The Morton Arboretum is releasing information monthly on growing degree days. Plants, insects and fungi all develop at various times depending on temperature. Development will speed up or slow down depending on the rise and fall of temperature. Several studies have worked to understand the relationship between heat and development. These studies and information from them help anticipate flowering of trees and shrubs and the emergence of insects based on how many growing days have accumulated. Continue reading “Figure out when your trees will bloom”
Pest
Porcupine and squirrel damage on trees
By Linda Williams, forest health specialist (Woodruff). Linda.Williams@wisconsin.gov; 715-356-5211, x232
During winter and early spring, damage to trees caused by porcupines and squirrels is evident in some areas. As spring arrives, new green leaves will mask the destruction.
This red pine had the bark stripped off it by a porcupine, which has wider incisors than a squirrel.
Porcupine and squirrels feed on the bark of trees, stripping it from branches and main stems. Stripping bark can girdle trees, resulting in branch dieback which shows up the year following the damage. If the branch isn’t completely girdled, it will start to grow callus tissue over damaged areas in an attempt to recover.
This maple bark was eaten by a squirrel. You can see where the tiny incisors scraped the bark down to the wood.
Both porcupines and squirrels feed on bark in the crowns of trees, so how can you tell which one is doing the damage if you don’t catch them in the act? The size of the teeth marks left in the wood is one clue. A gray squirrel’s incisors leave marks between 1.3 to 1.7 mm wide, while a porcupine’s teeth marks are nearly triple that, from 3.6 to 4.8 mm wide. You should also consider the species of tree being debarked: squirrels prefer maples while porcupines will feed on oak, pine, maple, and even spruce, as well as other species.
Rabbits, mice, and voles can cause similar damage to that caused by squirrels and porcupines, but damage will be located near the base of the tree instead of in the crown.
Another type of tree damage seen in late spring is when squirrels clip 4 to 6 inches off the tips of spruce branches, apparently to consume tasty buds. They drop the remainder of the branches to the forest floor, leaving a carpet of branch tips under spruce trees. I have yet to observe squirrels doing this, but the carpet of branch tips they leave prompts calls from concerned landowners each spring.
Spruce branch tips litter the ground where squirrels dropped them after clipping them from the tree. Although it can look alarming it rarely does enough damage to affect the overall health of the tree.
UW Extension offers a brochure about squirrels, including control options to share with landowners having trouble with these critters.
EAB biocontrol releases continue in 2018
By Mike Hillstrom, forest health specialist (Fitchburg). Michael.Hillstron@wisconsin.gov; 608-513-7690
In 2018, the Wisconsin DNR will complete its eighth year of releasing tiny, stingless wasps as biocontrol agents to help manage emerald ash borer. Columbia, Dane and Grant counties are slated for first-time releases this year, and there will be new release sites in Brown, Door and Sheboygan counties. The wasps will be released for a second year at established sites in Brown, Green, Jefferson, Milwaukee and Sheboygan counties. The same wasps that were released in 2017 will be used this year: Tetra sticus planipennisi, Spathius galinae and Oobius agrili.
Adult Spathius galinae wasps venture out to find some tasty EAB larvae to parasitize.
Biological control sites for emerald ash borer in Wisconsin 2011-2018. Figure by Bill McNee.
Statewide quarantine for emerald ash borer
By Jodie Ellis, DNR Forest Health Team, communications specialist (Madison), Jodie.Ellis@wisconsin.gov, 608-266-2172
An adult emerald ash borer.
Photo: Leah Bauer, USDA Forest Service Northern Research Station, Bugwood.org
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) enacted a statewide quarantine for the invasive insect emerald ash borer (EAB) on March 30, 2018. Previously, individual counties were quarantined when EAB was confirmed within each’s borders. Since EAB has been found in 48 of 72 Wisconsin counties, DATCP officials have determined that statewide regulation of the devastating ash tree pest is warranted.
Movement of ash wood, untreated ash products and hardwood firewood of any type to areas outside of Wisconsin will continue to be regulated by USDA’s Animal and Plant Health Inspection Service, Plant Protection and Quarantine. (APHIS PPQ).
Within the state, Wisconsin businesses and members of the public will be able to freely move ash wood, ash products, and hardwood firewood to or from any Wisconsin county. Firewood restrictions will remain in effect on state and federal lands.
Items affected by the statewide EAB quarantine include ash wood with bark attached, larger ash wood chips, and hardwood firewood of any kind. County-by-county quarantines for gypsy moth, another invasive forest pest, remain in effect.
The move to a statewide quarantine does not mean that the state has given up on managing EAB; it is simply a shift in strategy as EAB continues its slow spread through the state. The Wisconsin DNR will continue releasing tiny, stingless wasps -natural enemies of EAB – at appropriate sites, which it has done since 2011. The DNR also continues participation in silvicultural trials in which different ash management strategies are being tested.
Most importantly, campers, tourists, and other members of the public are strongly encouraged to continue taking care when moving firewood within the state. “The actions taken by the Wisconsin public during the last few years have significantly slowed the spread of emerald ash borer and other invasive forest pests in the state,” said Wisconsin DNR EAB program manager Andrea Diss-Torrance. “We can continue to protect the numerous areas within our state that are not yet infested – including those in our own backyards – from tree-killing pests and diseases by following precautions.” Public members should continue to obtain firewood near campgrounds or cabins where they intend to burn it, or buy firewood that bears the DATCP-certified mark, meaning it has been properly seasoned or heat-treated to kill pests.
Emerald ash borer is native to China and probably entered the United States on packing material, showing up first in Michigan in 2002. It was first found in eastern Wisconsin in 2008.
For further information on EAB in Wisconsin, visit https://dnr.wi.gov/ using key words “emerald ash borer.”
Prepare for the return of gypsy moths
By Bill McNee, DNR forest health specialist (Oshkosh), bill.mcnee@wisconsin.gov, 920-360-0942
In a few weeks, gypsy moth egg masses will begin hatching in Wisconsin. Property owners interested in reducing gypsy moth populations should consider oiling or removing reachable egg masses well before the hatch begins. Horticultural oils that suffocate the eggs are available at many garden centers and large retailers. In general, these are applied when temperatures are above 40oF and freezing is not imminent. When physically removing egg masses, scrape them into a can of soapy water and then let them soak for a few days before discarding in the trash in order to kill the eggs. Additional management options for homeowners and woodlot owners are available at the Wisconsin gypsy moth website.
Gypsy moth egg masses
Property owners looking to hire a business to do insecticide treatments this spring should contact them soon. A list of certified arborists is available on the Wisconsin Arborist Association website. Additional businesses offering insecticide treatments may be found in the phone book under ‘Tree Service.’ Homeowners can also purchase insecticides, some of which are applied as soil drenches, at garden centers and large retailers. For larger areas, a list of for-hire aerial applicators is available on the Wisconsin gypsy moth website.
Although this winter’s cold temperatures in late December and early January most likely did not cause heavy egg mortality, the cold period will still help reduce gypsy moth populations this summer. According to the U.S. Forest Service, temperatures of -20°F lasting from 48 to 72 hours can kill exposed eggs. Eggs that are laid higher up on the bark of trees suffer higher mortality than those located near the ground because snow insulates the eggs from cold temperatures. Fluctuating spring temperatures can also cause heavy egg mortality.
2018 suppression spraying:
Dane County will be the only participant in the DNR gypsy moth suppression program in 2018. Aerial spraying will occur in mid- to late May at seven sites in Madison and one site in Sun Prairie. A total of 485 acres will be sprayed with a bacterial insecticide that affects only small caterpillars. Maps of the sites are available on the Wisconsin gypsy moth website.
Slow-The-Spread treatments announced:
The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) announced its planned 2018 Slow-The-Spread (STS) gypsy moth treatments in western counties. About 90,000 acres are scheduled for treatment at 36 sites in 14 counties, using low-flying airplanes. Treatments will begin in May and continue through late July or early August, using either bacterial insecticide or pheromones which cause mating disruption.
Proposed 2018 gypsy moth treatments will occur in these counties. Counties in yellow are scheduled for Slow-The-Spread (STS) treatments, while Dane County (in blue) will undergo a suppression spray.
Counties scheduled to receive aerial treatments are: Barron (3 sites covering 2,736 acres); Bayfield (1 site, 787 acres); Buffalo (6 sites, 11,754 acres); Burnett (2 sites, 4,529 acres); Chippewa (4 sites, 12,794 acres); Crawford (4 sites, 5,971 acres); Douglas (1 site, 789 acres); Dunn (5 sites, 43,986 acres); Eau Claire (1 site, 674 acres); Grant (1 site, 497 acres); Green (1 site, 392 acres); Lafayette (2 sites, 527 acres); Rusk (1 site, 463 acres); and Vernon (3 sites, 3,785 acres).
More information on STS treatments may be found online at the DATCP Gypsy Moth website.
Treat your valuable ash trees against emerald ash borer (EAB)
By Bill McNee, DNR forest health specialist (Oshkosh), bill.mcnee@wisconsin.gov, 920-360-0942
Wisconsin homeowners with healthy, valuable ash trees should consider treating the trees with insecticides this spring to protect against emerald ash borer (EAB). The pest is currently the most damaging threat to trees in the state, killing more than 99 percent of the ash trees it infests.
Infested ash trees have been attacked by woodpeckers looking for larvae to eat.
Woodpecker damage during the winter is often the first visible sign that an ash tree is infested, so it is important to examine your ash trees during cold months when leaves are absent. Now is a good time to consider protection with insecticides: insecticide treatments are usually applied between mid-April and mid-May once leaves begin to return. Treatments on already-infested ash trees are more likely to be successful if the trees exhibit only low or moderate levels of woodpecker damage.
Emerald ash borer has become so widespread that homeowners should consider treating valuable ash trees no matter where they are located in Wisconsin. The highest risk of EAB-infestation is within quarantined counties or within 15 miles of a known infestation. Outside of these high-risk areas, the danger of ash trees becoming infested with EAB is probably lower, but it is widely believed that there are additional, undetected EAB infestations within the state. A map of known EAB infestations can be found at the Wisconsin EAB website.
Location isn’t the only consideration when deciding whether to begin insecticide treatments. For example, such treatments are not economically practical for woodlot ash trees; they would need to be repeated every 1-3 years for the rest of the trees’ lives (frequency of treatments will depend on the product and method used).
What you should do
If EAB has been found locally or if you see any of the signs or symptoms of an EAB infestation in your ash trees, search for information online or seek advice from a tree care professional. You can fund a certified arborist at the Wisconsin Arborist Association’s website. Other businesses also conduct EAB treatments.
Some insecticide products can be applied by homeowners but others must be applied by a certified professional. Review the available options before selecting an insecticide and treatment method. Insecticide information can be found on the Wisconsin EAB website and EAB Information Network website.
Only ash trees need to be protected against EAB. Mountain ash and prickly ash trees do not need protection from EAB because they are not true ash trees and are therefore not attacked by the insect.
Consider the following
- Determine whether the tree is worth treating. Some ash trees are too heavily infested to save or have structural or health problems that make them poor candidates for insecticide treatment.
- Trees displaying large amounts of visible woodpecker damage may be too infested to be saved with insecticides. Consult a certified arborist for a professional opinion.
- Landscape trees improve views, increase property values, provide shade and cooling, and contribute to the quality of life in a neighborhood. Weigh those benefits against the expense of a treatment.
- Consider the cost of removing or replacing trees. You might be able to treat your ash tree for more than a decade yet still spend less money than it would cost to remove it.
- The cost of an insecticide treatment will depend on tree size and the product being used. Some products are applied annually; others are applied every two years.
- Check the credentials and insecticide applicator certification of any business you hire to treat your ash trees.
Signs and symptoms of an infestation
Stay informed and be on the lookout for emerald ash borer. Know where the pest has already been found and look for the signs and symptoms of EAB infestation. Watch ash trees closely for the following:
- Woodpecker damage (“flecking”) that looks like pieces of bark have been shaved off and removed;
- Sprouts growing from the base or trunk of the tree;
- Thinning leaves in the upper canopy;
- Tiny (1/8 inch), D-shaped exit holes in the bark; and
- Adult EAB beetles present during the summer.
Woodpecker damage is easy to spot during the winter
By Linda Williams, forest health specialist (Woodruff), Linda.Williams@wisconsin.gov, 715-356-5211 x232
Two elm trees with varying levels of bark stripping caused by woodpeckers feeding on larvae beneath the bark. Photos: Linda Williams
Have you noticed any trees this winter with the bark partially or mostly removed? These trees can stand out dramatically during the winter. Woodpeckers remove outer layers of bark so that they can more easily punch their beaks through the remaining bark to get at the tasty, plump larvae underneath. The three most common trees that you’ll spot this damage on in Wisconsin are elm, tamarack, and ash. So, what’s going on?
On elm, there are three bark beetles of interest. One is a native beetle, and two are exotic species – the smaller European elm bark beetle and the banded elm bark beetle. Adult bark beetles chew their way under bark and lay eggs during the spring or summer. The eggs hatch, and larvae begin feeding in the tree layers under the bark. Going into winter, larvae are plump and delicious (if you’re a woodpecker), and it’s these juicy morsels for which the woodpeckers will strip the outer bark from the tree, sometimes starting at the ground and working all the way to the top. Elm trees will often appear a rich red or burgundy color when outer bark is removed. The U.S. Forest Service offers a document with additional information on elm bark beetles, as well as photos of each of them.
Close-up of tamarack bark, showing the larvae of Eastern bark beetle at the tip of my (broken) knife. Woodpeckers remove the outer bark to make it easier to access these tasty morsels.
Tamarack trees (often referred to as larches) are attacked by a bark beetle as well. Eastern larch beetles attack stressed tamarack trees, although sometimes the stress is so minor that it’s not easily identifiable. The wet weather we had throughout the 2017 growing season definitely stressed some of tamaracks in Wisconsin; having roots in fully saturated soils for too long a period when the tree is actively growing can cause root mortality. Tamarack that have had the outer bark stripped off will appear dark red in color. More information on eastern larch beetle from the U.S. Forest Service can be found here.
Ash bark with pale areas where woodpeckers have removed outer layers of bark, as well as some small rough holes where the woodpeckers punched through bark and plucked out a nice plump EAB larvae.
Ash trees with the outer bark removed may be infested with either emerald ash borer or a native ash bark beetle. When woodpeckers remove outer bark of an ash tree, it makes the tree look very pale. Emerald ash borer populations build up to very high numbers as they move into new areas, which provides a great source of food for woodpeckers. A study published in 2012 showed that woodpecker numbers can increase due to the presence of EAB.
What about other woodpecker damage that you see on trees?
Pileated woodpeckers are large birds that can do a significant amount of damage to trees. The good news is that they tend to target trees that are dead or have a lot of decay in them. That’s not
to say that they won’t occasionally peck into a healthy tree, but the insects they prefer to feed on are more common in dead or severely stressed trees, or trees with a lot of decay in them. Pileated woodpeckers have tongues containing backward facing barbs that they can stick into an insect gallery to drag out the occupants for a meal. They can leave a pile of good-sized woodchips at the base of trees that they’re feeding in. The photo shows an example of the damage that they can do.
Sapsuckers are birds that drill orderly rows of holes through the bark of trees. The holes go through the bark to the cambial layer, causing the tree to “bleed” sap. Sapsuckers return to feed when the sap is flowing. Sapsuckers’ tongues have little hairs on them to help gather sap. Sapsuckers are migratory and may just pass through an area in the spring, but they will sometimes return to the same tree over multiple years, creating new rows of holes each year. Trees will attempt to grow over this damage, and are usually successful, although the damage to the bark may remain visible for many years. Loggers may note this damage when cutting logs; it is referred to as “bird peck”, and is considered a defect. Federal regulations prohibit people from killing sapsuckers, so control for yard trees is usually some manner of deterrent such as wrapping the main stem with hardware cloth or burlap, or using scare tactics in the tree.
Orderly rows of holes created by yellow-bellied sapsuckers. These birds will revisit these holes that they drill and lick the sap that flows from them.
Damage from pileated woodpeckers can be quite extensive. A single woodpecker can create this level of damage in a few days, or it may work at a tree throughout the season. Note the pile of large woodchips at the base of the tree.
New Wisconsin Wildcard available on beech bark disease
Written by: Linda Williams, forest health specialist, Woodruff. Linda.Williams@wisconsin.gov, 715-356-5211 x232.
A new Wisconsin Wildcard is available on beech bark disease (BBD). Wisconsin Wildcards are pocket-sized, collectible informational pieces available at Wisconsin state parks. The BBD Wildcard may be viewed at https://p.widencdn.net/clz4yw/Beech-bark-disease-wildcard and ordered by emailing a request to Forestry.Webmail@wisconsin.gov (ask for publication no. FR-218x).
Beech bark disease will eventually become a problem wherever beech is found. The native range of American beech (Fagus grandifolia) extends into the eastern third of Wisconsin. BBD is the result of a relationship between exotic scale insects and a Neonectria fungus. The disease was first identified in Wisconsin in 2009. Currently, the only known area of the state which has experienced mortality from BBD is Door County.
Front and back of the new beech bark disease Wisconsin Wildcard.
The scale insects feed by inserting their mouthparts through the bark on the trunk and branches and sucking the sap from the tree. The fungus, which “hitchhikes” on the scale insects’ bodies, enters the tree through those wounds. The tiny scale insects secrete a white waxy protective covering; when scale populations explode and there are millions of scales on a tree, the tree can appear white from a distance, making it resemble a birch tree. As the fungus enters the tree at numerous points and dead spots under the bark (called cankers) form, the tree becomes weakened, leading to a risk of “beech snap.” Beech snap can occur unexpectedly when the tree still has a full canopy of leaves remaining. Beech snap can create huge problems for park and campground managers who are trying to keep guests safe; there is no way to predict when a tree is going to fail from BBD.
Hundreds of tiny scale insects (covered in white fluff) are present on this small area of beech bark. Photo: Linda Williams
Eventually, the insects and disease take their toll and the beech trees decline and die. Any age of beech tree can be infested, so in stands with significant beech mortality, regenerating trees will become infested as well as mature ones. The good news is that three to five percent of American beech trees are resistant to BBD. Michigan has identified and propagated such trees for a number of years, and have established a seed orchard of resistant trees. BBD is not yet as established in Wisconsin, but already we’ve been able to identify a couple of resistant trees in the area where BBD has killed many trees.
For more info on beech bark disease, visit Wisconsin DNR’s webpage on BBD.
Ash mortality in Central Wisconsin
Michael Hillstrom, forest health specialist, Fitchburg. michael.hillstrom@wisconsin.gov, 608-513-7690
Forest health has relayed the message over the last few years that stand level ash mortality from emerald ash borer (EAB) is occurring in southeast Wisconsin and along some parts of the Mississippi River. Those areas of mortality continue to progress each year, but stand level mortality is no longer limited to just these areas.
All the ash in this stand near Roche-A-Cri State Park in Adams County are heavily flecked by woodpeckers feasting on EAB larvae. Extensive flecking indicates EAB has fully infested these trees and mortality is imminent. Photo by Mike Hillstrom.
February and March are good times to look for woodpecker damage to ash trees (known as “flecking”), and potentially find new EAB infestations or expansions of known infestations. Winter scouting has allowed us to detect ash mortality from EAB in unexpected places. I was in Adams County in mid-February looking for EAB biocontrol release sites. I was shocked to find a stand where all the ash trees were heavily flecked and likely dead or close to it. We had not previously confirmed EAB in that township or any of the townships directly surrounding it.
This incident further drove home the point for me that even isolated patches of ash are not safe from EAB. We are now past the point of thinking about taking action in ash stands in southern and central Wisconsin; we must now move forward with site assessments, with salvage/pre-salvage harvesting being a high priority for management. In addition, non-ash regeneration growing should be started sooner rather than later. Of course, in urban settings, now is the time to prophylactically treat high-value ornamental ash trees.
The EAB silviculture guidelines will be revised in 2018; stay tuned.
Tamarack mortality appearing in Marathon and Portage counties
Article by: Michael Hillstrom, forest health specialist, Fitchburg. michael.hillstrom@wisconsin.gov, 608-513-7690
Woodpeckers strip bark off tamarack trees infested with eastern larch beetle, causing them to appear red. Photo by Mike Hillstrom
Foresters reported several new areas of tamarack mortality this winter in Marathon and Portage counties. The culprit continues to be eastern larch beetle (ELB). Although historically there have been periodic outbreaks of this native bark beetle, we have seen damage in Wisconsin every year since 1999. ELB initially attack stressed tamarack but, once in a stand, they often sweep through it over a few years even without additional stressors. The droughts of 2012-2013, defoliation by larch casebearer in 2014 and 2017, and prolonged flooding of stands in 2017 were all likely contributors to ELB infestations in central and northern Wisconsin. Infested stands should be salvage harvested and regenerated when possible, given the difficulty of accessing many tamarack stands.