avocado on a tree

The avocado industry is booming, and farmers are always looking for ways to increase their yield. To keep your farm as productive as possible, it’s important to know about the diseases that affect avocados. Avocado diseases are a common problem for avocado trees in the United States. Most recent estimates suggest that nearly 30% of all avocado trees have been impacted by one or more diseases, and this number is only expected to rise as time goes on.

Here we’ll discuss some of the most common avocado tree problems you need to know about and the steps to take to protect your crops this season.


Anthracnose is a fungal disease that can severely affect avocado trees. It’s characterized by brown spots on the leaves and fruit, eventually turning black and falling off the tree. This avocado disease can be caused by either wet or dry types of spores. The most common form of Anthracnose to affect avocado trees is wet spores, which thrive during rainy seasons and eventually dry out when conditions are no longer favorable. 

They can be found in warmer climates with high humidity, where they infect flowers on different plants before moving onto their nearby avocado trees. The dry spores will thrive in the opposite conditions of wet spores and are usually found during periods with low humidity or drought-like conditions around the world. Both forms of Anthracnose are carried by insects such as thrips, flies, and mites that can spread them to other avocado trees if they’re not treated.

The spores can be carried on the wind, and it’s common for them to spread from avocado trees in Mexico into other parts of the US. If you’re not sure if your tree is infected with this avocado disease, there are a few signs that will alert you, such as fruit bunching or dropping off too early without ripening properly, yellowed leaves, lesions on leaves, stunting of growth, and dieback of branches or leaves.

The only way to know for sure is by cutting open a piece of the fruit, which will show you black inside or brown spots on the skin. It’s important to take action as soon as possible because Anthracnose can cause tree death within two years if left untreated. It also contributes to avocado tree decline. If you think your avocado tree has Anthracnose, there are a few things that you can do to control the avocado disease and prevent more avocado tree problems. These include:

  • Sanitation practices such as removing diseased fruit immediately
  • Keeping fallen leaves off of soil or plants so they don’t rot where insects like thrips can breed
  • Using fungicide applications that can prevent it from spreading

Armillaria Root Rot

Armillaria is a fungus that can grow on avocado roots and kill the plant. The first sign of infection is yellowing leaves followed by wilting. This fungus is most common in avocado trees planted too close together and can be treated with fungicide if caught early on. Leaves will fall off in autumn, but new buds form again during springtime until finally dying once more with an intense heatwave or drought. 

Infected trees often have sunken cankers in the trunk, which may be white or brown and cracked. Armillaria root rot is considered a serious avocado disease because it spreads quickly through avocado roots that are near each other, creating a dense mat of fungus.  There is no cure for this disease, but you can prevent it with careful planting and pruning. Armillaria root rot is a serious avocado tree problem that needs your attention to avoid an entire harvest. 

Some of the preventative measures include:

  • Planting avocados in groups of ten or fewer trees, so they have plenty of room, but not a lot of overcrowding that will cause root competition for nutrients. This is to prevent spreading this disease via close proximity to nearby trees.
  • Pruning avocado tree roots after planting or during the first year to help keep them from competing for nutrients and spreading the avocado disease
  • Fungal root washes using a water-based fungicide that can prevent avocado tree problems such as infections before it starts by washing underground fungus off of avocado tree roots.
  • Cultivating in a well-drained site with plenty of organic material, which will help reduce the competition for nutrients and ease soil compaction.

Avocado Black Streak

Avocado Black Streak Disease (BSD) is a bacterial disease that causes black streaks to appear on the trunk and limbs of avocado trees. These dark-colored lines can turn into large cavities in the trunks but are not fatal unless they cut deep enough through the bark’s protective outer layer. Bacterial diseases such as BSD are most severe when the weather is hot and humid with little air movement, which provides an environment for bacteria to grow at an uncontrolled rate. 

Symptoms of this avocado disease typically show in late summer or early fall. When BSD occurs, the avocado tree will grow a tuft of brown felt-like fuzz on the black streaks or cavities in its woody outer layer. The best way to prevent this disease is by planting new trees away from old ones and making sure that they have plenty of space so air can move freely around them. Treatment involves removing the diseased parts of a tree and keeping it well-watered during dry periods.

Verticillium Wilt

Verticillium wilt is a disease that affects a range of plants, including avocado trees. When affected, a plant’s vascular system will be clogged up with fungal cells, which then start to grow and spread throughout the tree, causing it to die slowly. Signs of this avocado disease include yellowing leaves, drooping branches, and scorched leaf tips. It’s a common problem in California avocado production where demand is rising. It’s most often spread through pruning tools that have been used on infected plant material or by soil to which the fungus is clinging.

The best way to avoid this avocado tree problem is simply not to use those tools for a while after you’ve finished with them–or to sterilize them. It can also be prevented by not planting avocado trees near infected plants, and if you do plant new trees in an area where the disease is known to exist, make sure they are at least 75 feet from any other tree that may have been exposed to it. While there are no known preventative measures for Verticillium Wilt, the disease can be treated with fungicides. 

Phytophthora Canker

Phytophthora Canker is one of the most common avocado diseases. It attacks avocado trees by infecting shoots and leaves. It spreads by spores from infected plants that land on healthy ones. Symptoms include dark lesions in leaf edges, browning, and the dying of leaf tips. Infested leaves eventually fall off the tree in a manner similar to wilting. A smell from rotting fruits is also present. The best way to get rid of Phytophthora Canker is by:

  • Removing infected plants or plant parts so that spores don’t spread further
  • Cutting back avocado trees and removing dying or dead branches
  • Burning infected plant material in a fire
  • Spraying copper-based fungicides on the avocado tree’s leaves

Dothiorella Canker


The Dothiorella Canker is an avocado disease that can be caused by many different factors. The most common cause of this problem is the invasion of an infectious plant fungus from soil and water contamination. There are other causes for this issue, including bacterial infection or insect infestation. This avocado tree problem starts as a small discoloration on the bark or branches, and it is most notable during wet periods. The fungus that causes this disease can be transmitted by an insect’s bite as well.

The good news is that there are many symptoms of this condition which will help to identify what caused it. It starts with small spots on the bark, which will take on a dark color and then spread until it covers most of the tree’s surface. The leaves may start to wilt or fall off before you notice other signs of Dothiorella Canker. There are no known cures for this condition, but there are ways to prevent it from spreading. A fungicide can be used to help control the infection, and you should also make sure that your tree’s roots are not in contact with any contaminated soil.

Learn More at Fruit Growers Supply

Avocados are a delicious and healthy fruit to grow, but diseases can be a problem for farmers. The key to successfully growing avocados is understanding their unique needs for temperature, water, etc., as these trees require more care than other fruits.

If you’re having trouble with your plants, finding the right supplies, or have any questions about avocado diseases, take time to visit FruitGrowerSupply.com and learn more or contact us to speak with a representative.

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