3/24/2014 - By Matthew Shultz

This month I would like to take a look at a group of beetles affectionately referred to as The Ambrosia Beetles. I have had several calls recently about these pests! In some parts of the country up to thirty species of Ambrosia beetles can coexist in the same area, but there are two species in particular that are of recent economic importance when it comes to ornamental and fruit production.

Red Bay Ambrosia Beetle

The first, the Red Bay Ambrosia Beetle is very important in the southeastern United States, mainly because this beetle is known to help spread the Laurel Wilt pathogen. This species of beetle is native to Asia and it is known to attack Red Bay trees which grow from Florida all the way north to parts of southern Delaware and Maryland.

This species was first detected in Georgia and has since been documented in neighboring South Carolina and Florida. Red Bay Ambrosia Beetles also attack a close relative plant, the Avocado tree, putting Avocado growers on high alert as well!

Male beetles of this species can’t fly, but females can. Most females start to take flight between the months of March through October in most of the south, peak flight around June. Both male and female beetles carry spores of the Ambrosia fungus in their gut. Once they bore into the trunks of their host plant they release the spores which grow inside the sapwood of the tree. This fungus is what the beetles feed on.

The female Red Bay Ambrosia Beetle has a special pouch in her mouth where she carries spores of the Laurel Wilt disease and is responsible for the spread of this disease. This beetle must be controlled preventatively because once they have bored into the trunk, control is unachievable since they don’t actually feed on the plant material but rather the Ambrosia fungus.

Infected plant stock should be burned or chipped or buried to prevent further spread. Trunk applications of a pyrethroid insecticide such as Talstar or Permethrin should occur every 14 to 21 days during the months of March through October while adults are active. Start at the ground level and spray the tree trunk up to a height of 10 feet. The addition of  Harrell’s Nonionic Spreader Sticker will help the insecticide adhere for longer periods of time to the plant trunk.

Granulate Ambrosia Beetle

The next Ambrosia beetle that I wanted to discuss is the Granulate Ambrosia Beetle. This species of Ambrosia Beetle first landed on US soil in South Carolina from Asia. In the last forty years the beetle has spread through all the Gulf States including Florida and as far north as Maryland.

The Granulate Ambrosia Beetle attacks a wide range of host plants including styrax, dogwood, redbud, cherry,  Acer, crepe myrtle, pecan, peach, plum, persimmon, golden rain tree, sweet gum, Oak, Chinese elm, magnolia, fig, and azalea.

The females of this species carry the Ambrosia fungus and they inoculate the host plant once they bore into the sapwood. Adults of this species will typically only attack trunks and branches between 1 to 3 inches in caliper.  Female beetles can be trapped using ethanol alcohol. Simple soda bottle traps work well once they have been baited with an ethanol strip.

Trunk applications of a pyrethroid insecticide such as Talstar or Permethrin should occur every 14 to 21 days beginning in March, once the first adult appears in monitoring traps. Both species can be found making toothpick sized sawdust posts which are excavated from boring galleries.

Sources Referenced:

• http://edis.ifas.ufl.edu/hs379
• http://www.ces.ncsu.edu/depts/ent/notes/O&T/trees/note111/note111.html