Forest Insect and Disease Newsletter

On the Horizonphoto: EAB beetle

New firewood regulation

The weather is warming up and that brings thoughts of finally being able to get outdoors without a parka, boots and frostbite. What better way of enjoying Minnesota's beautiful and varied landscape than camping at one of our 72 state parks or or enjoying a day outing at one of our 58 state forests and campgrounds or day-use areas? Of course, what is an outing without a campfire, but where are you going to get wood for a fire? Yes, many of us have firewood stacked up out back of the house or know someone that has wood, but the MNDNR requires you to leave your wood at home and there is a very good reason—insect and disease pests capable of destroying many of our forest tree species can catch a free ride right into the middle of our beautiful state recreational areas.

The MNDNR has an established program that allows sellers of firewood to become approved firewood vendors. Buying firewood from approved vendors means you are using locally grown wood and the risk of transporting tree pests long distances is reduced.

Changes in firewood regulations: Starting August 1, DNR-approved vendors can sell firewood for use in any DNR-administered location within 50 miles of where the wood was cut. This is a change in the regulation which previously allowed a 100 mile radius; the new 50-mile distance was put into effect by a new DNR Commissioner's Order in March of this year. The idea is simple—the use of locally grown wood keeps any pests in the area, not quickly spreading them throughout the state.

When purchasing wood from an approved vendor, be sure to keep the proof of purchase to show to DNR personnel at recreation areas. Remember that even though the state statute is in effect only for wood used on DNR lands, the transport of firewood long distances for use on private land has the same potential to spread destructive pests.

It's easy to find approved vendors and check out other information regarding firewood restrictions. Visit the DNR website for a list of approved vendors for each state facility - and don't forget to bring the fixings for lots of s'mores.

image goes here

Forest tent caterpillar- 2011 Update


Frest test caterpillars life cycle

photo:Forest tent caterpillars egg mass on twig

Forest tent caterpillars egg mass on twig

photo: Forest tent caterpillar

Forest tent caterpillars

photo:Forest tent caterpillars pupa inside its cocoon

Forest tent caterpillars pupa inside its cocoon

photo: Forest tent caterpillars as a moth

Forest tent caterpillars as a adult moth

Forest tent caterpillar populations are expected to expand somewhat from last year but the insect is not expected to be a problem in the northern third of the state. Last year, just over 70,000 acres were defoliated, primarily in the middle one-third of Minnesota in a crescent that extended from south of Mille Lacs Lake through St. Cloud to Wilmar and up through Detroit Lakes (see map below). There were also a few isolated areas of defoliation in Hubbard, Cass and Crow Wing Counties. Acres of defoliation are likely to increase in this same area with possible expansion to the north and east, but a full-fledged outbreak is not expected.

In the past two years, people have reported finding a caterpillar or two in their yards in scattered locations in northern Minnesota. This suggests there may be small, dispersed areas of defoliation seen in the northern part of the state but the population is not predicted to cause millions of acres of defoliation.

Egg mass surveys were conducted from the southern Aitkin County border up through Grand Rapids and along the Iron Range through Hibbing. The only egg mass found in this survey was on the east side of Mille Lacs Lake. The last outbreak of forest tent caterpillar peaked in Minnesota in 2001 and 2002 when over seven million acres of defoliation occurred in each year.

Forest tent caterpillars overwinter in egg masses of 100 to 350 in a band that encircles small twigs in the crowns of trees. When aspen trees start to leaf out, tiny caterpillars hatch out and begin to feed on the new leaves. Even though they are called tent caterpillars, they do not produce a tent. Peak defoliation occurs in mid to late June when the caterpillars grow to one and one quarter to one and a half inches long. They then spin a cocoon, pupate and emerge as moths in late June to early July. The female moths lay eggs that overwinter to hatch the next spring.

graphic: Forest tent caterpillar defoliation in 2010 Minnesota map

Forest tent carterpillar defoliation map- 2010

Thousand Canker Disease Survey in Southern Minnesota

Eastern black walnut trees are locally common in southern Minnesota, but planted as ornamentals outside their range in the western US. This summer, the DNR Division of Forestry will participate in a three-week survey of Minnesota black walnut trees at risk to a disease new to the eastern US known as thousand cankers disease (TCD). The disease was first found killing plantings of eastern black walnut in the western US in the 1990's, but last year the disease was discovered within the native range of black walnut in Knoxville, Tennessee. It is thought that the disease has been in the Knoxville area for 15-20 years.

The disease erupts when the tiny walnut twig beetle, native to Arizona, California and New Mexico, bores into black walnut trees and transmits a fungus that causes numerous small cankers in the phloem. The cankers enlarge, grow together, and restrict food transport within the tree, ultimately killing it.

The USDA Forest Service has requested the assistance of the Minnesota and Iowa Departments of Natural Resources in looking for black walnut trees with symptoms of the disease. The two states' Departments of Agriculture will also participate in the survey. The agencies hope to locate areas with significant concentrations of black walnut in several different settings, including riparian forests, urban areas, and industrial settings where there is interstate transport of black walnut. If trees suspected to have TCD are found, samples will be tested for TCD by the Forest Service Northern Research Station in St. Paul. Other project objectives include responding to reports of TCD from plantation owners, city foresters and other tree care professionals, and assistance with outreach sessions or detection training as planned by Forest Service staff.