If the new leaves on your peach tree came out thick, puckered and red or pink, and look almost blistered, you are looking at peach leaf curl. It is one of the most common problems on backyard peaches and nectarines. The frustrating part is that by the time you can see it, it is too late to spray. The useful part is that it is very predictable, so you can stop it next year.

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The short answer: peach leaf curl is caused by a fungus that infects leaf buds in late winter and early spring. Spraying after the leaves are curled does nothing. Apply a labeled fungicide once in late fall after the leaves drop and/or again in late winter before the buds swell. This season, water the tree, thin the fruit more than usual and let it push a second set of healthy leaves.

What peach leaf curl looks like

The disease is caused by the fungus Taphrina deformans. According to the University of California Statewide IPM Program, the signs appear as the leaves unfold in spring:

Leaves are thickened, puckered and curled, often red, pink or purple.
Affected leaves later turn pale and powdery as the fungus produces spores on the surface.
The leaves then yellow or brown and drop.
Shoots can be stunted and swollen, and fruit may develop raised, wrinkled, reddish areas.

A healthy peach then pushes a second flush of leaves, which usually stays clean because the weather is warmer and drier by then.

How much harm does it do?

One bad year is rarely fatal. A healthy peach usually recovers with its second flush of leaves. The damage adds up when leaf curl hits several springs in a row: the tree keeps spending its reserves on replacing leaves, shoot growth slows and the crop shrinks. That is why the dormant spray is worth doing every year on a susceptible variety, even after a spring that seemed mild.

Why spraying now does not work

The fungus survives on the bark and buds over winter. Infection happens when the leaf buds begin to swell and open in late winter or early spring, during cool, wet weather. Once the fungus is inside the developing leaf, no spray can reverse the damage. UC IPM is clear on this point: treatment after symptoms appear is not effective.

When to spray

Timing is everything with peach leaf curl. UC IPM and Clemson’s Home & Garden Information Center both point to the dormant season:

Late fall, after most leaves have dropped. This treatment is especially useful where winters are rainy.
Late winter, before the buds swell. This is the most important window in most regions. Once you see green or pink at the bud tips, it is late.

Products used include fixed copper fungicides and other materials labeled for peach leaf curl on home fruit trees. Product availability varies by state, so check the label and your extension office. Cover the whole tree, including the bark and all buds, and do not spray when rain is expected within a day.

When	What to do
Spring, leaves curled	Do not spray. Water, thin fruit, remove badly affected fruit
Summer	Keep the tree watered and growing; no spraying needed
Late fall, after leaf drop	First dormant spray
Late winter, before bud swell	Second dormant spray, the critical one

Helping the tree this season

A tree that loses its first leaves to curl spends energy rebuilding them. You can help:

Water deeply in dry spells so the second flush of leaves can develop.
Thin the fruit more heavily than usual, so the tree is not carrying a full crop on a reduced set of leaves.
Remove and dispose of fallen infected leaves. They are not the main source of next year’s infection, but tidying up does no harm.
Do not fertilize heavily. A moderate feeding based on a soil test is fine; a big nitrogen push is not.

Choosing a resistant variety

If you are planting a new peach, ask about leaf curl resistance. UC IPM lists several varieties with good resistance, including ‘Frost’, ‘Indian Free’, ‘Muir’ and ‘Q-1-8’. Availability and suitability depend on your climate and chill hours, so check with a local nursery or extension office.

Is it leaf curl or something else?

Aphids can also curl peach leaves, but the leaves curl tightly downward and you will usually find the insects inside the curl. Leaf curl leaves are thick, blistered and colored, with no insects. If your peach is oozing gum from the trunk, see why a peach tree oozes sap. If it did not bloom at all, see why a peach tree did not bloom.

When to get help

Your county extension office can confirm the diagnosis from a few leaves. If a tree has had severe leaf curl for several years in a row and is losing vigor, a certified arborist or experienced fruit grower can help you decide whether it is worth keeping. The ISA Find an Arborist directory can help you find one.

More peach and pear guides are in the Fruit Trees hub.

Sources

Peach Leaf Curl, UC Statewide IPM Program
Peach Diseases, Clemson Cooperative Extension, Home & Garden Information Center
Pruning Fruit Trees, Penn State Extension

Top photo: Giancarlo Dessì, CC BY-SA 3.0, via Wikimedia Commons

Peach Leaf Curl: When to Spray and How to Stop It