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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 neonicitinoids. Neonicitinoids 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 neonicitinoids 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 neonicitinoid, 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 neonicitinoid) 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 neonicitinoid (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 neonicitinoid. 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 neonicitinoids 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.

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.

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.

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 slovenlyness, 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 liklihood of killing beneficials. My worst garden pest is the fourlined 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 fourlined plant bugs. Avoiding the use of synthetic pesticides in your garden and on your lawn is recommended.


Late Fall Vegetable Gardening - Pest Management

Cindy Tong, UMN Extension Specialist

UMN Dept. of Entomology

Photo 1: Adult Colorado Potato Beetle

Take care of those pests, or they might just come back next year! Two of the recurring pests common to most gardens are weeds, weeds, weeds and Colorado potato beetles. Weeds are plants that have evolved successful strategies for competing against other plants, like developing spreading rhizomes (think Creeping Charlie) or lots and lots and lots and lots of small seeds (amaranth). If your garden has weeds that are blooming or forming seeds, it's worthwhile to take them out even now. Otherwise, those lots and lots and lots and lots of seeds will drop to the ground and stay in the soil, making up a big part of the seedbank, from which future generations of weeds will grow.

Colorado potato beetle adults may still be laying eggs, even if your potato plants are going to be dug up soon. Even if there soon won't be anything for those beetles or their young to eat, it's still worthwhile killing the adults because they can overwinter in nearby brush, and then come back out next spring!

Don't Confuse Yellowjackets and Bees

Jeffrey Hahn, Extension Entomologist

Jeff Hahn, Univ of MN Extension

Photo 1: Yellowjackets are black and yellow with few hairs and construct nests made of a papery material.

As the summer winds down, people have been commonly finding insects nesting in and around their homes. There can be confusion whether people are seeing yellowjackets or honey bees. There is tendency for people to call all stinging insects "bees". This has been compounded with the recent attention in the media on honey bees so people are thinking about them even more. While yellowjackets and honey bees both can sting, they have very different biologies. At this time of the year, people are most often seeing yellowjackets.

Jeff Hahn, Univ of MN Extension

Photo 2: Honey bees are brown and black and hairy. Don't confuse them with yellowjackets.

A yellowjacket is about ½ inch long (this can vary some), black and yellow, and relatively slender with few hairs. A baldfaced hornet, actually a kind of yellowjacket, is a little larger, about 5/8th inch long, and mostly black. Honey bees are about ½ inch long brown and black, relatively slender but have more hair.

Yellowjackets construct their nests from a papery material with the combs surrounded by an envelope, while honey bees produce combs made of wax. Yellowjacket nests can be aerial, e.g. hanging from trees or attached to buildings; hidden in cavities, such as wall voids in buildings; or subterranean e.g. constructed in old rodent burrows. In cases where the nest is hidden or subterranean, a person can see the yellowjackets flying in and out of an opening but cannot see the nest.

Honey bees typically nest in artificially constructed hives. It is possible for them to nest in cavities in homes but this is not very common. While honey bees don't nest in the ground, bumble bees do. Bumble bees are stout, robust insects, usually black and yellow, and hairy. Both yellowjackets and bumble bees have annual nests, i.e. they last one year; they die when freezing temperatures arrive in the fall. However, honey bees have perennial nests which survive the winter and can live for multiple years.

Dan Martens, Univ of MN Extension

Photo 3: While people wonder if nests like this are bee hives, the papery material it is constructed from tells us this belongs to yellowjackets

It is very important to distinguish between yellowjackets and bees. If people believe they have honey bees, they may take steps to try to protect the nest or even try to have it moved despite the potential risk of stings. While it is true beekeepers can remove and relocate honey bees from a nest (if you have a confirmed honey bee nest around a home, contact the Minnesota Hobby Beekeepers Association), they do not want to and will not get involved with a yellowjacket problem. While yellowjackets are beneficial because they are important predators, they do minimal pollinating and do not need to be saved.

If you have a yellowjacket nest on your property, there are several options for dealing with it. If the nest is located a reasonably safe distance from where people may be present and the risk of stings is minimal, then just ignore it. Eventually, all of the insects in the nest die after hard frosts occur.

If a yellowjacket nest is present and you want to control it, keep a few things in mind. First, treat the nest during late evening or early morning when the yellowjackets are least active; this will help minimize the chance of stings. If after a day there is still activity, i.e. yellowjackets are still flying in and out, then repeat the treatment. If you are uncomfortable treating a yellowjacket nest, it is always an option to hire a pest management professional to deal with it; they have the experience and the appropriate tools to expertly eliminate nests.

Jeff Hahn, Univ of MN Extension

Photo 4: Yellowjacket commonly nest in the ground too!

When yellowjackets are nesting in the ground, the most effective means of controlling them is with a dust labeled for ground dwelling insects; the workers get the dust on their bodies and carry into the nest spreading it to the rest of the colony. Pouring a liquid insecticide into the nest entrance is less likely to be effective as the liquid may not reach the nest depending on where it is located within the burrow

Jeff Hahn, Univ of MN Extension

Photo 5: Hidden yellowjacket nests are tricky to control for residents; they should hire a pest management professional to do this type of job.

If you can see the nest, e.g. it is attached to the eaves, use a wasp and hornet aerosol spray and treat directly into the nest. However, yellowjacket nests that are found inside homes in wall voids, attics, concrete blocks, or similar spaces are much more challenging to control. An aerosol insecticide is not very effective. In fact, an aerosol spray can sometimes cause the yellowjackets to look for another way out, which often leads them to the inside of homes. Also, don't seal the nest opening until you know all of the yellowjackets are dead as this can cause the same reaction. It is usually best for a pest management professional to control hidden nests in buildings.

Ultimately, yellowjackets do not survive the winter. If a nest can be ignored until freezing temperatures arrive, all of the workers and the queen will die. The only survivors are the newly mated queens which have already left the nest. They will seek out sheltered sites in which to overwinter. Next spring, they will start their own nests in different sites (old nests are not reused).

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