Amy Grotta's Tree Topics

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Serving small woodland owners and managers in the Willamette Valley and northwest Oregon
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Watching out for the Emerald Ash Borer & other Invasives

Mon, 07/14/2014 - 9:19am
Large purple plastic triangular boxes illustrate monitoring activity

by Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension, Benton, Linn and Polk Counties and Wyatt Williams, ODF Invasive Species Specialist

A large purple box hanging in the trees along Airlie Road last year caught my attention at 55 mph. Pulling over I recognized it as a monitoring trap for one of the current invasive species threatening Oregon’s woodlands. Luckily ODF and others are watching out.

The emerald ash borer (EAB), an invasive insect from Asia, has killed an estimated 100 million trees and caused more than $3.5 billion dollars’ worth of damage and property value losses in the eastern U.S. since its arrival in the 1990′s. All 16 North American ash species are threatened with extinction, including our native Oregon ash. The furthest west population yet detected is in Boulder, Colorado – a day’s drive or so from Oregon in a motor home. Originally introduced to the U.S. via wood packaging material, it is now spread across the continent in infested firewood.


With summer travel and camping season upon us, you can do your part by educating people about the dangers of moving firewood. There is a whole national campaign about this: Don’t Move Firewood. If like me, you enjoy bossing people around, insist your visitors not transport wood!

ODF is working with Oregon State University and OSU Extension, the Oregon Department of Agriculture, the US Forest Service, APHIS, and Washington Department of Natural Resources in order to ‘save our ash.’

Of course this is not the only invasive we worry about, as human travel and commerce create ever increasing opportunities for insects and diseases to jump around. Chestnut blight and Port-Orford-cedar root rot are some older examples and sudden oak death a more recent arrival. Here in the Willamette Valley, people are becoming aware of a problem in black walnuts. Here is a good article about the thousand canker disease which is killing black walnuts in the area that was just posted last week.

Wow.  That is a lot of grim information.  We’ll try to find something happier next time…..

 

Categories: OSU Extension Blogs

Yellowjackets

Thu, 07/10/2014 - 3:17pm

by Chal Landgren, OSU Extension Christmas Tree Specialist

Anyway it is spelled- Yellowjacket, Yellow Jacket or Yellow-Jacket, these insects are feared and hated not only by picnickers, but by many working in the woods, and in Christmas trees.  For Christmas tree growers they can inflict physical and economic pain, since they are unwanted hitchhikers in many shipping destinations.

First some biology- These are not honeybees. Rather, two predatory insects in the genus Vespula, whose common names are the Western Yellowjacket and German Yellowjacket. The Western

Comparison of queens. Photo courtesy ODA

Yellowjacket (V. pensylvanica) is a common native.  Yes, they are predators, but also scavengers, which makes them a pest at summer BBQs and picnics.  The German yellowjacket (V. germanica)  is an uncommon non-native species (not wanted in Mexico).  Both these insects feed on other insects as well as nectar, honeydew and fruit.

Queens will overwinter in protected locations above or below ground and emerge in May. After the queen emerges she will begin her colony which eventually can include hundreds to thousands of workers. Fertilized queens will emerge again in October or November. Males (stingless) begin to emerge in large numbers in late July.

Control strategies are very time sensitive. Some growers have observed fewer nests being formed if they can get out their lure traps before the females start forming colonies (May).  If you can trap a queen you can begin to control the populations. Once the females begin colonies they do not fly and the lure traps catch only workers or males.  Workers can fly ¼ mile or so from the nest in search of food. That “food” can be honeydew from aphid feeding on Christmas Trees, if present.

Where they conflict with work or recreation, nests can be targeted with insecticides. The PNW Insect Management Handbook reminds us wasp nests should be treated in evening when wasps are less active with a pesticide formulated specifically for wasp nests (rather than gasoline), and also that some professionals in the PNW collect wasps to be used in the manufacture of allergy injections. Find more here.

There are registered baiting options that can be useful around homes, campgrounds and zoos. The insecticide Onslaught is a microencapsulated version of esfenvalerate (a pyrethroid) is approved for use in bait stations. A company out of Bend, Alpine Pest Management, makes the bait stations.

Categories: OSU Extension Blogs

What’s causing all that die-back in Incense-cedar?

Fri, 06/27/2014 - 2:44pm
A ratty-looking incense-cedar near Corvallis

by Brad Withrow-Robinson, OSU Forestry & Natural Resources Extension, Benton, Linn and Polk Counties

You’ve probably noticed that incense-cedar (Calocedrus decurrens) is looking pretty ratty in the mid-Willamette Valley this year.
Driving around, I am seeing many trees showing a mosaic of healthy and dead foliage. The dead foliage is reddish to muddy brown and may be individual fronds or small branches. It often seems to be in the lower parts of the tree. Symptoms seem to vary dramatically between trees, even adjacent ones.
So what is going on? Quite likely any of several things.
Incense-cedar rust  is a common and familiar foliar disease. It is most recognizable in the spring, when it produces orange gobs of jelly-like goo on the infected fronds. It commonly kills small sprays of leaves and causes a loss of tree vigor in severe cases.
Then there is the less-well-known incense-cedar branch canker  which has been showing up in our area recently. It too can cause branch die-back by killing small branches, generally in lower sections of the tree. It seems to hit mature landscape plants. Look for canker lesions and swellings on branches. The canker is sunken, generally a distinct line between live and dead tissue can be seen if you cut back the bark.
Finally, we had a couple periods of record cold weather last winter, with recurring sub-zero temperatures in some areas. I am not seeing injury patterns typical of freeze damage (zones of dead needles, often on the south side of the tree), but suspect that winter temperatures could be a contributing factor.
As I nose around, I’ve found cankers on some trees, and no clear causal symptoms on others. So I cannot blame this die back on any one thing.
Whatever is going on for these individual trees, it is worth noting that incense-cedar is kind of an exotic tree. Sure, it is a native Oregon tree, but it was not a common tree in the Valley historically. We lie at the extreme northern edge of incense-cedar’s native range, a situation where it will likely experience stressful conditions. So it should not be surprising to see it looking ratty from time to time.

Some typical, yet inconclusive symptoms….

 

 

Categories: OSU Extension Blogs

The boom-and-bust life of defoliating insects

Fri, 06/20/2014 - 12:35pm

By Amy Grotta, OSU Forestry & Natural Resources Extension – Columbia, Washington & Yamhill Counties

It is shaping up to be another exciting year in forest health here in northwest Oregon. Fortunately, neither of the two defoliating insects currently on the scene are serious threats to forest or human health, but they are certainly causing a stir.

Right now, Columbia County is in the midst of the largest documented western tent caterpillar outbreak that Oregon has seen in two decades, according to the Oregon Department of Forestry. I first noticed a few tent caterpillar clusters on one site in the area two years ago. Last summer, our Extension office received many calls as the caterpillar population built up.  Aerial surveys done a few weeks ago show that at least 13,000 acres are affected in the county this year.

Map and aerial view showing extent of western tent caterpillar defoliation, early June. Affected areas are brown in the photo. Source: Oregon Department of Forestry

The caterpillars are everywhere in the most heavily affected areas. It’s impossible to move without stepping on them, and looking up through a stand of alder, it looks like early spring as there are no leaves left on the trees.

Western tent caterpillars infected by a virus hang in an upside-down V. Photo: Amy Grotta

When the population gets to this level, natural parasites and diseases set in. Upon closer inspection, one can see that some of the caterpillars are hanging limply from their midsections: a symptom that these diseases are beginning to take hold, signaling the end of the boom years and the beginning of the bust.

Other defoliating insects follow similar boom-and-bust cycles, in concert with their respective natural enemies. The western oak looper, which made its appearance in 2012 and 2013 in the mid-Willamette Valley, and the pine butterfly, which affected over 250,000 acres in eastern Oregon in 2011-12, are two examples. Reports are beginning to trickle in that the oak looper is still on the scene in places this year, but the pine butterfly outbreak is over. In 2013, researchers in eastern Oregon observed abundant “boom” populations of two insects that are predators of the pine butterfly larvae.

In Columbia County, 2014 will go down in the books as another “year of the caterpillar”. Longtime residents can recall the years marked by previous outbreaks of these insects, just as with big floods and wind storms. One Rainier old-timer recalls another big tent caterpillar year in the 1950’s.

The interactions between these forest insects and their natural enemies are an example of how biodiversity at the smallest scale within a forest system leads to patterns that we can observe. Sadly, in our coastal ecosystem, a pathogen is killing off sea stars in unprecedented numbers. It remains to be seen whether the sea stars will be able to rebound, or if they will be busted for good.

Categories: OSU Extension Blogs