Most Wasps are Beneficial

Wasps Should be Respected, But Most Are Beneficial

Allan Robinson: Ask a Master Gardener

Tuesday Sept. 12, 2017

Q: I have noticed a lot of wasps buzzing around and landing in my yard lately. What is going on, and should I be concerned? Beth H., Tulsa

A: There are several types of wasps that we encounter throughout the year. The more popular ones are red wasps and yellow jackets, both of which are quite aggressive toward humans and produce a painful sting. But there are a couple of other less common wasps that are much more beneficial, as they tend to attack other pests rather than humans.

First, digger wasps come in many sizes and colors including yellow/black-striped, black, blue, brown, white/orange or yellow. In general, they will use the same area of the yard over and over until their population is eradicated. While they are not aggressive and do not defend their nests, stay clear of them because their sting and venom may cause an unexpected allergic reaction. The first year these pests start to nest, they usually go unnoticed but then grow exponentially each year thereafter. Working in the same area, most prefer to dig in bare ground between grass and plants, through cement mortar joints and even under walkways. Most are predatory feeders, foraging for grubs, small flying insects and ground-dwelling pests. Once food is found, it is stung to death, brought back to the nest and buried. Eggs will be laid on it so that hatching larva will have a ready food supply.

They are generally beneficial and do not need to be controlled. But if you choose to do so, control is fast, easy and effective once the general nest site has been found, using an insecticide dust labeled for wasps. It generally works as a desiccant and will dehydrate all active wasp stages in just a few minutes.

Secondly, the cicada killer is a large black, orange and yellow wasp that prefers to nest in bare areas around homes and in flower beds feeding on flower nectar. The females catch and paralyze cicadas, place them in a burrow in the soil and lay an egg on them to provide a fresh food source for their larva. Because they specialize on one type of prey, they tend to become more numerous as cicada activity increases in late summer and fall.

In spite of its formidable size and burrowing habit, this wasp is unusually docile and harmless. Although capable of inflicting a painful sting, the female cicada killer wasp is usually difficult to provoke. Mating males are aggressive and are more easily disturbed but cannot sting. An unsightly mound of soil surrounds the burrow of each cicada killer as they prefer to nest in areas of sparse vegetation.

Garden tips

·        Now is a good time to submit a soil sample to the OSU Extension office for testing. Do this before reseeding fescue or creating a garden bed this fall. Call the Master Gardener office at 918-746-3701 for instructions.

·        Tall fescue should be mowed at 3 inches and up to 3½ inches if it grows under heavier shade. Don’t fertilize fescue lawns until it cools in September, then fertilize again in November.