NORTHERN "AG" EXPOSURE

by Mark Miller
Rolette County Extension Agent

Published in the Turtle Mountain Star May 14, 2001

"BUMPS" IN LAWNS

Clientele have complained about an abundance of "bumps" in their lawns this year. This is the result of wet summers producing a near ideal environment for nightcrawlers, or angle-worms. A few are good for the turfgrass environment, as they expertly recycle the nutrients through their digestive systems, and in doing
so, aerate the lawn. But, too much of a good thing can lead to problems - like the "bumps."

Taken to excess, which is happening in many cases, the topography of the lawn becomes so choppy that it literally becomes difficult to walk across the lawn or mow it properly. At this point, appropriate action is necessary, and I like to start with the minimum effort first, to see if that is effective enough.

The minimum effort would be to use a ballast roller - one that can be filled with water - and go back and forth across the lawn while the soil is still soft from spring rains or snowmelt. This, along with the arrival of warmer and drier weather, limits the worm activity, and usually, there are no more bumps to contend with. A step-up in effort would be to rent a power rake and run it over the lawn to a depth that would take off the surface bumps
resulting in a smoother lawn surface. The problem with this method is that it involves quite a bit of work, as using the power rake also pulls up considerable thatch which then must be cleaned up, taking considerably more time than the power raking.

A final step is to apply a insecticide to control grubs - everybody’s lawn has them - don’t worry. The product of choice is usually Sevin in the granular form or liquid and water it in. This step not only provides grub control, but also reduces the population of the worms by about 30%, which is usually tolerable enough to make the lawn surface acceptable. Subsequent insecticide applications would have similar reduction effects on the worms.

Black Knot

Now is a good time to scout Prunus species (chokecherry, plum) for the telltale sign of Black Knot. The fungus that causes this disease, Apiosporina morbosa, overwinters on twigs and branches as a mass of fungal fruiting structures that appears like a corky, swollen, and very black "knot" on the tree. These knots represent older infections and are easier to see in a tree before the leaves are fully out. New infections in a tree occur when spores produced in these knots in the spring are windblown or rainsplashed to wounds or new green growth; and they may occur in the same tree in or in previously healthy trees near by an infected tree. New infections in a tree will appear as olive-green  swellings on a branch, often swelling to the point of cracking the bark.There is no fungicide specifically for this disease. The only way to treat infections (both old and new) is to prune them out. Pruning cuts should be made 3-4 inches below the knot or swelling. Remove and destroy pruned branches so that spores from the knots cannot infect other trees. Lime sulfur may be used as a dormant spray after removal of the knots. This disease is relatively easy to control by removing knots as they appear, but wild plants or neighboring trees that are left unmanaged could continue to cause new infections. It is best to completely remove heavily infected trees. Look for resistant varieties of trees when replacing or planting new trees.

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