Red Pine Pocket Decline Trial at LaCrosse County Forest

By Jim Dalton, Fourth Quarter 2002

Red Pine Pocket Decline has invaded Hoeth Forest in LaCrosse County where pockets of mysteriously dying trees have been observed since the 1980’s. The fungi responsible for much of the damage has been recently identified as Leptographium spp, that causes a root disease and increases susceptibility to various insects that ultimately kill the trees. The fungi travel along the surfaces of underground roots and move from one tree to another where the roots come into contact beneath the soil surface. The pattern of mortality usually occurs in a quietly expanding circle or pocket as the years go by.

The LaCrosse County Land Conservation Department, in cooperation with WDNR, funded a trial in the 400 acre Hoeth Forest to test a technique designed to stop the underground spread of Leptographium root disease on 14 pockets of dead and dying red pines, ranging in size from 1½ acres to ¼ acre. A rented trenching machine was operated by a LaCrosse Co. highway equipment operator to sever the root grafts at the edge of a buffer zone 30-40 ft. from the last symptomatic tree, measured from the outer edge of the pocket towards healthy trees. The trench lines ware flagged around the pockets by foresters Chris Widstrand, Pat Murphy, Todd Lanigan, Kathy Nelson, Scott Laurie and Jim Dalton. The trial will be monitored for the next several years by Todd Lanigan, West Central Region Forest Pest Specialist, who will mark the trees on the outer edges of the trench lines with numbered aluminum tags.

It became readily apparent that the trenching machine could not negotiate the underbrush, saplings and stumps from previous thinnings in the 45 to 50 year old plantations. Bulldozers (JD 450) were requested and graciously sent from DNR ranger stations at Black River Falls and Tomah to clear the path ahead of the trenching machine and back fill the trench with soil brought up and deposited off to the side. The trenching machine operator was then able to use the machine to its capabilities, maneuvering around one pocket and on to the next. Forestry technicians Dewayne Mashin and Garry Rapala from Tomah and John Larkin and Scott Loveland from Black River Falls expertly roughed out paths along the flagged lines with their dozers and filled in the trenches to cover up the freshly exposed roots.

The trenching machine traveled slowly, but placed a 5” to 6” wide trench 3½ ft. deep into the ground. Tree roots were severed down to the bottom of the trench, but were much more abundant in the upper 1’ to 2’. Severed roots were still in close proximity to each other, but not connected or necessarily touching. Soil was returned into the trench as soon as possible, in a matter of minutes and not hours. Stumps presented the most frustration to the operator; lifting up and moving over was the best way to deal with them.

Costs for the project included trenching machine rental…$750.00; DNR bulldozer use and mileage…$800.00; 30 hours labor for the machine operator and county truck & trailer…$1,021.00. It was necessary for a forester to be on-site during the 4-day project (Oct. 28-31) to coordinate and direct machinery to sites, evaluate the work and identify problems and solutions as the project progressed. Some back filling of trenches with hand tools was also needed and became part of the final check of each treatment site. Contact Jim Dalton at 608-785-9007 for information about the project.