We want to talk about curly leaves on fruit trees.

It’s one of the topics we’re regularly asked about. It’s also one of the topics that causes the most confusion among home fruit growers.

The confusion is probably because there are lots of potential causes for curly leaves, and they’re all different. The four most common types are caused by (a) fungal disease, (b) insects, (c) nutritional problems, and (d) water.

Nectarine and Peach Tree Leaf Curl

The most common cause of curly leaves in peach and nectarine trees is a fungal disease called—wait for it—Leaf Curl.

It’s a very common disease, and in fact, ONLY infects these types of trees. If you have curly leaves in a plum, citrus, or another tree, it’s caused by something else.

Leaf curl disease shows up in spring, does the damage, and then disappears (until next spring). It will have disappeared by late summer. However, you may still be able to find signs of it, if you know what to look for.

If your trees were infected last spring, they should have completely recovered by now, in late summer. They’ve probably grown lots of healthy new leaves (that should look something like the photo below).

Hugh with a healthy young peach tree
Hugh with a healthy young peach tree

Nestled in amongst the healthy leaves, you may still be able to spot some remnant diseased leaves in your trees.

They’ll look something like this:

The dried up remnants of leaf curl disease
The dried up remnants of Leaf curl disease

This is one of the diagnostic tools you can use to help identify whether your trees had this disease. It’s all part of the ongoing detective work you need to do to become an awesome fruit grower.

These dead and shrivelled leaves are a powerhouse of fungal spores sitting in the tree. They’re just waiting to infect the buds that are forming this year and start the disease cycle all over again.

A fresh Leaf curl infection on a peach tree in spring
A fresh Leaf curl infection on a peach tree in spring

Preventing Leaf curl disease

It’s been often and hotly debated whether it’s worth removing infected leaves from the tree as they emerge in spring. On balance, the answer seems to be no. There’s no evidence to show that it reduces the spread of infection once it’s started.

However, the jury is still out on whether removing the leaves in summer will help prevent re-infection the following spring. Here at Grow Great Fruit central we always err on the side of caution.

So…if you have the time and inclination, you may as well get rid of them!

Many of these leaves will probably have fallen off of their own accord and rotted away under the tree. If there are any still in your trees, it can’t hurt to remove and dispose of them.  

Hot compost is the perfect disposal method. The high temperatures in the compost pile will kill off the fungal spores. This also preserves the organic matter in the leaves.

Prevention is better than cure

Remember, prevention is much better than cure. Hygiene is one of the best defenses you have against all pests and diseases.

The most important defence against Leaf curl is spraying with an organic fungicide, at the right time.

This latter factor is absolutely key. It can be different for every variety! Find out how to do this safely and effectively in the short course Better Fruit with Wise Organic Spraying.

Another key to success is to use ONLY allowable organic sprays. This avoids damage to the trees and the environment.

Curly leaves caused by insects

If you notice curly leaves in your plum trees, by definition it must have a different cause. As we mentioned, peach Leaf Curl disease only affects peach and nectarine trees.

The most likely culprit for curly leaves in plum trees is aphids.

Curly leaves caused by aphid infestation
Curly leaves caused by aphid infestation

This photo (above) shows the curly leaves you would typically see as a result of an aphid infestation.

Here’s another example (below), this time in a peach tree. It’s important to note that both black and green aphids can affect peach and nectarine trees.

So, if you have curly leaves in your peach trees, there are multiple potential causes!

Aphid infestation in a peach tree, causing the leaves to start to curl.
Aphid infestation in a peach tree, causing the leaves to start to curl.

If you have curly leaves on your fruit trees, the first step is to carefully look inside the leaves. Even if you can’t see insects crawling around visibly, look carefully inside a few of the curled-up leaves.

In particular, look for any sap-sucking insects (like aphids) that might be lurking in there.

Even if you can’t see any live insects, check very carefully for tiny, dried-up insect bodies. This will tell you if there were aphids, but they’ve already been taken care of by predators.

Nutritional issues

The third main reason you might see curly leaves in your fruit tree is because of nutritional problems. Essentially, the tree can’t get the nutrients it needs from the soil. This is commonly seen in lemon trees, for example.

A lemon tree demonstrating the classic curly leaves and yellowing that indicate a nutritional problem
A lemon tree demonstrating the classic curly leaves and yellowing that indicate a nutritional problem

In young trees, this may have happened because the tree’s roots were damaged or dried out when the tree was being planted.

It could also be because of the particular soil in or under the hole where this tree was planted. It could also possibly be because the particular variety is not happy here for some reason.

The most likely answer is in the soil.

The solution is to improve the health of your soil. Bear in mind that citrus trees are heavy feeders. This means they need access to more nutrition than many other fruit trees. This may mean adding extra compost or aged manure than you do to your other trees.

Is mulch good for soil health?

Mulch under your trees may also be part of the problem. In general, mulch is fine, but it’s not as good (in terms of building healthy soil as quickly as possible) as having plants growing under them.

Your aim should be to have a variety of green and growing plants under your fruit trees all year. In the terminology of eminent soil scientist Dr. Christine Jones, this is called “year-long green”. The fabulous Dr. Jones presented two masterclasses for us on building soil health, and on establishing living understorey beneath your fruit trees. You can find them here. We highly recommend them, they’ll change the way you think about “weeds”, particularly under your fruit trees.

It can be useful to think of the space under your fruit trees as more garden bed space. You may be able to use the space to grow herbs or veggies, for example.

Depending on how you like to garden, it can also be useful to choose some perennial groundcover plants (like flowers) for these beds. These take less work to care for and replace than annual vegetables.

How can water make the leaves on your fruit tree go curly?

Strangely, both over and under-watering can be the cause.

Underwatering (also called water stress) will often show up as curled leaves. The leaves will often curl in a longitudinal fashion, i.e. they curl in on themselves lengthwise. This is different from the outward mid-leaf curling that is typical of nutritional issues that you can see in the photo above.

Over-watering can also show up in the leaves. While there may be some curling associated, the more common symptom is for leaves to go brown and crunchy.

If you’re not sure what you’re seeing and suspect it may be related to water, ask yourself the following questions:

  • is the tree getting watered enough?
  • are you monitoring the soil moisture?
  • could the site have poor drainage?
  • any signs that it’s waterlogged?

Water stress is easily remedied. Just water the tree more!

Excess water can be more difficult to solve. The first thing is to figure out where the water is coming from. The area may be getting constant outflow from natural drainage, greywater, or a drainpipe, for example.

Curly leaves on your fruit trees can be caused by lots of different things. The good news is that once you’ve figured out the culprit, finding a cure is much easier!

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