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Sunday, August 18, 2019  Spokane, Washington  Est. May 19, 1883
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Pesky aphids disappear within days

Aphid larvae occupy the underside of a leaf.
 (File/ / The Spokesman-Review)
Aphid larvae occupy the underside of a leaf. (File/ / The Spokesman-Review)
The Spokesman-Review

Is there anything to help reduce the clusters of small gnats that hover over the lawn?

Joan Hall, Suncrest

The “gnats” that appear about this time of year are actually an aphid that goes by several names: conifer root aphid, blue ash aphid, Oregon ash aphid or smoky-winged ash aphid. What you see in the fall is the winged females moving back to their host plant. The good news is under normal circumstances they are not harmful to most garden plants; they are just an annoyance flying around. Scientists believe that the aphid alternates between ash and conifer trees through the year. In the spring the eggs laid the previous fall on ash trees hatch into wingless females that feed on the sap of the leaves. The all-female colony keeps growing without mating until a critical mass is reached. When this happens, winged females are produced and these females fly to the secondary host plant, members of the true fir family for the summer. On the firs, they burrow to the roots and feed on the sap rarely causing much of a problem for the tree. In the early fall male aphids are produced and they mate with the winged females. The winged females then return to the ash trees to begin the cycle again the next spring. What you are seeing in the fall is this migration of winged females back to the ash trees. There is nothing you can treat them with and since they are around for only a few days, just ignore them.

Crowd out crabgrass

How do I get rid of bentgrass and crabgrass in my lawn?

Martha Brandle, Suncrest

Removing bentgrass and crabgrass from lawns is a challenge. Because they are both grasses, they aren’t affected by broadleaf herbicides you use to kill dandelions and the like. They, like the weeds, move into lawns that are not healthy. Bentgrass appears as a flat fairly fine-textured mat with more of a blue-green color than the Kentucky bluegrass. The only way to remove it is to dig out the patches or kill them with Roundup and then reseed the areas. To improve the chances of keeping it at bay, make sure your lawn is as healthy as possible by aerating it regularly, treating for weeds, applying a good quality fertilizer regularly and watering deeply and for longer periods (30-45 minutes every two to three days) especially during hot weather. A bluegrass lawn should get an inch to and inch and half of water a week.

Because crabgrass is an annual, controlling the seeds will help reduce it. Apply a pre-emergent crabgrass control in mid-to late March into April before the seeds have a chance to sprout. The chemical creates a barrier on the soil surface that stops the seedlings. If you miss the window in the spring, herbicides such as Roundup can be used on the worst spots, but it will kill everything. As with bentgrass, a healthy thick lawn is still the best defense against a weed invasion.

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