Forest Health News

Basswood bark “explosions” caused by Nectria cankers

Posted on by jodieellis

Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov, 715-356-5211 x232

Many small Nectria cankers are present on this basswood tree.

Many small Nectria cankers are present on this basswood tree. Photo: Linda Williams

Winter is a great time to look for cankers on trees, so I thought I’d highlight one this month that you may have noticed but not recognized.  Most of you probably know Nectria as “the target canker” because growth patterns give the canker face a series of rings, expanding outwards as the canker ages, causing it to resemble a target. But on basswood, the cankers can appear very different at first glance.  On basswood, it may look like there are small “explosions” that occurred under the bark. The bark may be popped out a bit, may have oddly shaped outward growths, and it may or may not be clear that it’s hollow underneath the bark. When you peel away the outer bark and all the gnarly growths, you do end up with a typical Nectria canker face, but on basswood, you often have to dig to get to it. Accompanying photographs show the “bark explosion” appearance that you might notice, as well as what it looks like when you remove the bark.

Nectria cankers are perennial, meaning they grow a little each year. They are made of solid wood (not decayed wood unless another fungus has caused the damage). They typically have staining associated with them; this can cause degrade in lumber value of your final product.  If the cankers occur on small branches they can grow to girdle the branch, but the cankers found under the “bark explosions” on the main stem of basswood trees are not typically going to be able to cause that level of damage, and will instead simply continue to grow for many years.

Although this article focused on Nectria on basswood, the fungus can infect a number of other hardwood species. In those other species, you won’t find the “bark explosions” that you see on basswood, and instead will typically find a target shaped, open-faced canker.

Closer examination of one of the Nectria cankers on the basswood tree shown in the first photo. You can see how the bark appears to be “exploding” from the inside.

Closer examination of one of the Nectria cankers on the basswood tree shown in the first photo. You can see how the bark appears to be “exploding” from the inside. Photo: Linda Williams

Same canker as in the second photograph, starting to peel away the bark covering the canker face.

Same canker as in the second photograph, starting to peel away the bark covering the canker face. Photo: Linda Willliams

After removing the bark covering the canker, you can see the typical target-shaped canker formed by perennial growth of the fungus.

After removing the bark covering the canker, you can see the typical target-shaped canker formed by perennial growth of the fungus. Photo: Linda Williams

Another example of odd bark growth on basswood associated with Nectria canker.  These growths were very thick and solid, but underneath was a small Nectria canker.

Another example of odd bark growth on basswood associated with Nectria canker.  These growths were very thick and solid, but underneath was a small Nectria canker. Photo: Linda Williams

This cross section through a Nectria canker shows the staining that occurs in the tree due to Nectria.

This cross section through a Nectria canker shows the staining that occurs in the tree due to Nectria. Photo: Linda Williams

 

New finds of emerald ash borer in Wisconsin

Posted on by jodieellis

Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov, 715-356-5211 x232

Emerald ash borer (EAB) continues to be found in new areas in Wisconsin, where EAB is tracked at the municipality and township levels. Recently, the insect was found for the first time in Eau Claire County, and there were additional finds in Dane, Dodge and Door counties where EAB is already established.

ounties shaded in tan are quarantined for EAB; this includes much of the southern half of  Wisconsin as well as other counties. Areas shaded in green represent the townships and municipalities where EAB has actually been identified, and show that not all counties that are quarantined are fully infested.

EAB quarantine map: counties shaded in tan are quarantined for EAB, green areas within counties depict townships and municipalities where EAB has been confirmed.

 

 

 

How did the cold snap over Christmas and New Year’s affect insects?

Posted on by jodieellis

Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov, 715-356-5211 x232

Are you wondering how the bitterly cold weather we had in Wisconsin over Christmas and New Year’s affected the insects in your area? You’ll probably be disappointed to learn that, in general, our forest pests handle cold snaps just fine. Here are some examples of what it would take to have an impact on some of our insect pests: 

Gypsy moth: Well, it depends. If egg masses were covered by snow (either near the ground or on branches), they were protected from the cold temperatures. If egg masses were exposed, according to a study done in Michigan, it would take several days of temperatures lower than -15 °F to start seeing mortality in eggs. The more days eggs spend below that temperature, the more mortality, although super-cooled eggs or eggs covered by snow can withstand much lower temperatures and survive. 

Forest tent caterpillar eggs form a band around an aspen twig. The protective hairs coating the eggs have been removed to show the eggs. Photo: Linda Williams

Forest tent caterpillar eggs form a band around an aspen twig. The protective hairs coating the eggs have been removed to show the eggs. Photo: Linda Williams

Forest tent caterpillar: This native insect enjoys our northern climes, so it should be no surprise that it handles the cold quite well. One study found that at temperatures below -45 °F, there was significant mortality. The egg masses of forest tent caterpillars are found near the tips of branches, which are not typically covered with snow. 

Spruce budworm: As with forest tent caterpillar, this native insect thrives in the cooler regions of North America and temperatures lower than -40 °F are required to see any mortality. 

Emerald ash borer: You may recall in 2014, when we also had bitterly cold temperatures, there was quite a media furor about EAB mortality and some research that was going on in Minnesota. Everyone was hoping EAB would be killed completely in those cold areas. Although some mortality did occur, researchers found that because EAB larvae and pre-pupae are protected under the bark of the tree, temperatures need to be drastically low, or very low for a certain number of days, to see significant mortality. That being said, EAB mortality can occur at temperatures below -13 °F, and, if enough mortality occurs, the spread of the population may be slowed as it has to rebuild from the few individuals that survived the bitter cold. 

Multicolored Asian ladybeetles cluster together in protected places to wait out the cold. 

Multicolored Asian ladybeetles cluster together in protected places to wait out the cold. Photo: Linda Williams

Household pests like ladybugs and flies:  Those kinds of insects find protected places to spend the winter (sometimes in your house!), and although there can be significant mortality outside, there will be many that survive the cold just fine.  They often find protected places that are slightly warmer than ambient air temperatures. 

Ticks:  Wood ticks and deer ticks overwinter on the ground, under snow, so in areas of the state where there is plenty of snow cover, they’re doing fine so far.  Desiccation is usually a much more important problem during the life of a tick than overwintering cold. 

Some insects seem to enjoy winter weather, like snowfleas (also known as collembolans or springtails), and winter cutworm, both of which can be found crawling on snow during warmer winter days. 

How can insects survive winter? Different types of insects overwinter during different life stages.  Some insects overwinter as eggs, because eggs are often quite resistant to desiccation, can have “hairs” covering them, are laid in protected areas, or inserted into needles/bark/etc. to give even more protection.  Some adult and larval insects survive winter by supercooling, which is a process in which they eliminate water molecules from their bodies (which, if left behind, could create deadly crystals in their systems).  Supercooling is the equivalent to using antifreeze, allowing the insects to survive very cold temperatures.  One problem insects can have is when there is a warm-up followed by a sudden cold snap, a situation which also causes problems for trees.  When we have steady cold temperatures, insects tend to just hang out like we do, waiting for spring.

 

 

 

 

 

National Invasive Species Awareness Week

Posted on by jodieellis

Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov, 715-356-5211 x232

National Invasive Species Awareness Week (NISAW) was held from February 26 to March 2 this year. The annual event helps raise awareness and identify solutions to invasive species issues at local, state, tribal, regional, international and national scales. The event not only addresses insects and diseases, but all invasive species, including plants, reptiles, birds, and everything else. Visit the National Invasive Species website for things that you can do increase your awareness of invasive species, or click here to learn about ways you can help.

 

 

 

Update on EAB in West Bend

Posted on by Ellen Clark

Written in conjunction with Mike Jentsch, West Bend Parks and Forestry

West Bend EAB mapThe city of West Bend is in Washington County, about a 30-minute drive north of Milwaukee. More than 32,000 people call West Bend home. Emerald ash borer was first confirmed in West Bend on June 9, 2010. The DNR Urban Forestry team previously showcased West Bend’s efforts to mitigate EAB in the city. We are showcasing West Bend again to show how their EAB efforts have changed as the pest grows and effects more and more trees. Their efforts can help shed light their hard work and guide communities that are just now being affected. Continue reading “Update on EAB in West Bend” →

Comments sought re: change in gypsy moth rule

Posted on by jodieellis
Aerial spraying of Btk for gypsy moths.

Aerial spraying for control of gypsy moths. Photo: John Ghent, bugwood.org

The WI DNR is proposing to deactivate the gypsy moth suppression program as requests for treatment have fallen to very low levels and this small need can be met by private businesses. The DNR is taking input on the proposed change to rule NR 47.910. If you have questions, concerns, or comments about this proposal you may give your input by attending a hearing or in writing. Input must be received on or before Tuesday, Dec. 19, 2017 to be considered.

Public hearings will be held on Dec. 19, at 11:00 a.m. at DNR service centers in Fitchburg, Milwaukee, Green Bay and Eau Claire. Input may be given verbally or in writing at the hearing.

Written comments may be submitted by U.S. mail, e-mail, or through the internet. Written comments will have the same weight and effect as oral statements presented at the public hearing.

E-mail comments may be made at: DNRAdministrativeRulesComments@wisconsin.gov (Please include “Attn: Andrea Diss-Torrance” in subject line.)

Written comments and any questions on the proposed rules should be submitted to:
Department of Natural Resources
Attn: Andrea Diss-Torrance
P.O. Box 7921
Madison, WI 53707-7921

Written by: Andrea Diss-Torrance, invasive forest insects program coordinator, Madison. Andrea.DissTorrance@wisconsin.gov; 608-264-9247

Pesticide applicator training offered in 2018

Posted on by jodieellis

The University of Wisconsin Pesticide Applicator Training (PAT) Program will offer two training sessions for forestry training (Category 2.0) in 2018. The trainings, which will each last one day and be conducted indoors, offer attendees an opportunity to review materials in the PAT training manual. The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) will administer a certification exam at the end of each session.  Dates and locations of the training sessions are:

Preregistration is required. The cost to attend a training session is $30.  For more information, visit UW Extension’s website.  

Written by: Kyoko Scanlon, forest pathologist, Fitchburg.  Kyoko.Scanlon@Wisconsin.gov; 608-275-3275

Gypsy moth numbers rising in northern WI

Posted on by jodieellis

 

Fig 1. Average gypsy moth trap counts in northern Wisconsin counties. Map credit: Adapted, Slow The Spread Foundation, Inc.

Fig 1. Average gypsy moth trap counts in northern Wisconsin counties. Map adapted from the Slow The Spread Foundation, Inc.

Annual surveys conducted by the Wisconsin Department of Agriculture, Trade, and Consumer Protection (DATCP) indicate gypsy moth populations have increased in several northern Wisconsin counties and by 20% statewide. High moth counts were detected in pheromone traps in Ashland, Bayfield, Burnett (Dewey Township), Iron, Oneida, and Vilas counties, with the highest overall count in Bayfield County (14,354 moths total).  Areas with an average catch per trap of 100 moths or more will likely experience damaging levels of defoliation by gypsy moth caterpillars in the following year or years (Fig. 1).

Defoliation can be reliably predicted at the stand level by counting gypsy moth egg masses from August through March before egg hatch; these estimates help determine if preventive measures, such as physical controls, insecticide treatments, or delaying thinning activities are needed until populations collapse. 

In recreational and residential high-use areas, physical controls such as sticky bands and burlap barriers may be used to help reduce nuisance and aesthetic impacts from gypsy moths.  Aerial treatments are used when gypsy moth populations are high. In managed forests, use of silvicultural techniques may be economically feasible to reduce productivity problems caused by the pest.

Learn more about prevention and management options for your property by consulting with your local DNR forester or regional forest health specialist.

More information about population sampling and management options is available online at www.gypsymoth.wi.gov.

Written by: Paul Cigan, forest health specialist, Hayward.  Paul.Cigan@wisconsin.gov; 715-416-4920

Recent finds of emerald ash borer in WI

Posted on by jodieellis

Emerald ash borer (EAB) continues to be found in new areas in the state. Wisconsin tracks EAB at the municipality or township level. Quarantined counties are shown in tan; infested areas are shown in green on the map.

New county quarantines

EAB quarantine map. Counties shaded in tan are quarantined for EAB, green areas are townships and municipalities where EAB has been confirmed. Map courtesy of WI DATCP.

  • none

New finds in counties already quarantined

  • Monroe County — Town of New Lyme
  • Richland County — City of Richland Center

Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov; 715-356-5211, x232

Updated forest health fact sheet – conifer bark beetle

Posted on by jodieellis
Spruce beetle (Dendroctonus rufipennis)

Spruce beetle (Dendroctonus rufipennis). Photo: Edward H. Holsten, USDA FS, Bugwood.org

The Division of Forestry’s forest health team recently updated another forest health fact sheet about conifer bark beetles. Like the oak wilt and hickory dieback and mortality fact sheets revised earlier this year, the conifer bark beetle publication offers information about biology, impact, prevention and management of the insects. The conifer bark beetle fact sheet is available on the DNR’s forest health webpage.

Written by: Mike Hillstrom, forest health specialist, Wisconsin Dells. Michael.Hillstrom@Wisconsin.gov; 608-513-7690