Disease

What’s that orange goo?!

By Mike Hillstrom, forest health specialist, Fitchburg, Michael.Hillstrom@wisconsin.gov, 608-513-7690

What’s the orange goo on that tree?!

Should I fight or should I flee?

I bet forest health staff can ID!

Close-up of orange gelatinous gall growing on cedar caused by cedar apple rust.

The spore-producing, slimy, orange gall caused by cedar apple rust fungus.

Continue reading “What’s that orange goo?!”

Pine tortoise scale can cause branch and tree mortality, sooty mold problems

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Pine tortoise scales are sometimes found at very heavy densities on jack and scotch pine twigs. In Wisconsin they prefer young jack pine trees, inserting their straw-like mouthparts into twigs and sucking out the sap. When populations are high, pine tortoise scale can cause branch mortality and even whole tree decline.

Tiny pine tortoise scales clustered on a pine branch tip.

Pine tortoise scales are so plentiful on this twig that they are practically on top of one another.

Continue reading “Pine tortoise scale can cause branch and tree mortality, sooty mold problems”

Plant disease diagnostics in the time of COVID-19

The University of Wisconsin Plant Disease Diagnostics Clinic (PDDC) has started to accept a limited number of physical samples.  However, clinic staffing and hours will be limited, and the number of samples that the clinic will be able to accommodate will be severely restricted. Prioritization of the samples currently goes to:

  1. Commercial production food and agriculture-related samples (e.g., vegetables, fruits, field and forage crops)
  2. Commercial/homeowner samples of regulatory importance (e.g., late blight, boxwood blight)
  3. Commercial production, non-food samples (e.g., nursery, greenhouse samples)
  4. Homeowner food samples
  5. Commercial/homeowner non-production, non-food samples (e.g., trees, shrubs, herbaceous ornamentals).

Continue reading “Plant disease diagnostics in the time of COVID-19”

New UW-Madison Plant Disease Diagnostics Clinic listserv

The UW-Madison Plant Disease Diagnostics Clinic (PDDC) provides expertise in diagnosing plant diseases, and information on plant diseases and their control to agricultural and horticultural producers and businesses, as well as home gardeners, throughout the state of Wisconsin. 

If you are interested in receiving regular updates on the educational materials and programs provided by the PDDC, please email Brian Hudelson at pddc@wisc.edu to have your email address added to the new clinic listserv, “UWPDDCLearn”.  This listserv will provide announcements of when new content is posted to the PDDC website (https://pddc.wisc.edu/), including (but not limited to) new and revised University of Wisconsin Garden Facts/Farm Facts/Pest Alerts fact sheets, the Wisconsin Disease Almanac (a weekly summary of diagnoses made at the PDDC) and monthly clinic web articles.  The listserv will also provide announcements about upcoming PDDC outreach programs. 

Continue reading “New UW-Madison Plant Disease Diagnostics Clinic listserv”

Educational HRD video now available

By Kyoko Scanlon, forest pathologist, Kyoko.Scanlon@wisconsin.gov, 608-235-7532

The Wisconsin DNR recently created a short video on Heterobasidion root disease (HRD) to compliment the updated guidelines that were released in 2019. The 5-minute educational video covers HRD biology, its significance as a tree disease, signs and symptoms, as well as preventative measures that landowners can take to reduce its introduction and spread. This is a great video for forestry professionals, landowners and the general public to learn more about HRD. Continue reading “Educational HRD video now available”

White pine blister rust can girdle branches

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

White pine branches that suddenly turn red may be a sign of white pine blister rust. White pine blister rust is a fungal infection that creates expanding “dead spots” or cankers on the branches or main stem of host trees. Eventually the fungus grows enough to girdle the branch or main stem and the needles fade from green to pale green to rusty red. Orange, spore-producing pustules erupt around the edges of the canker in the spring.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

Orange pustules erupt through the bark and around the margins of a white pine blister rust canker. Photo by Jean Romback-Bartels.

Continue reading “White pine blister rust can girdle branches”

Gall rusts on jack pine

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

There are three things you may find interesting about gall rusts on jack pine at this time of year. The first is that as winter recedes, closer examination of the galls on jack pine shows that squirrels like to chew on them. The squirrels seem to prefer the smaller galls, with most chewing marks being observed on galls less than 2” in diameter. They eat the galls by scraping off the outer layers, leaving behind telltale teeth marks.

Chewing marks on a branch gall caused by gall rust.

Squirrels sometimes feed on galls, scraping away the outer layers and leaving teeth marks behind.

Continue reading “Gall rusts on jack pine”

Damage from heavy winter snow and ice

By Linda Williams, forest health specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665

Heavy ice and snow loads can cause significant problems for trees. Branches can break under heavy loads, and entire tree tops loaded with snow can come crashing down in windy conditions. Trees that are repeatedly weighed down or tipped over by snow, only to have more snow pile up on them, can be further impacted.

Four images of winter damage to jack pine, including stem failure from gall damage, root failure due to Armillaria root disease.

Clockwise from top left: jack pine broken at site of gall on main stem; trees that break at their base due to heavy snow loads are not able to recover; previous attack from pine root collar weevil (yellow arrow) weakened this tree near its base; heavy snow load and a major root weakened by Armillaria caused this tree to break (yellow arrow) and tip over.

Continue reading “Damage from heavy winter snow and ice”

Protect oak trees by pruning after July, not before

By Don Kissinger, urban forester, 715-348-5746, Don.Kissinger@wisconsin.gov or Paul Cigan, plant pest and disease specialist, 715-416-4920, Paul.Cigan@wisconsin.gov

Anyone with oak trees in their yards or on forested lands should avoid pruning or cutting them from April through July to protect them from oak wilt.

Sap-feeding beetle on diseased oak tree in Sawyer County.

Sap-feeding beetle on diseased oak tree in Sawyer County.

Continue reading “Protect oak trees by pruning after July, not before”

Severe spruce needle diseases expected in 2020

By Bill McNee, DNR forest health specialist, Oshkosh, bill.mcnee@wisconsin.gov, 920-360-0942

Wet weather in 2019 created ideal conditions for Rhizosphaera kalkhoffii and other needle cast fungi to infect spruce needles. Since it takes about a year for the needles to show symptoms, heavy and widespread needle diseases are expected to be seen on spruce trees in 2020. 

Lower branches of an infected spruce tree have lots of missing needles and some that are browning.

Loss of older needles on an infected spruce.

Continue reading “Severe spruce needle diseases expected in 2020”