Ask Your PCA: How do I manage mites in avocados?

Issue Date: September 8, 2021
By Chris Boisseranc PCA, Southwest Ag Consulting Inc., Redlands
Chris Boisseranc PCA, Southwest Ag Consulting Inc., Redlands

In September, mites can be problematic for avocados, particularly if the weather is mild. There are two different types of mites: persea and the brown avocado mite.

Both mites affect the leaves on the canopy, but they don't damage the fruit. They stress the trees and cause defoliation by stripling the leaves with their feeding action. This weakens leaves and, in conjunction with strong winds, the leaves can blow off. This will slow the growth of the tree and can cause premature leaf drop and defoliation, and expose the fruit to sunburn.

The trees lose energy trying to re-establish the canopy, and sunburn damage can lead to worms damaging the fruit. While avocados are a hard fruit, there is a worm that can penetrate and cause damage in October and November.

Treating the mites is a combination of management and chemical control. Triple-digit temperatures for three to five days in a row will cause the mites to die off. Last year, mites started a little earlier in July and August, and there were explosive populations. In September, temperatures reached 120 degrees, which completely bottlenecked the mite populations. Mites are very weather-influenced, so typically how many treatments are applied within a season hinges on the weather conditions.

Reducing dust can also help reduce mites. Many of the avocados are planted on high slopes, so there isn't a lot of road dust from vehicles. Predatory mites are also released, but they're more effective for treating pockets of activity or smaller properties, and they are used by organic growers.

Chemical spray applications are generally done by helicopter. There are oils that are organically approved, and they will suffocate the mites. For conventional orchards, an insecticide is included with the oil, and both are effective if applied at the correct timing—before egg hatch.

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.

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