Insects and Diseases

Satin Moth

| Tim Parsons

I love getting emails from people concerning the landscape. After all, with more than 300 acres, there are probably things happening I’m missing. And in the chaos that is Commencement and Reunion, I was missing a big one.

Professor Jeff Byers wrote last weekend-

I  don’t know if there is anything you can (or would) do anything about, but there is an oak tree between BiHall and Coffrin that was in the process of being totally devoured by gypsy moth caterpillars!  There were so many that I could hear the hum of their munching under that particular tree.

I went right over. (the joys and perils of instant email on my phone-it was a Sunday.) I was terrified it was the giant Pin oak tree, the one that made the list of the twelve oldest trees on campus. Fortunately, it was one of the Poplars nearby. And was I impressed.

I couldn’t hear the munching, I think they were all fat and lazy by the time I got there. Much like me on a sunday. Not Jeff-have you read his blog? The last time I did a trail run up the wrong secret side of Snake Mountain I came down with Strep. I reached up to one of the many defoliated leaves, and grabbed a caterpillar.

 

Bugs don't freak me out, snakes do.
Bugs don’t freak me out, snakes do.

Jeromy Gardner, our elm guru from Bartlett Tree in Manchester, correctly identified it as Satin Moth. Not worrying, but has a habit of building a large population every so often and completly covering a tree, in this case our White Poplar. Here’s a great article, if you are interested. They were originally thought to only attack exotic poplars, such as Lombardy poplar and European White poplar (what ours is), but now also is seen in forest stands, and could become significant if defoliation occurs for several years in a row. It does, however, have plenty of natural enemies, including parasitic insects, bacteria, fungi, even birds.

Satin Moth-moth phase. Photo courtesy Perry Hampson, Bugwood.org
Satin Moth-moth phase.
Photo courtesy Perry Hampson, Bugwood.org

So all that remains on the tree are the major veins of all the leaves, everything in between them eaten. I fully expect the tree to re-leaf in a couple of weeks or so. What is even more interesting is the other white poplar about 30′ away, with only a minimal population. The infested one was in a construction zone a couple of years ago. Maybe the stress of root compaction has something to do with this? Or I’ll be writing about both trees being infested next year…

Skeleton-ized tree.
Skeleton-ized tree.

Thanks to Jeff for pointing it out. Maybe I’ll host a ‘trailrun’ of the trees on campus someday this summer. Better start training now.

Emerald Ash Borer Presentation-This Wednesday

| Tim Parsons

Part of my absence from the blog would be teaching my winter term class “Trees and the Urban Forest” again this semester. It’s a great class, in a super rushed sort of way all winter term classes probably are.

As you may well be aware, the Emerald Ash Borer is a small exotic insect invading the country, and is poised to enter Vermont in the next couple of years. It has the potential to eliminate all the native Ash trees from the state. Just on the campus grounds itself we have over 200 large Ash trees that will need to be removed at great expense, and replanted. For a quick explaination, see http://www.vtinvasives.org/invaders/emerald-ash-borer .

Two years ago my winter term class took a draft of an emergency preparedness plan for the eventual arrival of the insect from the State Department of Forests, Parks, and Recreation and completed it for the Town of Middlebury. This winter term we are now drafting the plan for Middlebury College. This includes surveying all the Ash on campus, coming up with options for treatment or removal, giving replanting options, and running a computer model to calculate the lost benefits from these trees, including stormwater and pollution abatement, carbon sequestration, and energy savings.

We’d be honored if you could join us to present the plan to the College community on Wednesday, January 28th at noon, in The Orchard, room 103 in the Franklin Environmental Center. I understand it’s short notice (sorry!) and winter term is crazy in even a relaxing year. Please feel free to email me with questions, and if you know of someone else that would be interested, please let them know!

Japanese Beetles

| Tim Parsons

Gardeners, and especially Vermont ones, seem to like to share maxims. Like “Don’t like the weather? Wait 5 minutes.” My Nebraska wife said she’d heard that one out there too, so don’t go thinking that our weather is more strange in the Green Mountains. The one I was thinking of a couple of days ago was on Japanese Beetles, and their annual appearance on the Fourth of July.

It held true this year, at least in my yard, with a small collection of them on some wild grape leaves. They’re a particualry nasty little pest, as their voracious appetite can seemingly eat anything in their path. In reality, though, they favor certain plants above all others, but it would be a dreary yard indeed if you didn’t have at least one plant they found tasty.

Japanese Beetles were introduced in August of 1916 in the Henry A. Dreer, Inc. Nurseries, about 2 1/2 miles east of Riverton, New Jersey. Closed in 1944, this very famous nursery owned the very first plant patent, the New Dawn Rose, a climber still in production today. Rutgers and the U.S. Department of Agriculture made a valiant effort to control the spread of the beetle, including attempting to keep sprayed a half mile radius of land around the point of discovery with Arsenate of Lead. The beetles turned out to be strong fliers, and would quickly fly to un-sprayed foliage. Control efforts moved to containment, but the Beetle was too strong for that as well. By 1920 the beetle occupied 50 square miles of New Jersey, 213 square miles in 1921, and by 1925 was over 500 square miles. (Read about the complete battle at the Rutgers Department of Entomology.)

Japanese Beetle, Popillia japonica, are very recognizable and familiar to many of us working outside. It’s bronze colored back is a dead give-away, with a metallic green body. Harder to identify, but equally destructive, is it’s larval phase, a white grub in prolific in lawns almost 2 inches long. The grubs are strong feeders of turf roots, but most people complain about the turf damage caused by raccoons and other creatures digging for a fast grub meal.

They are clumsy fliers, dropping when hitting a wall (don’t we all?), so that’s how the ubiquitous traps work, by having four walls coated in floral scent and phermone to lure the idiotic beetle to fly into, dropping in the bag below.The traps work great, too great, a victim of their own success. Multiple studies have shown that the traps lure insects not only into the trap, but into the surrounding area, thereby increasing the population. The best place for a trap? The next door neighbor’s yard.

Control of the beetle is best done at the source, the grub stage, but is quite tricky in Vermont. The best organic control is Milky Spore, a Bacillius bacteria that kills the grub, and reproduces itself inside the body, spreading into the soil. Unfortunately, Milky Spore does not do well in heavy, moist, cold soils, namely all Vermont soils. While it is somewhat active at soil temperatures of 60 degrees, it does best at 80, a range rarely seen this far north. Anecdotally I’ve heard of treatment succeeding quite well, but it’s time and expense I can’t rationally recommend.

Other control recommendations seem to almost change yearly, so you’re on your own. I’ve had good luck picking them off by hand or dropping them into a mason jar of soapy water-they aren’t the fastest things in the world. Systemic insecticides work well, but our bee population would thank you if you stay right away from those.Neem, or even hot pepper oil, acts as a deterrent in low populations, although higher populations will ignore them like a teenage boy in a line for pizza.

Cedar Apple Rust

| Tim Parsons

Once you see one, you start seeing them everywhere.

Cedar Apple Rust-Juniper Spore Horn

The first warm rain in the spring makes these spores appear on Red Cedar (Juniper) trees, completing part of its life cycle. Red Cedar is a first-growth conifer pretty common in Vermont in abandoned pastures, along roads, and elsewhere, so finding these disgusting things aren’t hard. Sometimes they are as big as your fist, sometimes just a golf ball, but they are always bright orange, and disgustingly slimy and gelatinous. I remember being thrown one by my landscaper employer in Connecticut, and being grossed out for the entire rest of the day, catching it absentmindedly.

This is brought to you by a fungus called Cedar Apple Rust, latin name (brace yourself) Gymnosporangium juniperi-virginianae. The fungus is a ‘dual-host’ fungus, needing two different type plants to complete its life cycle. Part is on the Red Cedar, where small galls sit and lie in wait for the warm rain in the spring to activate. They can be mistaken for cones for those not totally up on their conifer botany. Once activated, spores then alight on the wind, and carry to apple trees (or crabapples), where they infect the twigs and leaves. On this host, it appears like small orange or yellow spots. These spots then produce spores in July or August, and re-infect the juniper.

Because of the ubiquity of Eastern Red Cedar control is very, very difficult. Like many things, the best techinique is prevention, which entails removing all cedar from within a mile (!) of the orchard. Fungicide sprays are effective, but need to be done now, which is another whole host of problems, seeing as the apples and crabapples are starting to bloom, a delicate time to say the least. Apples and crabapples vary in their susceptibility to the disease. I fell in love with a crabapple once, a double flowered variety named ‘Brandywine’, with dark pink flowers like tiny roses (I won’t post a picture and tease you too), only to watch it totally defoliate by the end of July-not a leaf left the rest of the year-all from a severe infection. Resistant varieties can be found, though, and are probably a good idea.

 

Leaf Color

| Tim Parsons

I’ve been reading quite a bit this fall in various newspapers, web sites, etc. about the science of leaf change, and I thought, well, heck, there goes another blog post. I don’t see the sense to retread ground others are covering.

By now, you’ve probably read that leaf color changes by the shortening of day-length light triggers the tree to begin shutting down the leaves, and that chlorophyll breaks down, and sugar is absorbing into the tree. In a nutshell, the veins connecting the leaf to the tree are closed (abscission layer), and once this is complete the leaf falls.

Weather does play a part in leaf color, and in the color you see in the hills as you visit your children on parent’s weekend here (Hi parents! Your kids are doing fine. They want more money.) Many articles have talked about warm weather delaying fall, cool nights are good, drought bad. It’s easy to understand, though, if you think of it in terms of plant health.

A happy, healthy tree in a good growing season will more than likely have pretty spectacular colors. The factors responsible for bad fall color aren’t good for the tree health either. Drought is bad for fall color, and also bad for the trees. Southern Vermont this year had a pretty bad late summer drought, and when I was on route 4 a week or so ago near Woodstock the leaves were terrible, turning brown and falling off, rather than turning nice colors. Here at Middlebury it’s been a dry September, and then the recent rain storms came at just the right time, and the leaves held on long enough to turn well. Warm fall days and cool nights? Good for sugar production, and the breaking down of chlorophyll in the active leaf. A late spring or a severe summer drought can delay fall color-the tree holding on to it’s leaves as long as possible, storing as much energy as it can before winter.

Another leaf color fact plant geeks have probably noticed is called the Leaf Wave Model. An article at the University of Georgia discusses this: Peak color is an opinion. Different trees turn at different times, and in differing colors. Yellows dominate early, then oranges as both later trees turn, as well as some yellow leaves becoming more orange. Finally reds dominate the landscape, with accompanying orange. Browns come last, generally in oaks. The leaves in Vermont are spectacular because of the forest cover types found here, yellow Ash, orange and red maples, along with splashes of green from Pine and Spruce. By paying careful attention to the mountains in the fall you can watch this leaf color wave happen.

Some other reading I’ve been doing this fall was about the color red, something I’ve never thought about. An interesting question for botanists has been “Why red?”.  As chlorophyll disappears from the leaf, the other colors emerge, such as yellows and oranges provided by Carotenoids. Red, though, is expressed through Anthocyanin, but is not found in a leaf, and must be produced. The question, therefore, becomes why would a plant be producing a compound, expending energy, at a time in it’s life cycle when it is trying to store and conserve? There are two schools of thought, and probably both are correct, some for some plants, some for others.

One theory is that anthocyanin is produced in trees in nitrogen poor soils. In some varieties of trees, as the green chlorophyll breaks down, the leaves are vulnerable to bright sunlight, and this sunlight breaks down the produced sugars, thereby not being absorbed back into the tree as energy storage. The red pigmentation acts like a barrier from the sunlight, allowing the tree to absorb more of the sugars it has produced. Nitrogen poor soils means the tree would have produced less sugars, being weaker growing, so more red pigmentation would conserve more of the valuable food.

The other theory is one of coevolution, that red leaves are a signal to insects as a repellent, a red warning signal to the insects attempting to use the tree as an overwintering site. A study has shown this in aphids and apple trees, that wild apple leaves turn red in the fall, and suffer less aphid predation.

Big Huge Icky Giant Tar Spot

| Tim Parsons
Giant Tar Spot

The study of plant diseases made me terribly depressed in school, but also made me laugh on occasion. I imagined two plant pathologists walking around, looking at sick leaves. Of course, each of them wouldn’t admit to the other that they didn’t know or recognize some strange disease, so they’re making up names as they go along. Strange fungal spores on a cherry tree? Well, it looks like Black Knot, and the disease is named.

A fall arrival on campus (and occasionally in my inbox as a question) is always the blatetenly named Giant Tar Spot. (“Hey, what’s this?” “You don’t know that? Any idiot knows thats, um, Giant Tar Spot. Yeah, that’s it. Giant Tar Spot”) You guessed it, huge jet black spots on the leaves of primarily Norway Maple.  This, too, is a fungus, Rhytisma acerinum for you latinally inclined. It infected the leaves way back in early summer, but they don’t really show up until now. When it’s too late to treat.

Not that you need to. Late diseases and insects like this look terrible but, let’s face it, the leaves are only around for a couple of more weeks anyway. It’s not a bad year for it this year on campus, we’ve had it much worse. If you’re looking to get rid of it on your tree at home, rake and dispose of the trees at your neighbors…

When Good Plants go Bad

| Tim Parsons

My most depressing year at the University of Vermont would have been my junior year. All plant and soil science majors took Plant Pathology that year, two semesters worth. For all of you non-science plant geeks, plant pathology deals with diseases of plants-basically anything except insects. Virus, fungi, bacteria, even abiotic problems were addressed. After a year of learing the various ways plants die, I remember thinking about the hopelessness of it all, wondering how on earth plants even existed.

Insect pest management was the previous year. Insects, while a pain, can very often be sprayed, attacked by other bugs, or even crop rotated away. But most of plant pathology? Hopeless. At best, they are “controlled”, like most fungicides, at worst, well, here’s a list of plants if you have to replant that may not get that disease. No magical sprays, potions, or elixirs to help you along. Often the best defense against many of these problems is simply a good offense-a healthy thriving plant will suffer some little indignities here and there, but will fight on.

The recent spate of warm and wet weather has Verticillium Wilt  rearing its nasty little head around. I’ve gotten several emails about it recently, and am expecting more. Verticillium Wilt is a soil borne fungus that enters the roots, then both produces toxins and spreads spores throughout the xylem (water tissues) of the plant. The plant, in a bit of idiotic self defense, uses various compounds to plug the xylem further, ostensibly to stop the spread of the  fungus, but further restricting water movement inside. The name wilt is a descriptive, as the first symptom typically seen is the last, as the leaves wilt and die from lack of water.

In fruit trees, the fungus is called Black Heart, commonly seen in Apricots, but is also seen in many types of plants, such as potatoes, tomatoes, mint, and many types of trees and shrubs. The fungi, Verticillium albo-atrum or V. dahliae, can persist in the soil for up to 15 years, forming small black resting structures activated when roots grow near them.

On campus, Verticillium wilt is evident on some older plantings of lilacs, like on the picture below. This particular clump is near Battell, on the wetter, or beach, side. Lilacs don’t like wet feet (roots) to begin with, and this may help bring about the fungus.

Lilacs at Battell


Verticillium symptoms on Lilac

Another victim of Verticillium seems to be a Catalpa, know by my kids as the Green Bean tree, for the size seed pods it produces. Spectacular in flower, this tree was the subject of my first Twitter picture about a month ago. (Are you following Middland on Twitter? I’m having a blast posting pictures of plants in bloom around campus, I’m at http://twitter.com/middland.)

Verticillium wilt in Catalpa

The location is directly across from Emma Willard, blocking one of the special sightlines at Middlebury, that of the view from the front of Emma Willard looking up towards Old Chapel. While I mourn the loss of all trees, more than one person has lamented the unfortunate planting location of this tree, wishing it were elsewhere. This loss is particularly wrenching for me, as I watched it come down with this disease last year, but then watched it leaf and flower out again this spring. Thinking Verticillium more quickly virulent, I had false hope this spring, and now know better. Fortunately, the next nearest tree is a birch, resistant to Verticillium, so this loss should be confined to a single tree.

Wilting leaves on Catalpa

Fall Webworm

| Tim Parsons

Those disgusting silky web cocoons on branches on the sides of the road you’ve been seeing? Fall Webworm, (Hyphantria cunea (Drury)). I’ve been getting asked about it quite a bit, that’s why I bring it up. They were a random little unidentifiable white moth in May  and June, with the females laying their eggs on the undersides of the leaves. The webs form on the tips of the branches, as the caterpillar eats its way down the branch. Many larvae may be seen in one web.Pupation occurs in the ground or in the leaf litter beneath the tree. They are quite prevelant in Crabapples, cherries, Birches, and Lilacs, but I’ve even seen them in Elms along the road.

Control? Pesticide? Nah. Being this late in the year, the leaves are beginning their shutdown/fall off routine, aren’t providing much in the way of food for the tree anymore, so if some fall or get eaten prematurally, I don’t sweat it. I’ve always heard an organic control is to take a stick and tear apart the web, exposing the caterpillars to passing birds for a quick take-out meal, but I’ve never seen a bird indulge. Maybe someone (not me) that knows birds could shed some light here.

Hornets and Wasps

| Tim Parsons

Some early leaves are starting to turn on stressed trees, students are trickling back to campus, and it sure was chilly last night. Fall is coming, and we in the landscape department can tell from the gigantic hornet nests appearing seemingly out of nowhere. Continue reading →

Great Golden Digger Wasp

| Tim Parsons

This wasp, a Great Golden Digger Wasp, Sphex ichneumoneus, has been making its home around Bicentennial Hall as of late. Thanks to Professor Helen Young for the identification! It’s completely harmless (as are most bees and wasps), only stinging when pinched, walked on, teased, or threatened. This one, I didn’t catch her name, is seen making a nest in the ground next to the sidewalk by Discovery court. It’s about a foot away from the sidewalk, but that is the gravel underneath the sidewalk that she is working so hard to pull out. The species makes a hole in the ground, then preys after grasshoppers, katydids, crickets, etc. It then takes these insects, paralyzes them, lays an egg inside each, and stores it in a hole off of the main burrow. Still alive and fresh, yet paralyzed, (insect refrigeration), the egg hatches in the insect, and the young larvae consume their first take out meal.

There are several females burrowing around there, and probably males flying close by. Go over and say hi. They are quite good pollinators, as it feasts on nectar as an adult. With pollinators under siege lately, we need all of them we can get.