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Peach Leaf Curl: An In-depth Analysis and Control Measures
Symptoms of Peach Leaf Curl & Why Its Prevalent
For those of you who have a Peach or Nectarine and have recently discovered the leaves just don’t look right: they are weird looking, distorted, bulging on the upper sides, reddened, thickened, puckered, and the leaves curl. These deformed leaves are caused by a fungus called Peach Leaf Curl. The scientific name for this fungus is Taphrina deformans. Peach Leaf Curl seems to be more prevalent now because of our recent wet, cold, and cloudy winter and early spring. Peach Leaf Curl is a fungal disease that predominantly affects peach and nectarine trees. This disease, caused by the fungus Taphrina deformans, leads to severe deformation of the tree’s leaves and can affect the overall health and fruit-bearing ability of the tree. The prevalence of this disease has been noted to increase following wet, cold, and cloudy winters and early springs. Today, I want to provide you some background information relative to Peach Leaf Curl and how to control it.
Progression of the Disease and Impact on Tree Growth
As the fungus progresses, these thickened areas turn yellowish and develop grayish white velvety spores (ascospores) that are produced on the surface by the leaf curl fungus. Later, affected leaves turn yellow or brown and can remain on the tree or may fall off prematurely; they are replaced by a second set of leaves that develop more normally.
Effect on Tree Growth and Fruit Production
The loss of leaves and the production of a second set may result in decreased tree growth and fruit production. Defoliation in spring may expose branches to sunburn injury if conditions are right. In the initial stages of the infection, the leaves of the tree may appear bulging and distorted. As the infection progresses, you may notice a thickening and puckering of the leaves accompanied by reddening. The disease also impacts the blossoms, fruit, and shoots of the affected tree, making it a significant issue for backyard gardeners.
Controlling the Spread of Peach Leaf Curl
Manually removing the infected leaves from the tree can help control the spread of Peach Leaf Curl. The discarded leaves contain fungus spores that can overwinter in the soil beneath the tree and reactivate in the spring. Thus, prompt removal and proper disposal of infected leaves can disrupt the lifecycle of the fungus and help manage the disease.
Importance of Discarding Infected Leaves
The idea behind discarding the leaves is to help mitigate the spread of the fungus by disrupting the life cycle. The fungus spores are in the leaves and they can overwinter in the soil beneath the tree and become reactivated again in the spring.
Prevention of Fungus Reactivation
If leaf curl infection builds up and is left uncontrolled for several years, the tree may decline and need to be removed. There is no fungicide available to control the already affected leaves during the growing season (which is now), instead it is best to apply a dormant spray during the fall and winter. More on that later.
Protecting Against Sunburn Injury
Sunburning of the stems and branches could occur as a result of heavy leaf drop. If there is a warming spell that coincides with leaf drop, bare stems, and before the tree becomes entirely leafed out again, sunburn injury may result because there is no sun protection from the leaves shading the branches.
As a precautionary measure, it is recommended to apply a white wash (tree trunk paint) or Iv Organic Plant Guard or something similar to help protect and prevent damage to the tissue of the tree. Sunburn is a secondary issue that may arise if corrective measures are not taken. Simply apply the white wash material on the trunk and lower branches making sure to cover all exposed wood evenly and as thoroughly as possible.
Understanding the Lifecycle of Peach Leaf Curl
It is important to understand the lifecycle of Peach Leaf Curl so you know how and when to control this common fungus that affects most Peaches and Nectarines.
Initial Symptoms and Growth of Fungus
Leaf symptoms appear about 2 weeks after leaves emerge from buds. The fungus grows between leaf cells and stimulates them to divide and grow larger than normal, causing swelling and distortion of the leaf. Red plant pigments accumulate in the distorted cells.
Production and Spread of Ascospores
Cells of the fungus break through the cuticle of distorted leaves and produce elongated, sac-like structures called asci that produce sexual spores called ascospores, which give the leaf a grayish white, powdery or velvet like appearance. The ascospores are released into the air, carried to new tissues, and bud (divide) to form bud-conidia.
Survival and Reactivation of the Fungus
The fungus survives the hot, dry summer as ascospores and bud-conidia (asexual spores) on the tree’s surfaces. When the weather turns cool and wet in fall, the ascospores germinate to produce more bud-conidia. The new and old bud-conidia continue to increase in number by budding. Eventually a film of bud-conidia is formed on the tree’s surface. In spring, the bud-conidia is moved by splashing water from irrigation or rain and can infect new leaves.
Conditions Favoring Disease Development
Periods of cool, wet weather when leaves are first opening on the tree, favor the disease. Wetness from rain, dew, or irrigation for more than 12.5 hours at temperatures below 61°F is needed for infection. Maximum infection occurs when trees are wet for 2 or more days. Although leaves can be infected, symptoms might not appear if temperatures remain above 69F. Cool weather prolongs the period of disease development by favoring the pathogen and slowing leaf growth. Development of Peach Leaf Curl ceases when young tissue is no longer developing or when weather turns dry and warmer (79° to 87F). With all being said, this year is prime conditions for what you are experiencing now – Peach Leaf Curl.
Fungicide Application for Peach Leaf Curl Control
Before applying any fungicide be sure to bring in a sample in a sealed bag to one of our nursery professionals at your favorite Green Thumb Nursery for correct diagnosis. Fungicides work by disrupting the life cycle of the fungus, preventing its spread and further damage to the tree. The timing of fungicide application is crucial for its effectiveness. Since the fungus tends to reactivate in the spring, fungicides should be applied during the dormant or delayed dormant stage of the tree to protect the buds and shoots.
Importance of Correct Diagnosis
In the case of Peach Leaf Curl many are seeing the results of the fungus now. I recommend to write on the calendar when you need to start your dormant spraying. Apply copper fungicide as a dormant or delayed dormant spray to protect buds and shoots. During rainy period you may reapply after the rain stops and continue up until late bud swell.
Optimal Timing for Fungicide Application
Do not apply at less than 7-day intervals. Do not apply after full bloom. Apply Copper fungicide as a preventative. Your spraying program begins late fall! Usually, Thanksgiving signals the time to start dormant spray for fruit trees.
Fungicide Application Methods and Precautions
Even before trees are leafless in winter, they benefit from applications of disease control products. A horticultural oil spray may need to be mixed with the fungicide to be more effective. Always read, follow and understand the product labels before applying any garden chemicals.
Suggested Treatment Schedule
The suggested treatment schedule aligns with the life cycle of the Peach Leaf Curl fungus, targeting it during its dormant and active stages. Following this schedule can maximize the effectiveness of the fungicide treatment, preventing the disease from establishing and spreading in the tree. Mark your calendars for around these dates: Thanksgiving, New Year’s, and Valentine’s Day are holidays around which you should consider treating. The first spraying should be just prior to or at leaf fall around, Thanksgiving. A second spraying one week later helps ensure complete coverage.
Guidelines for Spraying Schedule
The plants’ bark contracts with the onset of cold weather sealing in disease-causing organisms It is, therefore, essential to spray before heavy frost or freezing weather sets in. If rains occur within 48 hours of applying, reapply spray. The last spraying is the most important and that occurs just before the new buds break in the spring.
Reapplication due to Weather Changes
This spraying may need to be done more than once especially if we have a false spring and the tree wants to break dormancy because of the warmer weather, but if the weather becomes cooler and more wet, then spraying may need to be reapplied.
Post-Infection Care and Maintenance
Once the tree is infected there is not much to be done to get rid of the disease that season. However, it is very important to maintain the vigor of the tree throughout the active growing season (which is now).
Feeding and Fertilizing
You want to keep your Peach or Nectarine strong, healthy, and vigorous by feeding it organic fertilizer. When fertilizing, you may want to add kelp meal to the tree to make the leaves stronger and thicker. Also, feed with nitrogen by mid-June, a good balanced fruit tree fertilizer is a good choice. Add earth worm castings to the soil to help the soil become stronger by adding bioactivity.
Mulching and Thinning
Mulching should be practiced to help keep down weeds, reduce water evaporation by up to 50%, and as it breaks down it will help return bioactivity to the soil. Thin the fruit to reduce the demand on the tree’s resources. Thin fruit to at least 3 inches apart.
Proper Watering and Cleanup
Remove diseased or cracked fruit and place in the trash, not your compost pile. Make sure the tree is properly watered, slow, deep, and less often is the rule of thumb. Clean up dropped leaves, twigs, branches, bark, and fruit around the base of the tree to reduce spreading to other trees. Don’t put these in the compost pile, the spores can remain dormant for some time
Conclusion
The Peach Leaf Curl disease can cause significant damage to peach and nectarine trees if left untreated. However, understanding the lifecycle of the fungus and implementing a timely treatment schedule can prevent the disease and allow trees to thrive.
Always remember to follow proper practices when using fungicides, and consider seeking professional advice before applying treatments to your trees. Prevention is key to ensuring the health and productivity of your trees.
In this guide, we’ve explored the steps needed to prevent and control Peach Leaf Curl. By following these recommendations, you can help ensure a healthy and productive growing season for your peach and nectarine trees.
By Richard Flowers, ACCNP-Green Thumb Nursery-Ventura
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