaves
  • Usage of resistant varieties
  • Cutting and burning of the attacked sprouts
  • Treatments with Systhane Plus 24 E, Score 250 EC, Topsin 500 SC, Captan 80 WDG, Dithane M 45.

Leaf blotch produced by Monilinia linhartiana

It is considered the most damaging disease of the trees cultivated in the cold and rainy areas. The attacked leaves hang without falling, the flowers brunify and dry, and the branches bend as a hook. The young fruits wrinkle, brunify and fall massive. The pulp of the mature fruits rots and on their exterior appear yellow-grey pillows. Finally, the fruits are mummified and remain in the trees, ensuring the transmission of the disease in the next year. The fungus winters on the mummified fruits and in the bark of the attacked branches.

Prevention and control measures:

  • Gathering and destruction of the attacked fruits
  • Cutting the affected branches up to the healthy area, appliance of a treatments with Bouillie Bordelaise 4-5% and covering the wounds with cicatrisant mastic resin
  • Chemical treatments in the vegetative rest with products based on copper (ex: Bouillie Bordelaise) and preventive treatments applied in vegetation with Switch, Score, Topsin.

Powdery mildew produced by Podosphaera clandestina

The attack appears on the leaves of young sprouts through the appearance of some white spots. Those will extend and will cover the whole leaf. The disease will evolve, and the mycelium will become grey and dusty. The attacked tissue wrinkles and dries. The fungus attacks the young fruits too. This are covered by a white mycelium felt. The fruits crack and rot.

Prevention and control measures:

  • Balanced fertilization
  • Usage of resistant varieties
  • The attacked sprouts and fruits will be burned
  • Treatments with Systhane Plus 24 E, Thiovit Jet 80 WG, Kumulus DF, Topas 100 EC, Karathane M 35 CE.


Main pests

Codling moth (Cydia pomonella)

It is a polyphagous species that attacks many species of fruit trees. The larvae attacks the fruits. The females lay their eggs directly on the fruit or on the leaves close to the fruit. After hatching, the larvae diggs galleries in the attacked fruits, leaving inside faeces.

Prevention and control measures:

  • Using the pheromone traps to identify the flight of the adults
  • Treatments with Reldan 22 EC, Novadim Progress, Laser 240 SC, Affirm, Calypso 480 SC.

Summer fruit tortrix (Adoxophyes orana)

It is a polyphagous species that attacks over 47 species of herbaceous plants and trees. The larvae eats in the spring the buds, inflorescences and leaves. The larvae penetrates in the fruit where it diggs superficial galleries. The wounds are gates for the funguses from the Monilinia genus.

Prevention and control measures:

  • Treatments with Nurelle D, Affirm, Bactospeine DF.

Apple blossom weevil (Anthonomus pomorum)

It has a generation a year and winter as an adult in protected areas (bark of the trees). The adults appear in the spring and feed with the young leaves. The females lays its eggs in the flowers or in the blossoms. The larvae feed inside the flowers or blossoms.

Prevention and control measures:

  • Treatments with Decis Mega, Reldan, Fastac, Actara 25 WG, Calypso 480 SC.

Apple leaf-curling midge (Dasineura mali)

It has 3-4 generations a year and winters in the superficial layer of the soil. The first signs of attack appear in may, when twisted and discolored leaves can be observed. Inside those leaves you can find yellow-orange vermiform larvae. If the attack is strong, the photosynthesis capacity is reduced and the yield too.

Prevention and control measures:

  • Treatments with Movento 100 SC, Calypso 480 SC, Faster 10 CE, Nurelle D, Affirm.

Spotted tentiform leafminer (Phyllonorycter blancardella)

This insect attacks a series of ornamental trees and fruit trees. The larvae will feed with the tissue found between the upper and lower epidermis of the leaves. A massive attack will reduce the ability of photosynthesis and implicitly decreases production.

Prevention and control measures:

  • Gathering and burning of the leaves fallen on the soil
  • Treatments with Actara 25 WG, Reldan 22 EC, Laser 240 SC, Coragen 20 SC, Kaiso Sorbie.

Oriental fruit moth (Cydia molesta)

It has 3-4 generations a year and winters as a larvae in a silky cocoon in the cracks of the bark. This moth attacks the sprouts, the leaves and fruits of the fruit trees, but the most damaged are the fruits. The larvae of the first generations attacks the sprouts and feed with the inside of them, producing big losses to the newly established orchards. The larvae of the third and fourth generations produce big damage to the fruits. This penetrate into the fruit through the peduncle area and eat irregular galleries around the stone. The apricots stop from growing, rot and fall.

Prevention and control measures:

  • Cutting and destroying of the attacked fruits and sprouts
  • Usage of attracting traps
  • Treatments with Mospilan 20 SG, Affirm, Decis Mega EW 50, Calypso 480 SC, Coragen 20 SC.

Woolly apple aphid (Eriosoma lanigerum)

It has 8-12 generations a year and winters as a larvae in the bark of the trees. It has great colonies on the branches, sprouts and roots. After the attack, the tissue hypertrophies and appears tumors as those produced by the Crown-gall.

Prevention and control measures:

  • Cutting and burning the attacked branches
  • Seedlings verification before planting
  • Treatments with Mospilan 20 SG, Actara 25 WG, Decis Mega EW 50, Confidor Energy, Actellic 50 EC.

San Jose scale (Quadraspidiotus perniciosus)

It is a polyphagous species that attacks over 200 species of plants. It has 1-3 generations a year and winters as a larvae on the bark of affected trees. The females and larvae spread on all the organs of the affected plant, including the fruit, this insect feeding with the cell juice of the host plant. If the attack is severe the shield that protects the body of the insect overlap and suffocate the trees. They stagnate from growing and in 2-3 years dry.

Prevention and control measures:

  • Application of the recommended treatments in the vegetative rest
  • Cleaning the branches with a scrub
  • Treatments with Nuprid AL 200 SC, Actara 25 WG, Calypso 480 SC, Faster 10 CE, Movento 100 SC.

Plum scale (Sphaerolecanium prunastri)

It is a polyphagous species that attacks many fruit trees, vine etc. It has a generation a year and winters as a larvae on the bark of the attacked branches. The adults and larvae colonise the branches and leaves producing tissue necrosis. Also, they can attack the leaves, producing deformations and their fall. The attacked plants are covered with their sweet droppings, that favors the appearance of some phytopathogenic fungus.

Prevention and control measures:

  • Cleaning the branches with a scrub
  • Treatments with Mospilan 20 SG, Nuprid AL 200 SC, Decis Mega EW 50, Calypso 480 SC, Faster 10 EC.

Peach twig borer (Anarsia lineatella)

This species attacks the sour cherry too. It has three generations a year and winters as a larvae under the exfoliated bark of the branches. In the spring, they leave their shelter and attacks the buds. In the young sprouts, the larvae eat holes to penetrate. The new appeared females will lay their eggs on the buds, and the larvae will penetrate in the fruits of the precocious species. The larvae of the next generations penetrate in the fruits that will ripen, where it diggs deep galleries.

Prevention and control measures:

  • Cutting and destroying of the affected branches (sprouts)
  • Treatments with Decis Mega EW 50, Karate Zeon 50 CS, Affirm, Mospilan 20 SG, Laser 240 SC.

Fall webworm (Hyphantria cunea)

It is a polyphagous species that attacks ornamental trees (Mulberry tree, London plane etc.) and fruit trees. It has 2 generations a year and winters as a pupa in the superficial soil layer. This insects produces defoliation of the trees and low fruit production. The caterpillars will stay on the lower side of the leaves and and will start to consume them. Also, they will weave some kind of nest, inside of which they eat.

Prevention and control measures:

  • Treatments with Faster 10 CE, Kaiso Sorbie, Affirm, Novadim Progress, Laser 240 SC.

Brown-tail (Euproctis chrysorrhoea)

It is a polyphagous species that attacks some shafts and fruits trees. It has a generation a year and winters as a larvae in a cocoon on the top of the sprout. The larvae attacks the buds and the leaves and can produce tree defoliation.

Prevention and control measures:

  • Elimination of the branches where the larvae are presented
  • Treatments with Karate Zeon 50 CS, Fastac Active, Laser 240 SC, Calypso 480 SC, Affirm.

Aphis pyrastri is a species that attacks aggressively the pear. In the spring the adults colonise the leaves. The aphids feed with the cell juice of the trees producing stress to them. After the attack the leaves deform, the tree has low growth, the resistance to frost decreases, and the fruit buds will differentiate weakly.

Prevention and control measures:

  • Treatments with Mospilan 20 SG, Actara, Decis Mega, Confidor Energy, Nuprin AL 200 SC.

The mites are insects that are hardly seen with the open eye. They are polyphagous species, that attacks a lot of plants and fruit trees, cultivated species and spontaneous species. They feed with the cell juice. After the attack, the leaves are having a parchment-look, the flowers abort, and the plants stagnates from growth.

Prevention and control measures:

  • Treatments with Nissorun 10 WP, Envidor 240 SC, Milbeknock EC, Vertimec 1.8 EC.

Sciaphobus squalidus

It is a dangerous species that attacks usually the flower buds and blossoms. It has a generation every 2 years and winters as an adult in the superficial layer of the soil. In the spring the adult appear, that climb in trees and feed with flower buds and blossoms. The larvae are not dangerous to the tree, they feed on the roots of the spontaneous herbaceous plants.

Prevention and control measures:

  • Moving the soil in the autumn
  • Treatments with Decis Mega, Reldan 22 EC, Fastac, Actara 25 WG, Calypso 480 SC.

Apple aphid (Aphis pomi)

It is a polyphagous species that attacks many species of fruit trees. The aphids colonise the lower part of the leaves. The attacked trees won’t grow, the fruit buds won’t appear, the fruits remain small, the yield being strongly affected. Also, the aphids transmit a some viruses.

Prevention and control measures:

  • Treatments with Mospilan 20 SG, Actara 25 WG, Decis Mega EW 50, Confidor Energy, Nuprid AL 200 SC.

Psylla pyri

It has 2-3 generations a year and winters as an adult in the cracks of the bark or inside them. The larvae and the adults feed with the cell juice of the trees. After the attack the leaves deforms, the tree realises slow growth, the resistance to frost decreases, and the fruit buds slowly differentiates.

Prevention and control measures:

  • Treatments with Actara 25 WG, Mospilan 20 SG, Vertimec, Confidor Energy, Movento 100 SC.


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

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] 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:


Bunch Grapes

Black rot

Diagnostic features: Small, yellowish spots on leaves sunken oval lesion with pycnidia of the fungus (black dots) shriveled mummies (infected berries)


Pycnidia in a mummified grapevine berry

Pathogen: Guignardia bidwellii

Comments: Annual pruning in February removing infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain. Sanitation is important. Remove mummified fruit! Disease spread is favored by moist, wet weather.

Powdery mildew

Diagnostic features: White powdery fungal growth on berries


Conidia
Cleistothecia

Pathogen: Uncinula necator

Comments: Annual pruning in February will help to remove inoculum remove infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain.

Downy mildew

Diagnostic features: Yellow, irregular-shaped lesions on upper surface whitish-gray fungal growth directly under lesions on lower surface of leaves


Conidiophores
Conidia

Pathogen: Plasmopara viticola

Comments: Annual pruning in February remove infected berries both on the ground and on the plant. After pruning, only the permanent trunk, one-year-old fruiting canes and short spurs should remain.

Pierce’s disease

Diagnostic features: Scorched leaves with a defined margin and yellow/chlorotic border

Pathogen: Xylella fastidiosa - Bacterial disease

Comments: Vectored by various sharpshooters (such as glassywinged sharpshooter). New growth is stunted, yellow, deformed (resembles zinc deficiency). Choose more resistant cultivars native grapes are generally more resistant. Do not propagate from symptomatic vines. Do not plant vinifera wine or table grapes at elevations below 1,300 feet. Muscadines are generally resistant, and some other native grapes have limited resistance.

Phomopsis

Diagnostic features: Small, black pycnidia of the fungus on the cane


Two spore types: alpha and beta conidia

Pathogen: Phomopsis viticola

Comments: A late dormant application of lime sulfur is very beneficial for control of this disease.

Botrytis bunch rot

Diagnostic features: Masses of gray conidia covering infected grapes

Pathogen: Botrytis cinerea - see Blueberry botrytis blight

Root knot nematode


Note: Image not of fig roots (D. Langston, UGA)

Diagnostic features: Knotty, galled roots

Pathogen: Meloidogyne spp.

Comments: Prune tops to balance weakened roots attentive watering and fertilization may prolong tree life. Nematode infested plants usually die sooner or later regardless of treatment. Plant new trees away from this site!

Diagnostic features: Small, reddish pustules on the underside of the leaves


Pustule (uredinial stage) on underside of leaf
Urediniospores

Pathogen: Cerotelium fici

Comments: Not fatal but will reduce tree vigor and size and quality of fruit. Attacks the leaves, usually in late summer. Infected leaves turn yellow-brown and drop. Underside of leaves have reddish brown spots/pustules. Sanitation is important.

Anthracnose

Pathogen: Glomerella cingulata - see Apple bitter rot

Comments: Not serious increase air circulation and avoid excess irrigation sanitation.


Fruit Fungicide and Pesticide Application

Fungi-caused infections are one of the most prevalent orchard diseases. They are often managed with either fungicidal or fungistatic pesticides. Fungicides are separated into two categories: protectants and systemics.

Protectant fungicides are designed to protect plants against infections at the application site. Systemics prevent diseases from developing on parts of the plant away from the application site. Discover more with Penn State Extension’s resources on fungicide resistance, proper usage and maintenance, and fungicide recommendations for apple diseases.

Fruit growers can find guidance and tools for spray products usage, such as the Spray Record-Keeping spreadsheet. Advice on apple insect and mite control is also available, as well as certification training for private pesticide application.


Watch the video: Προσβολή διαφόρων φυλλοβόλων οπωροφόρων δένδρων από Κλεωνό ή Περίτελο