This online assessment tool is intended to help evaluate the presence of ISHB on your property. Consider the level of infestation, potential safety hazards, economic and ecological tree value, available resources, and factors unique to each situation when using this tool. Simply click the link below for access.
Because ISHB are tiny beetles that spend most of their lives inside the tree, it can be difficult to find and identify them. However, infested trees show signs and symptoms that can help us determine if the tree is infested with ISHB-FD.
Beetle Entry Hole
The most accurate way to visually determine if a tree is infested with ISHB is to find beetle entry holes that are the right size and shape. The typical entry hole to an ISHB gallery is perfectly round and about 0.85 mm (less than 0.04 inches) in diameter, or about the size of the tip of a ballpoint pen. The abdomen of the female beetle can sometimes be seen protruding from the entry hole. The entry hole may also be plugged or covered by sap, exudate, or frass (sawdust from boring) from the tree. When sending photos to a specialist for identification, include a picture with a pen for scale. ISHB galleries run perpendicular to the trunk. If ISHB are present, shaving off bark will reveal a round gallery up to 2 inches deep in the wood, surrounded by darkened, diseased wood.
Signs of Infection
Fusarium causes dark discoloration of the wood around the beetle gallery. Lightly scraping away bark from around the entry hole will reveal dark brown to black staining.
Other Symptoms of Attack
Entry holes are typically accompanied by attack symptoms, which are the tree's visible response to stress. These symptoms and examples of species that produce them include:
- Staining: may be wet and dark or dry and light-colored (e.g. sycamore trees, oak trees)
- Gumming: thick resin that sometimes pushes the beetle out of the gallery (e.g. silk trees, Koelreuteria species like Goldenrain tree)
- White powdery exudate: may form "sugary volcanoes" that appear to be crystalline foam (e.g. avocado)
- Frass: produced by the beetle's boring activity, may be present on any host tree especially when infestation level is high. It can appear as long "matchsticks" of frass (e.g. box elder, coral tree, and willow species)
Some of these symptoms may be washed away or obscured by rain or irrigation water.
Each tree species reacts differently to ISHB attacks. The combination of symptoms can be unique to each host tree species. Use the following tool as guidance to see how the symptoms may look in many of the species of reproductive hosts.
Select a tree to view ISHB symptoms on that species.
Advanced infestations lead to branch dieback and overall decline. Watch for beetle attacks concentrated on a branch or branch collar. Infestations in this area can lead to limb failure.
The first step to a successful management program is the correct identification of the pest. Unfortunately, many other pests and diseases cause similar symptoms to ISHB-FD and can appear on the same plant species. The easiest way to distinguish ISHB-FD symptoms from the ones caused by other pests and diseases is the presence of an entry hole that is the right size and shape.
Do these scenarios apply to the symptoms you see? If so, consider these look-alike pests, diseases, and conditions:
Many trees respond to ISHB attacks the same way that they react to other kinds of damage: by producing staining, gumming, or exudate. Be aware of any recent management activity on the suspected tree, and look for entry-holes of the typical ISHB size and shape to avoid a misidentification of tree symptoms.
Sources of injury: pruning cuts, injection sites, staples (often used to hang strings of lights around trunk/branches), nails, other mechanical damage