What is growing on that oak tree?

Posted on by patricialindquist

By Todd Lanigan, DNR Forest Health Specialist, Eau Claire, todd.lanigan@wisconsin.gov or 715-210-0150

This time of year, you may be noticing some large growths on oak leaves. You are either seeing oak apple gall and/or wool sower gall. These galls are formed by a small, stingless wasp, known as a Cynipid Wasp. 

For the oak apple gall, when the female lays her egg, she injects a growth regulator that causes the leaf tissue to form around the egg. When the larvae begin to feed for the wool sower gall, this causes the gall to form. The galls in both cases protect the developing wasps from the elements and predators. 

Oak apple galls are round and initially are green in color. Eventually, the gall turns brown as the wasp larva matures inside.

Oak apple gall growing on the underside of a leaf.

An oak apple gall

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Oak Shot Hole Leafminer And Spiny Oak Sawfly

Posted on by patricialindquist

By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or  920-360-0665. 

Two very different insects are creating holes in oak leaves this spring, the oak shothole leafminer and the spiny oak sawfly. 

Oak shothole leafminer

In 2019 and 2020, many eastern U.S. states noted damage from this insect. While this is mostly a cosmetic issue for the tree, it can cause concern for homeowners and landowners when it appears that their trees are defoliated. The good news is that this damage rarely has an impact on the health of larger trees. 

Small holes in the leaf, often with similar holes on the both sides of the main vein, indicate damage from oak shothole leafminer adults.

Small holes in the leaf, often with similar holes on the both sides of the main vein, indicate damage from oak shothole leafminer adults.

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Oaks Hit Hard By Frost/Freeze Prior To Memorial Day

Posted on by patricialindquist

Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

A frost/freeze on the night of May 28 strongly impacted our oaks in areas of central and northern Wisconsin. Some leaves were completely killed while others had portions of the leaf that were impacted. Those leaves with some dead spots have continued to expand and grow but the dead parts of the leaf are causing them to curl and pucker. 

Oak leaves killed by the frost are brown, curled and puckered.

Oak leaves killed by the frost.

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Balsam Fir Needle Rust

Posted on by patricialindquist

By Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

Balsam fir needle rust is infecting current year needles on balsam fir trees in north-central Wisconsin. Balsam fir needle rust has white pustules that emerge from the lower surface of infected needles. Infected needles will turn yellow and the combination of white pustules and yellow needles gives the trees a pale, ghostly appearance from a distance.

Bright yellow needles are infected with balsam fir needle rust.

Bright yellow needles are infected with balsam fir needle rust.

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Pine Bark Adelgid Causes Needle Stunting

Posted on by patricialindquist

Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665. 

Pine bark adelgids are tiny insects that suck the sap of white pines. Once they insert their mouthparts into the tree, they won’t move any more during their lifetime, so for protection, they grow a white, woolly covering around themselves. A young, white pine plantation in Vilas County is suffering severely stunted needles from the 2020 growing season due to very high populations of pine bark adelgid. 

All branch tips on this white pine sapling have needles that were stunted by heavy populations of pine bark adelgid.

All branch tips on this white pine sapling have needles that were stunted by heavy populations of pine bark adelgid.

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Giant Hogweed: Rare But Harmful

Posted on by patricialindquist

By Bernie Williams, DNR Invasive Plant Specialist. Bernadette.Williams@wisconsin.gov or 608-444-6948. 

Giant hogweed is a non-native, invasive plant that has gradually gained a foothold in the northeastern U.S. Once popular for its massive size and white umbrella-like flowers, it was introduced as an ornamental as early as 1917. Now known for its harmful blisters, it is recognized as a public health hazard and controlled wherever possible.

Characteristic purple blotches and white hairs on green stem of giant hogweed. Photo credit: Herkulesstaude_Fritz Geller-Grimm

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Watering Trees In A Drought

Posted on by patricialindquist

By Olivia Witthun, DNR Urban Forestry Coordinator, Plymouth, olivia.witthun@wisconsin.gov, 414-750-8744 

Photo credit: City of Minneapolis Forestry Division

Things just keep getting drier and it seems like there is no end in sight. The trees are thirsty, and they need your help!

Watering Newly Planted Trees

Newly planted trees need extra watering until they are established. The amount of water depends on tree size and on your soil type (sandy versus clay).

  • 1-2 weeks after planting: water daily.
  • 3-12 weeks after planting: water every 2 to 3 days.
  • After 12 weeks, water weekly until roots are established.

Watering Tips

  • Deep watering is best. Try to get the soil wet to a depth of at least 6 inches.

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Public Awareness Ideas For Watering Trees In A Drought

Posted on by patricialindquist

By Olivia Witthun, DNR Urban Forestry Coordinator, Plymouth, olivia.witthun@wisconsin.gov, 414-750-8744 

Most of you are doing your best to keep things watered, but you could always use some help. Below are a few ideas for public awareness and pleas to get homeowner assistance in watering trees. As always, contact your DNR Urban Forestry staff if you’d like more specific examples.  

  • Social media is a great avenue to get these types of messages out. Use your community’s Facebook, Twitter and other social platforms to your advantage.
  • Consider dropping off a doorhanger reminding folks to water trees. Perhaps work it into your watering schedule; each address you stop at gets a doorhanger.

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Fire danger remains high

Posted on by Kirsten Held

Normally by this time of year, spring wildfire danger is over. Due to minimal precipitation, the danger isn’t over yet.

Since June 1, the DNR has responded to 106 wildfires in DNR protection areas. Fire danger remains elevated in many parts of the state, with much of the northern half of Wisconsin currently experiencing High to Very High fire danger.

DNR-issued burning permits will be suspended in some counties. As always, check for restrictions in your area daily after 11 a.m.

Be cautious with anything that could inadvertently start a wildfire. Ensure all tow chains are secured, avoid parking vehicles on dry grass, keep ATVs and UTVs on the trail and avoid any fireworks use. If you’re doing any woods work, avoid setting down hot chainsaws on dry grass or leaves.  Never leave your campfire unattended and make sure it’s fully out – drown and stir until all material feels cool.

DNR Urban Forestry Coordinator Don Kissinger Retires

Posted on by patricialindquist

By Jeff Roe, DNR Urban Forestry Team Leader, Madison, jeffrey.roe@wisconsin.gov or 608-535-7582

Don Kissinger, Urban Forestry Coordinator for the north-central region, is retiring after nearly 29 years at the Wisconsin Department of Natural Resources (DNR). His last day in the office was May 21, 2021.

Don’s contributions are significant.  His best days were spent out in the field working and conversing with community forestry managers in his 18-county service area. Don never missed an opportunity to share his passion for urban forestry and arboriculture.

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