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Extension > Yard and Garden News > October 2014

Friday, October 31, 2014

Millipedes in vegetables

Jeffrey Hahn, Extension Entomologist


Jerry Wenzel

Photo 1: Despite the circumstantial evidence, the millipedes did not damage this carrot; they are taking advantage of previous damage.

A couple of home gardeners encountered millipedes in some of their vegetables during October. In one case they were in a few potatoes, in another instance they were infesting a carrot. There was concern whether the millipedes were attacking healthy vegetables. Fortunately, the millipedes were not causing damage in the garden. They have weak mouthparts and are only capable of feeding on decaying organic matter. It is possible for them to feed on plants that have already been damaged but they are not attacking healthy plants.

A 2012 research article in the Journal of Applied Entomology looked at the potential of millipedes and wireworms to attack carrots (also sweet potatoes). They found the presence of the millipedes was associated with wireworm damage to carrots. The millipedes themselves were not causing damage but were there as a result of preexisting wireworm injury. That is also what is probably happening with the presence of millipedes in the potatoes. The millipedes were not damaging the tubers but were there because of other damage (probably wireworms).

Fortunately wireworm damage is not common in home gardens and this kind of injury (as well invasion by millipedes) should not be a problem very often.

Thursday, October 30, 2014

Don't worry about snowfleas

Jeffrey Hahn, Extension Entomologist


Diane Peterson

Photo 1: These strange black lines are composed of large numbers of snowfleas

A couple of homeowners discovered an odd situation in their lawns during mid to late October. From a distance, they could see long, black lines in the grass. Upon closer inspection, they discovered that the black lines were actually due to many tiny insects. Examining the insects under magnification revealed that they were snowfleas, a type of springtail.

Springtails get their name because of their ability to jump. They feed on decaying organic matter as well as fungi, pollen, and algae. They are very abundant insects but because of their small size and that they are usually found in leaf litter, soil, and other generally hidden places, people do not usually notice them. Until, that is, they occur in large numbers.


Jeff Hahn, Univ. of Minnesota Extension

Photo 2: Snowfleas are most commonly seen on top of snow.

Snowfleas are particularly interesting because they are cold tolerant. They are typically seen during late winter and early spring as the snow starts to melt and they congregate, often in large numbers.  Fortunately, whether you see snowfleas now or on top of snow later, they are harmless to turf and should be ignored. They will eventually go away on their own.

Monday, October 27, 2014

WCCO "Smart Gardens" Radio Show - October 18 & 25, 2014

Thanks for listening!

We aren't always able to answer everyone's texted questions on the air, so we try to post a few along with answers here in the Yard & Garden News blog. Remember that you can always visit the U of M Extension Garden website for loads of gardening resources. And feel free to share your gardening stories here by clicking on "Leave a comment" above.
Hope you join us and our host Denny Long every Saturday, 8-9am, on WCCO Smart Gardens and happy gardening!

American Bittersweet 'Autumn Revolution': Thanks to to listeners last week who shared via text the bittersweet cultivar 'Autumn Revolution' (Celastrus scandens 'Bailumn') developed by Bailey Nurseries, Newport, MN. This bittersweet has 'perfect' flowers - male and female parts on each flower - unlike the species bittersweet which has separate male and female flowered plants.

Overwintering perennials in containers: Perennials are best overwintered planted in the soil. However, they are used in container plantings and some listeners have asked how to overwinter them. There's no guarantee, but certainly worth a try. The goal is to allow the plant to gradually go dormant as it would in the ground, but protect the roots from cold air as they would be in the soil. Try overwintering these plants by tipping the container over onto the soil and covering in leaf mulch, wood mulch or straw. Or try placing the container in a cool location such as a cellar or heated garage (about 40-50 degrees F.) If it's not too much work, you could also dig a hole in your garden or compost pile and bury the container up to its rim, covering the top of the soil with straw or leaf mulch. Do not water them, but allow them to go dormant. When the weather warms up and you start to see plants emerging in your garden,  tip the container over / move the container out into the sun and start watering.

Do pileated woodpeckers cause oak wilt? This was the first time someone has asked me this - and I truly never thought about it! Oak wilt is spread overland by sap-feeding beetles, and underground by infected roots grafting onto healthy roots. I could find nothing that indicated woodpeckers or other birds spread oak wilt. As home owners, be alert to the signs and symptoms of oak wilt, and avoid pruning oaks April - June or whenever you see the active beetles. Remember that dates provided are recommendations - you still need to be vigilant in your yards and gardens. For more on oak wilt: MN DNR 

Dividing perennials: If you are considering dividing your perennials - including hardy hibiscus (Hibiscus moscheutos) as asked by one listener, here is a terrific publication / chart Dividing Perennials you can use as a reference. Notice that there are some perennials that should not be divided - and Hibiscus moscheutos should be divided every 10+ years according to the above publication. Make sure your planting location is large enough for your selected plant to grow to full maturity.

Must I wait till freeze to dig calla and canna bulbs? Calla and canna are summer-blooming tuber-like rhizomes and really quite stunning plants. However, unlike bulbs like tulips and daffodils that require cold treatment, calla and cannas do not survive our winter temperatures and must be dug in the fall and re-planted each spring. Dig them now as you don't want to risk the rhizomes freezing. According to our Extension publication Calla and Canna Lilies: "They bloom mid-summer to frost. In the fall, dig up the rhizomes, cut the stems back to 2-3 inches, and let them dry. Leave them in a box in a cool part of the house where they will not freeze, such as a basement where the temperatures range between 40-50 degrees. Every few years, the rhizomes may be divided. When dividing, each piece must have an eye or growing point on it. Let the cut-up rhizomes dry for a few days before planting them."

Thursday, October 23, 2014

Turf and Bees: What's the buzz on pesticides in lawns?

By Ian Lane, Graduate Research Assistant

If you have been paying attention to the news lately, you know that bees have been making headlines. News outlets have done an amazing job of helping scientists sound the alarm on unsettling declines in bee pollinators. While we have good evidence for declines in honey bees and some of their cousins, the bumble bees, the cause of this decline is hard to pinpoint. Current thinking in the scientific community puts the decline down to a number of interacting factors, including reduction in stable food sources, introduction of bee diseases, and the irresponsible use of insecticides. While it's difficult to tease apart how these factors interact, we do have some good knowledge about how lawns fit into this theoretical framework.


Sam Bauer

Photo 1: White clover and dandelion can provide great early season forage for pollinators in lawns


Herbicides


Lawns are home to a number of weeds that are the bane of homeowners. While our gut reaction may be to reach for a herbicide, it's worth noting that many weeds actually can provide high quality forage for bees. Two of the most important lawn forage plants are the common dandelion (Taraxacum officinale) and Dutch white clover (Trifolium repens). Dandelions are one of the earliest, and often only, blooming flowers of spring. This early source of pollen and nectar is essential to overwintering honey bee colonies as they begin the process of raising new workers. White clover is another spring bloomer (though not as early) that provides highly nutritious pollen throughout the year. While the exact nature of bee's relationship with these flowers isn't widely studied, recent research at the University of Kentucky sought to characterize the types of bees visiting dandelions and clover. They found surprising diversity on white clover, including a number of at risk bumble bees (Larson et al. 2014). Similar preliminary research here at the University of Minnesota confirms many of their findings.

There may also be some solutions for homeowners looking to control weeds but leave clover in their lawn. One common herbicide known as 2,4-D is effective on many broadleaf weeds, but generally ineffective on clover. Small demonstration trials at the University of Minnesota confirm that 2,4-D has relatively low action on clover but is relatively effective against other weeds.

Insecticides


The another type of pesticide that can make a big impact on bees are insecticides . Much of the recent attention on pollinators has focused on a class of insecticides known as the neonicotinoids. Neonicotinoids are used in turf to help control a number of insect pests, most importantly grubs. They work by "dissolving" into the irrigation water or rain, which is then taken up by the plant and becomes part of the leaf and root tissue. This ensures that any insect munching on the tissues of your grass gets a lethal dose, and your lawn stays green. While bees would never have a reason to take a bite of your grass, your helpful lawn weeds are a different story. It turns out that not only do these insecticides move into plant leaves and roots, but the nectar and pollen of the flowering weeds as well.

Many studies have looked to see if neonicotinoids applied to lawns full of clover have negative effects on bumblebee colonies. The researchers in Kentucky do this by getting a colony of the commercially available common eastern bumble bee (Bombus impatiens), placing it on a patch of flowering clover that is treated with a neonicotinoid, then caging them so they are forced to forage on the treated clover. These experiments are always accompanied with a similar set-up but on a non-treated patch as a point of comparison. Here again the University of Kentucky has been leading the way with a study published in 2002 (Gels et al. 2002) that found if imidacloprid (a type of neonicotinoid) was applied to flowering turf without any post application irrigation that bumble bee colonies suffered worker weight loss, increased worker death, and sluggish behavior. However, if irrigation was applied directly following these imidacloprid applications, no negative responses were seen.

Similar responses were seen in a study investigating clothianidin, another type of neonicotinoid (Larson et al. 2013). Bumble bee colonies that were confined over patches of flowering clover, and that had the high label rates of clothianidin applied to the turf, saw dramatic effects on the number of workers, new queens, as well as total colony weight when compared to control colonies. The effects of irrigation were not part of this study, but when clover nectar from nearby sights that had been applied with clothianidin were sampled, they found high amounts of the neonicotinoid. This study's main aim was to compare clothianidin to a new chemistry of insecticides called anthranilic diamide (specifically chlorantraniliprole). This new class of chemical had seemingly no adverse effects on bumble bee colonies when compared to the controls. While there is more research to be done, this is a promising alternative to neonicotinoids for insect control in turf. You can currently purchase chlorantraniliprole for use on residential and commercial turf, and trade names include "Scott's Grubex" or Syngenta's "Acelepryn".

While urban landscapes and lawns are only one part of a very large system, they are nevertheless an important part of a vast majority of people's lives. Promoting animal diversity in urban landscapes, be it pollinator or other, helps improve important issues related to stormwater runoff (rain gardens and buffer strips) and urban agriculture (pollination and biocontrol services) and also enriches everyday life through learning opportunities and aesthetic value. Even the smallest effort, such as leaving some weedy flowers or choosing a safer insecticide, may make a difference.

Stay Informed


A new series on pollinators is being offered by the University of Minnesota Landscape Arboretum. "Pollinators: What you need to know and how to make a difference" is a 3-part series focusing on: 1) Plants and People, 2) Pesticides and Other Problems, and 3) Policies and Politics.

The Minnesota Turf and Grounds Foundation will be offering a 1-day session on Super Tuesday of the Northern Green Expo, January 13th, 2015. "Bee Aware: The importance of pollinators in the landscape" will feature expert presenters discussing real world issues surrounding pollinators, as well as practical strategies to promote them in the landscape. Stay tuned to www.mtgf.org as this program develops.

Works Referenced


Gels, J. A., D. W. Held, and D. A. Potter. 2002. Hazards of Insecticides to the Bumble Bees Bombus impatiens (Hymenoptera : Apidae ) Foraging on Flowering White Clover in Turf. J. Econ. Entomol. 95: 722-728.

Larson, J. L., A. J. Kesheimer, and D. A. Potter. 2014. Pollinator assemblages on dandelions and white clover in urban and suburban lawns. J. Insect Conserv. 18: 863-873

Larson, J. L., C. T. Redmond, and D. A. Potter. 2013. Assessing insecticide hazard to bumble bees foraging on flowering weeds in treated lawns. PLoS One. 8: e66375.

Sunday, October 12, 2014

Forest Pest Workshops Scheduled in SE Minnesota

Jeffrey Hahn, Extension Entomologist

Rochester will host two workshops in response to the recent discovery of emerald ash borer (EAB) in Olmsted County. The first will be a Forest Pest First Detector workshop to be held on Wednesday, November 5th from 9 AM - 3:30 PM. The cost is $40 (lunch included). In addition to EAB, other pests to be discussed include gypsy moth, Asian longhorned beetle, thousand canker disease, and Oriental bittersweet.



Jeff Hahn, Univ. of Minnesota Extension

Photo 1: Learn about emerald ash borer and other forest pests at a First Detector workshop.

The Minnesota Forest Pest First Detectors training program is designed to help identify the occurrence of Emerald Ash Borer and other forest pests in Minnesota. First Detectors are the front line of defense against likely infestations. Meeting, working with and educating the public about exotic forest pests are key activities of Forest Pest First Detectors.

Everyone is welcome to attend - even if you do not wish to become a Forest Pest First Detector! Anyone with a background in tree or forest health should consider becoming a Forest Pest First Detector.

Forest Pest First Detectors must complete online training modules before attending the one-day Forest Pest First Detector training and commit to being available and involved with the program after completing the training. Involvement includes being accessible to the public, willing to conduct site visits if necessary, report forest pest-related activities, protect confidential information, and notifying organizers of current contact information.

Visit My Minnesota Woods for more information.

To register, visit here.

An Ash Management for Woodland Owners workshop is scheduled on Wednesday, November 12 from 9 AM to noon. Ash Management for Woodland Owners will include information about EAB and managing your woodland in the era of EAB. An outdoor field tour will follow an indoor presentation. This workshop is intended for woodland owners. There is a $20 fee to attend this workshop.

To register for one or both classes go to this site.

Thursday, October 2, 2014

October 1st Issue of Yard and Garden News

In this issue:

Don't Confuse Yellowjackets and Bees

Late Fall Vegetable Gardening - Pest Management

Ground nesting BEES Colletes Part I: Building a nest

Ground nesting BEES Colletes Part II: Foraging

Ground nesting BEES Colletes Part II: Foraging

Karl Foord, Extension Educator - Horticulture

Watching these bees leave their nest and returning covered with pollen was quite enjoyable.

I will let the video speak for itself. Please enjoy. Colletes foraging.

Ground nesting BEES Colletes Part I: Building a nest

Karl Foord, Extension Educator - Horticulture

One of our early emerging vernal native bees is in the genus Colletes. These bees are commonly called plasterer bees, cellophane, or polyester bees. This is because the bee builds an underground nest and then paints/applies/lines her nest with a cellophane-like plastic material secreted from an abdominal gland. The bee applies this material with her two-lobe tipped tongue. This secretion helps protect the developing bees from fungal disease and acts as a waterproof barrier. It is so effective that ground-nesting species can occupy areas prone to flooding.

I photographed a Colletes bee digging a nest. The nest took several hours to dig which I videoed and then cut out much of the inactivity to create a 5 minute video.

One of today's landscaping rules-of-thumb is to cover bare soil with mulch to both prevent erosion and discourage weed encroachment. This makes sense, however should we reconsider this practice in light of our need to provide nesting habitat for native bees? Perhaps there are areas in the garden or proximal to the garden which could be left open and undisturbed.

Though not specifically stated open soil areas were considered a sign slovenliness, something not tolerated in my upbringing environment. Somewhat along the line of "There are no dirty or lazy Zimmerman's". Something my maternal grandmother used to say.

The two main threats to most pollinators include habitat loss and pesticide use.

You can create a welcoming environment to ground nesting bees by doing the following:

1. Leave bare patches of ground in your garden or yard to help provide nesting sites. It may look unkempt but it is unkempt with a purpose.

2. Plant a variety of bee friendly nectar and pollen rich native plants. A good place to start is "Plants for Minnesota Bees" by Elaine Evans.



Elaine Evans

Photo 1: Plants for Minnesota Bees (front)





Elaine Evans

Photo 2: Plants for Minnesota Bees (back)

3. I have decided that to the extent possible I would rather watch what is happening in my garden then attempt to kill certain pests with the high likelihood of killing beneficials. My worst garden pest is the four-lined plant bug which attacks my anise hyssop. Given how I feel about anise hyssop (possibly the best bee plant I have encountered) you can imagine how motivated I would be to remove these pests. I have controlled them to my satisfaction by clapping my hands on the leaves where I see the bugs. The leaves tolerate this much more than the four-lined plant bugs. Avoiding the use of synthetic pesticides in your garden and on your lawn is recommended.
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