A tree near our condo complex on Oahu has suddenly become covered with hundreds of quarter-sized, perfectly round holes with a slightly raised edge and it is totally dead in just a few weeks! Unbelievable! What happened and whom do I call to protect other endangered, perhaps, trees! The tree looks like a kakui nut, the state tree. It is in a woods full of grass and trees, uninhabited. Is it a threat to other trees? Could I see a picture or find one, of the perfect quarter-sized holes?
There are many types of borers which could be responsible. The short list includes any kind of roundheaded borer which can leave exit holes that are generally round with a pushed out edge. The edge is caused as the adult pushes outward on the bark trying to escape the inside of the tree. Adults “drill out” of trees causing these holes and once out in the open, will look for a mate and start egg laying as soon as possible.
Now trying to guess which species you have active is a bit of a challenge and really, there is no way to be sure without a sample. But there are two ways you can go about trying to figure it just which kind may be in the tree.
The first option would be to visit the tree daily looking for any new ones that might be emerging and coming out. Drilling exit holes will usually take some time and one can find emerging adults when they’re active because this process can take the good part of a day. Based on the fact that you’ve only recently noticed these holes, it’s entirely possible more adults will be coming out in the coming weeks and if you keep a watchful eye on the tree by checking it out 1-2 a day, you could very well catch one in action as they’re coming out. At that time you could trap it in a zip lock bag and get it identified by a local nursery or garden center.
The second way you might be able to find out what species is active would be to do some local investigation. A good source of information would no doubt be the local extension agent as well as some garden centers. Someone in any of these locations should be able to tell you what type of borer would be inclined to infest this type of tree. They should also know what borers are generally active in your region which would also narrow the choices.
But in the end, no matter what species it turns out to be, there is always a chance of some spreading to nearby trees. And if you want to prevent the problem from spreading, you’ll need to do a little bit of preventive treatments.
The simplest thing to do would be to soil drench any tree you want to protect with a systemic. DOMINION 2L is easy to use and treatments will last an entire season. Once absorbed by the tree roots, no type of pest will be able to feed on the trees leaves or bark.
You can can also spray the exterior bark of any tree you wish to protect with CYPERMETHRIN and/or CYKICK AEROSOL. The Cypermethrin will usually absorb into the tree and last a couple of months; the Cykick is ideal for treating exit holes which many times will be reused for egg laying.