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Wednesday, March 14, 2018

Last Chance to Prune Oaks

M. Grabowski, UMN Extension Educator

Fresh pruning cuts on an oak tree.
M.Grabowski, UMN Extension 
If you have oaks in your landscape that need pruning and you live in an area of Minnesota where oak wilt occurs, pruning must be done before the oak wilt fungus and it's insect vector become active. Oak wilt is a fatal disease of oak trees that can be found in some counties of Minnesota. If you live in an area where oak wilt occurs, it is critical to prune oak trees before the high risk infection period begins in April. The risk status for oak wilt is updated as weather conditions change, but in a normal year high risk of oak wilt infection occurs in April, May, and June. Check in with My MN Woods to find the current oak wilt risk status before you prune.

Oak wilt has been found within
20 miles of all areas colored pink
Oak wilt is caused by a fungal plant pathogen. Spores of the oak wilt fungus are carried by sap feeding beetles in the Nitidulidae family. These small beetles are attracted to wounds and fresh cuts on oak trees. When they arrive at the cut branch, spores of the oak wilt fungus are knocked off and can infect the open wound.

Red oak trees are highly susceptible to oak wilt and can wilt and die in as little as 4 weeks after infection. Once infected with oak wilt, there is no way to save a red oak tree. White and bur oaks can also become infected with oak wilt. These trees are able to slow the infection but will eventually succumb to the disease in a few years. Some treatment options are available for white and bur oak trees if the disease is identified at the early stages.

Friday, March 2, 2018

Prune out cankers and galls now

Michelle Grabowski, UMN Extension Educator
Black knot gall on a wild cherry tree.
M. Grbaowski, UMN Extension

An important late winter gardening task is pruning to remove diseased branches. Winter is the best time to prune for several reasons. Diseased and damaged branches are easily seen when leaves are not present. Winter temperatures are not ideal for the fungi and bacteria that cause disease in trees and shrubs. The pathogens will still be present but at much lower levels than during the growing season. By pruning out infected branches now, gardeners can significantly reduce the risk of the disease spreading within the plant and to neighboring plants once the growing season begins.

Several types of disease can affect branches of landscape trees and shrubs.

Gall rust on a pine tree. M. Grabowski,
UMN Extension
A gall is an unusual overgrowth of plant tissue caused by a pest or pathogen. Fungi and some bacteria can cause galls to form on branches of trees and shrubs. Galls can be round, oblong, or irregular in shape. They are made of wood but may have discolored bark due to the infection. Galls can girdle a branch and kill all leaves and shoots beyond the gall. Some trees and shrubs will tolerate galls and will not suffer any damage as a result.

Golden canker causes the reddish purple
bark of pagoda dogwood to turn yellow.
M. Grbaowski, UMN Extension 
A canker is an infection of the sapwood and living bark caused by a fungal or bacterial plant pathogen. Cracked, discolored, or blistered bark in an isolated area of a branch indicate that there is a canker. In some trees and shrubs a thick hard layer of resin or sap may cover the infection. If the bark is peeled back, reddish brown discoloration of the wood can often be seen.

A canker will eventually grow to encircle the branch, cutting off the flow of water and nutrients. This results in death of the branch, and any shoots and leaves beyond the canker. In some diseases, the canker can progress into the main trunk and result in death of the tree.

Make the pruning cut a minimum of
4 inches below visible symptoms at
a branch union. M. Grabowski,
UMN Extension 
How to prune out cankers and galls
First examine the tree carefully to find any branches with discolored, cracked or blistered bark or with any unusual tumor like growths. The infection will extend beyond the visible discoloration of the bark so the pruning cut should be made at a minimum of 4 inches below symptoms of disease. The tree will heal the pruning cut most rapidly and easily if the cut is made just above a bud or a branch union.

All branches with galls or cankers should be removed from the area and burned or buried. Pruning tools should be cleaned with undiluted Lysol (active ingredient .1% alkyl dimethylbenzyl ammonium saccharinate) or a 10% solution of household bleach in water.

Your Winter Garden: Pest tips for houseplants

By Julie Weisenhorn, Extension Educator - Horticulture

Just like in our summer gardens, we need to keep an eye out for pests in our indoor winter gardens (houseplants). Pests may sometimes hitchhike on houseplants that spend the summer outdoors, and emerge in the warmth of our homes. New plants may also bring in new pests. Insect eggs laid on the underside of leaves or in the soil may hatch indoors and suddenly appear too.

Hand showing plant debris accumulated on the soil of a potted plant.
Remove plant debris
Tips to reducing pest issues in your winter garden:

Groom plants that come in from the outside. Clear away dead plant debris (leaves, flowers) and prune off dead or overgrown stems and branches. Remove dust that can filter light by wiping off leaves with a soft, damp cloth or spraying the plant with water.

Scout for signs and presence of pests.
Look at the undersides of leaves and along edges and the bottom of  pots for insects and egg masses and remove or treat. Shiny, sticky leaf surfaces (honeydew) can be a sign of sucking insects like scale and aphids. Fine webbing is a sign of spider mites. Household insects

Some plants may be outgrowing their containers and need re-potting. 
Take this opportunity 
to check the underside of the plant as well as
roots, and to prune off any roots that are dark brown and mushy.
Re-pot plants in fresh, sterile soil and a clean pot.
Use fresh soil and a clean pot.

Give new plants plenty of space. Quarantine new plants for a couple of weeks away from your current, pest-free plants to make sure the new fella is pest-free too.

Follow pesticide labels. Many pests can be eliminated from houseplants by hand-picking, wash or a blast of water. If you do choose to treat with a chemical, use one for houseplants and follow all pesticide label precautions. This is especially important with indoor plants as they live where we live. Household Insect Control
    Examine all parts of plants.
    Cottony scale on orchid
  • Look to treat outside on one of those warm winter days or in a ventilated garage. 
  • Bag the plant in a plastic garbage bag, and poke a small hole in the bag for your spray nozzle. Then spray, apply a piece of tape over the hole, and let the plant site covered. Remove the bag when the plant is dry. This contains the pesticide till dry and protects furniture and walls from spray. 

Thursday, March 1, 2018

Perfect Timing for Pruning Your Apple Tree

Produce more apples

By Gail Hudson, Extension Communications Specialist for Horticulture

Photo courtesy: Julie Weisenhorn
By the end of the winter, most gardeners are itching to get outside and start doing something! You certainly can--by pruning your apple tree(s). Extension Educator Annie Klodd, a fruit and vegetable specialist, says late February, early March is just about right for Minnesota gardeners. The trick is to do it at the end of winter just as the temperatures are rising a bit, but before the tree's buds emerge. 

Pruning an apple tree is an important task for home growers, she says, for several reasons: 
  1. It's a good time to get rid of diseased, damaged and dead wood on your tree.
  2. It gives the apple tree a nice shape and allows more light to get to the buds and fruit.
  3. The tree will be healthier, produce more fruit and grow better overall. 

Tools to use

Line up the right tools before you begin pruning. Depending on the size of your apple tree, you'll need at least a pair of hand clippers for a small one.  For a large tree, large loppers work as well as a pruning saw.

For more information about growing and maintaining apple trees, read this article by University of Minnesota Horticulturist and fruit expert Emily Hoover:

Wednesday, February 28, 2018

Your Winter Garden: Watering house plants the right way

Plus, how much light does your plant need?

By Gail Hudson, Extension Communication Specialist in Horticulture

Now that it's early March, we've still got piles of snow on the ground in Minnesota. That means our efforts to garden inside will continue for a little while longer!

If your window sills are filled with plants, you know it's easy to run into trouble with these greenery, by not providing enough light or too much light, with pests, diseases and/or a lack of water or too much water.

Keep your plants un-stressed

The trick is to keep your plant happy and un-stressed.  You can do that by giving your  plants the right amount of water.  In this video, Extension Educator Julie Weisenhorn has some tips and reminders for those of you with an indoor green thumb, plus she'll show you how to prevent leaf spot diseases with a simple watering tip.

Too much light may not be a good thing

As the sun grows stronger in the windows of your home, particularly those south-facing windows, be careful with your tender house plants. You may think they welcome the spring-time sun as much as we do, but high intensity light can.  Plants exposed to too much light may become scorched, bleached and limp. Review these tips from Extension Educator David Whiting.

Wednesday, February 21, 2018

Seed Catalogs Decoded!

Michelle Grabowski
Annie Klodd
Extension Educator Annie Klodd browses
peppers in the 2018 Rupp seed catalog

For many gardeners, the first sign of spring arrives in the form of seed catalogs in the middle of winter. Glossy color pages provide the promise of flowers, fruits, and vegetables in the coming season. Seed catalogs can open up a wide array of possibilities not to be found in local garden centers. Savvy gardeners can choose from multiple colors of flowers or vegetables, find disease resistant plants or varieties especially well-suited to their growing conditions.

To make the most of what seed catalogs offer, it is important to understand the terms, abbreviations, and numbers that can be found in the description of each variety.

Wednesday, January 31, 2018

Help save Minnesota's forests from invasive pests: Become a 'First Detector'

Workshop registration now open

Jeffrey Hahn, Extension Entomologist

Want to be part of Minnesota's award-winning Forest Pest First Detector volunteer program? Registration is now open for this year’s required workshops for volunteers who help detect invasive pests around Minnesota.

Workshop attendees participating in small group discussion
about invasive pests, part of the activities during a Forest
Pest First Detector workshop.
The workshops are being taught in Andover on February 28 and Mankato on March 21. Space is limited so register early! The cost is $50 which includes the online course and in-person workshop, including lunch and refreshments.

The Minnesota Forest Pest First Detector training program is designed to help identify the occurrence of invasive forest pests in Minnesota, including emerald ash borer, gypsy moth, Asian longhorned beetle, Japanese barberry and Oriental bittersweet.
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