Bugs Eating Avocado Tree Leaves: What You Need to Know

Author
Recent Posts

Sydney has over 15 years of experience in lawn maintenance, landscape design, and organic gardening. She has an A.A.S. in Landscape Design/Organic Produce Production from the Nebraska College of Technical Agriculture.

Common Avocado Pests

Unlike some other fruits, avocados don’t attract many pests that cause lasting harm. If something is eating your tree’s leaves, the culprit is probably one of the four we’ve mentioned. Let’s have a look at each of these.

Western Avocado Leafroller (Amorbia cuneana)

Western avocado leafrollers, often called amorbia or amorbia moths, spend almost their entire life cycle within avocado trees.

They begin as light-green eggs, laid on top of a leaf near the midrib (a large vein on the leaf). After hatching, they grow into green caterpillars just under an inch long with a single black line just behind their heads. As adults, the moths have bell-shaped, orange or tan wings.

Young caterpillars nibble on the leaves’ surface and create webs that form a nest between leaves. Mature caterpillars eat entire leaves before pupating inside a rolled leaf.

When they emerge as moths, the cycle begins again–in warmer areas, growers may see three whole generations of leafrollers in a single growing season.

Leafrollers are most common in California. If you live near a commercial avocado grove, you may be more likely to see them in your own tree.

If you have a colony of leafrollers in your tree, the most obvious symptoms will be holes in leaves, rolled leaves, and webbing. The damage is most likely to be on terminal leaves, at the very ends of branches. Occasionally, leafrollers will eat the rinds of fruits as well (source).

If left uncontrolled, leafrollers will skeletonize leaves to the point of defoliating your tree. When that happens, your tree’s young branches and fruit will be more prone to sunburn (source).

Persea Mites (Oligonychus perseae)

There is more than one type of spider mite that is attracted to avocados, but out of them all, persea mites are the most likely to cause extensive damage.

Like leafrollers, many persea mites spend their entire life cycles in avocado trees. They begin as tiny yellow eggs with red eye spots and emerge as larvae with six legs. As they mature, they develop two more legs.

Adult females range in color from yellow to dark green, and their bodies resemble flattened ovals. Males are yellow and pear-shaped.

Another trait they share with leafrollers is webbing. Persea mites often spin “nests” to protect them as they feed or reproduce.

Persea mites first appeared in Mexico but can be found in avocado groves as far away as Israel. In the United States, they are common in California and Florida (source).

If you live in an affected region, you can confirm Persea mite damage by looking for brown spots or dense webbing on the undersides of your leaves.

A very large colony of Persea mites will do more extensive damage. They can cause leaf drop, defoliation, and significant tree stress. Depending on the age of your tree, some of this damage is irreversible (source).

Omnivorous Looper (Sabulodes aegrotata)

Sometimes called avocado loopers, omnivorous loopers are moths whose favorite habitat is avocado trees.

They begin their life cycles as pale green eggs shaped like minuscule barrels and emerge as pale yellow caterpillars only 1.5mm in length. As they mature, they become quite distinctive: just over two inches long, with black, brown, green, or orange stripes running the length of their bodies.

Like leafrollers, loopers create cocoons out of rolled leaves and webbing, emerging one to four weeks later as a brown moth. The life cycle then restarts; in a single growing season, an avocado tree could play host to four or five generations of loopers.

Omnivorous loopers don’t limit themselves to avocado trees, but they are fairly common in avocado groves throughout California and Florida.

If you suspect loopers may be feeding on your leaves, look for a brown membrane on the surface of terminal leaves. You may also notice leaves that are completely skeletonized or eaten all the way down to the stem.

Loopers also feed on fruit. If you notice fruit that is misshapen or scarred, loopers may be responsible.

If the damage is severe, your tree may experience sunburn and reduced fruit yields in the next growing season.

Avocado Lace Bug (Pseudocysta perseae)

Avocado lace bugs, like the previous three insects, make themselves at home in avocado trees for their entire life cycles.

Lace bugs are extremely small; their eggs look like specks of black pepper. As adults, they resemble very small flies, only about 2mm long.

Lace bug colonies are easiest to identify by their excrement, which is black and sticky. They spend their egg and nymph stages under a covering of excrement on the underside of leaves.

Avocado trees may be the home of several generations of lace bugs each year. Their life cycles are slower in the winter, but they can survive cooler temperatures at any stage.

In the U.S., lace bugs are most common in Florida and other warm regions of the southeast. They have been noted in avocado groves in California, but not as extensively (source).

It can be easy to misdiagnose a lace bug infestation. They feed by sucking chlorophyll and other nutrients out of leaves, but don’t chew through the leaves themselves. This results in dead-looking spots on the leaves that at first glance appear to be symptoms of drought or sunburn.

However, if you look at the leaves’ undersides and see black spots and small “flies,” you have a lace bug problem.

In addition to defoliation, lace bug damage leaves your tree vulnerable to bacterial infections that could cause much more extensive damage in the long run (source).

How to Manage Existing Pests

It’s understandable to want to reach for a pesticide when insects have invaded your avocado tree, but that is definitely not the best solution for any of the four pests described above.

Leafrollers, for example, usually only appear in trees after a pesticide has killed their natural predators. The same is true for Persea mites, and loopers.

For all four of these pests, unless the infestation is extensive, the controls are simple:

Use a strong hose to spray them off the leaves they’ve settled on. You can repeat this procedure as many times as necessary.
Prune terminal branches so that they don’t touch. Touching leaves and branches give bugs easy access to other parts of the tree.

If necessary, applying an insecticidal soap to infected leaves may help, but avoid applying broad-spectrum pesticides that will keep predator populations low.

How to Prevent Pests From Settling In

Maintaining the health of your avocado tree is the best way to prevent long-term insect damage.

Avocado trees, if they are healthy, can withstand some insect damage. In fact, the four pests above are considered harmless in small populations in healthy trees. Consistent irrigation, pruning, and proper fertilization will keep your tree healthy and resistant to the long-term effects of defoliation.

When you fertilize, avoid quick-release products that are especially high in nitrogen. Increased nitrogen can lead to more robust insect populations.

You can also reduce pest populations by reducing weeds, ornamentals, and other plants known to host avocado pests.

Be sure to read our guide on reasons an avocado plant may be dying.

Conclusion

Western avocado leafrollers, persea mites, omnivorous loopers, and avocado lace bugs are common leaf-eating insects that plague avocado trees. At their worst, they cause defoliation, tree stress, and fruit loss.

However, in most cases, their numbers are small enough for growers to manage easily with a strong jet of water and consistent pruning practices. You can prevent future damage by avoiding pesticides that kill pests’ predators and keeping your tree healthy with good growing habits.