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Showing posts from September, 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 …

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 …

Remove white mold infected annuals

M. Grabowski, UMN Extension Educator

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. 


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 …

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.

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 general…

EAB found in Duluth again

Jeffrey Hahn, Extension Entomologist

(The following information is modified from a Minnesota Department of Agriculture news release).

The Minnesota Department of Agriculture (MDA) is issuing an emergency quarantine for the southeastern portion of St. Louis County (see below map) after confirming a second emerald ash borer (EAB) detection within the city of Duluth. EAB was found in Superior, Wisconsin across Lake Superior from Duluth in August, 2013. It was first found in Duluth in October, 2015 on Park Pointe; the quarantine at that time was restricted to only this island.

The emergency EAB quarantine limits the movement of firewood and ash material out of the quarantined area of the county. The quarantined area now runs from MN Highway 33/US Highway 53 on the west to the Lake County border on the east. The northern border of the quarantine runs from US Highway 53 along Three Lakes Road (County Highway 49) east to the intersection of Vermilion Trail. It then continues along t…

EAB is found in Dodge County

Jeffrey Hahn, Extension

(The following information is modified from a Minnesota Department of Agriculture news release).

The Minnesota Department of Agriculture (MDA) has placed Dodge County under an emergency quarantine after emerald ash borer (EAB) was found in the city of Kasson last week. Kasson is about 13 miles west of the nearest known EAB infestation in Rochester (Olmstead County). The EAB was found in a United States Department of Agriculture (USDA) trap. MDA staff has since conducted a search of the area and discovered an EAB infested tree.

Because this is the first time EAB has been identified in Dodge County, the MDA is enacting an emergency quarantine to limit the movement of firewood and ash material out of the county. This will reduce the risk of further spreading the tree-killing insect. Currently 12 other Minnesota counties and Park Point in the city of Duluth are under quarantine to prevent the spread of the emerald ash borer.

The biggest risk of spreading EAB co…

Turf War: Overwatering our lawns is sucking up our water supply (Star Tribune)

Sam Bauer, Extension Educator
Over the weekend the Star Tribune ran an article discussing lawn watering and its impacts on our pocketbooks and our water supply.  The author, Hannah Covington, spent a day with our Extension Turfgrass Science Team as we conducted irrigation audits for several homeowners in Apple Valley.  This study is sponsored by the Metropolitan Council with the ultimate goal of reducing the amount of water being applied to our home landscapes, much of which is wasted water.  With this study, we are conducting a survey (which many of you filled out- thank you!) and we are also selecting residents in the 7-county Metro Area to have their home irrigation systems being audited.  The audits entail checking irrigation system components, conducting performance testing and making recommendations on how to save water through basic irrigation system adjustments.  You can read more about how to properly conduct an audit of your irrigation system in the previous Yard and Garden…

Water Wisely: Auditing Home Lawn Irrigation Systems

Sam Bauer, Extension Educator

Auditing irrigation systems is an important practice for maximizing water use efficiency in the home landscape.  Audits entail checking for irrigation uniformity and converting minutes of irrigation to a depth in inches of water applied.   A full irrigation audit should be conducted at least every three years, although proper irrigation requires more frequent monitoring of irrigation system components to ensure that everything is working properly.  Broken sprinkler heads and irrigation of impervious surfaces are very common issues that we observe and these must be repaired in a timely manner. 
Basic Irrigation Auditing Procedure
Step 1: System inspection Run each irrigation zone.  Look for broken sprinklers, low water pressure and arcs or angles of water spray that are distributing water where it is not needed (i.e. on streets or driveways).  Replace sprinklers, correct water pressure issues, and make adjustments to the water distribution so your system is…