Almonds are the perfect snack for traveling or in-between errands. Plus, they’re gorgeous trees with lots of fragrant blossoms. No wonder so many gardeners grow this tree in their backyard. Sadly, almonds can be victim to some nasty pests and diseases that can ruin your harvest.
Ideally, you want to catch any problems as soon as possible so you can deal with them and prevent any potential long-term issues. So, let’s take a look at what you need to look out for when growing almond trees at home.
Common Almond Tree Diseases
When you decide on growing any type of tree there is always a risk of diseases infecting your garden. That’s why it’s important to know about the growing requirements as well as the common problems that can happen when growing almond trees.
1. Almond Leaf Scorch
This almond disease looks like you’d probably imagine it does. At the margins of the leaves, a brown scorched area forms. As the disease progresses, a yellow band develops between the scorched part and the green tissue.
It usually starts on just one stem, but the rest of the tree will look fine. As the years go on, it will spread to more and more of the tree until the whole thing is impacted. Once the whole canopy is infected, it looks like the tree has golden yellow fall leaves all year long.
The tree will usually survive, at least for a while, but it will be less productive and the growth will be stunted. It may eventually die.
It’s caused by the bacteria Xylella fastidiosa, which also infects grapevines and alfalfa plants. Rubus species, nettles, and many grasses can act as a host. It’s spread via insects.
There’s no effective treatment, so your best bet is to remove a young tree if it shows symptoms, or remove the infected branches in an attempt to slow the spread.
Alternaria leaf spot is an almond disease caused by the fungi Alternaria alternata, A. arborescens, and A. tenuissima. The first sign is large brown spots forming on the leaves. These expand and turn black, before causing the leaf to fall.
If the disease is bad enough, it can defoliate a tree entirely by the early summer.
The cultivars ‘Butte,’ ‘Carmel,’ ‘Sonora,’ ‘Monterey,’ ‘Winters,’ and ‘Butte’ are susceptible.
To learn more about this common disease and treatment options, you might be interested in our handy guide.
Almond trees can be affected by the disease anthracnose, which causes the flowers to be blighted, the leaves to become spotted and die without falling off the tree, and the nuts to form orange lesions. The twigs might also dieback.
In most cases, this disease will only infect your tree when the weather is warm and wet as this gives the fungus the perfect opportunity to spread.
To get rid of anthracnose, apply a copper fungicide every 10-14 days until symptoms are no longer present. Remove any dead leaves or twigs.
4. Bacterial Spot
Bacterial spot (or bacteriosis or bacterial shot hole) is one of the common diseases to encounter when growing almond trees. It’s caused by the bacteria Xanthomonas arboricola pv. pruni and can impact stone fruit trees as well.
It thrives in warm, wet conditions and spreads via water. It looks for an opening in the tree, whether that’s insect damage or pruning cuts.
The leaves are normally the first place you might notice signs of bacterial spot, where small lesions will form. The fruit will also develop lesions that may produce amber gumming. The lesions on both the fruit and leaves will expand.
Leaves may eventually drop and twigs may develop lesions. The bacteria overwinter on dried-up fruit on the tree.
If this disease is present, treat the tree during the growing season with a copper-based fungicide. The most effective treatments are a few days before a rainy period and before temps climb above 77°F.
‘Fritz,’ ‘Nonpareil,’ ‘Butte,’ ‘Carmel,’ and ‘Price’ are all susceptible.
5. Crown Gall
Crown gall is a bacterial infection that causes galls to form on the trunk and stems of almond trees. To learn all about this disease, and what to do about it, head to our guide.
6. Shot Hole Fungus
One of the main diseases that infect almond trees is caused by the fungus Wilsonomyces carpophilus. (synonym: Stigmina carpophila). Known as shot hole disease, Coryneum blight, or Stigmina fungus, you can spot this illness by examining the leaves, though it also infects the fruit and the wood.
Most of the time, this fungus starts as a few brownish-purple spots with yellow halos. As the spots mature, the center turns black and then falls out, leaving little holes behind. Fruit and stems will form cork-like brown spots and the stems might become girdled.
The disease needs a lot of moisture and temps above 34°F to thrive.
To be sure you don’t just have an insect problem, look for the black fruiting bodies at the center of each hole.
When you spot these symptoms, it’s best to cut off the infected branches and remove them from the rest of the tree. This will stop the disease from growing to more parts of the tree and will give you a better chance of saving its health.
After you’ve removed the infected area, treat the entire tree with a copper fungicide once every three weeks. The disease can reinfect your tree multiple times in a growing season, so multiple treatments are needed.
7. Verticillium Wilt
Verticillium wilt is a fungal disease that attacks all kinds of different trees, shrubs, and vegetables. In almonds, you rarely see symptoms on mature trees. Instead, your yield will be reduced and the tree might not be as vigorous as it could be.
To learn more about treatment and symptoms, head to our guide.
Common Almond Pests
There are several different pests that feed on almond trees. Some are relatively harmless, and others can cause serious problems. Here are the most common ones to watch for.
1. Almond Borers
Prune limb borers (Bondia comonana) and American plum borers (Euzophera semifunerali) will attack almond trees. The larvae are about an inch long and white or cream. The larvae overwinter in cocoons and the adult moths emerge in the spring, but it’s the larvae that cause problems.
They bore into the woody parts of the tree, leaving behind frass and gummy pockets as they go. While a mature tree will likely heal and survive, younger trees or trees that have been heavily pruned are more susceptible.
They can be weakened enough that the branches will break in heavy wind or with a load of fruit. If you notice these tell-tale gummy pockets, you’ll need to treat the tree every few weeks for several months.
Use an insecticide that contains carbaryl, such as Sevin.
Ants need protein to survive, and almonds can be a great source for them. If you’re out near your almond tree and you see a bunch of ants, you need to act quickly so they don’t damage your delicious nuts.
Use ant baits to destroy any colonies you find.
3. Leaf-Footed Bugs
Leaf-footed bugs (Leptoglossus spp.) are easy to spot. They are about an inch long and brown, black, or gray. The bodies are long with pointed ends and their feet resemble tiny leaves. These pests use their sucking mouthparts to feed on plants like almonds.
While they don’t usually cause significant damage to the tree itself, if they feed on young fruit, it will cause it to abort. It also leaves the tree susceptible to fungal infections.
However, they do love to eat on almonds trees. To stop them from munching on your harvest then you can spray a solution of insecticidal soap. This should ensure that they leave your trees alone.
Wasps like Gryon pennsylvanicum are natural enemies, and you can physically remove any bugs you see. You should also remove any weeds around your trees to deny the bugs a place to hide and overwinter.
Fruittree leafrollers (Archips argyrospila) and oblique-banded leafrollers (Choristoneura rosaceana).
These little caterpillars are around an inch long. They often have dark heads and green or brown bodies. To begin with they will roll up and eat the young leaves before making their way through the whole tree. When they feed on the blossoms, they ruin the chance of fruit.
The easiest way to remove caterpillars is by cutting off the leaves that they are living on. After you’ve picked off the pests, you can throw them in some soapy water.
Leave your tree for a week or so and come back to see if there are any more signs of leafrollers. Hopefully, you will have caught them all the first time!
If they continue to plague your tree, use an insecticide that contains Bacillus thuringiensis.
5. Stink Bugs
Another pest that can be found on almond trees is stink bugs. Specifically, watch for green stink bugs (Acrosternum hilare), red-shouldered stink bugs (Thyanta custator accerra), and uhler stink bugs (Chlorochroa uhleri).
As their name suggests, their distinctive feature is their smell. They release this odor to warn off predators and protect themselves in the wild. All of them are green and may have orange, yellow, or red as well. Overwintering bugs may be brown.
You will probably find these bugs in spring after they’ve been hibernating during winter. The bugs leave their winter home and lay eggs on the leaves and nuts of the tree. The larvae emerge and feed on the tree, and the mature adults will, too.
Damaged nuts will ooze a gummy substance and will become wrinkled and misshapen.
By treating your tree quickly you can avoid the possibility of more stink bugs taking up accommodations in your garden. These little pests can be tricky to remove, but there are some natural options you can try.
You can remove debris and weeds from the surrounding area as stink bugs like to take cover under rocks and grass. They can also be found in logs and other shelters around the garden.
Encourage natural predators and, if all else fails, treat the tree with a product containing bifenthrin according to the manufacturer’s directions.
Keep Your Almond Trees Healthy
A healthy almond tree is more able to withstand pests and diseases. To keep yours healthy, make sure to provide:
- Full sun
- Rich, well-draining, loamy soil
- Slightly acidic soil
Head to our article on growing almonds for more tips.