Ambrosia Beetles in Maryland

Introduction
Order: Coleoptera: family: Scolytidae: Sub family Scolytinae: Scolytini: Xyleborina

In Maryland we have many species of native ambrosia beetles. These native species of ambrosia beetles have evolved over time with the native species of plants. We generally observe that these native ambrosia beetles usually only attack weakened trees. We do not generally worry about the native ambrosia beetles as major nursery or landscape pests.

There are two non-native invasive species of ambrosia beetles, Xylosandrus germanus and Xylosandrus crassiusculus that are causing us concern in Maryland. Xylosandrus germanus was introduced from Japan into the United States in 1932 and has spread through most of the northeast. Xylosandrus crassiusculus was reported in many southern states for years. It has been recorded in Maryland. The beetles overwinter as adult females and start flight activity early in the spring. Early detection is a key component of dealing with these two tree borers.

Wet areas on bark is a sign of ambrosia beetles

Frass is pushed out by adult female ambrosia beetles as they enter the tree to lay eggs

Damage from the ambrosia beetle, Xylosandrus germanus,  reached new high levels in Maryland in 2008.  We have recorded this beetle damaging honeylocust (Gledistia triacanthos), London plane tree, zelkova, river birch, American holly (Ilex opaca), sweet bay magnolia (Magnolia virginiana), Chinese dogwood (Cornus kousa), yellowwood, and Styrax.

Management

Pyrethroids have been found to provide control of attacking adults if applied prior to the closing of the galleries with frass. In the nursery either permethrin (Astro) or bifenthrin (Onyx) has been used to control ambrosia beetles by applying these materials to the main trunk and major branches. Permethrin (Astro) is also labeled for landscape use. Once the beetles are in the tree and have frass packed in the entry holes they are isolated from the outside. If infestations occur, affected plants should be removed and burned or chipped and composted, and trunks of remaining plants should be treated with an insecticide labeled for this pest. Once an infestation starts some nursery managers left the tree severe as trap trees and destroy the trees before the end of the 55-day life cycle.