Ambrosia beetles get their name from the ambrosia fungus they consume, farm and harvest for their larvae. While their name may suggest something delicious or wonderful, like ambrosia salad, they are anything but wonderful for the health of your trees.
Beyond the interesting name, Ambrosia beetles are also interesting creatures. They are one of the only insects that farm its own food. The females bore into tree trunks, carrying the ambrosia fungus that they then “plant” in the tree’s vascular system. This clogging of the tree's vascular system is detrimental to the health of the tree. Like a human with clogged arteries, eventually something must give, and the tree starts to decline and eventually dies if left untreated.
One indication that you need to be on the lookout for these little beetles is the presence of phytophthora cankers. This is a “root rot” fungus that should also be addressed for the health of the tree even if ambrosia beetles are not present. This disease is like a homing beacon and lets the beetles know this tree might be the perfect place to raise their offspring and build their fungus farms.
Ambrosia beetles generally attack trees that are already vulnerable due to phytophthora or other diseases, but even healthy-looking trees are at risk. If not detected right away, most trees do not survive.
Phytophthora resembles a bleeding wound on the tree. Often it will present as a dark canker on the roots or the trunk of the tree. Other indicators you may notice are die back in the canopy leaves or chlorosis, which is loss of color from the leaves.
The presence of phytophthora often goes hand in hand with ambrosia beetles. If you see one, you are likely see the other and preventative measures should be taken.
One indication that a tree may be infested with ambrosia beetles is something called “frass”. This residue resembles saw dust or even toothpicks around the base of the tree. This refuse is left behind by the boring beetles on their way to deposit their fungi feast.
If you notice these signs, call your arborist right away so they can evaluate the tree, determine the severity and come up with a plan of action. Time is of the essence in cases where tree preservation is the goal.
In the case of widespread infestation, extreme measures are taken. To prevent further infestation, we use an insecticide applied to the base of the trunk of the tree. This is similar to a person using bug spray to prevent mosquito bites. It will not last forever, and there’s still a chance of bites, but it’s our best defense.
The best treatment is prevention by keeping your trees healthy and happy. Trees with limited soil area, compaction or other soil concerns, can benefit from soil care and fertilization. Your trees can also thrive with proper watering and mulching.
With proper care, preventative treatments, and some help from your local arborist you can ensure your trees have a long, healthy life providing enjoyment and enrichment to your space.