Persea Mite: This pest is present in all the groves we look at and we've begun to treat groves with both predatory mites and by spraying horticultural oil. To evaluate the Persea Mite population in your grove, get your hand lens (or order one from us) and check the leaves on your trees, both young and old, for signs of the mite. You'll see semi-circular spots about 1/4 to 1/2 inch in diameter along the veins on the undersides of the leaf. As the mites feed, the cells die and turn tan to brown to black. These spots show through to the upper surface of the leaf and make them look like they have measles.
The mites themselves live under the shiny webbing that covers the spots; they are yellow with small, variable black spots. The lifecycle includes the egg, two immature stages and the adult, all of which are found in nests under the webbing the adults spin. To see them you'll probably need a hand lens between 10X and 20X since they're pretty tiny ('mitey small', as we say in the business). There is a fast Counting Method to determine how many mites per leaf there are in your grove. See Persea Mite Strategies for a discussion on options for controlling this pest.
Looper: This pest is usually kept in check by natural enemies but this year it is building up in many groves, causing feeding damage to leaves and fruit. There are two treatments for this caterpillar; the first is to release an insect (Trichogramma platneri) that attacks the eggs of the moth and thus prevent the caterpillar from ever hatching. The second treatment, if needed, is to spray a bacteria that causes a disease in the caterpillars. This bacteria, Bacillus thruingiensis, does not affect any other insect besides caterpillars nor any other kind of plant or animal, so it is very safe and targets the pest specifically.
The looper adult populations can be monitored with pheromone traps, which are available at most ag supply stores. We treat with 1 card of T. platneri per acre when moth counts reach about 250 per week per trap to time the parasite release for the time of maximum moth egg presence.
Prepared by Jim Davis, California PCA License #2759