West Central WI forest health

Fall webworm

Fall webworm started showing up around the middle of July.

Fall webworm web

Fall webworm web

This is a native insect that feeds on deciduous trees and shrubs, and it is makes an appearance every year in yards and forests. Fall webworm forms loose webbing over branch tips and if it is a small tree, the entire tree can be completely webbed.

Inside the webbing you’ll find caterpillars (alive and dead), partially eaten leaves and frass (caterpillar poop).

Fall webworm caterpillars

Fall webworm caterpillars

 

 

Fall webworm is more of a cosmetic problem than a tree health problem, but if you want to control them, the easiest way to do that is to open up the webbing. You can take a rake, fishing pole, long stick, or whatever and open up the webbing. This will allow predators to get at the caterpillars inside the webbing.  Or you can use the rake, fishing pole, etc. and roll the webbing up. Then peel the rolled webbing off and place the entire web in a container of soapy water for a couple of days. If you want to use an insecticide, you need to make sure the insecticide is labelled for caterpillars/fall webworm and the spray needs to penetrate inside the webbing. With all pesticides, the user needs to read and follow label directions. There is no need to prune off the branch. If the tree is healthy, the defoliation should not harm the tree.  You can find more information on fall webworm here. 

Written by: Todd Lanigan, forest health specialist, Eau Claire (Todd.Lanigan@wisconsin.gov)
715-839-1632

Heavy Diplodia shoot blight following hail storm in Polk and St. Croix Counties

Stand of mature red pine with heavy crown browning from Diplodia shoot blight following a hail storm in June.

Hail-induced Diplodia shoot blight. (Photo by Paul Cigan)

Red pine stands in a localized area of southwestern Polk and northwestern St. Croix counties are displaying heavy crown browning, shoot blight, and tree mortality following a June hail storm that left many red pine injured in local plantations.  In many stands, the entire crown on most overstory trees has turned brown, leaving behind a stark illustration of just how damaging the fungal pathogen, Diplodia pinea, can be to red pine following hail storms.  Bark-breaking hail wounds on red pine of all ages serve as entry points for wind- and rain-dispersed spores of the disease.  Wet and warm spring and summer weather, similar to conditions observed this year, can promote spore production and intensify infections.  Cankers soon develop at infected wound sites, enlarge, and may cause death of branches and terminal shoots within weeks.  Landowners affected by hail and Diplodia damage should contact their local DNR forester to evaluate the extent and severity of damage, discuss management options, and identify contacts in wood-utilizing industries to coordinate salvage operations on smaller acreages.

Bleeding canker caused by Diplodia at the site of a hail wound on red pine branch.

Bleeding Diplodia canker

Generally, salvage and pre-salvage harvest efforts should prioritize the removal of pine with greater than 50% crown browning and those with at least 3 feet of terminal leader dieback.  Trees with less damage should be monitored for bark beetle attack for two years after thinning and be promptly removed if crowns begin browning due to bark beetle attack.  To reduce bark beetle attack during harvesting March through August, remove all material greater than 2 inches in diameter within three weeks of harvest.

 

Written by Paul Cigan, forest health specialist, Hayward (Paul.Cigan@Wisconsin.gov), 715-416-4920.

Defoliation by rose chafers and Japanese beetles is showing up.

Rose chafers and Japanese beetles are starting to cause problems in some areas this summer. So far reports and damage are generally light for Japanese beetles, but in some areas rose chafer defoliation is noticeable. 

Rose chafers are beetles that can defoliate many plant species. They have fairly long legs, and are a dusty mustard color.

Rose chafers are beetles that can defoliate many plant species. They have fairly long legs, and are a dusty mustard color.

Rose chafer defoliation was reported from Florence, Marinette, Oconto, Vilas, and Waupaca counties this year. Rose chafers are more common in areas with sandy soil where they will lay their eggs. The eggs hatch into white grubs which live in the soil and feed on grass and weed roots. My books inform me that birds can die if they eat adult rose chafers because of a poison in the beetles that affects the heart of small, warm-blooded animals. For information on rose chafer control, check out UW Extension publication A3122.

The last significant defoliation that I noted from rose chafer was in 2012, and before that it was 2005. These beetles feed on a wide variety of plants and prefer blossoms, but they will skeletonize leaves as well. Control is difficult because the adults are good fliers and can easily fly in from neighboring areas to re-infest your freshly sprayed plants. 

Japanese beetle populations will emerge in southern Wisconsin first, typically by the first part of July. Some areas of the state have building populations while others, like the Madison area, may have populations that exploded in the past and are more stable now. These insects are occasionally mistaken for EAB because they have some metallic green coloring near their heads.  More commonly people will refer to the multicolored Asian ladybeetles as Japanese beetles, but the ladybugs are ladybugs and Japanese beetles are scarab beetles.

Japanese beetle adults feed on the flowers and leaves of over 300 plant species, including trees, shrubs, and herbaceous plants. They can cause significant defoliation. The larval stage of Japanese beetle is a white grub that lives in the soil and feeds on plant roots.  University of Wisconsin Extension has a Japanese beetle webpage including information on the damage caused by the adults, the damage caused by the white grubs, and control measures that are useful on the adults and the larvae. 

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

Woolly alder aphids on maple

Woolly alder aphids secrete waxy filaments or fine hairs to protect themselves from predators. They live part of the year on maple and part of the year on alder.

Woolly alder aphids secrete waxy filaments or fine hairs to protect themselves from predators. They live part of the year on maple and part of the year on alder.

Maple trees with white fluffy, stringy things on their leaves and twigs have woolly alder aphid (Paraprociphilus tessellatus). Populations seem rather high this year. This aphid species requires both alder and maple to complete its life cycle, spending spring and summer on maple and the remainder of the year on alder. While on alder they are a plump, bluish colored aphid covered by white, waxy filaments. They will often be found in a group, forming a solid mass of white fluff on the stems. 

When present on maple they are sometimes referred to as maple blight aphid. They don’t usually do any significant damage to either maple or alder but they can be quite noticeable at times because of the large patches of fluff when they congregate in an area.  High populations of these aphids on maple can create enough honeydew (aphid excretions) to create a sticky layer on any objects underneath the maples. Sooty mold can then grow on the sticky layer, so it is recommended to wash off things under these trees on a regular basis. I’ve seen or had reports of woolly alder aphids on maple from Door, Langlade, Oconto, and Oneida counties.

Woolly alder aphids often congregate in large white masses on alder where they will overwinter.

Woolly alder aphids often congregate in large white masses on alder where they will overwinter.

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

Rhizosphaera needlecast on balsam fir

Rhizosphaera needlecast of fir produces rows of round black fruiting bodies on the needles. Photo by Colton Meinecke.

Rhizosphaera needlecast of fir produces rows of round black fruiting bodies on the needles. Photo by Colton Meinecke.

Rhizosphaera needlecast was found on balsam fir in Shawano County, with additional reports from Todd Lanigan (West Central WI) and Paul Cigan (Northwest WI). It causes chlorosis in the needles which drop off prematurely, giving the tree a thin appearance. This disease is related to the Rhizosphaera needlecast of spruce which you may be more familiar with. Literature indicates that it is most common on fir trees in shaded damp areas, or on trees that are under stress from other issues. You will see small black fruiting bodies on the undersides of the needles, although what really stands out is the thin foliage or off-color needles compared to other unaffected trees. 

Needles from the previous year have turned brown and will drop off prematurely due to Rhizosphaera needlecast.

Needles from the previous year have turned brown and will drop off prematurely due to Rhizosphaera needlecast.

Additional info can be found in this pest alert from the Forest Service.  

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

Wind and hail damage caused by the April 9, 2017 storm

The National Weather Service local storm reports map shows hail was most commonly reported, with some tree damage, and one tornado (west of Wausau).

The National Weather Service local storm reports map shows hail was most commonly reported, with some tree damage, and one tornado (west of Wausau).

During the night of April 9-10, 2017 a strong line of storms moved through Wisconsin. Reports ranged from pea sized to tennis ball sized hail, with most stating quarter sized hail. Immediately following the hail, winds picked up and straight line winds took down trees in a number of areas around Oneida and Vilas Counties. The National Weather Service reports that there was a tornado touch down west of Wausau, and reports of tree damage showed up in the National Weather Service’s local storm reporting page.

Damage to trees from hail was most noticeable on the conifers which had needles knocked off, creating a green carpet below the trees. Fine twigs on white pines were damaged by the hail and some fine branch mortality may occur if the twigs were damaged badly enough. Damaged red pine may be more prone to getting diplodia where the twigs were wounded.

Hail wounds on fine branches of white pine appear as dents with cracks in the bark. Those cracks will dry further as spring progresses and the cracked areas will increase slightly in size.

April 9 hail wounds on white pine branches (yellow arrows) appear small but will dry, and the bark will crack further as spring progresses. Some branch dieback may occur.

Hail wounds on young aspen and the fine branches of mature aspen from the April 9-10 storm appear as scuffed bark (yellow arrows). These will callus over relatively quickly.

April 9 hail wounds on young aspen and the fine branches of mature aspen appear as scuffed bark (yellow arrows). These will callus over relatively quickly.

Small wounds on young aspen should callus over.

 

 

 

 

 

 

 

Written by: Linda Williams, forest health specialist, Green Bay, (Linda.Williams@wisconsin.gov), 920-662-5172.