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8/12/2013 - 8/18/2013

Best Practices to Promote Pollinator Habitat

By Matt O’Neal and Erin Hodgson, Department of Entomology

The European Union’s restriction on the use of neonicotinoids and the joint USDA/EPA report of a continued decline in honey bees reminds us of the on-going issues with pollinator health. Specifically, the decline of honey bee populations is reaching a breaking point for pollinated crops in the United States. In an article published in Wired magazine (Keim 2013), entomologist Dennis vanEngelstorp from the University of Maryland noted, “We’re getting closer and closer to the point where we don’t have enough bees in this country to meet pollination demands.”

Although the factors thought to be causing this decline are many, there are some simple things we can do to help conserve bees. All bees share some basic needs: something to eat and someplace to live. As noted in the USDA/EPA report, the habitat that is available to bees in the United States is shrinking in size and declining in quality. To reverse this trend, several universities, including Iowa State University, are investigating how to get more high-quality habitat in our landscape. This article will review this work and provide some ‘best practices to conserve bees.


Providing bees food

Midwest researchers have focused on native plants as a food source for bees and other beneficial insects. These plants include flowering perennials commonly found in prairies. At Michigan State University, Doug Landis is leading a team to study which of these plants and plant mixtures is most attractive to beneficial insects and least attractive to pest insects. Their research is summarized on a website that rates plant attractiveness and gives recommendations for growing them. Also, a chart showing when these plants bloom is included. They recommend selecting a combination of plants that provide flowers from spring to fall so that bees have a constant source of nectar and pollen.

Photo 1. Cup plant (Siplhium perfoliatum) is a perennial plant that bees find very attractive, like this bumble bee. These plants grow 4 to 10 feet tall and produce several flowers during July and August in Iowa. Photo by Adam Varenhorst.


At Iowa State University, we investigated if the MSU recommendation would be more attractive to beneficial insects than other plants commonly found in the Iowa. We created a mix of plants from the list provided by MSU that were rated the most attractive to beneficial insects. The mix was constructed of 12 plants that provided a habitat that flowered throughout the growing season. With funding from the Leopold Center for Sustainable Agriculture, we observed during a two-year study that the ‘best-bet mix’ attracted more bees than single plant species (e.g., corn, switch grass, alfalfa or willow) and a mix of prairie plants currently recommend for reconstructing prairie. Furthermore, if the plant mixture was reduced to just two species, such as cup plant (Photo 1) and golden alexanders, it still out-performed most of the single plant treatments.


Photo 2.The ‘MSU best bet mix’ is comprised of 12 species of plants commonly found in prairies. This picture was taken in August when cup plant, pinnate coneflower (Ratibida pinnata) and swamp milkweed (Asclepias incarnate) are flowering. The best bet had the most bees of the nine different treatment options tested. Photo by Adam Varenhorst.


Providing bees a place to live

Bees also need a place to live. For honey bees, this is usually a hive box provided by a beekeeper. But honey bees are only one of the nearly thousands of bees found in North America. Most of these bees are not social and build nests alone. Depending upon the species, these nests can be found in the ground or in living or dead plants. Creating nesting habitat for bees can include providing undisturbed soil to building ‘bee hotels’ that offer material like stems, drinking straws and wood blocks with holes. The Xerces Society is a non-governmental organization that is focused on pollinator conservation. The Xerces Society has several fact sheets for how best to provide nesting habitat for ground nesting and stem nesting bees. Included in these recommendations are guides for building artificial nests.


Reducing harm from insecticides

After providing food and nesting habitat, beekeepers can take an extra step to reduce the impact of insecticides. The Iowa Department of Agriculture and Land Stewardship has an apiculturist (honey beekeeping expert), Andrew Joseph, who maintains a registry of honey bee hives in Iowa. This registry is available for insecticide applicators so that they can contact beekeepers. By registering hives, beekeepers can make adjustments to limit exposure. At the same time, applicators are required to adjust their application time to early evening, when honey bees are less likely to forage.



Keim, B. One-third of U.S. honey bee colonies died last winter, threatening food supply. 2013. Wired.


Matt O’Neal is an associate professor of entomology; contact him at or phone 515-294-8622. Erin Hodgson is an associate professor of entomology with extension and research responsibilities; contact her at or phone 515-294-2847.

Sign Up Now for Late Season Disease Workshop

By Alison Robertson and Daren Mueller, Department of Plant Pathology and Microbiology, and Stuart McCulloh, Field Extension Education Laboratory

Registration is now open for the annual Late Season Disease Workshop that will be held August 21-22 at Iowa State University's Field Education Laboratory located between Ames and Boone. This hands-on, two-day field workshop will be a good opportunity for those in agribusiness to improve their knowledge of corn and soybean diseases. Both days will include field and lab exercises as well as in-depth presentations. To improve participants’ diagnostic skills, each day of the workshop will feature a comprehensive session on disease diagnosis that will include “lab” work and field scouting.  

Dr. Greg Tylka will cover the biology of nematodes that feed on corn and soybean cyst nematode. He also will discuss on-going research related to these pathogens, as well as management techniques for today and in the future.

Dr. Alison Robertson will lead a discussion on Goss’s wilt and leaf blight as well as Stewarts wilt and leaf blight of corn. The entire class will also partake in a field trip to a nursery inoculated with both pathogens. Dr. Daren Mueller will lead a discussion on sudden death syndrome of soybean. The disease cycle of these important diseases will be reviewed and recent research results shared by graduate students and post-docs.

Participants have the option to sign-in for a total of 11 pest management continuing education units (CEUs) for certified crop advisors. Registration may be done at

Class size is limited, and registrations are taken on a first-come-first-serve basis. If you have questions, please email Alison Robertson,, Daren Mueller,, or Stuart McCulloh,

Scout Crops for Aphids

By Erin Hodgson, Department of Entomology

Earlier this summer, I found aphids in V4 corn in central Iowa. This early establishment is unusual because most aphids that feed on corn have to migrate from the southern United States every summer. My lab also found soybean aphid in vegetative soybean at most of the Iowa State University Research Farms in June. Although they can overwinter in Iowa, larger colonies have not recently formed until after bloom. Pea aphids have also been reported in alfalfa in northeastern Iowa. All these aphid detections prompted me to summarize a few scouting reminders and treatment thresholds for aphids in field crops.


Soybean aphid

This is the only species in Iowa that will colonize soybean. Scout weekly from plant emergence until seed set. Aphids prefer to feed on the undersides of leaves and will establish on the newest leaves. If a large colony develops, they will feed on stems. Initial infestations are patchy and located near field edges, but winged aphids can quickly disperse within and between fields. Commercial fields that have reached uniform infestation should be closely monitored in August. 

Photo 1. Turn over soybean leaves to estimate soybean aphid density.


The economic threshold for soybean aphid is well established for the north-central region. Consider a foliar application when the average density exceeds 250 per plant. Populations should be increasing and most of the plants have to be infested (>80 percent) to justify an application. This threshold is appropriate until plants reach mid-seed set (R5.5; Photo 2). Spraying at full seed set (R6) or later has not produced a consistent yield benefit.

Photo 2. Mid-seed set (R5.5) have seeds that are expanding in the pod. Photo by ISU Extension.


Aphids in corn

There are several species of aphids that can feed on corn. They prefer to feed on small grains, but will use corn as a host. Aphid infestations in corn have been sporadic in Iowa the last five years, but should be monitored after silking. A widespread outbreak occurred in northwestern Iowa in 2011. Populations are typically aggregated at field edges, but winged aphids can move to field interiors. Aphids will colonize the stalk, leaves and ear (Photo 3).

Photo 3. Pay special attention to aphids at or above the ear leaf. Photo by Brian Lang.


Currently, there are no treatment thresholds for aphids in corn past tasseling. But regular sampling will help you make educated decisions about a foliar application at this time. Consider a foliar application when most of the plants are infested (>80 percent), and aphids are have exceeded 500-1,000 per plant. An insecticide may be warranted if aphid honeydew and sooty mold are evident above the ear leaf and plants have not reached hard dent (R5).


Aphids in alfalfa

Like in corn, there are several species of aphids that will feed in alfalfa. Although considered secondary pests, aphids can build up to high densities. Scout fields weekly to monitor for aphid arrival and spread within a field.

Photo 4. Pea aphids can be pink or green. Photo by Brian Lang.


Treatment thresholds for aphids in alfalfa depend on the species and size of plant. Use Table 1 as a management guideline. Depending on the cutting cycle, harvest would be an effective control strategy instead of insecticides.

Table 1. Treatment guidelines for aphids (per stem) in alfalfa.


General aphid management

Ideally, droplets should make contact with the aphids for the greatest knockdown. Increasing volume and pressure will improve the efficacy of foliar insecticides. For ground applications, use 20 gallons of water per acre and 40 pounds of pressure per square inch. Be aware that some foliar insecticides have a 60-day preharvest interval. Check the label and the calendar when making product selections.


Erin Hodgson is an associate professor of entomology with extension and research responsibilities; contact at or phone 515-294-2847.

This article was published originally on 8/19/2013 The information contained within the article may or may not be up to date depending on when you are accessing the information.

Links to this material are strongly encouraged. This article may be republished without further permission if it is published as written and includes credit to the author, Integrated Crop Management News and Iowa State University Extension. Prior permission from the author is required if this article is republished in any other manner.