January 2012 Archives
Jeffrey Hahn, Asst. Extension Entomologist
Many people are familiar with boxelder bugs, multicolored Asian lady beetles, cluster flies, and other nuisance insects that can be found in homes. But occasionally less familiar insects are found inside. On one such occasion, a homeowner reported finding a lot of wasps nesting in her home. In fact, she had identified them from the internet as Cerceris fumipennis.
This wasp species is a solitary wasp in the family Crabronidae. It has gained fame recently as a method for detecting emerald ash borers (EAB). This native ground nesting wasp hunts buprestid beetles, including EAB, which it paralyzes and carries back to its nest to feed its larvae. Location of a nest with captured EAB indicates the presence of EAB in the area. More information on Cerceris wasps can be found here.
This wasp's status is unclear in Minnesota and nests have not been discovered so far. Ultimately, you would not find this wasp indoors in the winter as they do not overwinter as adults.
A sample of insects was requested from the homeowner with the expectation being that paper wasp queens, Polistes spp., which overwinter gregariously in homes would be found. It was therefore quite a surprise to find that not only were the insects not paper wasps, but were instead flies. A run through the diagnostic keys identified them as soldier flies (family Stratiomyidae). These flies are typically black and yellow insects that can appear to be wasp- or bee-like.
A run up to the museum, and with the help of John Luhman, the soldier flies were identified specifically as Ptecticus trivittatus. This is a species that is particularly associated with composts. The conclusion was that these soldier flies most likely originated from a compost nearby in the neighborhood and they found their way to this home in which to overwinter. There had a mild stretch of weather when the homeowner first noticed the flies which would have been sufficient to cause overwintering insects to become active. There are other flies, such as cluster flies and face flies, that overwinter in structures so this made sense.
The homeowner kept insisting that these insects were nesting in her home. She was continuing to see consistent numbers of them; at one point she was seeing as many as 20 - 30 at a time. She eventually asked whether these flies could be associated with composts. They had brought a worm compost box indoors so the worms would not freeze. It was in a plastic tub with a cover but there were small air holes. She wondered whether the soldier flies could be in the compost. That of course was the source of the problem and why they were seeing such persistent numbers. The adult flies would be short-lived but to put an end to the problem it was important to erect some kind of screening so the flies could not escape.
A good example of how the identity and biology of an insect has a direct impact on its management.
Kathy Zuzek, UMN Extension Educator, Horticulture
An enormous interest for most gardeners during our long winter is the search for new cultivars that can be added to next year's garden. But is new always good? The answer to that question depends on whether new cultivars have been shown to perform well in Minnesota gardens before their introduction into garden centers. Horticultural professionals should provide customers with the best performing plant selections for Minnesota's difficult climate. But the current trend in horticulture is to move new plants onto the market in the shortest possible time frame, creating a rapid process of both cultivar introduction and elimination in the market.
This creates several problems for gardeners interested in sustainable gardening and in planting cultivars known to have long-term landscape value. New cultivars are now introduced to Minnesota gardeners from breeding and evaluation programs around the world. When new cultivars are rushed to the market, there is often no time for the evaluation of the plant's performance in Upper Midwest gardens prior to introduction. Purchasing and planting new un-trialed cultivars among annuals or herbaceous perennials may be an acceptable risk for gardeners to take. These plants are relatively inexpensive and establish and grow to maturity quickly. It is much riskier in terms of money, labor, and time invested if gardeners purchase and grow un-trialed shrubs and especially trees that take decades to reach maturity.
If newly introduced cultivars are displaced quickly by even newer cultivars, there is also little time to evaluate their long-term potential in the landscape between their introduction and their elimination from nursery catalogs. This sets up a situation where newer cultivars prove to be a good performer in our Minnesota gardens but by the time this fact is recognized, the plant has already been removed from nursery catalogs.
The emphasis on new cultivars may also result in the elimination from the nursery trade of much older cultivars as they are removed to make room for new cultivars in a nursery's production schedule. The introduction of new cultivars that have been shown to be improvements over older cultivars is an exciting event for gardeners, especially for northern gardeners who have a smaller pool of plants to choose from than southern gardeners. But what if older cultivars that have proven their long-term landscape value over decades of time are replaced with un-trialed cultivars that fall short of the mark?
As wise gardeners, we can help solve these problems by asking "What's good?" rather than "What's new?" Finding information on plant performance in Minnesota or the Upper Midwest can be a tough go though. Here are some suggestions:
Take advantage of the information available from plant evaluation programs. Plant evaluation programs for the Upper Midwest are few and far between but here are a few examples:
The goal of this program is to determine, through scientific evaluation, which annuals, perennials, vines, shrubs, and trees are superior for gardens in the Upper Midwest. Information on the program and the 35 Plant Evaluation Notes published to date can be found here.
Look for information on cultivar introductions and evaluations from universities and their affiliated Extension services in the Upper Midwest.
Visit the Minnesota Landscape Arboretum grounds and website regularly to view plants that are hardy enough to grow in Zone 4 and sometimes Zone 3. The arboretum is home to thousands of ornamental cultivars of annuals, herbaceous perennials, ornamental shrubs and trees, and vegetable and fruit cultivars.
A visit to this webpage can provide information on wholesale and retail nurseries that provide mail order service and carry your plant of interest. The webpage also has links to and lists of other websites, books, and magazines carrying information about and photos of your plant of interest.