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Avocado Thrips

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.

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.

2010 Research

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.

2008 Research

It will still be another year or two before new pesticides are available to assist in control of avocado thrips and persea mite. At present, we are depending heavily on the use of abamectin (Agri-Mek and generic abamectins) and there is strong potential for resistance to develop in situations where this material is overused. Once resistance develops, it is likely to spread (via thrips flying around and to some degree, being moved via human traffic), it may or may not revert slowly, and could likely confer cross resistance to the spinosyn class of chemistry (Delegate, Success, and Entrust).

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.

2007 Research

We cannot emphasize enough that it is likely that avocado thrips will develop resistance to abamectin (Agri-Mek and generic abamectins) if this material continues to be heavily relied on as the major means of controlling avocado thrips and especially if it is also used for control of persea mite (and possibly Neohydatothrips burungae if this species were to become problematic in commercial areas).

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, trunk injection – to establish the methods that will provide the best uptake of insecticide for the protection of the trees. Our primary research focus is on the avocado thrips and the avocado lace bug. Despite its recent introduction, the avocado thrips is already an established pest of avocados in California.

2006 Research

Insecticides are an important component of pest management in California avocado groves. In this study, we are evaluating the efficacy of systemic neonicotinoid insecticides against an established pest, the avocado thrips, and a newly introduced pest, the avocado lace bug. The potential benefits to the industry from the use of neonicotinoids are numerous. This class of insecticide has a novel mode of action, thereby minimizing the risk of cross-resistance between the neonicotinoids and those chemicals currently being used for avocado pest management.

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.

 

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