QUESTION: We have several very large anthills in our yard. We are worried that they may invade our house and cause structural damage. How do we get rid of them?

ANSWER: Thatching ants are sometimes referred to as “mound” ants because they construct mounds from small sticks, grass stems, leaves and pine and fir needles. They may also nest in decayed logs. Under most circumstances, thatching ants should be considered beneficial, since they are fierce predators of other insects. However, when they occur in lawns, rockeries, picnic areas and other locations of human habitation, they can become a severe annoyance.

Thatching ants are often injurious to seedling trees or plants near their nests and they have been known to damage the buds of apple, pear and plum in the spring. Although you may occasionally find a thatching ant in your home, they do not cause structural damage. Physical contact with them is unpleasant, since they can bite quite hard and usually spray the area they have bitten with formic acid to produce a painful sensation or even blistering if the skin is not washed.

An interesting phenomenon demonstrated by thatching ants, as well as other ants, is the habit of “herding” and maintaining aphid colonies on trees, shrubbery and weeds. This occasionally leads to an aphid problem because while keeping the aphids for their sweet honeydew, they protect the aphids against natural control organisms such as wasps and lady beetles. However, they deter other more serious plant pests, so even in heavy aphid infestations they are still beneficial.

Most species of thatching ants are bi-colored red and black. A few are all black. They are medium to large ants averaging 3/16 to 5/16 inch long, with a notch or depression on the top of the thorax when viewed from the side. This feature alone is perhaps the best way to distinguish them from carpenter ants which have a smoothly rounded thorax. This diagnostic tool works only when comparing workers of either species. Their reproductive swarms (winged males and queens leaving the colony) occur in late summer to early fall.

Be sure these ants are indeed a threat if you find them residing on your property since they are beneficial. If they are a pest and you have to get rid of them, WSU currently recommends using insecticide products containing the active ingredient cyfluthrin or cypermethrin. The entire surface of the nest should be treated as well as the subterranean portion. One method is to penetrate the nest by digging deeply and stirring the nest contents with a shovel while pouring the recommended dosage of insecticide into the nest and surrounding area.

QUESTION: Now that our strawberries have finished fruiting, is there anything we should do to insure a good crop next year?

ANSWER: You can maintain strawberry plantings for several fruiting seasons if you properly manage and renovate them after harvest. Renovation is not recommended for day-neutrals or ever-bearers however.

After the crop has been harvested, mow the foliage to about two inches above the top of the crowns. You can use hedge clippers or a rotary lawn mower with the blade raised high. Be careful not to damage the crown of the plant. Remove and plant debris and bury it.

Narrow the rows to a strip 8 to 10 inches wide using a rototiller, or hoeing no deeper than 1 to 2 inches. Thin out old and weak plants. The best plant density is about five to six plants per square foot of row.

Keep the planting weed free by cultivating. Loose soil also promotes rooting of runners. Remove all excess runners as they form. All excess runners should be removed by Sept. 1 since they won’t have time to root and form flower buds for next season’s crop.

Strawberries should be fertilized now. For plants set out this last spring, apply 4 to 6 ounces of ammonium nitrate or 12 to 18 ounces of 10-10-10 per 25 feet of row. Brush fertilizer off the leaves to avoid leaf burn. For plants in the second year of growth, increase the application rate to 6 to 8 ounces of ammonium nitrate or 18 to 24 ounces of 10-10-10 per 25 feet of row. The more favorable the growing conditions for strawberries in August and September, the larger the fruit will be next spring. Just a week without water can stress the plants resulting in smaller spring berries.