In his biblical battle with Pharaoh, Moses neglected to rain down one of the worst plagues imaginable: If he had sent voles to attack the Egyptian ruler’s well-manicured lawn, Pharaoh would have been putty in his hands after seeing his turf in tatters.
Moses should have thrown in an infestation of crabgrass, just for good measure.
Voles and crabgrass are two lawn troubles that can reach epidemic proportions. I don’t recall the last time I saw so much vole damage in area lawns, at least in certain communities. When lawns are damaged, crabgrass often follows.
Voles, the brown-gray, short-tailed field mice, can indeed reach plague proportions. Washington State University reports that one pregnant female vole, with their quick generation rate, can produce more than 3,000 vole descendants in just four months.
Across the region, vole population explosions can be expected every three to five years. Vole damage to lawns becomes visible as snow melts, revealing a random network of trails and winding fluffs of dead grass where voles fed safely under the snow.
Why the increased damage this year? Uniformly deep snow cover gave voles free run of many yards, safe from hawks, owls and other predators. A wet autumn prevented many of us from giving our lawns the final short mowing that deters vole activity. And longer grass invited vole infestation.
Will vole damage kill the affected lawn patches? Not usually. Voles tend to chew the turf low, but the grass crowns, or growing points, are often left healthy and intact.
To remedy vole damage, wait until the lawn is dry and firm enough to walk without depressing soft soil, which can cause compaction and adversely affect the lawn. Then rake up the loose, dead grass laying on the surface.
Damaged areas will usually regrow as weather warms and lawns begin active growth. If by early May damaged areas aren’t showing signs of greening, grass seed can be broadcast and raked in.
To nurse damaged lawn areas back to health, apply lawn fertilizer in mid- to late May and provide good moisture with deep, but less frequent, watering to encourage deep, vigorous roots.
How do we prevent future vole damage? Traps baited with peanut butter and rolled oats or peanuts are effective. With pet and children safety in mind, baits can be placed in PVC pipes laid horizontally along the ground.
Instead of poison baits, many gardeners including the University of Kentucky report success using vole repellents with the active ingredient castor oil. Such repellents don’t kill the voles, but drive them from the area and should be applied shortly before winter’s first snowfall.
Applying granular lawn fertilizer in late fall may also be a deterrent.
Following winters with heavy snow, crabgrass is often more prevalent, as it tends to grow in lawn areas and boulevards damaged by snow removal equipment, road and sidewalk salt and voles.
Crabgrass is an annual weed, meaning it doesn’t regrow year to year from a root system that survives winter. Instead, new seedlings sprout each spring from seeds dropped in past years.
The name “crabgrass” is often mistakenly given to other wide-bladed, coarse, weedy grasses in lawns, which is unfortunate because products applied to control crabgrass won’t affect quackgrass and tall fescue, which are actually more prevalent than crabgrass.
Crabgrass, besides emerging later, tends to be yellow-green, lays flatter and less upright and produces a three-pronged seedhead, nicknamed a “goosefoot” seed structure. Because its seed doesn’t sprout in spring until soil temperatures warm to above 50 degrees, crabgrass doesn’t appear in lawns until late spring or early summer.
Other wide-bladed weedy grasses like quackgrass and tall fescue begin strong growth early from perennial root systems. If a weedy grass is observed vigorously growing in late April to mid-May, it’s likely not crabgrass.
To prevent crabgrass, apply a crabgrass pre-emergent herbicide to kill seeds as they sprout. Apply the granular product slightly before soil reaches 50 degrees at the 1-inch turf depth.
If applied too late, crabgrass will already have started growth. If applied too early, the products can lose effectiveness. Daily soil temperatures for North Dakota and northwestern Minnesota can be viewed at http://ndawn.ndsu.nodak.edu//soil-temps.html.
If crabgrass is detected after it’s already sprouted, there are several post-emergent crabgrass killers on the market. To be effective, they must be applied early in the season when crabgrass is very young and small. Often when crabgrass is noticed, it’s too late for effective application.
Crabgrass is more prevalent in lawns mowed short. Mowing at the recommended height of 3 inches tends to shade out and diminish the low-growing crabgrass.
Don Kinzler, a lifelong gardener, worked as an NDSU Extension horticulturist and owned Kinzler’s Greenhouse in Fargo. Readers can reach him at firstname.lastname@example.org.