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Sunday, January 31, 2016

A Pictorial Ode to Insect Flight

Karl Foord - Extension Educator, Horticulture

This is a smorgasbord of insect flight.

Magnificent Monarchs - Karl Foord

Karl Foord -  Extension Educator, Horticulture

One of my goals as an extension educator and photographer is to enable people to see things that are beyond our human physical capacity of perception. I am particularly interested in insect flight, because of my work on pollinator awareness.

Friday, January 29, 2016

Don’t Wait to Prune out Cankers and Galls

M. Grabowski, UMN Extension Educator

Black Knot Galls
A traditional recommendation in Minnesota is to prune trees in February and March. One goal of pruning during these months is to remove branches infected with cankers and galls. The fungi and bacteria that cause cankers and galls on trees overwinter in these infections. When weather becomes warm and wet many of these pathogens start to reproduce and spread the disease within the canopy and to neighboring trees.

Climate change is increasing Minnesota’s average temperature and adding days to Minnesota’s frost free season. Spring in Minnesota has been arriving earlier and is warmer. Weather data from the twin cities metro area over the previous five years reveals that in February an average of 7 days reached a maximum daily temperature over 32 F, and in March an average of 23 days reached a maximum daily temperature over 32 F.

There are several common canker and gall causing pathogen that can reproduce and infect at temperatures just above freezing, although infection rates are low at these temperatures. Black knot, a common fungal gall disease found on Prunus trees in Minnesota, was reported to begin spore release at temperatures as low as 37 F. The fungi that cause coral spot canker and perennial Nectria canker on a number of hardwood trees can begin to germinate and infect at temperatures just above 32 F. In 2012, March had 9 days with a daily maximum temperature greater than 68 F. At that temperature range, many different canker and gall causing pathogens are actively reproducing and spreading.
Nectria canker on maple -  J. Hartman, UKY
We cannot predict exactly when warm weather will arrive in 2016. To prevent canker and gall causing pathogens from reproducing and spreading, gardeners should prune out and destroy canker and gall infections while temperatures remain consistently below 32 F. When fresh new plant growth emerges from dormant buds, it will then have a clean healthy start to the growing season.

When pruning to remove cankers and galls, make the pruning cut just above a lateral bud or at a branch union that is 10-12 inches below visible symptoms of the infection.  Remove the infected branches from the area and burn or bury them.  Black knot galls left lying in an orchard after pruning were found to continue to release spores for four months.

If warm weather comes earlier than expected, pick a dry day with no rain in the forecast for the next several days to prune. Many fungal and bacterial plant pathogens release spores in response to rain, heavy dew or high humidity and need moisture on the plant surface to start a new infection. Dry weather provides a period where trees can heal the pruning wound under conditions that are less than ideal for infection. 

Extension publications: New & Revised in 2016

One Bad Apple

M.Grabowski, UMN Extension Educator

Sunken black rings of fungal growth on a stored pumpkin
If you have stored garden produce from your own garden or the farmer's market be sure to regularly inspect this produce for problems. One bad apple spoils the barrel succinctly describes how post harvest rot organisms can start in one bad piece of fruit and grow to infect everything sharing the same storage bin. Fungi and bacteria can both cause rot of garden produce in storage. Some of these organisms are weak pathogens that infect the plant in the garden but do not cause damage until after harvest. Others, like common bread mold (Rhizopus sp.) and blue mold (Penicillium spp.) are saprophytes that can easily be found in soil or plant debris.

Post harvest rot organisms take advantage of wounds like small cuts, bruises, or chilling injury to infect plant tissue. To avoid problems with storage rot harvest fruits and vegetables when they are fully mature but not overripe. Take care not to bruise or damage the fruit during the harvest process and do not store produce that is already showing signs of rot or has obvious cuts or bruises.

White mold  spreads through stored carrots. W. Brow Jr. Bugwood
Store each kind of produce in ideal conditions for that fruit or vegetable. Regularly inspect stored produce for signs of rot. Look for small round sunken spots, discolored areas, or soft tissue. Any produce showing these symptoms should be promptly removed. If caught early, the infected area can often be cut out and the remaining healthy tissue can be cooked and eaten. If the rot has taken over the majority of the fruit, remove the rotten fruit as well as all of the fruit touching it. Discard any rotten produce and use the neighboring produce in cooking as soon as possible as it has been exposed to the rot organism and will not likely store for long.

Wednesday, January 20, 2016

Forest Pest First Detector workshops in 2016

Jeff Hahn, Extension Entomologist

Registration is now open for the 2016 Forest Pest First Detector workshops!  There will be four workshops conducted during February at the following sites:

Wednesday, February 17, 2016, Marine on St Croix
William O'Brien State Park, Visitor Center
16821 O'Brien Trail North, Marine on St. Croix, MN 55047

Thursday, February 18, 2016, Mankato
Loose Moose Saloon & Conference Center
119 South Front Street, Mankato, MN 56001

Wednesday, February 24, 2016, Carlton
Carlton County Transportation Building, Meeting Room
1630 County Road 61, Carlton, MN 55718

Thursday, February 25, 2016, Fergus Falls
Otter Tail Government Service Center, Meeting Room
500 West Fir Avenue, Fergus Falls, MN 56537

Whether you would like to become a Forest Pest First Detector or are already one and would like to
Participants at a past workshop examining invasive pest
samples.  Photo: Jeff Hahn, UMN Extension
attend to receive updated information, consider registering for one of these workshops. Among the topics we will cover will include emerald ash borer, Asian longhorn beetle, gypsy moth, brown marmorated stink bug, Oriental bittersweet as well as other potential forest pests.

Workshops are from 8 AM - 3 PM. Workshop registration fee is $50 which includes lunch.  Participants must preregister and the registration fee is due during the online registration process. To register for any of these workshops or for more information, visit the Forest Pest First Detector website.

Hope to see you there!

Wednesday, December 9, 2015

Nutsedge and Ornamental Sedges: What’s the Difference?

Yellow Nutsedge
Pacocha Landscaping Services, Inc.
Mary H. Meyer, Extension Horticulturist and Professor, University of Minnesota

Nutsedge is an aggressive long-lived weed (some consider it one of the world’s 5 worst weeds) in the genus Cyperus whereas the ornamental sedges are in the genus Carex and although some are aggressive, they can easily be controlled. Taxonomically, the ornamental sedges have separate male and female flowers, born separately along the flowering stem, whereas yellow nutsedge has perfect flowers that are in a terminal, fairly conspicuous umbel (upside down umbrella) cluster, see image below. Yellow nutsedge, Cyperus esculentus, and Carex spp. are both in the Cyperaceae family which is known for triangular stems and leaves in three ranks thus the rhyme: Sedges have edges, grasses are round and hollow right up from the ground.

When you pull up yellow nutsedge, you might get a small tuber often referred to as a nut at the end of the root, thus the common name ‘nut sedge’. This tuber is edible (the word esculentus means edible) and is grown for food in some cultures, earth almond is another common name. The tuber is a great source of stored food and helps the plant to grow, from as deep as 32 inches; it also makes translocation of chemical control difficult, as tubers can escape systemic chemicals, remain viable although dormant for as long as 10 years in the soil, and one plant can produce hundreds if not thousands of tubers in a year. Nutsedge has evolved to be a long lasting plant, and a great weed!

Photo by Jack Kelly Clark,
courtesy University of California
Statewide IPM Program
Yellow nutsedge prefers wet sites, but it will grow in many soil types and can flower when quite short at even 6-8 inches in height. The flowers are an umbel or cluster of several stems arising from a central point. Each flower has thousands of viable seeds, so removing flowers does help control the plants, but by far the small tubers and rhizomes are the primary means of propagation.

Yellow nutsedge is very aggressive; its pointy foliage can pierce black plastic and organic mulches. It often grows in patches with many plants quickly covering an area. For years I have had it in my community vegetable garden in Plymouth. While it is less common in cultivated areas, it still persists due to the heavy stand it makes each summer in the walkways between vegetable plots. Even walking on it does not slow its growth.

Control for yellow nutsedge is either vigilant cultivation and removal of plants, tubers, and rhizomes by hand and mechanical tilling; or repeated use of non-selective herbicide. Nutsedge is a difficult weed to control, but it can be managed.

View additional nutsedge images along with a list of appropriate herbicides.

Pennsylvania sedge, Carex pensylvanica
flowers in early spring in MN
and tolerates dry shady sites.
Photo: Mary H. Meyer
Comparison of Nutsedge and Ornamental Sedges

  • Cyperus genus (perfect flowers in terminal clusters)
  • Shiny, yellow-green foliage
  • White leaf base
  • Triangular stems; 3 ranked foliage
  • Leaves have conspicuous midrib
  • Fast growing, Very aggressive
  • Small nut among roots
  • Yellow umbel of flowers

Landscape or Ornamental sedges
  • Carex genus (male and female flowers separate, often separated along stem)
  • Foliage color varies: striped, blue-green, green, coarse to fine texture
  • Leaf bases red, brown or green, not bright white
Sprengle’s sedge, Carex sprengelii
is an easy to grow native sedge in MN.
Photo: Mary H. Meyer
  • Triangular stems, three ranked foliage, but may be difficult to locate with much of the plant being basal foliage
  • Slower growing
  • No nut like bulbs at roots
  • Flowers brown or green, usually not conspicuous, often along stem


Lanini, W. T. and Wertz, B. Yellow Nutsedge. accessed 4 December 2015. Penn State Extension.

Shonbeck, M. Weed Profile: Yellow Nutsedge (Cyperus esculentus and Purple Nutsedge (C. rotundus). Organic Agriculture at eXtension. Accessed 8 December 2015.

Uva, R. J. Neal, and J. Ditomaso. 1997. Weeds of the Northeast. Cornell University Press, Ithaca, N.Y.
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