Month: September 2018

Brown branch tips on jack pine

Posted on by jodieellis

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

After brushing away sawdust, exit/entrance holes, as tiny as the beetles themselves, become visible. A beetle is inside, peeking out. The marks at the bottom of the photo depict millimeters.

After brushing away sawdust, exit/entrance holes, as tiny as the beetles themselves, become visible. A beetle is inside, peeking out. The marks at the bottom of the photo depict millimeters.

Jack pine tip beetle (Conopthorus banksianae) is a tiny bark beetle that bores into the twig tips of pines. Damage from jack pine tip beetle was observed this summer on jack pine trees in Marinette, Vilas, and Lincoln counties and on white pine in Waupaca County. These beetles attack and kill the outer 4-6 inches of twigs, leaving hollow piths. The piths can be diagnostic in determining whether an insect or disease killed the branch tip. The damage, which may appear significant since the dead needles remain on the branch tip and there can be many dead branch tips on a single tree, is rarely severe enough to be detrimental to the tree; no control is recommended.

Jack pine tip beetles kill the outer few inches of twigs. The two yellow circles show where sawdust was pushed out of the twig by adult beetles. Photos: Linda Williams

Jack pine tip beetles kill the outer few inches of twigs. The two yellow circles show where sawdust was pushed out of the twig by adult beetles. Photos: Linda Williams

Oak leaves dropping (but not from oak wilt)

Posted on by jodieellis

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

Heavily-spotted oak leaves began to drop in early August. Spots appeared on both the front and back of leaves. Photo: Linda Williams

Heavily-spotted oak leaves began to drop in early August. Spots appeared on both the front and back of leaves. Photo: Linda Williams

Last year, Forest Health News published an article about oaks prematurely dropping leaves although they were not infected by the fungal pathogen Ceratocystis fagacearum, the cause of oak wilt disease. Oak trees infected with oak wilt disease in springtime rapidly wilt and drop green leaves in July or August. However, oak wilt disease is not the only reason oak trees prematurely drop leaves. Continue reading “Oak leaves dropping (but not from oak wilt)” →

Tree decline and mortality observed at many wet sites this summer

Posted on by jodieellis

By Bill McNee, DNR Forest Health Specialist, Oshkosh. bill.mcnee@wisconsin.gov; 920-360-0942

An aerial view of tree mortality in very wet areas. Photo: Bill McNee

An aerial view of tree mortality in very wet areas. Photo: Bill McNee

Site visits and aerial surveys conducted on trees in eastern Wisconsin by the Wisconsin DNR forest health team in July and August found multi-species decline and mortality common at many very wet sites. Continue reading “Tree decline and mortality observed at many wet sites this summer” →

Oak leaf fold galls and itch mites

Posted on by jodieellis

by Mike Hillstrom, forest health specialist (Fitchburg). Michael.Hillstrom@wisconsin.gov;
208-513-7690

Oak leaf fold galls on red oak leaves. Photo: Mike Hillstrom

Oak leaf fold galls on red oak leaves. Photo: Mike Hillstrom

Ethan Lee, parks supervisor for the City of Janesville, recently reported symptoms of oak leaf fold galls on an oak tree on the University of Wisconsin – Rock County campus. Oak leaf fold galls, caused by fly larvae, are generally harmless to trees. However, new information links oak leaf galls with a recent invasive mite from Europe, Pyemotes herfsi, commonly called the oak leaf itch mite. Although no evidence of itch mite was found on the affected red oak tree, more than 50% of the tree’s leaves contained leaf fold galls. Continue reading “Oak leaf fold galls and itch mites” →