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Showing posts from July, 2016

Ground-nesting solitary wasps

Jeff Hahn, Extension Entomologist

There have been a lot of questions about solitary wasps lately. The most common questions have been about cicada killers (Sphecius speciosus) but residents have also seen great golden digger wasps (Sphex ichneumoneus), steel-blue cricket hunters (Chlorion aerarium), and sand wasps (Bembicini).

These wasps are generally large insects. Cicada killers range in size from 1 – 1 ½ inches with a stout body, black and reddish brown thorax, amber colored wings, reddish brown legs, and a black abdomen with yellow bands. Great golden digger wasps are about one inch in length, a more slender body with a black head and thorax covered with short golden hair with a reddish-orange and black abdomen and reddish-orange legs. They have smoky, dark colored wings. Steel-blue cricket hunters are also about one inch in size and relatively slender with iridescent dark blue bodies and wings. Sand wasps are smaller, most are close to ½ inch in length and are typically black a…

Resistance does not equal immunity

M. Grabowski, UMN Extension
Planting disease resistant plants is a great way to reduce disease problems in the garden without pesticides or the added time and labor needed for many cultural control practices. A disease resistant plant is able to defend itself against a plant pathogen. In some cases, a resistant plant is very successful in its defense and the gardener will not see any visible symptoms of disease. In other cases the plant may develop low levels of disease but is able to slow the pathogen and prevent severe damage from disease. These plants may be marketed as disease tolerant, moderately resistant, or resistant.
This year, weather conditions have been highly favorable for apple scab, a fungal disease of apple and crabapple trees. The apple scab fungus infects both leaves and fruit. Leaves have olive gray to black spots with a feathery undefined margin. Severely infected leaves turn yellow and fall off mid-summer. This year, due to weather conditions favorable for apple…

Clubroot of cabbage

New sightings of an old foe

M. Grabowski, UMN Extension

Club root is an unusual disease that results in swollen distorted roots of plants in the cabbage family. Although a few reports from the 1950’ and 60’s indicate that clubroot occurred in Minnesota at one time, this disease has not been common in recent years. To determine just how wide spread this disease is in Minnesota, the Minnesota Department of Agriculture has been looking for clubroot as part of their pathways survey for new and emerging invasive plant pests. The disease was identified in Ramsey county on edible mustard greens in the 2016 survey. 
What is clubroot? Club root is a plant disease caused by Plasmodiophora brassicae, an interesting microorganism that can only grow and reproduce within the roots of an infected plant. The clubroot pathogen infects members of the cabbage family including broccoli, cauliflower, radish, turnip, Brussels sprouts, rutabaga, and mustard greens. Although the pathogen can infect and survi…

Earwigs are temporary nuisance

Jeffrey Hahn, Extension Entomologist

Some people across the state have been encountering earwigs on their property this month. While most people recognized these insects, some were not sure what they had found. Earwigs are distinctive looking. They are about 5/8 inch long, beetle-like, with a flat, reddish brown body and very short wings. The feature that makes them easy to identify is the conspicuous pinchers (cerci) on the tip of their abdomen. 

Most questions deal with earwigs as nuisance invaders into homes and other buildings (some people also have problems with them in their gardens damaging plants).  Earwigs can enter buildings, sometimes in large numbers. Although they do not cause any actual damage, they are annoying and people want to control them. If you are having problems with earwigs in your homes, try these steps to minimize them.

You can reduce the number that is outside by using traps in the landscape. This could be with rolled up newspapers, cardboard tube…

MSHS hosts Will Steger to speak on global warming

Eyewitness to Global Warming
Thursday October 13, 7 to 8:30 p.m.
McNeely Hall, University of St. Thomas
2060 Summit Ave, St Paul.
$20 MN State Horticulture Society members, $25 nonmembers
Pre-registration required: https://www.northerngardener.org/ Tel: 651-643-3601 or 800-676-6747

Will Steger, world renowned polar explorer, educator, photographer, writer and lecturer will present a retrospective of a life in the arctic regions of the world. He has logged thousands of miles of travel by dogsled and has become a voice calling for understanding and the preservation of the arctic. Join us for his vivid account of the changes that he’s witnessed firsthand, caused by global warming pollutants, in Arctic regions over four decades of polar exploration. Steger shares stunning photographs from his expeditions along with compelling data and satellite imagery to document the deterioration in the polar ice caps.

While the issue is critical, and the presentation is dramatic, Steger’s message is o…

What to do about Japanese beetles

Jeffrey Hahn, Extension Entomologist

Japanese beetles have taken a lot of people by surprise by their abundance this summer, especially in the Twin Cities. They were numerous in the early 2010’s but a series of very dry summers reduced their populations. Japanese beetle eggs and recently hatched grubs do not survive very well in dry soils. However, we have had more normal precipitation the last few years which has allowed Japanese beetle numbers to rebound. Japanese beetles also started emerging sooner than expected this year as they were first sighted in late June. As a consequence, a lot of people are faced with damaged plants and questions about what they should do now.

One common question people ask is whether their tree will die because of Japanese beetle feeding. If the tree is healthy and mature, the tree is not going to die in one year from Japanese beetle feeding. Trees are quite resilient and can tolerate a lot of defoliation.

It is actually easy to kill a Japanes…

Dealing with Wind-Damaged Trees

Kathy Zuzek, Extension Educator

High straight-line winds and tornadoes have been all too common in Minnesota in June and July. If trees on your property were damaged during these storms, you may be wondering whether to salvage them and how to salvage them. Here are some considerations.

Safety always comes first!
As you start to assess tree damage, check for any downed power lines. Stay away from any power lines and call 911. Check tree canopies for hanging large limbs that may drop to cause injury. If they are present, call a professional arborist
Assess the damage to determine if your tree should be salvaged. Many factors play into this assessment:

Health of the tree prior to wind damage: If previous issues – unattractive habit, poor health from diseases, decay, insects, soil problems, salt damage, etc. – were already present before the wind damage, you may want to remove and replace your tree. Windthrown trees with roots ripped out of the ground: This usually occurs on larg…

From the DNR: Advice for dealing with storm damaged trees

Reprinted from the MN DNR - July 6, 2016


Cleanup following a storm can be an overwhelming task for homeowners. Knowing which trees to save and which to remove can impact safety and the survival of remaining trees, according to the Minnesota Department of Natural Resources.

DNR forestry outreach specialist Jennifer Teegarden offers the following tips.

Do:
Approach damaged trees with caution. Stay clear of downed wires and call 911.Carefully inspect standing trees for damage and deal with hazardous trees first. If possible, ask a forester or arborist for advice.Trees should be removed if more than 50 percent of the trunk or live branches in the crown are damaged, and if the tree is unnaturally leaning or roots are damaged.Watch for detached branches, loosely hanging branches and split or cracked trunks that can cause injury or further damage.Use proper pruning techniques to remove broken limbs by cutting just outside the branch collar, but limit pruning to making the tree safe. T…

Prevent blossom end rot

M. Grabowski,  UMN Extension
The current warm, dry weather combined with fast growing tomato plants creates ideal conditions for blossom end rot, a common problem in garden tomatoes. Fruit affected by blossom end rot have a tan to black, flat, leathery area on the bottom (blossom end) of the fruit. 
Fungal spores may be visible on the discolored area and rot may extend into the fruit, but this problem is not caused by a pathogen.  Blossom end rot is the result of a calcium deficiency in the growing tomato fruit. Any bacteria or fungi present are secondary organisms, taking advantage of the weakened fruit.
Although blossom end rot is caused by a calcium deficiency in the fruit, it does not mean that there is a lack of calcium in the soil. Often blossom end rot occurs as a result of several cultural or environmental factors that affect the plant’s ability to take up calcium. Fluctuations in soil moisture, heavy applications of nitrogen fertilizer, and injury to roots can all predispose…