Disaster: Ambrosia Beetles in a Special Tree

There is a 26-year old Japanese maple near the house, visible from our dining and living room windows. It is one of several Japanese maple seedlings I planted in 1990 after a tornado devastated our property. It has matured into an astonishing specimen with multi-colored leaves that are breathtaking, especially in fall when they glow with fiery magnificence.

The Japanese maple in front of the house can be seen here, behind the arch in this fall view of the front garden.

It has always been a healthy tree, until last week when I noticed that some of its leaves were dying. At first I attributed this to heat stress, but then I noticed a pile of sawdust at its trunk. Closer inspection revealed unmistakable borer holes, and my heart sank:

I emailed photos to an entomologist at the Plant Diagnostics Lab at Auburn University, and I soon had a grim diagnosis: Granulate Ambrosia Beetle. Most ambrosia beetle species don't ingest wood tissue; instead, the sawdust resulting from their excavation is pushed out of the borer holes, forming little columns of sawdust. This is exactly what is seen on my tree. Females bore into twigs, branches, or small trunks of susceptible woody plants and excavate a system of tunnels. They feed on a symbiotic fungus that they introduce into their tunnels. High humidity promotes reproduction of ambrosia beetles, and we have had a very humid summer. Eggs, larvae, and pupae are found together in the tunnel system excavated by the female.

Photo of Granulate Ambrosia Beetle with pupae and black fungus. Photo from Wikipedia.This insect usually attacks apparently healthy hardwoods less than 3 inches in diameter, and their appearance in larger wood often is an indication that the tree is highly stressed or dying, although my tree did not appear stressed or dying until this beetle attack. Prognosis is poor. There are no chemicals that one can apply that will kill ambrosia beetles inside a trunk. Systemics will NOT work as the beetles are inside the vascular tissue of the tree.

Mine is an older tree with a number of trunks. Since some of the trunks are affected and others not, the entomologist recommends that we remove the infested trunks and dispose of the wood. So this is what we are going to do. It will greatly affect the shape of the tree, and the tree may yet die.More leaves have died in the past few days. One can clearly see which trunks are affected.

This Japanese maple provides filtered shade to nearby azaleas and ferns, and it also keeps hot sun from shining directly into the house. If it dies, I will greatly miss it. However, I have learned to adapt to what nature hands me in the garden. I am already thinking about how I will replace it, if that becomes necessary. 

My Tree Frog

We keep a large rain barrel down in the woodland garden.While it does collect rainwater, without a downspout only a small amount of water goes in the barrel. Rather, we fill the 65 gallon barrel with a garden hose, and the barrel then serves as a handy water reservoir. A small attached hose and a spigot on the side allow for easy filling of watering cans, which I keep nearby. This is much easier than hauling water all the way from the house to the woodland garden.

Yesterday I planned to check the level of the water in the barrel, to see if it needed to be refilled. I lifted the top off and got a surprise:

An American tree frog ( Hila Cinera) was resting on the metal grate at the top of the barrel, which is designed to keep debris out of the barrel. The frog did not seem too startled, so I took a few photos before carefully replacing the lid.

Then I began to worry about him. Maybe he was trapped. Maybe he could not find his way back out through the round opening in the lid. I was concerned that he would perish if I did not get him out. I decided to tell Lou about the frog and ask his opinion. 

"Oh, he's fine," Lou assured me. "He's been in there all summer. Sometimes I see him when I am filling the barrel, and sometimes I don't, so he knows how to come and go."

American tree frogs like to live in ponds, streams and other bodies of water, so apparently this one has decided to live inside our rain barrel. Without a better option on our property, the rain barrel has become his favorite retreat. The container's lid offers him good protection from predators, and he must enjoy the moist environment. I am sure there are plenty of small insects inside the barrel for him to consume. The thought of him down there gobbling up mosquitos makes me very happy.

Look at this photo:

Look on the left side of his mouth. Something is hanging out of his mouth. I think this may be his tongue. Or is it something he has caught? Drool? Here is a close-up:

A tree frogs uses its long tongue to catch its prey. An unfortunate insect doesn't have a chance against this sticky adhesive strip of pure muscle. The frog catches its prey and pulls it into its mouth within 15/100 of a second! 

I admit my tree frog has sneaky eyes. Nevertheless, I think the creature is cute; but then I am not a mosquito!

You may also enjoy my previous post New Options for Watering.