Article By: Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
Have you seen small round holes in acorns? These holes are a sign of acorn weevil damage that can occur in all Wisconsin oak species.
Two acorns show exit holes of acorn weevils. / Photo Credit: Wisconsin DNR
Article By: Bill McNee, DNR Forest Health Specialist, Oshkosh
bill.mcnee@wisconsin.gov or 920-360-0942
In 2021, gypsy moth populations increased for a second consecutive summer due to favorable weather conditions. Populations typically increase with an average or mild winter, below average spring precipitation and above average May through June temperatures.
Regional variation in weather can result in significant differences in populations. If weather conditions are favorable again in 2022, the most noticeable increase in caterpillar numbers would likely occur in southern counties, where conditions were driest during this past spring and summer.
Populations experience the fastest growth rate and are first noticed on:
Gypsy moth egg masses found in Walworth County in fall 2021.
Photo Credit: Gypsy moth egg masses KMSU
Continue reading “Take Action! Look For Gypsy Moth Egg Masses”
Article By: Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
Tree damage from white pine weevil is noticeable across Wisconsin this time of year. White pine weevils attack several different Wisconsin species, including eastern white pine, jack pine and spruce.
Adult weevils lay their eggs on terminal leaders in the spring. After the eggs hatch, larvae bore into the terminal and begin feeding downwards just under the bark which can result in the killing of a 1 to 2-feet section of the terminal leader as they feed. Terminal leaders will often have a wilted or “shepherds crook” appearance, and they will turn rusty red to brown late in the fall season. These dead terminal leaders will often break off during the winter.
Dead terminal leader caused by a white pine weevil attack on a young white pine.
Photo Credit: Wisconsin DNR
Article by: Mike Hillstrom, Forest Health Specialist
In 2020, forest health staff in Wisconsin, Minnesota and Iowa received calls about black walnut stands being defoliated and webbed. In 2021, the defoliation expanded to multiple additional black walnut stands in southwest Wisconsin, while northeast Iowa and Minnesota continued to see damage. Recently, molecular work completed by the Wisconsin Department of Agriculture, Trade and Consumer Protection has identified the larvae causing the damage as a native Tortricid moth, Gretchena amatana.
G. amatana caterpillars on tree.
Fine webbing covers walnut tree trunk.
Article By: Linda Williams, DNR Forest Health Specialist, Woodruff
Linda.Williams@wisconsin.gov or 920-360-0665
The oak slug sawfly (Caliroa quercuscoccineae), sometimes called the scarlet oak sawfly, has the appearance of a small, slimy slug. Its slime helps it stick to leaves it feeds on. The oak slug sawfly’s tiny larvae feed in groups on the undersides of oak leaves, scraping out the green material from between the veins of the leaves. The upper leaf surface is usually left intact, creating a “stained glass window” look. Oak slug sawfly has the ability to completely defoliate leaves before dropping to the ground to pupate.
Oak slug sawfly larvae cause defoliation on oak leaf after feeding.
Photo Credit: Wisconsin DNR
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665.
For the third year in a row, colonies of redheaded pine sawfly have been noted on understory red pine in northern Wisconsin, with the most reports coming from Vilas and Oneida counties.
Redheaded pine sawfly larvae feeding on red pine needles. Note the needle stubs where they have eaten nearly to the base of the needle. Photo Credit: Wisconsin DNR
Continue reading “Redheaded Pine Sawfly Numbers Remain Elevated In Northeastern Wisconsin”
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665.
White pine trees in many counties in northeast and northcentral Wisconsin have developed rusty-colored wilting needles on outer branch tips scattered throughout the tree’s crown. These dead branch tips are associated with the feeding by white pine bast scale. The scale is a tiny insect that inserts its straw-like mouthpart into the twig to suck sap from the outer layers of phloem called bast. Damage has been observed on trees over 20 feet tall this year.
Branch tips on this white pine indicate a problem with bast scale and the disease Caliciopsis. Photo Credit: Wisconsin DNR
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov, 920-360-0665.
Pear slug sawflies (Caliroa cerasi) feed by scraping off the upper layer of the leaf, leaving the veins and the lower leaf surface. Severe defoliation has been observed and reported recently on crabapple, apple, mountain ash and serviceberry in Oneida, Forest and Oconto counties. The first generation occurs earlier in the summer, so the larvae and defoliation seen now are due to the second generation of the insect, which is larger than the first generation.
Pear slug sawfly larvae feed by scraping off the upper layers of the leaf. Photo Credit: Wisconsin DNR
Continue reading “Pear Slug Sawfly Defoliation: Treatment Tips”
Written By: Todd Lanigan, DNR Forest Health Specialist, Eau Claire, Todd.Lanigan@wisconsin.gov or 715-210-0150
As we head into September, fall webworm is starting to make its presence known. This native insect feeds on deciduous trees and shrubs and appears every year in yards and forests. Fall webworm forms loose webbing over branch tips and can completely cover a small tree with webbing. You will find both live and dead caterpillars, partially eaten leaves and frass (caterpillar poop) inside the webbing.
Fall webworm larvae inside webbing. Photo Credit: Wisconsin DNR
Written by: Linda Williams, DNR Forest Health Specialist, Woodruff, Linda.Williams@wisconsin.gov or 920-360-0665
Oak wilt symptoms are active right now, but so are several other oak issues that may be mistaken for oak wilt symptoms. Issues including Tubakia leaf spot, Botryosphaeria canker, kermes scale damage and mite damage are all causing problems and may be mistaken for oak wilt.
Oak Wilt Leaf Symptoms
Trees in the red oak group (those with points on their leaves) that became infected with oak wilt in the spring will suddenly start to drop their leaves in July and August. Trees that were infected later in the high-risk period (April 15 – July 15 in northern Wisconsin) may start to drop their leaves later, in September or even into October.
Leaves dropping from oak wilt trees can be fully green, tan or a water-soaked, greenish color away from the petiole (leaf stem). There will often be an area that is still green near the petiole, even though the leaf has fallen to the ground. Wilting leaves typically start near the top of the tree and progresses downwards.
Recommended control measures depend on if you have just one tree actively wilting (and no others have died in past years) or if you are dealing with established pockets that have been present for more than a year. Contact your regional forest health specialist to discuss these control options if you think you have oak wilt.
Leaves dropping from trees dying from oak wilt often are brown or water-soaked on the outer portions of the leaf with green still found near the base of the leaf. Photo Credit: Wisconsin DNR
Continue reading “Oak Leaves Turning Brown? There Are Several Reasons This Year.”
