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Pear Tree Leaf Curl: Learn About Leaf Curl On Pear Trees

Pear Tree Leaf Curl: Learn About Leaf Curl On Pear Trees


By: Mary H. Dyer, Credentialed Garden Writer

Why do pear tree leaves curl? Pear trees are hardy, long-lived fruit trees that usually produce fruit for many years with minimal care. However, they are sometimes susceptible to diseases, pests and environmental issues that cause leaf curl. Read on for possible reasons for curling pear tree leaves, and tips for pear tree leaf curl treatment.

Why Do Pear Tree Leaves Curl?

Below are some of the most common reasons behind the curling of pear tree leaves and what can be done to alleviate the problem:

Pear Curling Leaf Midge

A native of Europe, the pear curling leaf midge has found its way across most of the United States since it first arrived on the East Coast in the 1930s. It is often responsible for curling pear tree leaves in young trees.

This small pests pupate in the soil, and then emerges to lay eggs on new, unfurled leaves. When the eggs hatch, the larvae feed on the leaves for a couple of weeks before dropping onto the soil where they wait to start a new generation. Although the pests are small, they can cause serious damage to young trees, evidenced by tightly rolled leaves and red swellings (galls). Eventually, leaves turn black and drop from the tree.

To control the pests, remove rolled leaves and dispose of them properly. Severe infestations can be treated by application of organophosphate insecticides. Damage is generally not significant on mature trees.

Pear Tree Leaf Blight

Often known as fire blight, pear tree leaf blight is a highly destructive bacterial disease. Curling pear tree leaves is only one sign. If your tree has fire blight, it may also display brown or black leaves, blooms with a water-soaked appearance, discolored bark and dead branches.

There is no cure for pear tree leaf blight, but pruning of infected branches may staunch progress of the disease. Certain chemical antibiotic sprays may be effective when applied before development of symptoms.

Aphids

Aphids are tiny, sap-sucking pests that attack primarily young, tender growth. They are often controlled by aiming a strong stream of water directly at the leaves. Otherwise, insecticidal soap spray is a safe, effective solution that can be repeated as needed.

Caterpillars

A variety of caterpillars enjoy dining on pear tree leaves, often rolling themselves tightly in the protective shelter of the tender leaves. Encourage birds and beneficial insects to visit your garden, as they sometimes eat the pupae and larvae. Look for rolled leaves and other signs of damage and prune as needed. Heavy caterpillar infestations may require chemical control.

Drought

Wilted or curled pear tree leaves may be a sign that your tree isn’t getting enough water. According to many resources, young trees need about a gallon of water every seven to 10 days during normal conditions. During hot, dry weather, however, your trees may need double that amount.

Established trees rarely require supplemental irrigation, but drought-stressed mature trees benefit from an occasional deep watering.

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Read more about Pear Trees


Transplant Shock: Caring for Newly Replanted Trees

Steve Nix is a member of the Society of American Foresters and a former forest resources analyst for the state of Alabama.

Tree seedlings that have lived several years and are growing under comfortable cultural conditions, develop and thrive on a careful, natural balancing of leaf surface and root growth. For an undisturbed, healthy tree, the root system is normally very shallow. Even the major structural roots grow almost horizontally.

With an adequate supply of water and nutrients, a seedling or sapling will continue healthy growth until roots become confined to a container or other barrier. In most cases, the root system extends out and beyond the spread of the branches and a considerable portion of the roots are cut when the tree is moved.


Transcript

TINO CARNEVALE: I have a long-standing love affair with certain stone fruit trees - peaches, apricots and nectarines. Unfortunately so does a fairly nasty fungus called Peach Leaf Curl.

The main symptom of Peach Leaf Curl is red pimple-like deformation on young leaves which, as they grow, become unsightly, reduces the tree's ability to photosynthesise and fruit abundantly. If left untreated, the problem will get worse year after year, but the good news is, it's a fungal disease that's easily treated.

The fungal spores take up residence over the winter in the nooks and crannies of the tree, but mainly, they reside in the leaf bud scales, so as soon as the leaf bud bursts, the spores jump onto the leaf. tree infected.

The treatment is simplicity itself. Just apply a fungicide containing copper hydroxide, right now. Be sure to do a thorough job of it - paying attention to the leaf bud scales and all the nooks and crannies in the bark and for severely affected trees a second application the following autumn as the leaves drop, will help too.

If you follow this regime every year, you can control this fungal problem 100 percent and a happier stone fruit tree means better fruit.


Pest & Disease Control for Pear Trees

Every fruit tree has the future potential for disease and insect damage. Factors such as location and weather will play a part in which issues your tree encounters. Disease-resistant trees are the best option for easy care and for all trees, proper maintenance (such as watering, fertilizing, pruning, spraying, weeding, and fall cleanup) can help keep most insects and diseases at bay.

NOTE: This is part 7 in a series of 11 articles. For a complete background on how to grow pear trees , we recommend starting from the beginning.

Crown Gall

Trees appear stunted and slow growing leaves may be reduced in size, little or no fruit. If tree is dead, inspect roots for hard, woody ‘tumors’. Note: many things can cause stunted trees.

  • Consult County Extension Agent

Scale

Usually on bark of young twigs and branches, encrusted with small (1/16”) hard, circular, scaly raised bumps with yellow centers, may also be on fruit. Sap feeding weakens the tree.

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bayer Advanced™ Complete Insect Killer

Tarnished Plant Bug

Yellow-brown winged insect may have black spot or red stripes. Injects toxins into the buds and shoots causing ‘dwarfed’ shoots and sunken areas (cat facing) on fruit.

  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Insecticidal Soap

  • Bayer Advanced™ Complete Insect Killer

Leafroller

Pale yellow or ‘dirty’ green worms. Leaves are rolled and webbed together where insects feed. Eventually becomes ‘skeletonized’.

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Captain Jack’s™ Deadbug Brew
  • Bonide® Thuricide® Bacillus Thuringiensis (BT)

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bayer Advanced™ Complete Insect Killer

Spots on young leaves are velvety and olive green turns black leaves wither, curl and drop. Fruit also has spots, is deformed, knotty, cracked and drops.

  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Copper Fungicide Spray or Dust

Leaf Spots

Fabraea Leaf Spot

  • Most often occurs in areas with warm, wet, humid summers. Young leaves develop red to purple pinpoint spots on top or bottom. Spots enlarge, turn dark brown, may coalesce, and could drop. Usually worse on lower half of tree, fruit may also develop spots and crack.

Septoria Leaf Spot

  • Infection mainly on foliage and on the upper surface of the leaf. Spots are grayish-white with purplish margins, which are sharply defined at maturity. Centers have scattered black dots. Dead tissue may fall out giving a shot-hole appearance. When infection is serious, leaves fall in late summer.

  • Remove all infested leaves and debris and bury or burn them.

  • Consult County Extension Agent

Pear Psylla

Adult is transparent, yellow-brown 1/8” jumping winged insect. Immature has no wings. Usually on underside of leaves and leaf stem. Sap feeding weakens the tree. Sticky residues become growth media for Sooty Mold.

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

  • Bonide® Borer-Miner Killer
  • Bonide® Total Pest Control
  • Bayer Advanced™ Complete Insect Killer

Aphids

They are the size of a pinhead and vary in color depending on the species. Clusters on stems and under leaves, sucking plant juices. Leaves then curl, thicken, yellow and die. Produce large amounts of a liquid waste called “honeydew”. Aphid sticky residue becomes a growth media for sooty mold. Dormant Oil will kill eggs, use next dormant season, also during ½” green kills newly hatched except Rosy Apple aphid.

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

  • Bonide® Borer-Miner Killer
  • GardenTech® Sevin® Concentrate Bug Killer
  • Bayer Advanced™ Complete Insect Killer

Green Fruitworm

Bluish-gray moth. Larvae are 1” long, usually green or brown with white spots and body stripes. Feeds on young leaves and young fruits. Disfigures the fruit.

  • Bonide® Borer-Miner Killer
  • Bonide® Total Pest Control
  • Bayer Advanced™ Complete Insect Killer

Fireblight

Blossoms and fruit spurs withered looks as if ‘scorched’ by fire, with dark brown or blackened leaves tips of leaves curl under. Twigs and branches die. Cut back infested branches 4” below disease. Disinfect shears between cuts with 1 part bleach and 10-part water solution. Dispose of pruning. Fall cleanup is essential, including all mummified fruits and leaves hanging on the tree. The above steps need to be done exactly as stated.

  • Prune out infected area.

  • Ferti-lome® Fire Blight Spray (not on west coast)

Plum Curculio

Adult is brownish-gray 1/5” long, hard-shelled beetle with long snout and 4 humps on back. Cuts a crescent shaped hole under fruit skins and lays eggs. Worms hatch and tunnel into fruit. Premature dropping of fruit can occur.

  • Bayer Advanced™ Complete Insect Killer

Tent Caterpillar

Hairy caterpillars that enclose large areas in webbing and feed on enclosed leaves. Remove web with rake and burn. Caterpillars are pulled out with webs.

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray
  • Bonide® Thuricide® Bacillus Thuringiensis (BT)
  • Remove web with rake and burn.

  • Bonide® Total Pest Control

Codling Moth

Adult is moth, gray with brown patches on wings. Worms about 1” long. Fruits have holes from side to core.

  • Bonide® Captain Jack’s™ Deadbug Brew
  • Traps

  • Bonide® Borer-Miner Killer
  • Bonide® Total Pest Control
  • Bayer Advanced™ Complete Insect Killer

Mites

Pinpoint size, many different colors. Found on undersides of leaves. Sap feeding causes bronzing of leaves. Severe infestations have some silken webbing.

  • Bonide® All Seasons® Horticultural & Dormant Spray Oil
  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

  • GardenTech® Sevin® Concentrate Bug Killer
  • Bayer Advanced™ Complete Insect Killer

Black Rot, Frog Eye Leaf Spot

Leaf symptoms begin 1-3 weeks after petal fall as small purple flecks. These enlarge into lesions with purple margins and tan to brown centers, resembling ‘frog eyes’. When heavily infected, leaves may fall. Fruit infection can begin as soon as bud scales loose and appear on young fruit as red flecks that develop into purple pimples. These do not grow much until fruit begins to mature. Spots on mature fruit are irregular, black with red halo. As they enlarge a series of concentric rings form alternating from black to brown. Lesions stay firm and are not sunken. Fruit mummifies and stays attached to the tree. Rot in seed cavity or around core may be caused by early infections, but these usually fall within a month after petal fall with no surface symptoms. May be reddish-brown sunken cankers on limbs.

  • Consult County Extension Agent

Japanese Beetle

Adult is a metallic green beetle. It skeletonizes leaves. Larvae are a grub, which feeds on turf roots. Check turf product labels for timing of control of grubs. This is more of a problem east of the Mississippi river.

  • Bayer Advanced™ Complete Insect Killer

Leafhopper

Various colors and similar to aphids this small, active, slender-winged insects are usually found on the underside of leaves. Retard growth, leaves become whitened, stippled or mottled. Tips may wither and die. This insect carries virus of certain very harmful plant diseases.

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

  • Bayer Advanced™ Complete Insect Killer

Rose Chafer

Beetle has ½” long, tan wings with reddish-brown edges. Long, thin hairy legs. Skeletonizes leaves and flowers. Present in large quantities in June and July. Worst on sandy sites near grassy areas.

  • Bayer Advanced™ Complete Insect Killer

Gypsy Moth

Egg masses are about 1” long, hairy and buff colored, found attached to buildings, walls, fences and trees. Caterpillars hatch out in April and feed on fruit and forest trees (including conifers). Cocoons are formed in late July and the moth emerges about a month later. Males are dark brown, less than an inch long. Females are buff-colored and heavy.

  • Bonide® Thuricide® Bacillus Thuringiensis (BT)

Thrips

Tiny, slender, fringed wing insects ranging from 1/25 to 1/8” long. Nymphs are pale yellow and highly active and adults are usually black or yellow-brown, but may have red, black or white markings. Feed on large variety of plants by puncturing them and sucking up the contents.

  • Bonide® Insecticidal Soap
  • Bonide® Citrus, Fruit & Nut Orchard Spray

Leaf and Stem Blight

Leaves are soft and water soaked. Brown and black irregular blotches appear and spread to cover the leaves. Areas on the stems turn black, soft and sunken.

  • Bonide® Copper Fungicide Spray or Dust


Preventing Peach Leaf Curl in the Future

There are certain varieties of peach and nectarine trees that are resistant to peach leaf curl, and I suggest you seek those out in whatever zone you are in, as I expect different varieties will be more or less resistant depending on your zone.

If you've had infected trees before, you should always use a dormant-season fungicide - one that contains lime sulfur spray (or a Bordeaux mixture), but you will need to wait until the last leaf falls. Then, in the spring, spray them again before any new leaves appear. If you wait until buds are open on the tree before using a fungicide, you have waited too long and there is no need to spray again.

For severe infestation, a fungicide spray in the late fall and late winter or early spring might effectively manage peach leaf curl.

If you have peach orchards, you will need to wait until almost all of the leaves have fallen or before bud swell in the spring to attempt to control the disease. During those times, applying a fungicide (chlorothalonil) or copper spray would be appropriate.

Growers in future seasons will have to monitor the upcoming February temperatures closely because if temperatures are forecast to be above average, the dormant fungicide spray will need to be applied prior to those warmer days in order to effectively control the fungus around the buds.

The most effective prevention will usually consist of planting only stock that has been acquired from reliable nurseries and pruning any twigs/leaves that have signs of infection.


Transplant Shock

Transplanting a tree seedling or sapling can be the most stressful time in its entire life. Moving a tree from its original comfort zone to a new location should be done under the right conditions while preserving most of the life-supporting root system. Remember, when transplanted to a new location, the plant has the same number of leaves to support but will have a smaller root system to supply water and nutrients.

Major stress-related problems can often result from this inevitable loss of roots, especially feeder roots. This is called transplant shock and results in increased vulnerability to drought, insects, diseases and other problems. Transplant shock will remain a planting concern until the natural balance between the root system and the leaves of the transplanted tree is restored.

Of all newly planted trees that do not survive, most die during this very important root-establishment period. The health of a tree and its ultimate survival can be assured if practices that favor the establishment of the root system become the ultimate gold standard. This takes persistence and involves regular care during the first three years following transplanting.


Peach leaf curl mainly affects peach, nectarine, and almond trees. Apricots are generally immune to peach leaf curl (instead, the major apricot diseases are blossom wilt and branch dieback caused by Monilinia fructicola in the spring and Eutypa lata in the summer). [4] [5] However, in an isolated case in Hungary in 2011, peach leaf curl was also identified in apricot trees. [6]

Peach leaf curl is a distinctive and easily noticeable fungal disease, and the severity of the symptoms depends on how early infection has occurred. Diseased leaves can usually be identified soon after they emerge from the bud, due to their red color and twisted shape. As the leaves develop, they become increasingly distorted, and ultimately thick and rubbery compared to normal leaves. The color of the leaves changes from the normal green to red and purple, until a whitish bloom covers each leaf. Finally, the dead leaf may dry and turn black before it is cast off. Changes in the bark are less noticeable, if at all. Fruit may fail to develop from diseased blossoms. Any fruit that does develop from a diseased tree is usually normal, but sometimes may also be affected, showing a reddish color. [3] Infected leaves fall early. The tree usually produces a second flush of leaves that is rarely diseased, except in an unseasonably cool and wet spring, because the fungus is not infectious at the normally higher temperatures in late spring and early summer.

The fungus T. deformans causes deformed young leaves, red blisters, and ultimately the whitish bloom that covers the leaf as the infection progresses. This white color is made of asci that break through the cuticle of the leaf. One ascus consists of eight ascospores that create conidia, which are ejected in early summer and spread by rain and wind. The fungus survives the winter on the surface of the host plant, such as on bark or buds. [2] In late winter or early spring, rainwater washes spores into the buds as they burst. Once this happens, no treatment is effective. In the spring, about two weeks after blossom, new leaves emerging from the infected buds are infected by the conidia. The disease may not occur every year due to variation in temperature and rainfall. Specifically, for successful infection, the fungus requires wet winters, where rain (not fog or dew) wets the tree for more than 12.5 hours at temperatures below 16 °C (61 °F). [7] The fungus cannot grow at temperatures below 9 °C (48 °F). [8]

Various methods are applied.

  • The most effective method [9] is to plant peach trees against a house wall under an overhanging roof, possibly covered by a mat during the winter, to keep winter rain from the buds before they burst (and incidentally to delay blossoming until spring frosts are over), until the temperature exceeds 16 °C (61 °F) in the spring, deactivating the fungus.
  • Commercially, spraying the leaves with fungicides is the most common control method. The toxicity of these fungicides means they are not legally available to noncommercial growers in some countries. Spraying should be done in the winter well before budding. If trees are not sprayed early enough, treatment is ineffective. Copper-based mixtures (such as Bordeaux mixture) and lime sulphur are two fungicides commonly used. [2][10]
  • Peach cultivars can be planted which show some resistance to peach leaf curl, or at least regenerate rapidly, such as the white-fleshed Peach 'Benedicte'. [11] For nectarines, the cultivar Kreibich is reported to have some resistance. [8]

If a tree has peach leaf curl in a particular year, the disease will inexorably take its course, but measures can be taken to sustain the tree or maximize crop yield: protecting the tree from further rain at temperatures below 16 °C (61 °F), providing nitrogen and excess water to minimize stress on the tree applying greasebands around the trunk to protect from insect infestation and thinning the fruit. It is unclear whether removal of infected leaves from the tree is beneficial. [8] Removing the infected leaves and fruit after they fall to the ground is sometimes also suggested but superfluous if, in the following winter, fungicides or rain protection are applied.

Peach leaf curl was first introduced in America in 1852 and has now spread all over the country. By 1947, the disease was costing the United States $2.5 to 3.0 million annually. [3]