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Showing posts from August, 2010

Contents: September 1, 2010 and Monarch Caterpillars

Knowing when it's time to say goodbye.

Gary Johnson, UMN Extension Professor, Urban and Community Forestry, Department of Forest Resources

Preventative cabling such as this dynamic system greatly reduces the likelihood of failure during wind, ice or snow loading events.
Gary Johnson.No one willingly lets go of old friends, whether they're human, pets or (ahem) trees. But the reality of life is that there's an aging process that's inevitable and not all problems can be diagnosed and successfully treated. So that old friend that sheltered you from harsh winter winds, shaded you on hot summer afternoons when the heat index was over 100 degrees, greeted you in the spring with a bouquet of flowers...must eventually or prematurely be removed.

Four Questions Before Letting Go

Gardeners of all shapes and degrees tend to be incredibly hopeful. For example, when news comes along that there's a new cure for emerald ash borer (have you heard about the fruit juice and dish soap treatment yet?), the urge is to try it wit…

September Home Lawn Care To-do List

Bob Mugaas, UMN Extension Educator

1. One of the very best times of the year to be fertilizing your lawn is from about Labor Day through the middle of September. Applications that put down about one pound of nitrogen per 1000 square feet will help provide the necessary nutrition through the late summer / fall period - a time of active grass shoot and root growth.

2. It is important to avoid serious water stress on lawns this time of year. As noted above, the late summer /early fall period is a time of active growth. Hence, not only is sufficient nutrition important but ample soil water is just as important to sustain and encourage growth. Early in September, the average rule of thumb of one inch of water per week including rainfall should be sufficient. As we get later into September and early October, that same one inch of water may be sufficient for two or even three weeks depending on weather conditions. That is, the warmer and drier the weather the more frequentl…

Dogwood Sawflies

Jeffrey Hahn, Asst. Extension Entomologist

Dogwood sawflies been found defoliating dogwoods during late August. In all of the reported cases, defoliation was severe and apparently appeared suddenly. However, despite the apparent sudden appearance, these sawflies have a actually been present for weeks but just went unobserved when they first started feeding.
Adults are active any time from late May through July. After the larvae first hatch, they are covered in a whitish material which some entomologists believe helps the sawflies resemble bird droppings, protecting them from predation. The young larvae skeletonize leaves, i.e. feed between the veins. Older larvae consume the entire leaf except for the midrib. As mature larvae, dogwood sawflies are about one inch long. Also, the whitish material comes off, revealing their greenish - yellowish, conspicuously spotted bodies.

When they are done feeding, they wander off looking for places to pupate, preferring rotted wood. Dogwood …

Woolly Oak Gall

Jeffrey Hahn, Asst. Extension Entomologist

People have been commonly finding about one inch long fuzzy or woolly looking growths on the leaves of oak trees, especially species in the white oak group. These galls are either reddish or whitish or sometimes both. Despite their appearance, these growths are not disease, but is abnormal plant tissue due to the feeding of the larvae of tiny non-stinging insects called cynipid (sin-IP-id) wasps. These galls are common and like other leaf galls, have very little, if any, impact on tree health, especially if they are vigorous, mature oaks. These galls generally do not become very abundant and their numbers vary from year to year on individual trees. By the time you see leaf galls, it is already too late treat them, just ignore them.

Mildew Aplenty on Minnesota's Pumpkins, Squash and Cucumbers

Michelle Grabowski, University of Minnesota Extension Educator

Two types of mildew can be seen on pumpkins, squash and cucumbers in Minnesota this August. Powdery mildew and downy mildew have both been reported. Despite the similarities in their names, these two diseases are caused by very different pathogens and have very different symptoms and control strategies.

Powdery Mildew
Photo 1: Powdery mildew on squash M.Grabowski, UMN Extension.Powdery mildew is caused by the fungus Podosphaera xanthii. As its name implies, this disease can be recognized by the powdery white fungal growth on leaves and stems. Infections often start as a few white powdery spots but can quickly grow to cover the entire leaf in a layer of powdery white fungal spores and mycelia.

Although the powdery mildew fungi do not commonly attack squash fruit, yield of infected plants can be reduced because infected plants have less energy to invest in fruit. Often severely infected plants produce fewer and smaller squash, c…

Winter Damage in Apples

Karl Foord, UMN Extension Educator

Preparation for winter

Plants acclimate or develop hardiness to freezing temperatures in response to changes in light duration and temperature. Acclimation is a two-stage process. The first stage is initiated by decreasing day length and results in partial hardiness. The second stage is initiated by subfreezing temperatures and results in full hardiness and acclimation. The hardening response in a plant may vary from year to year because of variation in temperatures over that year. The degree of cold hardiness of a plant is determined by the genetic capacity of a plant to acclimate to freezing temperatures and transform its tissues from a non-hardy to a winter hardy state. Plants are often given a cold hardiness rating based on the lowest midwinter temperature that plant tissues can endure relative to the USDA winter hardiness zone temperature bands. For example, Honeycrisp has a winter hardiness rating of USDA hardiness zone 3 (-40 to -30 F).


The Taste of Minnesota Apples - An Adventure

Karl Foord, UMN Extension Educator

I did an apple tasting exercise with 24 young people last summer and we tasted the following apples traditionally available at grocery stores, Granny Smith, Golden Delicious, Jonagold, Tentation, Fuji, American Cameo, Royal Gala, and Red Delicious. More then half of the young people chose Fuji as their number one choice. Given this array of apples my taste buds agreed with theirs.

Then I started tasting local Minnesota Apples. Quite frankly I was astonished. These were excellent apples and in my opinion outclassed all of the commercially available apples previously tested. Granted the store apples had either been grown in Washington State and stored for 10 months, or had been shipped from either Chile or New Zealand. The Minnesota apples were fresh. Certainly tastes differ significantly among people and a recommendation is simply my opinion. You must discover for yourself as it is your taste and opinion that will render the final decision.

We …

Fungus Among Us

Photo 1: Stinkhorn fungi Photo by M.Grabowski UMN Extension.Frequent summer rains, wet soils and humid conditions have created a favorable environment for a wide variety of fungi this summer. Gardeners are noticing mushrooms, shelf fungi, and other odd and interesting fungal spore producing structures of all shapes, sizes and colors sprouting in the landscape. The question then arises, which of these fungi should a gardener be concerned about?

Although it is true that more plant diseases are caused by fungi than any other type of pathogen, only 11% of all fungi are capable of causing disease in plants at all. The grand majority of fungi are saprophytes. That is they survive by breaking down organic matter and absorbing nutrients from it. In many cases, the mushrooms sprouting in the woodchip mulch or pushing up through the lawn are not harming the nearby plants, but are working on breaking down woodchips, plant debris or other organic matter.

Two saprophytic fungi commonly found in Minn…

Be On the Watch For Yellowjackets

Jeffrey Hahn, Extension Entomologist

The early spring has contributed to an above average number of yellowjackets this summer. Yellowjackets can be found nesting in a variety of different places, depending on the particular species. They range from aerial nests, e.g. hanging from tree limbs or the eaves of homes to subterranean nests, e.g. nesting in old mouse burrows to nesting in various voids in buildings. These nests, especially the cryptic ones, are present all season, but may not be noticed until late summer when the workers are more numerous.

If a yellowjacket nest is located in a site away from human traffic and is not a risk for stings, then just ignore it. Yellowjackets are beneficial because of the insects on which they prey. All of the inhabitants of the nest will eventually die in the fall when freezing temperatures arrive. If however, the nest is located somewhere where people could get stung, then the nest should be eliminated. There are some situations where you…

Plant Hardiness Zones Revisited

Karl Foord, UMN Extension Educator

If a particular temperature recording station has an average minimum low temperature of between - 30F to - 25F then the station would be in 4a. If the range was - 25 F to - 20 F then this station would be part of the 4b hardiness zone. The same logic determining the temperature ranges for Zone 2b [-45 to -40 F], Zone 3a [-40 to -35 F], and Zone 3b [-35 to - 30 F].

The average part of this calculation gave me concern because if it is an average then there must be numbers less than and greater than the average. The question then becomes how wide is the distribution around the average?

Minneapolis is in the 4a plant hardiness zone with a low minimum temperature range of -30 F to - 25 F. Over the last one hundred and eleven years low minimum temperatures have exceeded this range 10% of the time, but only by four degrees at the most1. Temperature data for the last 10 years (2000-2009) places Minneapolis in hardiness zone 4b. If we are willing to accept …

Garden Calendar: August 15, 2010

The apple harvest is starting, with Paula Reds and State Fairs already ripe. The Zestar in Southern Minnesota should be ready for harvesting within the next week or two.
Sooty blotch and fly speck fungi have shown up. (See pictures)
Disease and insect pressure has been high this summer.

Photo credits: Karl Foord

Yard and Garden News Editor: Karl Foord

Technical Editor: Bridget Barton