Lychee erinose mites pose serious threat to lychee trees in Brevard | Sally Scalera

This article is for everyone with an interest in lychee trees.

A new pest in the state is a serious threat to lychee trees, so everyone growing one will want to learn how to protect it. This new insect, the lychee erinose mite, goes by the scientific name Aceria litchii.

LEM is a native of Asia and is considered a major pest of lychee (Litchi chinensis) trees. It is a world traveler and has made its way to Hawaii, Australia and Brazil, and is considered a prioritized pest in the continental United States and other territories.

LEM was first discovered in Florida in a lychee grove in Sarasota County in 1955, and again in 1995 in Miami-Dade County on imported plants from China. In both of those cases, they were eradicated and never became established in the state. The sad news is that is no longer the case. On Nov. 1, FDACS suspended eradication efforts throughout Florida due to a lack of funding and the widespread distribution of the pest.

Florida produces more lychee and longan in the United States than Hawaii and California, with approximately 90% of the commercial production concentrated in Miami-Dade County. LEM has been discovered in Brevard County and Martin, Palm Beach, Broward, Miami-Dade, Collier, Hendry, Lee, Charlotte, Sarasota, Manatee, and Pinellas counties.

LEM is microscopic but can be detected by the symptoms that first appear on the newest leaves. Check the immature foliage for small blisters with silver-white hairs visible with a hand lens or eye loupe. As their feeding damage continues, LEM causes the leaf epidermal cells to become a reddish-brown hairy mass that becomes very visible on the entire underside of the leaf, causing the leaf to become distorted and/or curled. Sometimes the undersides of the leaves can turn almost black.

As the mite population grows and their feeding spreads, these symptoms can also occur on the stems, petioles, panicles, flower buds and fruit. LEM infestations can result in an 80% reduction in a tree's fruit production. Follow this link for the Florida Department of Agriculture and Consumer Services LEM information fdacs.gov/Agriculture-Industry/Pests-and-Diseases/Plant-Pests-and-Diseases/Lychee-Erinose-Mite.

Because of their extremely small size, LEM can be spread by air currents, honeybees, tools, humans (who touched symptomatic leaves), and the movement of infested plants. Cleaning your tools after pruning infested branches and changing your clothes before moving to another area of lychee trees will help stop their spread. All tools and equipment used on lychee trees, including clippers, loppers, hand saws, chain saws and hedgers, should be washed with a 10% bleach solution (1 part bleach to 9 parts water) before using them on another tree.

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You can also protect your tree from this potentially devastating pest by helping your tree grow as healthy as possible. A good start would be to test the soil if you have not done so in the past year or two.

Send the soil sample to the UF/IFAS Soil Testing Lab and pay for the $10 Test B.  The test results will include the soil pH and the levels of water-soluble phosphorus, potassium, magnesium, copper, manganese and zinc. The first three nutrients are macronutrients, which plants require in higher amounts. Deficient levels of any of these nutrients can stress plants and make them more susceptible to insect infestations and diseases.

The soil testing form can be found at edis.ifas.ufl.edu. (Search for "soil testing form".) It is not uncommon for soils to test low, or even very low, in potassium which is important for the plant’s root system and water regulation.

For general information on growing lychee trees, check out our bulletin, Lychee Growing in the Florida Home Landscape at edis.ifas.ufl.edu. (Search for "growing lychee trees.") This bulletin will cover numerous topics, including planting, watering and pruning.

After several years of fruit production, it is recommended that the tree be pruned back to a height of 10 to 15 feet. That should be done by selectively removing a few upper limbs, back to where they branch off a lower limb. Doing this yearly will allow sunlight to reach the lower canopy for future fruit production.

Nineteen cultivars of lychee trees grown in Florida are also discussed in the bulletin.

If you want additional recommendations to help your tree ward off insects and diseases email the UF/IFAS Extension Brevard County Master Gardeners at brevard-mg1@ifas.ufl.edu. They will send you easy instructions on inoculating your yard with beneficial soil microbes and a copy of my Recommendations for Growing Fruit Trees and Other Edible Plants and How to Add Life to the Soil bulletins.

If you are growing lychees, inspect the foliage to ensure your tree is LEM-free. If you don’t already own at least a 10-power eye-loupe to look for evidence of LEM, you may want to check out the 40-power jeweler’s eye-loupe with LED lights to see which one you would prefer. Once you have your eye loupe in hand, look at the new growth of your lychee trees.  Be on the lookout for blisters that are covered with silver-white hairs.

Hopefully, you won’t find any abnormal new growth, but if you are going to discover evidence of LEM, it’s better to find it at the very beginning of an infestation, because your trees will fare much better. Now is a great time to consider working with nature to improve the health of your lychee trees.

Sally Scalera is an urban horticulture agent and master gardener coordinator for the University of Florida’s Institute of Food and Agriculture Sciences. Email her at sasc@ufl.edu.

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This article originally appeared on Florida Today: Check your Space Coast lychee trees for damage cause by invasive mites