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Thursday, October 27, 2016

What to do about fruit flies

Jeffrey Hahn, Extension Entomologist

Fruit flies, Drosophila spp., can be a common insect in homes during fall. Also called vinegar or pomace flies, they are small, about 1/8th inch long with a brownish body and a dark colored abdomen. Fruit flies typically have red eyes which are a good feature to help distinguish them
Fruit flies are about 1/8th inch long and usually have red eyes.
Photo: Jeff Hahn, U of M Extension
between other indoors flies (however this color fades once the flies are dead).

Be careful as there are other small-sized flies, such as fungus gnats, moth flies, and humpbacked flies, that could be confused with fruit flies. There is even a couple of species of fruit flies with dark colored eyes that are a little larger than an average fruit fly. The control varies depending on what the type of fly is found so it is important to verify the insect you are finding in your home.

Fruit flies are associated with fermenting, moist, relatively undisturbed organic material. This is often due to overripe and decaying fruits and vegetables but can also be in a variety of other sources, such as soft drink, wine, and beer residue in unclean containers (and have been sitting around for a while) and trash containers with wet garbage that are not cleaned regularly.

These flies can also be found in unusual, unexpected sites. In one case they were found infesting an osage orange that had been set out to control spiders (which by the way does not work) and forgotten about. As it became soft and started to decay, it attracted fruit flies which infested it.

The best control of these flies is to find the source of the infestation and remove it. While this is straight forward, it can be easier said than done. You often have to be a detective to locate the problem as it may not be immediately obvious what they are infesting. Particularly examine areas where fruit flies are found but keep in mind that the infestation source may not always be near where fruit flies are found; it could even be in a different room. Keep inspecting after you find the breeding site as there may be more than one infestation source.

It may be tempting to kill the adults by spraying, swatting or trapping them but this rarely eliminates them. As long as a food sources remains, fruit flies can reproduce faster than you kill the adults. It is very difficult, if not impossible, to get ahead of the problem and eliminate all of the flies by directing control at the adults.

Friday, October 14, 2016

2017 Minnesota Gardening Calendar available

2017 Minnesota Gardening Calendar
30 pages of tips, photos, guidelines for MN gardeners
The 2017 Minnesota Gardening Calendar is a great resource for the gardeners in your life! It is a terrific holiday gift, housewarming gift (especially new homeowners who have never owned a yard), host gift, or just a thanks-for-watching-my-plants gift. Whatever your reason, this is the time to get your copies. Buy online or in person from selected University of Minnesota bookstores and the Minnesota Landscape Arboretum giftshop. Written by Extension Horticulturists. the 2017 Minnesota Gardening Calendar features monthly lawn care and gardening. Featured writer and turf extension Educator Sam Bauer contributes an informative article called Water Saving Strategies for Home Lawns and provides guidance on reducing our water use without sacrificing a great looking lawn. And then there are the photos! Each month features a timely photo that reminds us Minnesota landscapes are beautiful at any time of the year!
Timely photos each month
Timely gardening tips each month

Articles by Extension experts
Important guides for successful gardens

There's still time for dormant seeding - a good option for good lawn next spring

“I know I missed the best time for seeding my lawn which is mid-August to mid-September. Can I still seed even though it’s October and temperatures have been mild?” According to turfgrass Extension educator, Sam Bauer, “Just wait, dormant seeding in November will be your best option." True temperatures are warm during the month of October, and a homeowner could get some seed germination before winter snows, but this is touch0and-go. Bauer recommends saving your time and money and wait dormant seed in mid- to end-November. Read more ....

Thursday, September 29, 2016

Temperature Control in a Bumble Bee Nest

Karl Foord - Extension Educator, Horticulture

The previous post linked to a video showing a new born bumble bee. The following video is of the same nest but involves a different observation.

To view and photograph the nest I had to pull away the straw covering the nest. This exposed the nest to the direct sun and evidently increased the temperature of the nest beyond the acceptable range of the worker bees. In this video a worker bumble bee uses her wings to fan and cool the nest. The wings are moving so fast that they practically disappear, a little like airplane propellers.

To give a sense of perspective, the engine on a propeller driven airplane rotates some 43 times in one second. I timed the wing speed of bumble bees in one of my videos to 172 beats per second. No wonder the wings are impossible to see when filmed at regular speed. In the second half of the video I have slowed the speed of the action by a factor of 4 and it is still difficult to see the wings moving. You can see the wings just when they begin to move and when they stop moving. Enjoy the blur as another one of the fascinating things one can find in the garden.

Observe a Newborn Bumble Bee

Karl Foord Extension Educator, Horticulture

Some of the folks maintaining the Display Garden located on the St. Paul Campus discovered a Two Spotted Bumble Bee nest (Bombus bimaculatus). On June 5th I found the nest with the help of Julie Weisenhorn and took some video.

This is a young nest and relatively early in the season, so the worker bumble bees are significantly smaller than the Queen. This bee is identified in the video.

In addition a new born bumble bee appears from under the top end of the nest. This individual can be recognized by the white hair covering its body. Later the hair in some places will turn golden and in other places black. Other evidence that this is a new born come from the shape of its wings. Notice that the wings on this bee are flat and curve around the base of the abdomen. The bee will proceed to pump hemolymph (the fluid of their circulatory system) into the veins of the wings. This will will expand and straighten the wings after which they will dry and become hardened. Only after this will the wings become functional and enable the bee to fly.

Tuesday, September 20, 2016

Remove white mold infected annuals

M. Grabowski, UMN Extension Educator
Zinnias killed by white mold. M. Grabowski, UMN Extension

 White mold is a plant disease caused by the fungus, Sclerotinia sclerotiorum. This pathogen is capable of infecting over 400 plant species. Flower garden favorites like zinnia, petunia, salvia, and snap dragon are highly susceptible to white mold. In the vegetable garden, tomatoes, green beans, lettuce and cabbage can all be infected. Removal of infected plants is a critical management strategy for white mold. The pathogen can survive up to 8 years in specialized resting structures produced on infected plant material. 

Tomato stem with fluffy white fungal growth on the outside and
black sclerotia on the inside.  M. Grabowski, UMN Extension

Plants infected with white mold often wilt and die. The lower stems of these plants will be tan and dry. If the humidity is high, white fluffy clumps of fungal growth may be seen on the stems. Gardeners may also see small, rough, black structures that look like seeds or peppercorns forming along stems or inside of them. These are special resting structures, called sclerotia that are created by the fungus. Sclerotia can survive in the soil for up to 8 years. Each year the sclerotia produce tiny mushroom like structures that releases spores and starts new infections. 

Gardeners that are seeing white mold in their gardens now, need to remove infected plants before sclerotia are dropped into the soil. The entire plant should be removed as soon as possible. Infected plants can be composted if the pile heats up to a minimum temperature of 148 F. Alternatively infected plants can be deeply buried (6-12 inches below ground) in an area of the yard that will not be used for flowers or vegetables in the future like a mulched are around trees or shrubs. 

Petunia bed with multiple plants killed by
white mold.  M. Grabowski, UMN Extension

Lower stems of white mold infected petunias are clearly tan and dry.
M. Grabowski, UMN Extension 

Friday, September 16, 2016

Orb weaving spiders

Jeffrey Hahn, Extension Entomologist

Spiders are particularly common around homes and gardens during late summer and fall. Undoubtedly the most common types are the orb weaving spiders (family Araneidae). These spiders can be recognized from the large, circular, flat webs that they construct. They vary in size although many are moderate to large sized.  Some species are very colorful. They typically have round, plump abdomens with relatively short stout legs.
Black and yellow argiope spider, a
common spider during late summer and
fall.  Photo: Jeff Hahn, U of M Extension

There are two common groups of orb weaving spiders that people commonly encountered, spiders in the genus Argiope and those belonging to the genus Araneus.

Argiope spiders, also referred to garden spiders are large with a body length up to one inch long, and conspicuously colored yellow and black or silver, yellow and black. Their abdomen is more oval compared to most orb weavers.

Araneus species are typically moderate sized.  They can be either brownish or colored brightly, especially orange or yellow.  Their abdomens are generally more round, sometimes even somewhat triangular.  Common species include barn (orbweaver) spider, cross orbweaver, shamrock orbweaver, and marbled orbweaver. Click here to learn about other Araneus orb weaving spiders.

Fortunately despite their appearance, orb weaving spiders are not aggressive or dangerous to people and no control is necessary. In fact, orb weaving spiders are fascinating to observe and people should consider themselves fortunate to have an orb weaving spider in their garden or yard to watch.
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