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Showing posts from May, 2014

Phomopsis Spruce Decline Found in Minnesota

M. Grabowski, UMN Extension

M. Grabowski, UMN Extension
Photo 1: Needle loss from Phomopsis spruce decline

A new form of an old disease has been identified in Minnesota. The fungal pathogen Phomopsis sp. has long been known to cause shoot blight on spruce trees in nurseries and tree farms. The same pathogen has now been found causing cankers, needle loss, branch death and in severe cases tree death of mature spruce trees in the landscape. This disease has been named Phomopsis spruce decline. The first case of Phomopsis spruce decline in Minnesota was identified by the University of Minnesota Plant Diagnostic Clinic this spring (May 2014).

In nurseries and on tree farms, Phomopsis shoot blight causes young needles and shoots to turn brown and curl downward. In some cases dark resinous cankers formed on young stems but damage does not commonly extend beyond that years new growth. Although this disease causes damage in nurseries and on tree farms, it has not been a common problem in land…

Insects on the Loose: What's in Your Garden?

Jeffrey Hahn, Extension Entomologist

Jeff Hahn, Univ. of Minnesota Extension
Photo 1: Crucifer flea beetle and its feeding damage.

There are a variety of insects that are active now and could be in your garden. When you are inspecting your garden for pests, keep an eye out for these insects.

Flea beetles are very small, 1/16th - 1/8th inch long. They are usually dark colored although some can have red or yellow on them. An easy way to identify flea beetles is that they can jump. Flea beetles attack a variety of vegetables, including beans, broccoli, cabbage, potatoes, squash, and radish. Flea beetles chew shallow pits and small holes into leaves. This feeding can be particularly damaging to seedlings and cole crops. Go here for more information on flea beetles, including management.

Jeff Hahn, Univ. of Minnesota Extension
Photo 2: Colorado potato beetle larvae on eggplant.

Colorado potato beetles overwinter as adults and start to lay eggs in the spring. The adults are broadly ov…

European Pine Sawflies are Active Now

Jeffrey Hahn, Extension Entomologist

Do you have a pine, especially a mugo, Austrian, jack, or red pine, in your yard? Now is a good time to check it for European pine sawfly activity. These insects are caterpillar-like with black heads and gray green bodies and dark green stripes (when they are young the dark green stripes may not be visible). While they are relatively small now, they eventually will grow to be about one inch in length.

Jeff Hahn, Univ. of Minnesota Extension
Photo 1: Young European pine sawflies feeding gregariously.

Look closely for these insects as they are hard to see because they blend in so well with the needles. An advantage when inspecting for them is that they are gregarious, meaning that they occur in nonsocial groups, so there can be many feeding on a given branch (which easier to find than individual sawflies).

Your first clue that European pine sawflies are present could also be finding defoliation on branches. As feeding becomes more severe, it is …

Hardy Kiwi for the Home Garden

Written by Laura Marrinan, University of Minnesota student
HORT 1003 Horticulture for the Home Garden, Spring 2014

Kiwi is a tasty treat that is typically thought of as a tropical or warm climate fruit. However, Minnesota gardeners can get in on the action as well. The practice of growing kiwi in Minnesota has been around since University of Minnesota's Professor Samuel Green began growing cold-hardy varieties in 1892.

According to Drs. James Luby and Emily Hoover from the University of Minnesota's Department of Horticultural Science, kiwifruit in Minnesota needs to be one of the following species: Actindia kolomikta 'Arctic Beauty', A. arguta 'Bower Berry', or A. polygama 'Silver Vine' (2). These cold hardy kiwifruits don't look like the fruits you typically pick up at the grocery store. They are hairless, skinless and generally have a much higher sugar content. These fruits are also usually about the size of a grape. A. kolomikta can be grown succ…

Use caution when reading new bee and pesticide research

Jeffrey Hahn, Extension Entomologist

New research about bees and pesticides from Harvard University was recently published by Lu et al. in the Bulletin of Insectology. This research examined honey bee colonies that were fed high fructose corn syrup (HFCS) contaminated with two common neonicotinoids (imidacloprid or clothianidin) during late summer and then observed in the following spring. Both the control colonies and the insecticide exposed colonies did well going into fall. While both sets of colonies then declined, the control colony numbers rebounded while the insecticide exposed colonies suffered large losses. The authors' conclusions are that insecticides are the leading explanation for colony collapse disorder (CCD).

While this seems like compelling information on the surface, there are a number of concerns and flaws about this research that should cause readers to examine it very cautiously. The biggest concern for many is the concentration of insecticides which was …

Gooey Orange Fungi on Junipers

M.Grabowski, UMN Extension
Photo 1: Cedar apple rust galls on juniper

M. Grabowski, UMN Extension Educator

This time of year, several species of fungi from the genera Gymnosporangium are producing bright orange gelatinous spore producing structures on the branches of Junipers. The brilliant orange color of these fungi gives them their common name: Rust. Cedar apple rust is perhaps the most well known of the Gymnosporangium rust fungi, but here in Minnesota four different species can be found infecting junipers. Hawthorn rust, quince rust and juniper broom rust all produce similar gelatinous bright orange spore producing structures on junipers. Although these fungi can be startling to see, they rarely cause significant damage to the junipers. Spores produced in these orange gelatinous structures will not reinfect the juniper. Instead spores are carried by wind and rain to infect nearby trees and shrubs in the Rosaceae family. Each of the four Gymnosporangium rust fungi infect different …

Andrenid Bees Are Active Now

Jeffrey Hahn, Extension Entomologist

Jeffrey Hahn, University of Minnesota Extension
Photo 1: Andrenid bee searching for its nest

Andrenid bees are common in gardens and yards now. Common species are about ½ inch long with a yellow hairy thorax and a shiny black abdomen. Andrenid bees usually overwinter as pupae and emerge as soon as the weather becomes warm. Adults are relatively short-lived, surviving about a month.

Unlike honey bees and bumble bees which are social insects, andrenid bees are solitary with just one bee living in an individual burrow. However, they are also gregarious meaning that many nests can live close together. Andrenid bees like to nest in dry, sunny sites that contain sparse vegetation. People can become concerned when they see dozens of bees flying around a small area. Fortunately, these bees are very docile and nonaggressive and stings are very rare. People who are allergic to honey bee stings are not necessarily allergic to andrenid bees.

Tolerate a…

Pictorial Ode to the Dandelion - With Special Recognition of our Pollinators

Karl Foord, Extension Educator - Horticulture

Karl Foord
Photo 1: Honey bee on dandelion

Karl Foord
Photo 2: Honey bee on Dandelion

Karl Foord
Photo 3: Split and curled stigmas of dandelion

Karl Foord
Photo 4: Dandelion stigmas & honey bee corbicula

Karl Foord
Photo 5: Native Mining bee (Andrena spp.)

Karl Foord
Photo 6: putative - Plasterer Bee (Colletes spp.)

Karl Foord
Photo 7: Native Small Carpenter Bee (Male) (Ceratina spp.)

For years I used to fight the dandelions in my lawn. I used herbicides and a small trowel. It was a bit of a losing battle as there is a third of an acre of school property adjacent to mine where dandelions are not controlled. This being separate from the nearby sports fields where the weeds are controlled. Imagine the number of dandelion seeds that blew into my yard each year.

As I have become more aware of pollinators, I have come to accept and perhaps even embrace the "noble" dandelion. Dandelions are an important source of pollen and necta…

Pollination in the Vegetable Garden - Cucurbits

Karl Foord, Extension Educator - Horticulture

Karl Foord
Exhibit 1: Cucumber flowers

Exhibit 2: Cucumber flowers
Exhibit 3: Male squash bees in squash flower
Exhibit 4: Male squash bees in squash flower

The plant family Cucurbitaceae contains a number of our favorite garden plants. This includes: cucumbers, watermelon, muskmelon, pumpkins, squash, and gourds. This group is particularly fascinating in terms of its flower morphology. These plants are called monoecious because they have separate male and female flowers on the same plant (Exhibit 1). These flowers are most easily recognized by the shape of the stem below the flower. The stem below the female flower looks like a smaller version of the final fruit (Exhibit 2), and the stem below the male flower remains a single slender stalk.

Cucurbit flowers are short lived flowers that open a few hours after sunrise and are often closed by midday or early afternoon. Both male pollen viability and fe…

Be on the watch for ticks!

Jeffrey Hahn, Extension Entomologist

Jeffrey Hahn, University of Minnesota
Photo 1: Adult female blacklegged tick. This tick is a potential vector of Lyme disease.
As the amount of time we spend outside increases, be aware that ticks are also active now. There are two common species of ticks in Minnesota, the blacklegged tick (also known as deer tick) and the American dog tick (also called wood tick). While the American dog tick is mostly a nuisance, the blacklegged tick can potentially vector diseases to people, especially Lyme disease.

Take precautions when outdoors, especially in areas where ticks are known to occur. Use repellents, especially DEET to protect against ticks. Also check yourself over carefully after being outdoors for any ticks that may have found you. Remember that a tick has to be biting to be able to transmit a disease; if it is unattached it cannot vector a disease

Jeffrey Hahn, University of Minnesota
Photo 2: Adult female American dog tick. This tick is not an i…

Tough native perennials for wet sites

Mary Meyer, Extension Horticulturist

Mary Meyer
Figure 1: Ostrich fern background, maidenhair fern foreground

Mary Meyer
Figure 2: Gooseneck loosestrife has almost comical flowers

Mary Meyer
Figure 3: Northern sea oats' flowers are pendulous and easily self-seed

Mary Meyer
Figure 4: From left 'Northwind', Warrior', 'Thundercloud', and Cloud 9' Switchgrass

My backyard is at the bottom of a slope that easily floods when we have a 'rain event' of a few inches. The water can even stand in this area for 12-24 hours - fatal for some plants. To make matters worse, the soil is sandy, so when rain is scarce, the soil is bone dry- again fatal again for some plants. I have three tough perennials that have lived well in this area, all of which are shade tolerant: ostrich fern, Canada anemone and gooseneck loosestrife. All three of these plants have aggressive rhizomes that have helped them to live in this difficult site. I believe all of these plants will grow …

Pollination in the Vegetable Garden - Tomatoes

Karl Foord, Extension Educator - Horticulture
Figure 1: Tomato flower

Insect Pollination of Cultivated Crop Plants, S.E. McGregor, 1976 Figure 2: Tomato flower structure Photo 1: Bumble bee on tomato flower

Temperature Sensitivity of Flowers

Tomatoes are heat loving plants that require a long frost-free season and full sun. The flowers have optimal temperature ranges and are sensitive to extremes. The flowers will abort and drop from the plant when extremes are experienced. In early spring when night temperatures drop below 55 degrees F, the blossoms can drop. In summer when daytime temperatures exceed 90 degrees F or when nighttime temperatures remain above 75 degrees F, the flowers can abort. In addition drought stress can also cause flower abortion.

The Tomato Flower

The tomato flower is hermaphroditic containing both male and female organs (Figure 1). The flower is self-fertile but not self-pollinating. The tomato anthers fuse to form a tube that surr…