Forest health


Forest Insect and Disease Newsletter July 2016

New Forest Health Specialist in the Northeast

Jess JartshornMy name is Jess Hartshorn and I am so excited to be northeastern Minnesota's new Forest Health Specialist! I grew up in Dayton, Ohio and did not develop a passion for forest health until my undergraduate studies at Southern Illinois University. From there I went on to complete my MS and PhD in Forest Entomology at the University of Arkansas. During graduate school I studied the life history and mortality factors of a native woodwasp, in preparation for the invasion of a related non-native species. I am eager to learn about a new region with new issues and am looking forward to serving the community in any way I can. Feel free to contact me with questions, concerns, or to talk about my other favorite subject areas: cats, coffee, and yoga.


New Forest Health Specialist in the Northwest

Nice to meet you, Minnesota!
Mike ParisioMy name is Mike Parisio and I am proud to call myself the new forest health specialist for MNDNR's Northwest Region. I grew up in the Catskill Mountains of upstate New York, where I developed my love for forest ecology and many other related subjects. After watching emerald ash borer (EAB) destroy many of my favorite forested areas in Catskill State Park, I made the decision to attend the SUNY College of Environmental Science and Forestry to study forest entomology and more specifically, EAB biological control. Though I hope it will be quite a while before EAB spreads throughout northern Minnesota, I look forward to lending my expertise when that time comes. Aside from graduate school, I've gained much forest health related experience while working for the New York State Department of Environmental Conservation, the SUNY Research Foundation, and the NYS Office of Parks, Recreation, and Historical Preservation.

Though admittedly it will be a steep learning curve in such a large and new territory, I welcome the challenge of learning everything there is to know about the forests, geography, history, and people here in this great state. Again, I am grateful for this wonderful opportunity and I look forward to what I'm hoping will be a long and rewarding career here. Please do not hesitate to contact me if there is anything I can do to be of service, and hope to meet you soon!


Jack Pine Budworm—the Punctual Forest Pest

by Mike Parisio, Northwest Region Forest Health Specialist

Adult Jack Pine Budworm Moth
Adult jack pine budworm moth

Outbreaks of jack pine budworm (JPBW) are generally known to occur every six-12 years in west-central Minnesota, with 2008 marking the end of the last major JPBW outbreak event. Between 2005 and 2008, this widespread JPBW outbreak affected over 165,000 acres throughout the northern half of the state. Right on schedule, a dramatic increase in JPBW defoliation damage in 2015 marked the beginning of what is predicted to be the next three- to four-year JPBW outbreak period.

In 2015, aerial damage surveys revealed some 4,500 acres of JPBW defoliation. Due to the timing of aerial survey flights last year, we believe this is actually an underestimate. So far in 2016, initial observations on the ground show some stands in the areas surrounding Brainerd and Fort Ripley are experiencing a second year of moderate to severe JPBW defoliation. Mapping JPBW defoliation throughout the Northwest Region has been designated as high priority for aerial surveys this season. Flights began in early July and are scheduled to coincide with peak JPBW defoliation. This will provide a more accurate picture of the extent and severity of JPBW defoliation and allow for more-informed management decisions.

Jack Pine budworm feeding damage
Jack pine budworm pupal cases and feeding damage

Although young, vigorous stands of jack pine are relatively unaffected during such outbreaks, mature stands with prolific pollen cone production can be expected to support the largest populations of JPBW and be among the hardest hit. Multiple years of severe defoliation typically result in top-kill and mortality of many dominant and co-dominant trees. For certain stands that were already significantly defoliated in 2014, top-kill may even become apparent this season.

Foresters managing stands of mature jack pine in affected areas should monitor the situation closely and are encouraged to consult with forest health staff for more information. In situations where significant top-kill and tree mortality are inevitable, harvesting and regenerating mature jack pine stands may be an appropriate course of action to help minimize losses.


Herbicide Damage to Trees: Not Uncommon

by Brian Schwingle, Central Region Forest Health Specialist

Many people are busy at this time of year and have better things to do (so they think) than read lengthy articles (like this one, but please keep reading). Herbicide labels might be one of those categories of literature that many people don't pay as much attention to as they should.

Streamline?, an herbicide containing a synthetic auxin, was applied near this white pine.
Streamline®, an herbicide containing a synthetic auxin, was applied near this white pine.
Streamline? and Milestone, both containing synthetic auxins, were applied near this white pine.
Streamline® and Milestone, both containing synthetic auxins, were applied near this white pine.
Boxelder leaf that may have been damaged by drifting synthetic auxins.
Boxelder leaf that may have been damaged by drifting synthetic auxins.
The herbicide dicamba, a synthetic auxin, was likely applied under this linden. Photo contributed by Gina Hugo, Sherburne County Soil and Water Conservation District.
The herbicide dicamba, a synthetic auxin, was likely applied under this linden. Photo contributed by Gina Hugo, Sherburne County Soil and Water Conservation District.
Cupped leaves on a linden show a common symptom of herbicide damage. Photo contributed by Gina Hugo, Sherburne County Soil and Water Conservation District.
Cupped leaves on a linden show a common symptom of herbicide damage. Photo contributed by Gina Hugo, Sherburne County Soil and Water Conservation District.

I find that one group of herbicides, the synthetic auxins, commonly damages yard trees and trees bordering road and utility rights-of-way. Synthetic auxins are sometimes called plant growth regulators and are frequently used on lawns. One commonly-used lawn herbicide is generally referred to as a "weed and feed" and has two synthetic auxins in it. More examples This link leads to an external site.of such herbicides were listed by Purdue University. Synthetic auxins enter trees through leaves, roots, thin bark, natural bark openings, and wounds in bark. They distort plant tissue and can kill tree parts or entire trees.

An infamous example This link leads to an external site. of a turfgrass synthetic auxin that damaged trees is Imprelis®. The US Environmental Protection Agency halted sales of Imprelis® shortly after its release because of excessive, widespread, and unexpected tree damage. The same active ingredient found in Imprelis® can still be applied to rights-of-way with the herbicide Streamline®, which I've suspected as the cause of damage to conifers in some locations in Winona and Kanabec counties.

If homeowners who want to grow monocultures of uniform green blades scanned the labels of some lawn herbicides, they might read some statements that cause them to rethink whether or not they should treat their grass near their beloved trees. For example, labels might caution that the product:

Here are some tips on avoiding herbicide damage to trees:


Spruce Budworm Continues to Defoliate

SBW on white spruce.  Photo by Connecticut Agricultural Experiment Station,
SBW on white spruce. Photo by Connecticut Agricultural Experiment Station,

by Jess Hartshorn, Northeast Region Forest Health Specialist

As expected, spruce budworm (SBW) continues to defoliate balsam fir and white spruce stands in the Northeast region, with most defoliation occurring in Lake and St. Louis counties. These areas have experienced significant damage since 2014 and should expect another six years of these conditions. A full description of the SBW life cycle can be found in this University of Minnesota Extension article This link leads to an external site..

SBW larval feeding damage on white spruce.  Photo by Joe O'Brien, USDA Forest Service, Bugwood.org
SBW larval feeding damage on white spruce. Photo by Joe O'Brien, USDA Forest Service, Bugwood.org

Larvae reduce host photosynthesis by feeding on new growth in the spring, and partially-eaten needles may be webbed together by silk, eventually turning a reddish-brown color. Balsam fir can sustain moderate defoliation for many years and heavy defoliation for two to three years before branch death and top-kill occur. White spruce can sustain moderate to heavy defoliation for three to five years before branches start to die. If severe defoliation continues after branch death, tree mortality is possible. Patch mortality within stands is possible and whole stand mortality is uncommon.

Stands that contain high basal area of susceptible trees with few non-host species are more vulnerable to damage and mortality. Trees with a live crown ratio of 40 percent or lower are more susceptible than those with large live crown ratios. There is little to no market for dead or dying balsam fir and spruce, so we recommend pre-salvage harvests of merchantable stands. In young stands that have more than 800 trees per acre we recommend pre-commercial thinning and commercial thinning in 35-45 year old healthy stands. In both of these instances, we suggest removing approximately 50 percent basal area and leaving trees with 40 percent and greater live crown ratios. Stands more than 55 years old that have never been thinned, and older stands currently experiencing an SBW outbreak are not likely to respond well to thinning. In these cases, consider clearcutting to salvage or pre-salvage timber values.


Japanese beetles

by Val Cervenka, Forest Health Program Coordinator

Japanese beetle. Photo by Steven Katovich, USDA Forest Service, Bugwood.org
Japanese beetle. Photo by Steven Katovich, USDA Forest Service, Bugwood.org

Japanese beetle feeding on damage basswood

Japanese beetle feeding on damage basswood. Photo by Bugwood.org
Lady beetle adults: Bruce Watt, University of Maine, Bugwood.org
Multicolored Asian lady beetle adults. Photo by Bruce Watt, University of Maine, Bugwood.org
Multicolored Asian Lady Beetle Larva photo by: Joseph Berger, Bugwood.org
Multicolored asian lady beetle larva. Photo by Joseph Berger, Bugwood.org

Japanese beetles are having a heyday this year. It seems there are more Japanese beetles than summer road construction projects, and that's saying something! While these non-native beetles are common in the metro area of Minnesota, they are not found in all counties and go unnoticed in many years.

The Minnesota Department of Agriculture wants to know the location of beetles outside the known counties. Look here for a map of where Japanese beetles occur in Minnesota. To report Japanese beetles outside then known counties, contact arrest.the.pest@state.mn.us. For information on their life cycle and management, check out this University of Minnesota Extension publication.

When common names of insects are similar, it's easy to be confused. Many people refer to Japanese beetle when they're really talking about the multicolored Asian lady beetle. These lady beetles, also non-native, are not plant feeders, but are fierce predators of aphids and therefore beneficial. However, in the fall they become household nuisance pests, where they seek places to overwinter.




Meet Megarhyssa

by Mike Parisio, Northwest Region Forest Health Specialist

Megarhyssa

Also known as giant ichneumons, this genus of large parasitoid wasps are a fascinating sight to behold in Minnesota's forests. Here, a female Megarhyssa uses her long ovipositor (up to 15 cm long) to drill into a dead tree and lay eggs on the larvae of other insects feeding within. Don't worry—despite their large size, these wasps are completely harmless and cannot sting humans.


Giant Willow Aphids

by Val Cervenka, Forest Health Program Coordinator

Giant Willow Aphids
Photo by Wilma Bittinger

We recently received a question from southern Minnesota regarding the identity of a large group of insects feeding on a homeowner's tree. The photo accompanying the email revealed them to be giant willow aphids. Aptly named, they have a body length of 5.0 to 5.8 mm—giants in the world of aphids! They are not native to the US, but were introduced from Europe around 1872.

Interestingly, there are no males in this type of insect (not uncommon for aphids in general), and the females don't need males to reproduce. They bear live young that are all identical (clones).

Generally found on willow, giant willow aphids may also be seen on poplar, as shown in the photo. Ants feed on the copious amounts of honeydew they produce, and in turn, ants protect the aphids from natural enemies. Predatory wasps are also attracted to the honeydew. Although a mass of insects like this might be cause for alarm, these monster aphids apparently cause little if any harm to trees. They may be dislodged with a strong stream of water.