A reader recently reached out to me, asking if I knew why their pear tree leaves were beginning to curl. I’ve written articles about leaf curl for other fruiting plants, so I had an idea, but I wanted to do more research first. Here’s what I found causes pear tree’s leaves to curl.
Pear trees get curling leaves from under-watering, hot weather, transplant shock, and pests and diseases such as aphids and fire blight. To prevent curling leaves, water the pear tree when the top 2-4 inches of soil is dry and provide pest and disease management as needed.
So, while pear trees get curling leaves largely from under-watering and hot weather, how can we identify which issue is causing it, and from there—how can we fix it? Let’s take a closer look.
1. Under-Watering
Common symptoms of pear trees that are under-watered are leaves curling, browning, and dropping. The reason why leaves curl when they’re drying is to conserve moisture and if they’re left without water for too long, they’ll begin to brown (die) and drop from the tree.
Under-watering is easy to do as it’s difficult to tell how much moisture the soil is holding. This is made worse if you’re experiencing excessively hot weather or times of drought (more on these later).
So, what’s the ideal way to water pear trees?
The best way to water pear trees is to only water when the top 2-4 inches of soil is dry. To check this, push a finger into the soil under the tree’s canopy. The goal should be similar to the moisture of a wrung-out sponge. This practice prevents both under and over-watering.
Compost not only provides valuable nutrients but improves the water retention and the soil’s richness. For example, every 1% increase in the soil’s richness can hold an extra 20,000 gallons of water per acre (source). Many growers are also finding that compost can even replace chemical fertilizers.
Mulch dramatically reduces evaporation, regulates soil temperature, and prevents soil erosion. It’s also key for fruit trees as mulch mimics a forest’s ground cover—providing many of the above benefits and feeding the fruit trees.
Ideally, provide 2 inches of compost every 1-2 months and 4-12 inches of mulch every 3-6 months. When applying, keep these materials at least 3 inches away from the pear tree’s trunk to prevent mold.
But what if your pear tree’s soil is properly watered and the leaves are still drying and curling?
2. Heat Stress
Pear trees do best in USDA hardiness zones 4-7, but there are some warmer and colder pear varieties that can grow outside this range (source). Generally, avoid temperatures above 85ºF if possible.
In hot and dry climates, pear trees lose moisture from their leaves and soil quickly. Normally, pear trees cool themselves by sending moisture from their roots to their leaves, and through transpiration.
Much like humans, plants breathe and release moisture when hot. For plants, this is called transpiration. But when the climate is too hot and dry, transpiration and root moisture can’t effectively keep up to cool the plant and its leaves. As a result, the pear tree’s leaves droop or curl, and then dry, brown, and drop.
So, the hotter and drier the weather, the more energy the plant uses to transpire and survive, and the less energy it has to use to establish its root system and grow. This drain of resources can quickly stunt or kill the plant.
Hot Weather Tips
Here are some tips that will help your pear tree survive warmer weather and the occasional heat spell:
- Compost – apply 2 inches of compost to not only provide nutrients for your pear tree but hold more water in the soil and help prevent drought stress.
- Mulch – similar to compost, mulch goes a long way in water retention, but also offers other benefits such as shading and insulating the soil—regulating its temperature.
- Shade – shade further protects the tree’s leaves, roots, and soil from the heat. Some ideas to create shade for your pear trees are large umbrellas, shade sails, trellises, or other trees.
Many young fruit trees and other productive plants are sensitive and usually rely on the canopies of support species such as pine trees and other overstory trees to survive, at least until they are established themselves.
Because of this, provide young fruit trees with partial shade, especially from the hotter, afternoon, west-facing sun. Once the fruit trees mature and develop a larger canopy and root system, they’ll have a better chance of surviving on their own.
If you live in a drier climate and you’d like more information about the best drought-tolerant fruit trees, check out my other post: 30 Best Drought-Tolerant Fruit and Nut Trees (Ranked).
3. Transplant Shock
If a pear tree was recently planted or repotted, and it’s starting to die, it’s probably due to transplant shock. Transplant shock occurs when the plant is exposed to a new environment and has to establish a new root system. Avoid transplanting unless necessary as it can take up to 1 year for recovery.
Like many plants, pear trees are vulnerable to transplant shock, which can take up to a year for them to recover from. To help avoid transplant shock, I like to plant with the following steps in mind:
- Have the new ground (or pot) prepared
- Remove as much of the plant’s current topsoil as possible, without damaging the shallow roots
- Grab the base of the plant’s stem and wiggle lightly
- Using your other hand, scoop up and support the rootball
- Lightly place the plant in the new ground (or pot) and fill it in
- Make sure the soil is at the same level on the stem or trunk as before
- Apply 2 inches of compost and 4 inches of mulch to the top of the soil
- Water generously and add more soil as needed
4. Pests
Aphids
Aphids are small bugs that suck the sap from underneath the pear tree’s leaves. This loss of sugar and moisture causes the leaves to curl, discolor, and drop. They also deposit honeydew, which attracts ants. If left unchecked, aphids can damage the pear tree’s health and potentially stunt or kill it.
These bugs come in multiple colors including white, yellow, or black, and usually hide underneath the leaves. Typically, aphids won’t cause damage to the fruit, but because they suck sap from the trees, they can compromise its health and therefore reduce fruit size.
The best ways to get rid of aphids and mites on pear trees are by spraying the infected leaves with water or neem oil, or releasing ladybugs (a natural predator of aphids and mites). Most often, a jet of water is enough to get rid of them, but neem oil is a good second option.
For example, when my potted Kaffir lime tree had aphids, I found that a jet of water was enough to blast them off and prevent them from coming back. All I did was remove the hose nozzle and used my thumb to increase the pressure. Keep in mind that too strong of a blast will damage the leaves.
Caterpillars
Tent caterpillars are native to North America and typically hatch around March—the time that pear trees start to blossom. They’re commonly found on apple, crab apple, cherry, hawthorn, maple, peach, pear, and plum trees. Insecticides are largely ineffective, but parasitic wasps will help reduce their numbers.
These caterpillars eat the pear tree’s leaves, make silken nests, and can quickly overwhelm the tree in numbers. The leaves have been seen to be eaten partially (leading to brown and dropping leaves) or entirely. Some trees can be nearly defoliated. However, the tree usually grows new leaves the following season.
While insecticides typically won’t work with mature larvae, promoting natural predators such as parasitic wasps and removing eggs from trees in the winter brings the best results (source).
Midge
Midge is a small fly that lay eggs inside of young fruit tree leaves and fruit. When the larvae hatch, they feed on the leaves and make small exit holes, while the leaves curl in the process. After curling, the fruit and leaves turn red and black before dropping. The species of midge that affects pear trees is called pear leafcurling midge.
These pests aren’t common for pear trees, but here are the pear tree varieties that are most and least susceptible to midge.
| Pear Tree Variety | Susceptibility to Midge |
|---|---|
| Clapps Favorite | Very Susceptible |
| Red Bartlett | Very Susceptible |
| Alexander | Very Susceptible |
| Anjou | Moderately Susceptible |
| Bosc | Moderately Susceptible |
| Bartlett | Moderately Susceptible |
| Conference | Slightly Susceptible |
| Passe Crassane | Slightly Susceptible |
If your pear tree does get infected with midge, consider using organic sprays or encouraging natural predators such as birds, hedgehogs, and ground beetles (source).
5. Diseases
Fire Blight
Fire blight (Erwinia amylovora) is a highly infectious bacterial disease that affects members of the rose family—including apple, pear, crabapple, rose, cotoneaster, mountain ash, hawthorn, quince, spirea, and pyracantha. Fire blight causes the fruit and leaves to curl, brown, blacken, and become disfigured. Sometimes it will kill the tree.
This disease spreads most often in the springtime when it’s warm and wet (spreading the fastest when the temperature is above 70ºF). However, during the winter, fire blight is dormant. This is why providing preventative treatment to the trees during the winter is important in handling this disease.
The bad news is that fire blight is the most common pear tree disease, and there is no cure for it.
The good news is some treatments prevent and slow the spread of fire blight (more on these later). With these, fire blight is manageable and should have little to no further impact on your trees.
To see a fire blight map of the US, check out this map on uspest.org.
Also, to read more about this disease, feel free to visit my other post: Fire Blight Treatment: Non-Organic & Organic Solutions.
Pear Rust
Generally, young and budding plants are the most vulnerable and pear trees aren’t any different.
Budding pear trees occasionally get a fungal disease called rust. This disease affects pear tree leaves, flowers, and fruit and causes them to become discolored and disfigured. It’s common for pear trees to shed heavily infected leaves in the summer. Typically rust is caused by nearby cedar (juniper) trees.
In regards to management, some recommend removing all cedar and juniper trees within 1/4 mile or more, which isn’t feasible for most growers. However, there are other methods of prevention.
- Preventive organic sprays*
- Growing resistant pear varieties
*Keep in mind that some sprays mean the tree’s fruit cannot be eaten that season.
Some pear cultivars, such as Bartlett, appear to have moderate resistance to pear rust in Oklahoma gardens.
Jennifer Olson, Oklahoma State University Extension
