Like every other crop, avocados are plagued by insect and other pests. While most won’t seriously damage fruit production, you still don’t want to let them get out of control. As always at Food Gardening Network, we recommend natural methods of prevention and removal whenever possible, but there are times when insecticidal soap is called for.
For example, try this to wash away mites, thrips, and mealybugs: Add insecticidal soap to the soap dispenser in a pressure washer, making the pressure high enough to blast off the bugs but not so high it damages wood and foliage.
A natural pesticide useful against a number of avocado pests is bacillus thuringiensis, or BT. BT is common soil bacteria that have been used as microbial insecticides for the last century. They can be used on foliage, food storage facilities, soil, or water environments.
BT occur naturally, affect very specific insects, and are relatively inexpensive and safe for humans, birds, fish, and most beneficial insects. However, for them to work effectively, you need to know what type of insect you want to target and make sure that you buy a strain that will kill that particular species.
Here are some of the avocado pests you need to watch out for:
Caterpillars: Caterpillars attack foliage, flowers, and fruits. They feed inside protective nests made of leaves. BT is useful against caterpillars, if you’re careful to spray inside these folded-over or silk-bound leaves.
Borers: Borers tunnel into avocado trees to feed or lay eggs. You may spot entrance holes that are leaking sap, and branches weakened by borers may break easily. Borers prefer stressed trees, so keeping your tree healthy is a good preventative. Cut out infested branches and dispose of them immediately (not in your compost pile, where the borers will live to infest the compost). You can also treat an active infestation with BT.
It’s also a good idea to keep weeds away from your avocado trees as well as fallen leaves and other plant refuse. BT and neem oil are also useful in treating an active infestation. Be sure to plant the right species of avocado for your area; you can check with the local extension service to find out.
Lace bugs: These pests damage leaves when they are present. Feeding sites cause yellow spots that soon dry out and stressed leaves will drop, exposing fruit and wood to ultraviolet rays. When symptoms appear, sprays of horticultural oils or pyrethrin are recommended avocado tree treatment.
Thrips and whiteflies: Greenhouse thrips and ash whiteflies are tiny sucking insects that might gather on the undersides of avocado leaves to feed. Not all thrips are harmful—black hunter and six-spotted thrips feed on mites.
Avocado thrips are small, yellow insects that attack leaves and fruit. Fruit scarring begins at the stem and spreads over the rest of the avocado. The upper sides of leaves develop dark, rough patches. Check for thrips on the shadier side of the tree. The damage caused by thrips is mainly cosmetic and does not usually harm the tree or the inside of the fruit.
Control avocado thrips with predatory thrips such as black hunter thrips, or with an organic spray such as spinosad, pyrethrin, or neem oil. Careful pruning and fertilizing will help prevent thrips. Reflective mulch confuses thrips and whiteflies by directing UV light where they don’t expect it.
Mites: Brown mites, persea mites, and six-spotted mites are avocado enemies. They’re tiny, usually about the size of a pencil dot. Depending on the species, the mites leave dead spots on foliage and leave spider-like webbing underneath leaves, feed on upper leaf surfaces, or feed on the underside of leaves.
Mites can be controlled with predator mites, washing trees with powerful sprays of water or using horticultural oil (insecticides can cause a population explosion). Mites favor hot, dusty conditions, so plant your tree away from roads or open fields.
Avocado worms: These are leafrolling pests including the amorbia moth larvae and the omnivorous looper. They eat holes in leaves and bore into fruit. They are usually greenish, but may also be yellow or pink. You’ll notice fruit scarring, rolled leaves, and sometimes webbing. Control worms with parasitic wasps, handpick them from trees, or apply BT if it becomes necessary.
Oak trees attract fruit tree leafrollers, so don’t plant your avocado tree near oaks.
Rats and snails: These are two non-insect pests that will leave holes in your fruit. Rats climb the trees to eat fruit and gnaw on the bark, while snails munch on leaves and fruit, causing damage to the tree.
Tin trunk wraps keep rats from climbing trees, or, if you’re really desperate, try rat poison. For snails and slugs, handpick them off the trees in the early morning when they’re still active, or use commercial snail and slug bait.
How do you fight off avocado invaders? Please share your methods with us in the comments below.