Current articles from the University of Minnesota Extension Yard and Garden news and MN DNR seem valuable to pass along.
Removing lawn clippings is often thought to reduce the number of spring weeds. Research does not bear this out. Most of those weeds are from seed already present, sometimes from many years ago. Weed seeds respond to moisture and light. Removing clippings actually lets more light reach the surface, allowing existing seed to germinate.
Removing clippings also removes an important source of nitrogen for a lawn. Grass clippings add as much as 2 pounds of nitrogen every thousand square feet that generates a greener, more drought tolerant grass. Green clippings decompose rapidly, and do not contribute to thatch build up.
The obvious sign of a lawn mowed too short are brown patches this time of year. Late July and early August have been very dry here and unless you water, grass is now stressed to the limit. Leave it as long as possible. Mowing so short that you cut into the sheaf of the grass plant reduces its ability to nourish the roots.
Jeff Hahn, Minnesota Extension entomologist, has written an article noting that viburnum leaf beetles are being found in Minnesota. The larvae of the beetle feed on members of the viburnum family such as high-bush cranberry, arrowwood, and others. Visit the Yard and Garden website at extension.umn.edu to see photos and read the complete articles.
Those of you with bur oak trees will want to read an Aug. 8 article published by the Minnesota Department of Natural Resources <https://content.govdelivery.com/accounts/MNDNR/bulletins/257214f> describes bur oak blight symptoms and causes. In trees showing browning of the lower and inner leaves and spreading downward, the likely cause is bur oak blight. Trees with this disease may last many more years, unlike the rapid death of oaks with oak wilt, a more southern disease.
There is good news for those of you with jack pines in your yard or woods. The numbers of jack pine budworm crashed last year and have not begin to recover. Budworms like to feed on the new growth of needles and leave conspicuous webs and cause defoliation in high infestations. The USDA Forest Service has a good brochure that is available online describing the pest and management.
If you have paper birch, be on the lookout for birch leaf miner damage. The feeding of this insect leaves the leaf with transparent yellow areas. A tree will survive with extensive leaf miner damage if you take steps to make sure the tree is well watered throughout the summer. Since birch are an understory tree, the heat and drought they experience in an open yard or with rock placed around the tree is especially hard on them.
Good news for trees in this part of Minnesota is that no gypsy moths have been found here. Gypsy moth caterpillars will quickly defoliate a wide variety of trees, they are an extremely serious pest. They have been found in northeast Minnesota; avoid moving firewood anywhere around the state and check your gear after camping.
It is a good time to walk around and look carefully at your trees and the plants in your garden to recognize these pests and diseases. Both the U of MN and the DNR have both printed and on-line brochures to help you recognize pests and diseases of gardens, lawns, and trees.
Click on “Yard and Garden at the University of Minnesota Extension website for gardening information. Local Master Gardeners will respond to your questions via Voice Mail. Call 218-444-7916, leaving your name, number and question. Our Facebook page may also be of help to you: <https://www.facebook.com/Beltramicountymastergardeners/>.