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Showing posts from May, 2009

Consumers Beware!!

Michelle Grabowski, University of Minnesota Extension Educator
Downy Mildew, a potentially devastating fungal disease of roses has been found on several roses for sale in Minnesota. The disease has been identified on Double Knock Out®, Pink Knock Out® and Europeana®, but all rose cultivars are susceptible to Downy Mildew. This disease results in irregular purplish red leaf spots that eventually turn tan in the center. Infected leaves often turn yellow and fall off. Under very humid conditions gray fuzzy fungal growth may be seen on the underside of infected leaves. Downy Mildew also causes purplish black streaks on rose stems. Downy Mildew thrives under cool humid conditions. It spreads easily on the wind. If infected plants are brought into the garden, the disease could easily spread to other roses and raspberries in the area. Do not purchase roses with dark leaf spots!

The Wonders of Woolch™ - A New Mulch for Farm and Garden

Emily Tepe, University of Minnesota Research Fellow
If you grow strawberries you are familiar with the spring and summer task of crawling through the rows pulling weeds. It’s a time consuming, arduous task, but a very necessary one. Weeds rob strawberries of valuable water and nutrients, resulting in reduced vigor and fewer, smaller berries. Hand weeding is just about the only way to remove weeds in a strawberry plot because mechanical removal can easily damage the low growing strawberry plants, and approved herbicides are declining in number and becoming more and more expensive. Additionally, consumer interest in local foods grown without such chemicals is rapidly increasing, leading growers to look for alternatives. So with few options other than growing strawberries with plastic mulch (which poses its own environmental problems), growers get on their hands and knees each year in an endless battle against the unrelenting weeds.
But now there is hope for the achy knees, s…

Late May Lawn Care Tips

Bob Mugaas, University of Minnesota Extension Educator
Photo 1: The crabgrass plant on the left side of the picture is the 2-3 true leaf stage while the one on the right is at the 2-3 tiller stage. Bob Mugaas

Usually the middle to end of May is the prime time for putting down preemergence weed killer for crabgrass. In general early in the month is appropriate for the southern 1/3 of Minnesota while later in May is fine for middle to northern sections of the state. But what if I miss the prime window of application, how do I know if it’s too late to apply the product? That’s a good question. For all practical purposes, once the crabgrass seedlings have emerged from the ground it is too late for a preemergence product to effectively be put down. There is one notable exception and that is the preemergence weed killer known as dithiopyr. It is known in the trade by its product name Dimension. It is a common ingredient in many homeowner formulations. This product does provide som…

No Pests Allowed - Purchasing Healthy Plants to Start the Season Right

Michelle Grabowski, University of Minnesota Extension Educator
Whether you are looking for tomato transplants, annuals for a front garden bed or a new tree or shrub, one of the most important things you can do to ensure the future success of the plant is to start out with a healthy disease free plant.
Some plant pathogens live in our gardens in plant debris or soil, waiting for the right plant and the right environmental conditions to come along. Other plant pathogens come into the garden on wind, rain, or are carried by insects. Unfortunately many plant pathogens can be brought into the garden on infected plant material.
This later group of plant pathogens can be avoided by a disease management strategy known as exclusion. Exclusion is a strict ‘no pests allowed’ policy. For gardeners, this is one of the simplest pest management strategies to implement.

Photo 1: Petunia plants wilting due to Rhizoctonia root rot. RK Jones NCSU,
First, purchase plants from a reputab…

Garden Insects

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist
Flea beetles are active on crucifers now. These insects are about 1/16 - 1/8 inch long and an iridescent black violet (flea beetles on other plants are the same size and can vary in color). They overwinter as adults and are active in the spring, feeding on the leaves. They chew small, shallow pits and holes into the leaves. A heavily infested plant looks like it got shot with a BB gun.
Plants are most susceptible to damage in spring - seedlings are more vulnerable than transplants. If your plants are suffering 10 % - 30 % damage, you should treat plants to protect them from flea beetle damage. Apply a garden insecticide, such as permethrin, spinosad, or carbaryl. Different flea beetle species also attack potatoes, spinach, beans, squash, corn, and other plants so be on the watch for feeding injury on these plants as well. More information on flea beetles is available at this link (…


Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist
A couple of caterpillars were noticed recently. Eastern tent caterpillar is a common insect on apple, crab apple, cherry, and other fruit trees. They have a dark colored, hairy body with a yellow stripe down their back and grow to almost 2 inches in length. They overwinter as eggs on branches and emerge in the early spring. They construct webbing in the forks of branches which is where they rest at night and during cloudy, rainy days.
Cankerworms have also just emerged recently. A type of inchworm, they are yellowish green with a smooth body and grow up to 1 inch long. Cankerworms skeletonize leaves, i.e. they feed between the major veins. When they first start to attack leaves, this damage will begin as small oval holes between veins. As the caterpillars become larger, entire areas between the veins are consumed. Cankerworms feed on a variety of trees, including apple, linden, elm, ash, and hackberry.

Photo …

Be on the Watch for Ticks

Jeffrey Hahn, University of Minnesota Asst. Extension Entomologist
We are well into the beginning of tick season. There are two ticks that are of particular importance to people, the American dog tick, commonly called wood tick, and blacklegged tick, formerly called deer tick. Both ticks commonly bite humans. However while the American dog tick is basically just a nuisance and essentially does not transmit disease to people, the blacklegged tick is a known vector of Lyme disease as well as human anaplasmosis (formerly known as human granulocytic ehrlichiosis) and babesiosis.
Both ticks are found in hardwood forests and fields and other grassy, weedy areas, especially along trails and paths. If you are out in areas where ticks are found, take the proper precautions to avoid them. Stick to trails when you are walking and try to avoid moving through grassy areas. Wear protective clothing, such as long-sleeved shirts and pants. You can maximize your protection by tucking your p…

Harvesting Your Rain

Three picnic shelters at the Minnesota Landscape Arboretum are in the beginning phase of a transformation as the arboretum prepares for its 2009 summer exhibition called Waterosity.  When complete, the picnic shelters will be a new permanent display called Harvest Your Rain.  Each shelter is being modified to show three different ways of managing stormwater runoff from your property’s impervious surfaces such as rooftops, driveways, and sidewalks.  During rain storms and snow melt, rain barrels, rain gardens, and green roofs all “harvest your rain” decreasing the amount of runoff and non-point pollution that would otherwise pour over these impervious surfaces and into sewers and adjoining water bodies such as lakes, rivers, and wetlands.  Below are articles on rain gardens and rain barrels.  In June look for more Waterosity-related articles on green roofs, the new Cutting Edge on Lawns display at the Minnesota Landscape Arboretum, porous paving, and water-wise irrigatio…

Rain Gardens

Eleanor Burkett, University of Minnesota Extension Educator
Whether you live in the city or reside on a lake or river shore, managing stormwater runoff is worth considering for your landscape. Rooftops, roads, driveways and sidewalks create hard impervious surfaces which rainwater and melting snow cannot penetrate through to soak into the soil. Additional runoff created by impervious surfaces often is channeled into depressions on your property, often eroding soil along the way. The additional runoff also increases the amount of nutrients and sediment that are carried into lakes, rivers, and wetlands.
Simply put, a rain garden is a shallow depression filled with plants designed to collect rainwater runoff and allow it to filter into the soil, removing nutrients, sediments and other pollutants before reaching the groundwater. Small shrubs, flowering plants and ornamental grasses within a rain garden absorb nutrients, and the sediments settle to the bottom. Rain gardens add be…

What's Up With That?!

David C. Zlesak
The core or pith of plant stems are typically either hollow or contain loosely packed, spongy parenchyma cells.  The pith of this butternut or white walnut (Juglans cinerea) is distinctive in that it is chambered with dark bands of sclerenchyma plates separating hollow zones. Black walnut (Juglans nigra), a close relative, also has chambered pith and has bands that are typically a bit lighter in color. Parenchyma cells are relatively large, of variable shape, and have thin cell walls.  As developing stems elongate, parenchyma can tear and disintegrate in many plant species.  Another cell type found in plants is sclerenchyma. Sclerenchyma cells help provide support to plant tissue and have thickened, secondary cell walls containing cellulose and are often impregnated with lignin.  As stems of white and black walnuts grow, parenchyma cells eventually collapse leaving mainly sclerenchyma cells in distinctive plates.  

Emerald Ash Borer On Minnesota's Doorstep

Jeffrey Hahn, Asst. Extension Entomologist

Earlier this month, on April 7, Wisconsin reported a confirmed infestation of emerald ash borers (EAB) in the town of Victory.  This town is in Vernon county, about 20 miles south of La Crosse and on the banks of the Mississippi River about one mile from the Minnesota-Iowa border.  This the first time that EAB has been found in western Wisconsin.

The Minnesota Dept. of Agriculture has stepped up their surveillance efforts in Houston county which is right across the river from this infestation in Wisconsin.  So far, their surveys have not revealed any EAB.  Remember, that at this time, EAB has not been found in Minnesota (although the odds of finding it in Minnesota soon have gone dramatically up).  Because of the imminent danger of EAB, a quarantine has been put in place for Houston county, restricting the movement of ash trees, ash logs and branches, uncomposted wood chips, and any hardwood firewood.

Photo 1: Minnesota quaranti…

Simple Steps to Productive Apple Trees

Emily Tepe, University of Minnesota Research Fellow

Apples in the Home Garden

If you’ve ever dreamed about harvesting fresh fruit from your garden, apples are a great option. Sure, they require a bit more care than a typical landscape tree, but with a little TLC you could be harvesting juicy, crisp apples right from your own backyard!

There are a few things to keep in mind when growing apples that will help you achieve bountiful harvests of high quality fruit year after year. First it is important to know that apples require cross-pollination to reliably set fruit. This means planting more than one kind of apple tree. Your choice of varieties will largely depend on your priorities. If one tree will give you all the fruit you need you may want to consider planting a disease resistant flowering crab apple, such as Indian Summer or Snowdrift, for cross-pollination. Crabapples and edible apples can successfully cross pollinate. These trees are used in commercial orchards becaus…

Urban Gardeners at Minneapolis' Sabathani Community Center

Meleah Maynard, University of Minnesota Master Gardener
“Just opening the gate and stepping into the garden filled me with peace. My little plot looked like a bush and I brought my granddaughter [the see it] and she just felt everything with her hand.”—Sabathani gardener

They aren’t visible from the street, but just north of Minneapolis’ Sabathani Community Center, members of the Urban Gardener program are already busy working on plots that will soon be bursting with vegetables. Launched in 2007 with a grant written by Extension Urban Director Barbara Grossman, the program is about much more than gardening. It also aims to build community, help families stretch their dollars a bit further by growing some of their own food and offer information about nutrition and healthy eating.
Hennepin County master gardener Mollie Dean, who has been coordinating the program since its inception two years ago, says interest has grown quickly with over 275 people attending gardening classes s…

Easy Does It: Help Your Bedding Plants and Houseplants Transition to the Great Minnesota Outdoors

David C. Zlesak, University of Minnesota Extension Educator
Taking plants from the relatively low light and moderated temperatures of the home environment and plunging them suddenly outdoors in bright sunlight, wind, and temperature extremes can result in severe injury. Depending on the extent of the injury the plant may be capable of recovering relatively quickly, after multiple weeks, or in extreme cases not at all.  As plants grew indoors, the tissues that they produced were adapted to those environmental conditions.  With a gentle transition period, plant tissue can adapt to some degree when conditions change.
Plants use environmental cues to help them adapt their tissues to their current growing conditions.  For instance, leaves produced in shade typically have more surface area and are thinner in order to better intercept light and best invest energy resources into the most efficient type of tissue.  Leaves grown under brighter light are often thicker with additional la…

Distinguishing Disease from Winter Injury on Spruce Trees

Michelle Grabowski, University of Minnesota Extension Educator
Throughout Minnesota, purplish brown to rusty brown needles can be seen on spruce trees. A variety of problems can result in needle discoloration in spruces including insects, disease, and problems associated with environmental conditions. This time of year two common problems are Rhizosphaera needle cast and winter injury. Rhizosphaera needle cast is caused by a fungal pathogen. Winter injury is the result of environmental conditions. It is important to be able to distinguish between these two problems, since very different action is required to maintain tree health depending on the cause of the problem.
Rhizosphaera needle cast is caused by the fungi Rhizosphaera kalkhoffii and is most commonly seen on Colorado blue spruce, which are highly susceptible to the disease. White spruce and Norway spruce have greater resistance to the disease but can become infected when stressed. With the drought conditions present i…