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Pests

2011 Research

Over the period 23-25 January 2011 residential areas in Tijuana Mexico were surveyed for the presence of avocado trees, and when possible trees were inspected for arthropods associated with trees. Google Earth was used to pre-select six separate residential areas that showed high levels of greenery (i.e., parks, and well maintained residential gardens). In these six areas, 267 residential street blocks were surveyed. From these blocks, a total of 634 properties were inspected from the road. The percentage of street blocks with avocados in pre-selected sections of Tijuana ranged from 23% to 45% of blocks having at least one tree. A total of 80 avocado trees were found from these surveys. Of surveyed properties, 10% or 64 properties had at least one avocado tree. The number of avocados per property ranged from 1 to 5 trees. The GPS coordinates were recorded for each tree and when possible foliage was inspected for avocado pests.

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.

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.

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.

Before February 2007, avocados from outside the U.S. were not allowed entry into California. However, after these import restrictions were lifted, the CDFA detected several species of armored scale insects on avocados imported from Mexico that were not known to occur in California nor in some cases, anywhere in the U.S.

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.

Between 1914 and 2007, a quarantine protected California avocado groves from pests that might be introduced into the state along with fresh, imported avocados. Soon after Mexican avocados were first allowed entry on 1 February 2007, live specimens of several species of armored scales (Family

Between 1914 and 2007, a quarantine protected California avocado groves from pests that might be introduced into the state along with fresh, imported avocados. Soon after Mexican avocados were first allowed entry on 1 February 2007, live specimens of several species of armored scales (Family Diaspididae) not believed to be present in California were detected on Hass avocados entering the state from Mexico.

The California avocado industry is threatened by a number of exotic avocado pests that are being introduced into California on an ongoing basis by imports of fresh avocados from Mexico. These include a number of weevils, scales, and several lepidopteran pests. This project focuses on developing pheromone-based methods of detection for the exotic scale species, with two main goals. First, we are establishing colonies of the various exotic scale species, collected from avocado shipments as they come into California, to provide insects for study.

We are evaluating systemic insecticides for the management of current and newly emerging pests of California avocados. Current management practices for avocado thrips are centered on the use of foliar insecticides. Several foliar treatments are available (Agri-Mek, Delegate and Danitol) for the

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