Author: colleenrobinson

Tiny spikey aphids on maple leaves

These spikey aphids, marked with blotches of brown and tan, are maple aphids.

These spikey aphids, marked with blotches of brown and tan, are maple aphids.

As I wandered through the woods one day in September, I noticed some spots on a sugar maple leaf. When I flipped it over, I discovered tiny black dots on the underside. They looked like tiny flea beetles to the naked eye (they were very tiny), but I didn’t know of any flea beetles on maple. After putting them under the microscope, I discovered that my tiny bugs weren’t beetles at all, they were maple aphids! They are tiny, dark, and spiky! Cute little suckers! They weren’t doing any significant damage to the leaves that I could tell, although all the leaves in that area had at least a few aphids on the underside. I’ll watch this area next year to see if I can find them again.

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

 

Jumping galls cause defoliation on white oaks

Brown areas on these white oak leaves were caused by a heavy infestation of jumping oak gall.

Brown areas on these white oak leaves were caused by a heavy infestation of jumping oak gall.

Jumping oak galls caused by tiny wasps form on the underside of white oak leaves.

Jumping oak galls caused by tiny wasps form on the underside of white oak leaves.

If you were in Waupaca County this summer, you probably noticed that large white oaks were looking pretty brown. They were being defoliated by a tiny gall wasp called jumping oak gall (Neuroterus saltatorius). The small galls, which develop around tiny larvae on the undersides of oak leaves, fall off the leaves in late summer. Continue reading “Jumping galls cause defoliation on white oaks”

Acorn weevils

The round hole at the edge of the fallen acorn’s cap was created when an acorn weevil larvae chewed its way out to find a place on the ground to overwinter.

The round hole at the edge of the fallen acorn’s cap was created when an acorn weevil larva chewed its way out to find a place on the ground to overwinter.

In some areas of Oconto County, a large percentage of the acorns on northern red oaks dropped early. Most of those acorns were infested with acorn weevil, although at the time they dropped they looked whole. After sitting for a few days, acorn weevil larvae started to emerge in hopes of burrowing into the soil to find a place to spend the winter.

Adult acorn weevils have very long narrow snouts and feed on acorns that are still attached to the tree. They chew a small hole in the acorn, then lay an egg (or several eggs) in the hole. They then plug the hole with fecal pellets, camouflaging their work. The eggs hatch and larvae begin feeding within the acorns. In the fall, the acorn drops to the ground and the larvae chew their way out, after which they bore into the soil to spend the winter underground. There is a different species of acorn weevil that feeds on acorns that have already fallen.

Even though the acorns looked perfect when they dropped, the insects had already been at work on them. Floating acorns in water will allow you to sort out the ones that are damaged, even though you may not see damage on the outside.

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

 

Venturia shoot blight in northern Wisconsin

Sapling aspen with withered, drooping shoot killed by Venturia shoot blight.

Venturia shoot blighted aspen shoot. Photo by Gerred Carothers.

Venturia shoot blight has been observed throughout northern Wisconsin this summer. Venturia shoot blight is one of the most common fungal diseases of aspen and is favored by cool, wet spring weather. 

The pathogen rapidly kills expanding terminal and lateral shoots, causing shoots to wither and droop. It also causes leaf necrosis, appearing as black circles of varying sizes, necrotic curling at the margins, or complete leaf death. The disease is most damaging to seedling and sapling aspen, where it can reduce height growth and cause temporary stem crooking as lateral shoots are released and compete for apical dominance.  Disease control is unnecessary in a forest setting.

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

White spotted sawyer

Our native pine sawyer has a “spot” between the elytra (yellow arrow) that Asian longhorned beetle does not have. They also will appear dusty or pitted.

Our native pine sawyer has a “spot” between the elytra (yellow arrow) that Asian longhorned beetle does not have. They also will appear dusty or pitted.

White spotted sawyer, sometimes called Pine Sawyer, is a native longhorn beetle. It is often mistaken for Asian Longhorned Beetle (ALB). How can you tell the difference between our native beetle and ALB?  First of all, size: ALB is a big burly beetle, while our native sawyer beetle looks slim in comparison. Second, ALB has a very smooth shiny appearance with distinct white spots on black wing covers, whereas our native sawyer beetle will appear pitted or dusty, and the white spots may be less distinct or absent. Finally, our native beetle will have a nice white dot “between its shoulders” where the wing covers meet, and ALB does not have this. 

Adult pine sawyer beetles feed on the bark of twigs which can cause branch tip mortality.

Adult pine sawyer beetles feed on the bark of twigs which can cause branch tip mortality.

Pine sawyer larvae develop in weakened, recently dead, or recently harvested conifers. Larvae first feed in the phloem layer then progress to inner wood. They will pupate within the tree and adults will chew their way out leaving large round exit holes. Adults feed on needles and the bark of twigs. Areas this year which will attract white spotted sawyers include areas of storm damaged pine, and areas of conifer decline due to high water levels, as well as any other areas where conifers are stressed. 

If you find a beetle and are unsure whether it’s ALB or our native sawyer, please take some photos to send for identification. 

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

Poplar vagabond aphid

Poplar vagabond aphid feeding on the buds of aspen or cottonwood cause the tree to form a fleshy, hollow gall around the insects.

Poplar vagabond aphid feeding on the buds of aspen or cottonwood cause the tree to form a fleshy, hollow gall around the insects.

Galls caused by poplar vagabond aphid form at the ends of aspen and cottonwood branches. The galls are caused by aphids feeding at the tips of twigs. This feeding causes the tree to grow an elaborate structure that the aphids can live inside. One of the galls in the photo is broken open so you can see the aphids inside. This damage does not usually kill the tree, but reduces branch growth because the formation kills the terminal buds. The aphids feed during the spring and early summer within the gall, and then leave to feed on an unknown second host plant. When the aphids leave the gall it will turn brown and woody, and will remain on the tree for several years before weathering off. Adult aphids return later in the fall and lay eggs on the woody gall or in crevices in the bark. Eggs will hatch the following spring and repeat the process. For control, prune the galls prior to egg hatch early in the spring. Because the aphids return to the same trees with the original galls it is common to see a single tree heavily infested while a nearby tree will have no galls at all. I have always seen this problem in trees that are open grown, either along the edge of a stand, along a roadway or fence row, or in a yard. I’m not sure how much of a problem it is in the interior of a stand.

Poplar vagabond aphids, which are covered in a white waxy material, are protected inside the large hollow galls formed by the tree. They suck the trees’ sap.

Poplar vagabond aphids, which are covered in a white waxy material, are protected inside the large hollow galls formed by the tree. They suck the trees’ sap.

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

Oak leaf tier and oak leaf roller

Oak leaf rollers and oak leaf tiers fold over or roll leaves which protect them from predators.

Oak leaf rollers and oak leaf tiers fold over or roll leaves which protect them from predators.

Last month I reported on a location in Marinette where oak leaf tier and oak leaf roller were defoliating oak. Since then I had a report of this same combination of pests causing defoliation near Rhinelander. Typically this defoliation is not severe, but when the leaves are rolled up or folded in half it can make it look like the defoliation is more severe.

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

Of historical interest, 25 years ago (1992) and 50 years ago (1967)

25 years ago – 1992

  • Frost – On June 20, the temperature dropped to 25°F in many locations throughout Wisconsin. This caused injury to several tree species including: black ash, balsam fir, red pine, northern pin oak, and spruce in northwestern Wisconsin, and red pine and northern pin oak in Oneida and Vilas counties, north-central Wisconsin. Severe damage to new shoots of white spruce and balsam fir Christmas trees occurred in Taylor, Langlade, Oneida, Lincoln and Oconto counties. Injury to hardwoods often caused defoliation. Conifers affected by the frost had curled and crooked shoots that eventually died. In Vilas County, most of the injured red pine and oak did not reflush. In Eau Claire County, western Wisconsin, spruce, black walnut and several species of pine were injured. Seedling and sapling-size red pine were injured in Clark and Chippewa counties. Balsam fir, white spruce and white pine Christmas trees in northern Wisconsin were also injured by the early summer frost. Severe loss of new growth.
  • White Grubs – Phyllophaga In Marinette County, (Section 16, T30N, R20E) high numbers of white grub larvae were observed in plantings of ash, maple, oak and walnut. These trees were being planted in alfalfa. In Portage county, (NWNW, Section 4, T21N, R7E) all larval stages were present at the time of planting red pine in sod on a 13 acre area. In Washburn County, heavy mortality occurred in a red pine planting due to white grub feeding. Heavy numbers of grubs were reported in new tree plantations in Door, Kewaunee and Manitowoc counties. The adult stage of white grubs, the May and June beetles, were observed in large numbers at night in urban areas in Oconto, Marinette and Marathon counties. Progeny of these beetles could produce heavy damage to nearby young tree plantings in the next two years.

50 years ago – 1967

  • Pissodes approximatus Damage by this weevil was associated with red pine plantings on poor sites or frost pockets in the Northeast Area. The most severe infestations were found in Marinette, Oneida and Vilas counties during surveys for Scleroderris lagerbergii (Gremman).
  • White-Pine Weevil, Pissodes strobi (Peck). Populations were generally low in all areas of the state. About 10% of the leaders were infested in a small white pine planting in Washburn County (Section 8, T41N, Rl3W). A few terminals of Norway spruce and Scotch pine Christmas trees were infested in Langlade and Oconto county plantations, and survival of weevils was poor in the east central counties. Heaviest infestations were reported from the West Central Area where 20% to 30% of the current leaders were infested in a few white pine plantations and averaged 10% to 15%.  Although no white pine weevil control projects were conducted in the West Central Area this year, additional insecticide test plots were established on Black River State Forest plantations. Further investigation of a reported white pine weevil attack on red pine in Trempealeau County reported in 1966 (p. 7, Annual Report 1966) appears more likely to have been the work of Pissodes approximatus Hopkins. Large numbers of these weevils were found on stumps of red pine, cut for Christmas in the fall of 1966, when the site was re-examined in the spring of 1967. Older stumps showed evidence of previous attacks typical of P. approximatus.  Evaluation of evidence available indicated that terminal attacks in 1966 occurred because breeding P. approximatus populations exceeded available stump areas and overflowed to the stems and terminals of living trees.

Content taken from the Forest Pest Conditions for Wisconsin Annual Reports from 1967 and 1992.

Gypsy moth adults appearing now

Female gypsy moth lays an egg mass.

Female gypsy moth lays an egg mass.

As of mid-July, DNR forest health staff have received reports of adult gypsy moths present as far north as Burnett County. The brown-shelled pupae and white female moths can be crushed with a stick. The remaining caterpillars will also pupate soon, and where the caterpillars are a problem, they can be crushed, drowned in soapy water, or sprayed with insecticide or insecticidal soap. Continue reading “Gypsy moth adults appearing now”

Emerald ash borer new finds in Wisconsin

EAB emergence map as of July 10, 2017. Tan colors in the north are approaching peak emergence, light green is peak emergence, and olive is past peak emergence.

EAB emergence map as of July 10, 2017. Tan colors in the north are approaching peak emergence, light green is peak emergence, and olive is past peak emergence.

Much of Wisconsin has reached peak emergence of emerald ash borer adults.

EAB continues to be found in new areas. Wisconsin tracks EAB at the municipality or township level. Quarantine counties are shown in tan and infested areas are shown in green on the EAB Detections and Quarantine map below.

New county quarantines

  • none

New finds in counties already quarantined

  • Crawford County – city of Prairie de Chein
  • Grant/Iowa County — city of Muscoda
  • Milwaukee County — village of Whitefish Bay
  • Outagamie County — town of Grand Chute
  • Sauk County – village of West Baraboo
  • Waukesha County — village of Merton
EAB quarantine map. Counties shaded in tan are quarantined for EAB, and include much of the southern half of Wisconsin, as well as other counties. Areas shaded in green are the townships and municipalities where EAB has actually been identified, and show that not all counties that are quarantined are fully infested.

EAB quarantine map. Counties shaded in tan are quarantined for EAB, green areas are townships and municipalities where EAB has actually been identified.

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