Forest Entomology & Plant Pathology

Whoa, with a title like that, this sounds like it's going to be technical. C'mon, you know me better than that. I took the students in my class to the home of Pete Woyar, a former Forestry instructor. We were very rewarded with a variety of things we found throughout the property. This is a follow-up from a post I did in May 2011 called "what's in a log".

We were looking for both insects and fungi that have an effect on plant growth and health. For those who don't recognize this, it's American Chestnut, Castanea dentata. Over a century ago the Chestnut Blight fungus, Cryphonectria parasitica, was introduced to this country. Within 50 years our chestnut trees were virtually wiped out, not extinct, but nearly so. Root sprouts of chestnut still survive today, and will reach tree size. Eventually though, the blight will kill them. With the demise of chestnuts, the blight found refuge in the roots of oak trees, especially Scarlet Oak.

Like most fungi, the blight encircles the cambium layer and chokes the plant. Chestnut Blight goes a step further and causes the bark to crack and explode, thereby releasing its spores. Think of the scene from the movie Alien, and you'll get the picture. There are a few chestnuts that have been found that are quite resistant to the fungus, and they have been propagated in hopes of saving the species.

Chestnut Blight occurs in two forms. One that weakens the tree, another that kills it. You won't get both to occupy the same tree at the same time. Inoculating chestnuts with the weakening form is another method of saving it. In other words, sometimes you have to make the tree sick to keep it alive.

Chinese Chestnut, Castanea mollissima, has been planted in place of our native species. The fruit is just as edible. Ironically, it was the introduction of the Chinese Chestnut that brought the blight here to begin with! Creating hybrids between the two species is another way of preserving our chestnuts.

People who have chestnut trees often ask how to tell them apart. There are about a dozen ways, but the simplest way is to look at the vegetation. The above pic is American. Feel the underside of the leaves. Then look at the leaf petiole, buds, and new growth twigs. If it's American Chestnut, all parts will feel or look SMOOTH. If it's Chinese, all parts will be FUZZY.

Bustling among a wood pile was the Six-spotted Tiger Beetle, Cicindela sexguttata. This springtime beetle is one of the most common in the family. There are three white spots on each elytra or wing, giving it its common name. Photographing this guy was easy, but it led me to find something else on this batch of wood.

In this group of old logs I noticed piles of fresh sawdust. Turning the above logs over led to the culprit.

This is damage from the Carpenter Bee, Xylocopa virginica. Carpenter Bees chew a hole up into the wood to create living quarters.

After heading up, they turn sideways and create a gallery to raise the young. Nobody might care they infested these logs, but when they start boring through your roof eaves, all kinds of problems may result. Other than creating a series of holes in your house, when woodpeckers find them, they will tear your roof up even more trying to get to them.

Carpenter Bees look like Bumble Bees. The difference is in the abdomen. Bumble Bees have very hairy yellow and black abdomens. The Carpenter Bee has a shiny, mostly hairless abdomen.

This piece of cherry looks like is has old petrified mud dauber wasp nests on it. In actuality, when you put all the chopped pieces of wood back together, you can clearly see the tunnel galleries that were formed. This is damage from Carpenter Ants.

A student sent me this photo a while back. It shows the Cedar-Apple Rust in the reproductive stage. Rusts are fungi, most of which have to live their life cycle on two different host plants. In the case of Cedar-Apple Rust, Gymnisporangium juniperi-virginianae, the fungi starts an asexual stage on members of the Rosaceae, apple, cherry, plum crabapple, hawthorn, etc. It then spreads and matures on Cedars and Junipers where it produces these tumor like balls with orange octopus tentacles for spore production. It may not hurt the apple members, but cedars can be defoliated by this fungus. When landscaping, don't plant the two groups of trees together.

Another rust called the White Pine Blister Rust affects White Pine and Gooseberry shrubs (Ribes). It was devastating to the White Pine industry in the Great Lakes, especially in Michigan. People simply went out and cut all the Gooseberry to save the White Pines.

Rusts get their name due to the fact many of them are orange in color. This one is Arthuriomyces peckianus, the Rubus Rust. This species forms on the back of Blackberry and Raspberry leaves. Unlike most rusts, it lives its entire life cycle on a single species of plant. This fungi can reduce the fruit output on commercially grown plants.

Another fungus of Cherry and Plum trees is the Black Knot, Apiosporina morbosa. It can encircle a branch, or like this, completely cover the trunk. This Black Cherry, Prunus serotina, was killed by the fungus. Domestic orchards are vulnerable to this, as it can kill branches and lower fruit production.

This is what it looks like when it grows around a branch instead of the trunk.

Sticking with fungi, this is called Pine Needle Rust, Coleosporium sp. This rust lives its life cycle on members of the Asteraceae, most of which include sunflowers, asters, and goldenrods. Since these plants are found in open fields, forest growing pines are less susceptible. Christmas tree farms will most often show this rust. It's not fatal to the trees. The fruiting bodies are in white. The orange color is the spores themselves.

Here is an old USDA photo showing dead needles covered in mushroom sacs from this rust.

Not much of a picture, but when you're out looking for damaging agents, it's pretty obvious something is rotting away this tree. This is White Walnut Juglans cinerea. Nationwide the numbers of this tree have dwindled. What's killing our trees is the Butternut Canker, Sirococcus clavigignenti-juglandacearum (now there's a mouthful). Authorities aren't 100% certain, but it's believed this is an introduced fungus from outside the U.S. The fungus enters through small wounds on branches and spreads to the trunk where it is fatal. White Walnut is a shade intolerant tree. So those struggling to grow in a forested situation are more vulnerable than trees growing in the open.

In my previous post I discussed the Tuliptree Scale. Here is another attacking scale insect called the Pine Needle Scale. Because of its shape, it is often called the Oystershell Scale, Chionaspis pinifolia. These are also plant juice suckers, and heavy infestations will turn needles orange and kill entire branches.

Large outbreaks like this will make your pine trees look silvery-white. Chemical sprays, oil sprays, or Ladybugs can be used to control them.

Most scale insects are quite shy and bashful. They keep their head and appendages hidden underneath their waxy back. So I couldn't resist this mug shot of a photogenic cottony scale looking for a few minutes of fame! Thanks to Tony Champagne and the Times-Picayune for the use of this illustration.

Very abundant in the spring are these black flies with the yellow thorax. These are Snipe Flies of the family Rhagionidae. In particular Chrysopilus thoracicus. An appropriate latin name for something called the Golden-backed Snipe Fly. They are harmless to vegetation. Adults and larvae are predators and blood suckers on other insects. The larger female is on the right.

Those flies led me to another common sight on maple trees. Spider Mites, or in this case, the Sugar Maple Spindle Gall, Vasates aceriscrumena, are more unsightly than damaging. It's a matter of aesthetics, so you can pull off individual leaves, but no serious problems to tree health will result from their presence.

We have all seen bits of 'spit' on flowers, grasses and trees. These are from Spittlebugs, many of which are species specific to certain plants. This is the Pine Spittlebug, Aphrophora parallela. Immature bugs emit this as both a temperature and moisture control for the insect, as well as a protective shield from predators. Just like you would not want to grab peoples spit, neither do predators. Upon reaching maturity, adults can both jump and fly to avoid being eaten, so the bubbly froth is no longer needed. Large numbers of these insects can cause browning of pine branches.

This was found on root sprouts of that canker covered cherry tree I showed earlier. The V shape is distinctive of Malacosma americanum, the Eastern Tent Caterpillar. The web is empty and browning now. The larvae have long since left the feeding area and pupated into moths.

Deodar Weevils, Pales Weevils, and White Pine Weevils are beetles that can cause mortality in the terminal growth shoots of pine trees. They have chewing mouthparts and will eat a circle around the twigs and kill them. Most of these beetles come out at night, so it's hard to observe them doing the damage. The result is a bushy growth rather than a straight tree. Small one foot seedlings can be killed in a single nights feeding. A serious problem if you are raising Christmas trees.

This Plum fruit has a ball of sticky sap on the outside because the Plum Curculio has been here. This is a native Weevil that chews and eats small portions of the plum in spring. Later it will come back and cut a crescent shaped opening in the fruit where it lays eggs. Like finding a worm in an apple, the burrowing of the grubs will make most of this fruit fall prematurely. A student captured an adult, but silly me forgot to bring any containers. I should have photographed it while I had the chance.

When trees are invaded by fungi, they section off the wound. The tree emits defensive chemicals (sort of like white blood cells in us),  and builds these dark barrier zones. It's referred to as CODIT, or Compartmentalization Of Decay In Trees. Unlike animals, this area doesn't heal, but isolates the fungi so it won't spread. It's effective, but not 100% of the time.

New wood has completely grown over these old Sugar Maple taps. Trees have rays that transport nutrients up and down, like elevators in a skyscraper. If one elevator doesn't work, you don't shut down the whole building, just use another elevator. This is how trees work. 90% of a tree can be non-functioning, yet it can survive just fine. This is why you see old pictures of cars driving through hollowed out Redwoods and Sequoias. It's the outside of a tree that matters, not the center wood. Dutch Elm Disease and Chestnut Blight are stronger than the tree defenses. To use an old movie analogy again, if every elevator and exit is broken in a building, you get the Towering Inferno. So goes it with trees.

CODIT sometimes results in what is known as Ringshakes. This is when the barrier zone causes the later tree rings to actually separate from each other. While this is an old rotten log, imagine you invested in a timber sale, only to find the wood is not worth what was estimated due to this, not good!

Compartmentalization works on new wood being laid down. CODIT does nothing to prevent beetles from eating the heartwood. This is from the Hickory Borer, a long-horned beetle. Another example of how insects can affect the value of wood products.

We traversed a lot of acreage that day. You'd think with Pete being a forest management specialist, he wouldn't have all these problems. But I always make it clear  to students, as frustrating as it may be, there is no easy practical control for these pests on a forest wide basis. Besides, getting out and finding these things all in one day is something no inside classroom could ever duplicate.

Here are a couple of the many Long-horned Beetles that create galleries in the heartwood. This is the Red Oak Borer, Enaphalodes rufulus.

Red-headed Ash Borer, Neoclytus acuminatus.

Finally, I have been getting reports of people finding Periodical Cicadas the last few weeks. According to the brood times for this, the 17 year cicada should not be here right now. These orange winged, red eyed guys, are part of the 13 year group known as 'stragglers'. Some populations come out 4 years early. There are 3 common species of 17 year cicadas in Ohio. Should these straggler populations remain genetically isolated long enough, we may have a new species evolve. Of course we won't live long enough to see it.

Growers of small trees may be concerned over the damage they do, but overall, every 17 years the forest can handle a bit of natural pruning. Twigs are killed by cicadas when they drill and tear up the bark to deposit their eggs.

Part 2 on this subject can be found here, under what's in a log