Tropical Entomology - Ambrosia Beetles
(Coleoptera: Curculionidae: Scolitynae)
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Description
List of ambrosia beetles capable of carrying the LW pathogenAmbrosia beetles are small, elongate, cylindrical, fungus farmer beetles about 2 mm in length. They have obligate nutritional relationships with fungi that grow in their natal galleries in host-tree xylem (Six, 2012). Their larval stages feed upon these fungi until they reach the adult stage, which in turn carries the fungal symbionts from tree to tree in specialized structures called mycangia. Several native and exotic ambrosia beetle species are found in Florida (Carrillo et al. 2012). The exotic redbay ambrosia beetle Xyleborus glabratus Eichhoff has become established in the southeastern U.S during the last decade. This beetle attacks healthy trees in the Lauraceae and vectors the lethal fungus, Raffaelea lauricola, to native trees in southern Florida such as redbay (Persea borbonea) and swampbay (P. palustris), and the economically important commercial avocado (P. americana) . The pathogen causes a disease named laurel wilt and symptoms usually develop within 4 to 8 weeks of infection and include wilting, desiccation, dieback of stems and limbs and tree death.To date very few redbay ambrosia beetles have been detected in the commercial avocado production area (Carrillo et al., 2012; Carrillo et al., 2013). Recently, however, the LW pathogen has been found in or on at least 7 other ambrosia beetles present in south Florida, two of which (Xyleborus volvulus and Xyleborus ferrugineus) have been demonstrated under greenhouse conditions capable of transmitting R. lauricola to avocado trees (Carrillo et al., 2014). This disease is threatening the commercial avocado industry in South Florida.
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Damage
Part of plant damaged: Trunk
Ambrosia beetles burrow into tree trunks, stems and branches. Infested trees are regularly stressed before the attack, but frequently the trees appear to be healthy and vigorous. -
Management
Avocado trees killed by laurel wiltThe largest portion of the ambrosia beetle population is found inside infested trees. Contact insecticides have not been shown to prevent ambrosia beetle emergence from already infested trees or wood and only a few contact insecticides have been found to provide good control of ambrosia beetles on wood surfaces. Chipping and burning wood can eliminate ambrosia beetles inside tree stumps and wood and stop their reproduction. However, to kill ambrosia beetles outside of the tree stumps and wood, applications of contact insecticides and/or biopesticides are recommended to help control or prevent further beetle movement in the grove (e.g., Malathion, Danitol or Hero), plus adjuvant (i.e., NuFilm, Vapor Gard or Pentrabark). Some biopesticides (e.g., BotaniGard) have also shown promise as detrimental to ambrosia beetles. Avocado groves under organic production should chip and burn all wood (including the chips). Detailed recommendations for ambrosia beetle and laurel wilt pathogen control can be found on the Laurel Wilt-Ambrosia Beetle website.
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Images
Sapwood discoloration due to laurel wilt
Avocado logs, a major source of ambrosia beetles
Adults of ambrosia beetles
Adult female of Xyleborus glabratus
Xylosandrus crassiusculus female (left), male (right)
Xyleborus affinis female (left), male (right)
Xyleborus volvulus female (left), male (right)
Xyleborus bispinatus female (left), male (right)
Frass exuding from avocado trunks infested with ambrosia beetles
Holes on avocado trunks infested with ambrosia beetles
Holes on avocado trunks infested with ambrosia beetles
Holes on avocado trunks infested with ambrosia beetles
Sugary secretions on avocado trunks infested with ambrosia beetles