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Showing posts from June, 2015

Extension publications new & updated

Eight-legged friends or foes?

Lindsey Christianson, Recent M.S. Entomology Graduate

Spiders are common in and around homes this time of year. And while many may be fuzzy, not many people would consider spiders a warm and friendly type of fuzzy. However, in most cases, these creatures fall into the friendly category. Spiders eat insects and other arthropod pests and are considered beneficial. Some spiders inadvertently end up indoors and can be a nuisance by their presence. Two spiders in particular that have been noticeable have been the dark fishing spider and the bold jumper.

The most common species of fishing spider in Minnesota is the dark fishing spider Dolomedes tenebrosus. Fishing spiders are some of Minnesota’s largest and most conspicuous spiders, with bodies that can be up to an inch long. Fishing spiders have two rows of four eyes, and long “sprawling” legs. Dark fishing spiders tend to have brown and black banded legs and chevron markings on the abdomen. They are often found on tree trunks, b…

Spotted wing Drosophila is now active

The following was slightly edited from an article recently written by Eric Burkness and Suzanne Burkness of the University of Minnesota, Department of Entomology.

The first adult spotted wing Drosophila (SWD) fly of the 2015 growing season was detected in a trap collected on June 23, 2015, in Rosemount, MN (Dakota Co.). Based on this detection, home gardeners with soft-skinned fruit such as June bearing strawberries, summer bearing (floricane) raspberries, and blueberries should begin monitoring their fields, if they haven’t already.

Most June bearing strawberries in Minnesota should be nearing the end of fruiting but summer bearing raspberries and most blueberry varieties should have green fruit and potentially low levels of ripening fruit. Fall bearing (primocane) raspberries and blackberries should not be flowering yet, but these crops will be at increased risk later in the season as the populations of SWD should continue to increase.
The first detection of SWD consisted of a s…

Say blister beetle

Jeffrey Hahn, Extension Entomologist

There have been a number of reports of green beetles with orange legs in flower gardens. These beetles are ant-like, have soft wing covers and are about ¾ inch in length. This is the Say blister beetle Lytta sayi. They have been found feeding on a variety of flower blossoms, including roses, peonies, irises, and lupines. When they are abundant, they can cause serious damage to plants.

All blister beetles secrete a defensive oil called cantharidin which can be very irritating and can raise blisters when skin is exposed to it. Fortunately, the Say blister beetle generally does not have a high enough concentration of cantharidin to cause severe problems to people.

If Say blister beetles are in your garden, there are several options for their management. Physical removal is a good management method. If there is concern about exposure to cantharidin and blisters, wear gloves to be on the safe side. If you are interested in a low impact insect…

Euonymus caterpillars: Are they in your yard?

Jeffrey Hahn, Extension Entomologist

Unknown caterpillars were found defoliating a euonymus shrub in Ramsey County recently. They were identified as Euonymus caterpillars, Yponomeuta cagnagella. The larvae were up to ¾ inch long, cream to yellowish colored with rows of black spots. These caterpillars also produce silk and can envelop branches, even entire plants, with their webbing. They should not be confused with the feeding and webbing of eastern tent caterpillars. Eastern tent caterpillars primarily attack flowering fruit trees, such as crab apples, cherries, and plums and create their tents in the forks of branches.

Euonymus caterpillars are European in origin. They were first found in North America in 1967. They have been reported sporadically in the Midwest, e.g. in Wisconsin, Illinois, Iowa, and Michigan. This appears to be the first time euonymus caterpillars have been reported in Minnesota, although it is possible that they have been seen before, but not reported to…

Ants in turf

Jeffrey Hahn, Extension Entomologist

Ants are one of the most common insects we encounter. Many species nest in the soil and can cause problems in lawns and other turf areas. There are two common types of ants that residents may encounter: field ants and cornfield ants.

Field ants are about 1/4 inch long and black or red and black. Their nests are mound-like and can cover a fairly large area in the ground, up to two feet in diameter. Field ant can be found in healthy, vigorously growing turf.

Residents can confuse field ants with carpenter ants. While these two ants are somewhat similar in size and color, carpenter ants do not nest in the soil but prefer to nest in moisture-damaged wood. The mounds created by field ants can also lead some people to believe that they are fire ants. However, fire ants only occur in the southeastern area of the U.S.; the closest fire ants to Minnesota are in southern Tennessee. While field ants can bite, it is not as painful as the stings o…

Imported cabbageworms are active now

Jeffrey Hahn, Extension Entomologist

There have been sightings recently of imported cabbageworms on crucifer (cole) crops.  This includes cabbage, broccoli, cauliflower, radish,  kale, and turnips.  Watch for holes in the leaves to indicate that they are feeding.  Also watch for medium sized white butterflies in your garden.  This in the adult stage of this pest.  If they are present, watch your crucifers closely for evidence of the caterpillars.


Early detection is important; the sooner you can find imported cabbageworms, the sooner you can take steps to minimize their damage.  Be sure to look on both sides of the leaves when inspecting plants.  Handpicking can be effective management, especially if your garden is not too large.  Bacillus thuringiensis and spinosad are low impact insecticides effective against these caterpillars.  Effective, residual insecticides include permethrin and lambda cyhalothrin.

For more information, see Caterpillar pests of cole crops in home gardens.

Check your garden for Colorado potato beetles

Jeffrey Hahn, Extension Entomologist

Are you growing potatoes, eggplants, peppers, or tomatoes in your garden.  If so, now is a good time to check for the presence of Colorado potato beetles.  Both the adults and larvae feed on these plants.  Feeding can be severe and can impact production of your vegetables.  These beetles have one to two generations a year and are seen from spring until harvest.

There are several options for managing Colorado potato beetles.  Handpicking is an option as long as your garden is not too large and you have the time to remove them on a regularly basis.  Spinosad is a low impact insecticide that is effective against Colorado potato beetles and importantly there is no known resistance by these beetles to it.

Traditional insecticides such as carbaryl (Sevin) and permethrin are generally not effective as most populations of Colorado potato beetles have developed resistance to it.  It is possible that some relatively newer pyrethroids, such as lambda cyhaloth…

Four-lined plant bugs are out!

Jeffrey Hahn, Extension Entomologist

Many gardeners have been encountering four-lined plant bugs on a wide variety of plants, especially perennials, such as chrysanthemums, Chinese lantern, Russian sage, mint, and wild geranium.  They can also feed on shrubs, fruits, and vegetables.  Immature four-lined plant bugs are bright red when they first hatch and gradually become darker as the black wing pads become larger.  They eventually turn into yellowish greenish adults with four black stripes.

These insects use their piercing-sucking mouthparts to create small, sunken, dark-colored spots on the leaves.  Heavily damaged leaves can become browned and misshapen.  Despite the appearance, the injury is primarily cosmetic and the health of the plants is not typically impacted.  It is possible that when plants are severely attacked a few years in a row, that their health can be affected.

There are several options for treating four-lined plant bugs.  Insecticidal soap can be effective on nymp…

Anthracnose arrives with spring rains

M. Grabowski, UMN Extension

Fall leaves, brown leaf spots, and twisted distorted leaves are all symptoms that gardeners may be seeing on shade trees like oak, ash and maple. These symptoms are caused by anthracnose, a fungal disease that affects young growing leaves during wet weather. No management is needed as anthracnose is not a major threat to the health of the tree. As leaves mature they become resistant to the fungal pathogens that cause anthracnose. Warm dry summer weather will help to further reduce disease problems.