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Tuesday, October 13, 2015

What's That Fungus?

Have you ever wondered what mushrooms are growing in your yard or wanted to learn more about the fungi you saw on trees, logs or growing through the leaves last time you hiked in the woods? A great resource for those who would like to learn more about the fungi in our world has been created by the University of Minnesota Mycology Club. Free downloadable flash cards contain color photos, scientific and common names, habitat and descriptions of common Minnesota fungi. Check them out today!

Bacterial Canker of Tomato found in MN Gardens

M. Grabowski, UMN Extension

Bacterial Canker of Tomato - Heinz USA ,
Bacterial canker of tomato caused by the bacteria Clavibacter michiganensis sbsp. michiganensis (CMM), is an  emerging plant disease in Minnesota. Although this disease occurs regularly in other states, the first reported incidence of bacterial canker in Minnesota occurred just a few years ago. Bacterial canker can be a serious problem for vegetable farmers, especially tomato growers that use high tunnels or greenhouses to grow their crop. In addition, the bacteria can infect tomato seed under the seed coat and result in spread of the pathogen to new areas.

To determine just how wide spread this disease is in Minnesota, the Minnesota Department of Agriculture has been looking for CMM as part of their pathways survey for new and emerging invasive plant pests. In 2015, the MDA surveyed 90 community gardens, small vegetable farms and community supported agriculture farms. The pathogen that causes bacterial canker was found in Blue Earth, Carver, Dakota, Hennepin, Nicollet, Ramsey, Todd, Waseca and Washington counties.

What do plants infected with bacterial canker look like and how do I distinguish this disease from other common tomato disease problems?
The best way to determine if a plant is infected with bacterial canker is to send a sample to the UMN Plant Disease Clinic. The symptoms of the disease can vary greatly and it is easy to confuse symptoms of this disease with other problems.

M.A. Hansen, VA Polytech. Institute,
Infected seedlings may have few or no symptoms or may completely wilt and die. Older infected tomato plants have tan to yellow patches between veins on leaves and dark sunken streaks along leaf veins and petioles. If tomato leaves become infected from the edge of the leaf, the leaf edge turns dark brown and a yellow border often separates the killed leaf tissue from healthy green tissue.  Infected peppers have yellowing of the leaves that fades gradually into the green healthy tissue.

In severely infected tomatoes, the bacteria enter the main stem and a dark discoloration can be seen inside the stem if it is cut in half lengthwise. The stem often cracks and splits, creating a dark brown streak along the stem that may ooze sticky yellow liquid in wet weather. As the stem becomes more severely infected, leaves wilt, often first on one side, and eventually the entire plant collapses.

Fruit may develop a bird’s eye spot - a small raised spot with a white ring around it.

Where did bacterial canker come from and how does it spread?
The most common way that CMM enters a garden is through contaminated seed and transplants. It takes only one infected seed to bring in the pathogen. Once in the garden, CMM can be spread on hands and tools, and in splashing rain or irrigation water. The pathogen can survive in debris from infected plants and on weeds in the tomato family (solanaceae) for several years. It can also survive on contaminated tools and equipment for several months. Once established in a garden, CMM can be a difficult pathogen to eradicate and may be found in the garden again next year.

What should I do if bacterial canker is found in my garden?
CMM may be confirmed in your garden by the UMN Plant Disease Clinic. If the disease is identified early in the growing season, completely remove infected plants to prevent spread of the disease to nearby healthy plants. Infected plants should be buried or composted on site in a compost pile that heats up and results in complete breakdown of the plant material.

Bird's eye fruit spot of Bacterial Canker - Heinz USA ,
At this time, it is NOT recommended to bring infected plants to municipal compost sites. This is to prevent movement of the pathogen to areas of the state where it is not currently found. It should be noted that not all compost facilities achieve the heat necessary to completely kill the pathogen.

Tools should be soaked in a 1:9 solution of germicidal bleach in water for at least 5 minutes after working with infected plants. Gardeners should avoid working in plants when they are wet as the bacteria are easily spread at this time. Sprinkler irrigation should be avoided as splashing water will spread the pathogen. Use drip irrigation or soaker hose whenever possible.

At the end of the season, any infected plants should be buried at the site or composted on site. Cutting the plants into smaller pieces will speed up the breakdown process. Expect the bacteria to survive 2-3 years in this infected plant debris. Tillers and tractors can move infected plant debris through the garden or to new areas. To avoid spreading CMM, use equipment in known infected areas only after other areas have been tilled. Clean all soil and plant debris from the equipment and wash with a 1:9 solution of germicidal bleach in water before using the equipment in a new area.

G. Holmes, CA Polytech. State Univ.,
Avoid planting tomatoes or peppers in the area where CMM was found for 3 years. During this period, remove all weeds from the tomato family, like nightshade, as well as any pepper or tomato plants that grow from previous season’s fallen fruit.

Throw away wooden stakes, twine, bamboo or other structures made of natural material used in the garden. These are difficult to clean because they are extremely porous, making it difficult for disinfectants to reach the bacteria inside.

Tools, metal tomato cages or other equipment made out of metal or smooth material can be cleaned with a 1 to 9 solution of germicidal bleach and water.

  • Remove all soil and plant debris from tools and trellises. 
  • Wearing water proof gloves, mix 1 cup bleach with 9 cups water.
  • Soak all tools, tomato cages and other equipment in the bleach solution for at least 5 minutes.
  • Rinse all tools and equipment with clean water and dry before storing.

Do not save seed from infected plants or from tomatoes or peppers grown in a CMM-positive garden.

Are fruit from plants infected with bacterial canker safe to eat?
There is no record of CMM causing direct harm to a human. Gardeners should talk to their doctor if they have any concerns related to their health as many factors affect how individuals respond to microorganisms in the environment.

The major concern with plant pathogens infecting tomato fruit is that the infection can change the pH (acidity) of the fruit. This means that diseased fruit should never be used for canning because the pH plays an important role in keeping out other harmful microorganisms. The fruit can be cooked and eaten, cooked and stored, or frozen, cooked and eaten. The change in pH can let other harmful microorganisms enter the fruit so cooking is a best practice to kill microorganism that might be present prior to eating.

What can I do to prevent bacterial canker in my garden?
CMM is most commonly introduced on infected seed or transplants. Purchase seed from a reputable supplier. Do not save seed from infected plants. Seed from unknown sources should be avoided. If questionable seed is unavoidable, seed should be soaked in 1:4 solution of bleach in water for 1 minute and then rinse in water for 5 minutes prior to planting.

Purchase healthy transplants from a reputable grower. Avoid transplants that have been pruned or cut back as this procedure easily spreads CMM.   

Sunday, October 11, 2015

EAB now confirmed in Washington County

Jeffrey Hahn, Extension Entomologist

(The following information is taken from an October 8, 2015 news release from the Minnesota Department of Agriculture)

The Minnesota Department of Agriculture (MDA) today identified emerald ash borer (EAB) in Washington County. An adult EAB was found on a survey trap that had been placed at the Minnesota Department of Transportation’s St. Croix Rest Area on Interstate 94. During a follow-up visit, staff discovered a nearby tree had tunneling consistent with the invasive pest.
Emerald ash borer stuck on a purple sticky trap. 
Photo: Jeff Hahn, UMN Extension

Washington County becomes the 11th county in Minnesota to verify EAB. EAB was also confirmed in 2015 for the first time in Scott, Chisago, Fillmore, and Anoka Counties. This invasive beetle has also been found in Hennepin, Houston, Olmstead, Ramsey, and Winona counties

Because this is the first time that EAB has been identified in Washington County, the specimen has been sent to the United States Department of Agriculture (USDA) for confirmation, which is expected later this week. Pending confirmation, the MDA and USDA will work closely to determine appropriate follow-up actions.

One of the likely actions will place Washington County under an emergency quarantine, joining the other ten counties where EAB has been confirmed in a state and federal quarantine. The quarantine is in place to help prevent EAB from spreading outside of a known infested area. It is designed to limit the movement of any items that may be infested with EAB, including ash trees and ash tree limbs, as well as all hardwood firewood.

The biggest risk of spreading EAB comes from people unknowingly moving firewood or other ash products harboring larvae. There are several easy steps Minnesotans can take to keep EAB from spreading:
  • Don’t transport firewood. Buy firewood locally from approved vendors, and burn it where you buy it 
  • Be aware of the quarantine restrictions. If you live in a quarantined county, be aware of the restrictions on movement of products such as ash trees, wood chips, and firewood.
  • Watch your ash trees for infestation. If you think your ash tree is infested, go to and use the “Do I Have Emerald Ash Borer?” guide.
  • If you feel your ash tree may be infested with EAB, contact a tree care professional, your city forester, or the MDA at or 888-545-6684.
For more information about EAB, see Emerald ash borer in Minnesota. See also the MDA news release, MDA identified emerald ash borer in Washington County.

Friday, October 2, 2015

Cleaning Up after Plant Disease

M. Grabowski, UMN Extension Educator

By the end of the gardening season many plants are looking less than their best. At this point leaf spots, blights, fruit rots or other disease problems can easily be found in the yard and garden. An important piece of information about disease biology is that plant pathogens often survive from one season to the next in infected plant debris. As a result, a good garden clean up in the fall can reduce the number of pathogens that survive the winter and cause problems next year. Below are a few clean up strategies that can reduce disease in following growing seasons.

Trees and Shrubs
Crabapple leaves infected with apple scab
If leaf spot diseases are present, wait until leaf drop, mow leaves into the soil with a mulching lawn mower to speed up breakdown of infected plant material or rake up and remove all leaves from the site. Inspect branches for cracked or discolored bark that might indicate a branch canker or unusual tumor like growths known as galls. Flag these branches and mark your calendar to prune out diseased branches in February or March.

Perennial Flower Gardens
If leaf spot or blights are present, cut stems at the soil level and remove all infected plant material from the area. This is only necessary for diseased plants. Stems of healthy plants can be left until spring for winter interest and wildlife habitat.

Vegetable Garden
Early blight infected tomato plant
For large gardens, bury all plant debris as soon as possible after harvest to begin the break down process. Do not plant the same family of plants at that same location for 2-4 years. Next year, plants of the same family need to be a minimum of 10 feet away from the location of this year’s diseased crop.

For small gardens, which do not have space to rotate to a new location, remove all infected plant debris including leaves, stems, roots and fruit.

Do not save seed from infected plants.

What to do with Diseased Plant Material
In Minnesota, it is illegal to put yard waste in with your household garbage. The good news is that the majority of plant pathogens will be killed in a compost pile that heats up. Unless you are an avid back yard composter and know your pile heats up, consider bringing diseased plant material to your city or county compost sites. If this is not available in your area, find a commercial composter ( that takes yard waste. Hot composting is the best way to dispose of green plant material like leaves, fruit and green stems.

Woody plant tissue can be chipped and composted, or burned. Check local regulations about burning in your area. Some yard waste drop off sites also accept woody plant material.

Clean up Tools and Equipment
Tools, trellis, stakes or other equipment used with diseased plant material can be cleaned with a 1 to 9 solution of bleach and water.
  • Remove all soil and plant debris from tools and trellises.
  • Mix 1 cup bleach with 9 cups water.
  • Wearing water proof gloves wash all tools and equipment with the bleach solution.
  • Rinse with clean water and dry before storing.

Tuesday, September 29, 2015

End of the season gardening

Julie Weisenhorn, Extension Educator - Horticulture

Examine leaves
for insects.
Minnesota gardeners are very good at flexing with our changing weather. Many love the onset of fall with its brightly colored leaves, crisp apples, goofy squash and global pumpkins. Days are lovely - warm, breezy, sun-filled - perfect for noodling around in your yard. On the other hand, night temps can dip into the 30's and bring frosty mornings. This swing of the gardening pendulum can make us anxious about those last tomatoes still ripening on the vine, our beautiful Genovese basil, the annual flowers still blooming, and our houseplants that have been thriving out doors all summer. Relax. Here are some actions we can take as gardeners to get our plants through this transitional period while we prepare for the winter ahead.

  1. Frost advisory? Move plants into a garage or drape old sheets, lightweight tarps, and blankets over tender plants like annual flowers and vegetables, containers, tomatoes still on the vine and houseplants you haven't prepped yet for the indoors.  Floating row covers (available at garden centers and nurseries) can be used for larger plantings. Weigh down edges with bricks or boards.
    Remove debris
    from soil surface.
  2. Harvest what you can as soon as possible. Preserve by canning or freezing. (U of MN Food Safety Canning and Preserving). Dry or freeze herbs like basil, cilantro, and thyme. Make pesto and freeze in single serving containers. Plants like kale and cabbage can take the cooler weather, so no need to protect them.
  3.  Give houseplants special attention before bringing them indoors.
    • Examine houseplants well for insect pests. Look on the undersides of leaves, leaf nodes and in the crotches of branches.
    • Remove plant debris from the soil surface. 
    • Wipe off leaves with a damp soft cloth. Spray off smaller plants in a sink and larger plants in a shower. 
    • Re-pot with fresh soil to reduce / eliminate pest issues.
    • Wash pots with 10% bleach solution. Scrub off algae, fertilizer salt stains, insect egg masses and nests. Provide a large enough saucer for plants to drain adequately.
    • Many plants will experience leaf drop when brought indoors and into a different set
      Place potted herbs
      in a sunny window.

      of growing conditions (lower light, drier air, warmer temps). Prune houseplants for better form and to reduce the amount of foliage the plant is required to support. 
Gardeners can extend the growing season as well by using cold frames, hydroponic tables, and potting up herbs to bring indoors. Cold frames can be built or purchased as kits online and at garden centers for a wide range of prices. Locate cold frames in sunny sites directly in gardens. Plant crops like lettuce, arugula, chard, spinach and radishes now for fresh eating when the snow is flying. Grow plants indoors for year-round fresh food. U of M faculty Tom Michaels developed a hydroponic salad table for indoor use. It can be moved outdoors during the warmer months. Other alternative growing methods include growing walls and window farms. Or simply dig up a favorite herb, pot it up and place it a sunny window for fresh herbs through the cold winter ahead.

Thursday, September 24, 2015

September is head lice awareness month

Jeffrey Hahn, Extension Entomologist

With schools starting recently, you can expect that the number of head lice cases will also increase. What do you need to know if head lice make an unexpected arrival into your home?!

Head lice are pests because they bite and feed on the blood of people. They are annoying and cause itching but fortunately do not transmit any disease. They are found specifically on heads near the scalp at the base of hair shafts. These insects are very small, up to 1/8th inch long (nymphs are smaller). They are grayish or brownish, relatively slender and are wingless. Also look for nits (lice eggs) which are about the size of a pinhead, white and oval and are attached at the base of hair.
Adult head louse. Photo: CDC

Head lice need the warmth of people to survive and are not able to survive off humans for any more than one or two days. These insects do not jump or fly and primarily move from one person to another by direct head to head contact. They can sometimes move to new hosts when infested people share items such as combs, hats, scarves, coats, towels, and similar articles. People that are at the greatest risk from head lice are children and family members in a household with an infested individual.

To help prevent infestations of head lice, children should be taught to avoid sharing combs, brushes, hats and similar items. Heat treat any bedding or clothes that may have been exposed to a person with head lice. This can be done by washing items in hot water (use the hottest setting the clothes or bedding can tolerate) and dry on a high heat. Items can also be bagged and placed in a freezer for one to two weeks to kill any head lice that are present.

If despite your best efforts a family member becomes infested with head lice, there are a few options that can be used to deal with them. Physical removal with a nit comb can help. Nit combs are specially designed to comb through hair, catching lice and nits in the process. This is often a laborious process but is a good supplement before using a shampoo or lotion. Some people will use nit combs when they want to use only a non-chemical method.
There are a variety of insecticidal shampoos and lotions that are available for treating hair to kill head lice. It is critical that they are applied exactly as indicated by the directions. Do not apply a conditioner or a combination shampoo/conditioner before using lice medication. Do not wash treated hair for one to two days. Do not overapply products; do not use them more frequently than what is indicated by the directions.

Two products you can buy over the counter are those that contain permethrin (e.g. Nix) and pyrethrins (e.g. Rid ). A potential problem with these shampoos is that head lice have been shown to be resistant (not be affected) by these products in many parts of the country including Minnesota.

Adult, nymph (immature), and egg (nit) showing
relative size compared to a penny. Photo: CDC
Keep in mind that there are several reasons why it may appear that a treatment did not work: If head lice were misdiagnosed originally and the problem is caused by something else (an expert should examine a sample to verify head lice are present); if a product has not been used properly; if the person becomes reinfested. It is also possible that the head lice are resistant to the medication that is being used. If you suspect a shampoo or lotion containing permethrin or pyrethrins are not killing the head lice (and assuming head lice are confirmed and the product is being used correctly), discontinue using it and try a product with a different active ingredient.

There are some relatively new products that are available by prescription that are effective. Spinosad (e.g. Natroba) kills both head lice and eggs so retreatment is typically not necessary. Malathion (e.g. Ovicide) is effective against head lice and partially so against the eggs. Ivermectin (e.g. Sklice) works well against head lice. It is not considered to be ovicidal (kills the eggs), although it does appear to prevent immature head lice from living for long. Benzyl alcohol (e.g. Ulesfia lotion) kills head lice but does not affect the eggs; this treatment needs to be reapplied seven days after the first one.

Lindane is also available with a prescription. However people are discouraged from using as it is considered a more toxic product.

Don’t use vegetable oil, mayonnaise, or similar material to coat the hair in an effort to suffocate the head lice. This is an unproven method as well being difficult to remove. Also don’t treat a home with insecticides. Head lice are not a household insect problem and treating a home does not help to eliminate a head lice infestation.

For more information see the University of Minnesota publication Head lice and the Centers for Disease Control and Prevention (CDC) web page on head lice.

Monday, September 14, 2015

Q&A: Planting ideas for dry shade

Julie Weisenhorn, Extension Educator - Horticulture

Q: I have a large dry area shaded by mature trees. Can you give me an idea of how to approach planting
Mulch retains soil moisture and deters weeds.
Hosta and Heucherella  'Stoplight' perform
well in dry shade.
this area? What plants will add color and won’t be too expensive? I have a limited budget.

A: Here is a publication from U of M Extension: "The Best Plants for 30 Tough Sites". You'll see it contains plant lists for 30 difficult sites. This publication includes a list for dry shade as well as shrubs for shade, small trees for shade, and tall perennials for shade.

Because budget is a factor, approach this project in phases. You don't need to do all the planting in one year. Remove weeds first. Then cover the ground with 3-4 inches of shredded wood mulch to reduce weeds and hold soil moisture. Check with your county or municipality about free mulch options. You could apply the mulch this fall. Next spring (Year 1) plant major plants such as shrubs and perennials. Be sure to water after all plantings to minimize transplant shock and give the plants a good start. The following year (Year 2), add low-growing perennials that will spread and fill in spaces between the shrubs. Year 3 add some masses on the outer edges. Always space plants according to their mature size. It should be listed on the plant's label. 

Initially, your planting may seem sparse, but the plants will eventually fill in. By avoiding over planting, you'll keep your costs down and your plants will be able to grow to their mature size and form.
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