Research Library

Stenoma catenifer, the avocado seed moth, has been identified as an exotic pest that has the potential to enter and establish in California because of imports of fresh avocado fruit from Mexico and other Central and South American countries where this pest is endemic (e.g., Peru). This moth has been subject to extensive study in Guatemala over a 2.5 year period. One of the major outcomes of this work has been the isolation, identification, and successful field evaluation of the sex pheromone of this pest.

Feeding persea mites can cause extensive foliar damage to avocados and this pest is typically controlled with pesticides. Sustainable pesticide-based control programs must rely on accurate monitoring of persea mite numbers in orchards to determine if pest populations are approaching densities which require control thereby preventing economic damage to trees. Limited applications of pesticides at critical times will significantly delay resistance development by persea mite, save growers money, and promote IPM as a marketing tool for California-grown avocados.

The importance of honey bees as pollinators of avocado flowers is a contentious issue. The reason for this is that there is no clear or consistent experimental evidence unequivocally demonstrating that honey bees are essential for pollinating avocado flowers and promoting maximum fruit set. While many different types of insects are known to visit avocado flowers (e.g., beetles and flies) and it is assumed that these insects play some role in pollination, their exact importance is not known.

Persea mite was discovered attacking avocados in southern California in 1990. Avocado thrips was found in two isolated avocado groves, one in Orange Co. and the other in Ventura Co., in June 1996. Since then, these have become the two major arthropod pests of avocados in California although populations of each can vary in severity a good deal from year to year. Although it was an unusual year, according to Witney (2009), estimates of direct losses from avocado thrips damage to fruit and control costs for this insect combined to exceed $50 million in 2006.

We are evaluating systemic insecticides for the management of current and newly emerging pests of California avocados. Studies are being conducted in commercial avocado groves, under normal agronomic practices. Trees are treated using a variety of techniques – soil application and trunk injection – to establish the methods that will provide the best uptake of insecticide for the protection of the trees.

Our research is aimed at assisting with effective management of avocado thrips and persea mite. We will study how to use available pesticides most effectively, will search for new control materials, hopefully with different modes of action from available materials to reduce the potential for pesticide resistance development, and will evaluate alternative methods of pesticide application and timing of treatments.

Avocado thrips, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) was discovered in California in July of 1996, and spread rapidly to most avocado orchards in Southern California. The economic impact of this pest has been estimated at an annual short-run loss of between $7.6 and $13.4 million in 1998 from the combined effects of losses in quality and increased production costs associated with avocado thrips management. Since the introduction, methods to

As fast as possible, we hope to continue to suggest solutions to the avocado thrips problem based on sound scientific research. We will determine how to use available insecticides most effectively, will search for new control materials, hopefully with different modes of action to reduce the potential for pesticide resistance development, and will evaluate alternative methods of pesticide application and timings of treatments.

This project has two main goals. First, we are working to establish colonies and mass rear some of the exotic scale species that are coming into California on shipments of fresh avocados from Mexico. We are also doing studies on the biology of these scales because little or no information is available, even for parameters as basic as how many generations a year they are likely to have, and how many offspring females produce, and the longevity of males and females.

February 2007, avocados from outside the U.S. were allowed into California for the first time. During the first months of importation, CDFA inspectors at the border between Arizona and California found several species of armored scale insects on avocados imported from Mexico, that were not known to occur in California nor anywhere in the U.S.