Ambrosia Beetles a Concern Post-Freeze

Josh McGillfreeze, Georgia, Pests

Researcher Apurba Barman recently reported that ambrosia beetles could be a potential concern following the December 2022 freeze event in the cold-hardy citrus region. Barman is an assistant professor of entomology with the University of Georgia College of Agricultural & Environmental Sciences

Ambrosia beetle infestation (A) on a young citrus tree following the freeze event of December 2022 compared to a healthier tree (B) with no symptoms of infestation.

Ambrosia beetles are small insects that bore holes into stressed trees. While they have been seen attacking young pecan trees, Barman said this is the first time he has witnessed an infestation in citrus trees. 

Barman stated that in a young orchard in Georgia’s Lowndes County, a number of plants had high levels of ambrosia beetle infestation. The plants with the infestation were already significantly damaged following the freeze event. There was little to no ambrosia beetle infestation on trees which looked healthy and had lots of green leaves.

“It was comforting to see that the young, healthy trees were probably not vulnerable to the ambrosia beetles,” Barman said. “However, we want to make sure that the surviving trees are not stressed further and to protect the trees from potential pests and diseases. Therefore, I would urge growers and crop consultants to closely inspect citrus trees, especially those which have green leaves or emerging leaves, for any symptoms of ambrosia beetle attack.”

With the onset of spring and temperatures in the 80s, ambrosia beetles leave the woods and seek new host trees. Most of the attacks should be limited in the lower part of the tree about 2 to 3 feet above the soil. The beetles make holes to build their home and produce the next generation. 

There is not a good curative measure to control the ambrosia beetles as they actually do not feed on the tree. Barman reported that the best approach to prevent or reduce the chance of ambrosia beetle attack on young trees is to apply pyrethroid insecticide on the lower half of the tree trunk. Pyrethroids can both kill and repel ambrosia beetles which come in contact with the treated tree surface.

Pecan growers have had success painting the lower part of the tree (2 to 3 feet from ground, depending on tree size) with white latex paint and spraying pyrethroid on top. This method is likely to increase the retention of the active ingredient for a longer time, Barman stated.

Source: Georgia Citrus Association

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