Winter Storm Elliott brought freezing temperatures to the Florida Panhandle Dec. 24–28, 2022, resulting in significant damage to citrus in the cold-hardy growing region. Trees that received significant freeze damage are more vulnerable to pests and diseases.
Ambrosia beetles are among the pests being seen as a result of the storm. Because ambrosia beetles generally prefer dead or dying trees, they are not typically a problem for citrus trees. However, following a stress event, trees become more attractive and susceptible to the beetles.
Xavier Martini, Danielle Williams and Derrick Conover, all with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), recently provided ambrosia beetle monitoring and management information. Martini is an assistant professor of entomology, Williams is a multi-county commercial horticulture Extension agent, and Conover is a doctoral student and biological scientist. A summary follows:
To monitor for ambrosia beetles, growers can use white sticky traps near the first 3 feet of the trunk of the tree and/or an ethanol-baited bottle trap.
To create a bottle trap, use a plastic bottle (1 to 2 liters) and cut two rectangular windows on opposite sides. Hang the bottle on a stick or branch upside down with the lid screwed and fill the bottom with ethanol. Or use a pouch of ethanol lure, hang it inside the bottle and fill the bottom with soapy water. Beetles will be attracted to the ethanol odor and captured in the bottom of the trap.
Unfortunately, insecticides have limited efficacy against beetles as the pests live most of their lives within the wood. Therefore, the first line of defense should be removing infested trees and properly disposing of them by either chipping or burning.
Although insecticides have limited efficacy, a good preventive measure is the use of verbenone, which is an anti-aggregate and repellent that has been proven to repel a wide range of ambrosia species. Verbenone is sold by different providers either as pouches to hang directly on the tree or as SPLAT (SPLAT VERB®). SPLAT is a wax matrix that is slow-releasing verbenone and can be applied directly on the trunk. SPLAT or a verbenone pouch should be applied/attached on the first 3 feet of the trunk, where ambrosia beetles attack. Usually, SPLAT is efficient for up to six weeks. It is recommended to only apply SPLAT on trees with significant damage from the freeze that are at risk of attack by the beetles.
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