This week we’ve begun to notice scale insects on several tree species including maple, ash and others.
Galls are created by many different arthropods (aphids, pysllids, mites, and eriophyid mites).
The historic floods of 2011 caused millions of dollars in damage and have imposed great hardship on those affected. These floods will negatively impact the trees and forests within these areas as well.
An aerial forest health survey of the Turtle Mountains by the North Dakota Forest Service, in cooperation with the US Forest Service, in June revealed an outbreak of large aspen tortrix (Choristoneura conflictana).
Many people have been concerned in the last few weeks regarding problems with apple trees – both edible apples and ornamental crabapples – especially from the western part of the state.
Two weeks ago, while teaching a workshop in Mandan, I observed some ash leaves that had a distorted, orange-colored growth. I’ve seen this before on ash leaves, petioles and sometimes even the twigs.
I’ve recently received several e-mails and phone calls regarding flooded trees. The questions concern the tolerance – or intolerance – of specific species to flooding. Utilizing information about the natural characteristics of a species and years of observational experience has allowed the development of some general categories regarding different species ability to withstand flooding.
The NDSU Plant Diagnostic Lab has received reports of brown rot, a disease that affects stone fruits, from Jim Walla, research tree pathologist (NDSU, Department of Plant Pathology). He noted, “I have seen the shoot blight phase in Washburn, Fargo, and West Fargo, ND and Bemidji, MN in the last week. There was a lot in some of the situations.”
A disease known as ash anthracnose is once again occurring on ash this year, as it does every year when the spring is cool and wet. Symptoms may include one or more of the following: premature leaf drop, black blotches on leaves causing leaf distortion, and small brown leaf spots in the middle of leaves.
Spruce trees often thrive in North Dakota under the right conditions. However, spruce trees, like all plants, are also susceptible to attack by pathogens and arthropods, and they can suffer from environmental stress and other ‘non-contagious’ factors. This year, cool spring temperatures and wet conditions favor development of needle cast diseases on spruce.
Tent caterpillars are active in southeastern North Dakota and western Minnesota. Homeowners, arborists, and park managers should be on the lookout for tent caterpillar activity.
Last weekend I was looking at apple trees near Detroit Lakes, Minnesota. On one tree I noticed tiny caterpillars swarming the tips of two branches (Figure 1). I also found egg masses on those same branches. The larvae are forest tent caterpillar (Malacosoma disstria).
As floodwaters are receding in most parts of the state, I’ve begun to receive some calls about flood damage to trees. Flooding during the dormant season has little effect on nearly all tree species. Even Colorado blue spruce, one of the most flood-sensitive species around, is little affected by flooding when the trees are dormant.