Field Experiment II. Alternative Forage Pesticide Mitigation

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Bee kill on Rabun Gap-Nacoochee School campus October 12, 2016

For years, commercial beekeepers have experienced late summer bee kills and colony decline in the north end of Rabun County, Georgia, USA. Something was killing bees each summer. Corn was suspected. Bee kills and corn are often associated with neonicinoids. However, a previous experiment, Field Experiment I. Environmental Pesticide Concentrations showed that the problem here is not neonicotinoids, but cyhalothrin applied to sweet corn.

We are testing whether controlled plantings of alternative forage, timed to bloom when the corn tassels, will reduce insecticide levels in the hive. The theory is that providing a pollen source with higher protein content will attract bees and keep them off the corn. This is similar to a trap crop, but instead of attracting agricultural pests away from nearby crops, we would be attracting bees away from crops treated with insecticides. If this works, it could be considered a form of companion planting with great potential.

Proposed Methodology

  1. Identify insecticide in pollen.
  2. Determine source, timing of bloom and protein content of of contaminated pollen.
  3. Plant enough higher quality pollen sources in strategic locations to provide adequate pollen to the hives in the area.
  4. Survey number of bees on each corn plot:
    1. first time corn tassels and during pollen production.
    2. once a week twice a day, morning and afternoon.
  5. Trap pollen at the hive and determine quantities of each type coming in.
  6. Test pollen for cyhalothrin

Alternative Forage (Trap Crop) Requirements

Need crops that would meet our requirements of:

  1. a pollen source that honey bees work
  2. with a higher protein content than corn (maybe not - maybe should be "more attractive than corn"[1] )
  3. that can be planted to bloom from about the 3rd week in July through the end of August,
  4. that provides a benefit to the farmer (eg cattle feed, soil improvement),
  5. can be easily planted (maybe with the same equipment used to plant corn),
  6. easily grown without insecticides,
  7. can be planted in established pastures without burndown,
  8. will not interfere with premium honey production from the Sourwood (Oxydendrum arboreum) nectar flow.

Burndown required to reduce competition

Ideally, the field would be tilled or "burned down" with a herbicide to destroy existing foliage and reduce the competition to the trap crop. As this was an established fescue pasture, the farmer didn't want it plowed or burned down. Instead, cows were kept in the pasture longer than normal to try to give the buckwheat a head start by heavily grazing the fescue.

Crops that were considered

  1. Buckwheat Fagopyrum esculentum
  2. Lavender genus Lavandula
    • Requires hot, dry climate with well drained rocky soil
  3. Rapeseed (Canola)
    • Plentiful high quality pollen
    • Nectar crystallizes quickly
  4. Sunflower
  5. Vetch genus Vicia
  6. White Sweetclover or Hubam Melilotus albus
    • poorly suited for acid soils.
    • optimal germination occurs at temperatures less than 59 degrees F that occur in the spring.
    • can be invasive depending on climate and soil pH.
  7. Wildflower pollinator mix

Buckwheat was chosen because it grows well in this climate, improves the soil, will not interfere with normal pasture or hay production, is good forage and is relatively inexpensive.

2018 Experimental Buckwheat Planting


Overseeding buckwheat in fescue pasture with a no till grain drill.

Two fescue pastures (the test and the control) were treated identically. Both pastures were fertilized in the spring and were grazed until June 20 when the cows were removed. Twelve acres of buckwheat were planted in the test pasture with a no till grain drill at the rate of 50 pounds per acre. Half of the field was planted at approximately 12 mm (1/2 inch) depth, the other half was planted at approximately 25 mm (1 inch) depth. Two different planting depths were used to stagger emergence timing to prolong the bloom period. No additional fertilizer was added. June 20th was chosen as the planting date in order to not interfere with nectar flow from Sourwood bloom which usually blooms during the month of July.


  • Emergence was 7 days after planting.
  • It rained right after planting and germination was good.
  • There was no difference in emergence time between the two sections of the test fescue pasture planted at different depths.
  • Buckwheat initially outcompeted the fescue, but growth quickly slowed except where there was cow dung.
  • First bloom was 28 days after planting.
  • Bees were on the buckwheat at all times of the day.

Pollen Analysis

Pollen Collection

Students at RGNS separate and weigh pollen trapped at a hive.

A Dadant model M00682 10-Frame Bottom Pollen Trap was installed on a colony and the pollen collected one day each week. The pollen was frozen until school started in the fall.

Pollen Separation

As a lab in an elective science course, Botany, Microbiology and Entomology, students separated the pollen by color, weighed and identified each type.

Pollen Preparation and Identification

Each type of pollen was dried, stained and examined under a optical transmission (light) microscope.

Pollen Types and Quantities

Pollen Types by Weight.
Pollen Types by Percent.

There was not enough time to identify the species of the different types of pollen. They were identified to the genus (e.g. one pollen was identified as Aster, but not which species of Aster). Each type was labeled as herbaceous (having no persistent woody stem above ground) types 1 - 4 and woody (trees) type 1 and 2.

An unexpected finding was the peak in pollen collection on August 8. A pollen dearth in early August is generally expected by commercial beekeepers in the area.

Soil Nutrient Analysis

Soil analysis of buckwheat plantings before and after.

Soil samples from the test pasture of fescue were taken before the buckwheat was planted and again after the buckwheat was finished blooming.

All of the macro nutrients increased a minimum of 11.8% (phosphorus) to a maximum of 123% (manganese) except potassium which decreased 27.6%.

The pH increased from 5.8 to 6.1.

Forage Analysis

Hula hoops where thrown out in a random manner in the test pasture and control pasture. 15 samples from each field were taken All the vegetation within the hoops were cut to the ground, removed, dried and weighed. A mass per acre calculation was done.

  • Available forage in the control fescue pasture was 5392 lbs per acre
  • Available forage in the buckwheat/fescue field was 6600 lbs per acre.

Data from Cornell University indicates that the forage quality of buckwheat is good and cattle seem to be more than happy to eat it. Cost analysis from Cornell also indicates that it is valued at 65-70% the value of alfalfa hay or approximately the same value as fescue hay.


Preliminary Conclusions

  • To compete with a crop, the alternative forage must also be treated as a crop (tilled, fertilized, weed suppressed) in order to have healthy forage that will attract bees..
  • We need to learn more about the types of corn planted and the type of pests.

Where do we go from here?

  • At this early stage of the project, we should do more basic or fundamental exploratory research. We should plant smaller test plots of widely different forages. We are considering:
    1. Sunflowers
    2. Canola
    3. Buckwheat
    4. Vetch
    5. Wildflower Pollinator Mix


Item Amount
Buckwheat Seed $549.83[5]
Planting $250.00
Soil Analysis $40
Public presentation of findings $45
Total $884.83


Major funding was provided by an $800 grant from the NRCS-USDA.

Special Thanks

Special thanks to Ricky James and crew at Osage Farms where sweet corn is available from July 1 to frost. "This place is always jammed. Quality of produce, fair prices, lots of choices and incredible silver queen corn on the cob that's really fresh." Google Reviews


Amanda Ellis, Jamie Ellis, Michael O'Malley, and Catherine Zettel Nalen The Benefits of Pollen to Honey Bees

Plant species differ in the quantity and quality of pollen produced. Some plants may produce an abundance of pollen, but the pollen may be of poor quality, whereas others may produce very little but high quality pollen. Plants that are closely related (within the same genus) tend to have similar amounts of crude protein available in their pollens. Plants with relatively high crude protein values include canola (Brassica napus – 23%) and almond (Prunus dulcis – 26%), while plants with lower crude protein levels include raspberry/blackberry (Rubus spp. – 19%), willow (Salix spp. – 17%), sunflower (Helianthus annuus – 16%), and pine (Pinus spp. – 7%). It is important to note that there are several different methods used to analyze protein content in pollen which, in turn, can yield different results. Consequently, one must use published protein levels in various pollens as a general guideline and not a definitive value.

It has been observed that honey bee workers choose pollen based on the odor and physical configuration of the pollen grains rather than based on nutritive value.[1] A typical size honey bee colony (approximately 20,000 bees) collects about 57 kg of pollen per year. On average, 15-30% of a colony's foragers are collecting pollen. A single bee can bring back a pollen load that weighs about 35% of the bee's body weight. Bees carry this pollen on their hind legs, on specialized structures commonly called "pollen baskets" or corbicula (Figure 3). Once pollen is brought back to the colony, the workers condition it by adding glandular secretions containing enzymes and acids that prevent harmful bacterial activity and prepare the pollen for long-term storage (Figure 4). Stored pollen often is called "bee bread". Bees also add beneficial microbes to the pollen and they produce enzymes that help the pollen release nutrients and amino acids. Bee bread is consumed by a colony relatively quickly and only stored for a couple of months if there is a surplus. A colony's annual requirement for pollen has been estimated to range from 15 to 55 kg.

Fat Bees Skinny Bees – a manual on honey bee nutrition for beekeepers A good publication to review for protein content of many common plants. The authors of this manual include a list of pollen compositions from some common Australian plants. When reviewing the list, remember that plants within the same genus often have similar protein contents. This list can serve as a guideline for predicting protein content of pollen from similar plants in the United States.

Robert Brodschneider, Karl Crailsheimet (Crailsheimet al., 1992). Nutrition and health in honey bees A worker bee consumes on average 3.4–4.3 mg pollen per day, with a peak at the age of nurses

Chia-Hua Lin and Reed M. Johnson Identifying pollen sources used by honey bees in central Ohio's agricultural landscape Department of Entomology, The Ohio State University


  1. 1.0 1.1 Amanda Ellis, Jamie Ellis, Michael O'Malley, and Catherine Zettel Nalen The Benefits of Pollen to Honey Bees "It has been observed that honey bee workers choose pollen based on the odor and physical configuration of the pollen grains rather than based on nutritive value."
  2. D. C. SOERGEL, N. OSTIGUY, S. J. FLEISCHER, R. R. TROYER, E. G. RAJOTTE, AND G. KRAWCZYK Sunflower as a Potential Trap Crop of Halyomorphahalys (Hemiptera: Pentatomidae) in Pepper Fields
  3. North Carolina State University Sunflower pollen has medicinal, protective effects on bees
  4. Jonathan J. Giacomini, Jessica Leslie, David R. Tarpy, Evan C. Palmer-Young, Rebecca E. Irwin & Lynn S. Adler Medicinal value of sunflower pollen against bee pathogens
  5. Buckwheat seed was $35 for 50 lb and was planted at a rate of 50 lb/acre