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By: Tracey Baute – Field Crop Entomologist and Greg Stewart – Corn Specialist, Ontario Ministry of Agriculture, Food and Rural Affairs
A high level of concern was raised last spring regarding bee kills and corn planting. Many growers are asking what actions they can take to help reduce the risk of bee kills this spring during planting. We will try to clarify the situation, and give the best recommendations we can provide at this time.
In the spring of 2012, coinciding with corn planting, there were approximately 200 incidences of what was likely acute poisoning of honey bees in Ontario. Representatives from the Ministry of Environment (MOE), Pest Management Regulatory Agency (PMRA), and OMAFRA investigated affected bee hives, taking bee samples for residue analysis by PMRA. Though final results have not been released, PMRA’s initial lab results indicate “that pesticides used on treated corn seeds may have contributed to at least some of the 2012 spring bee losses that occurred in Ontario, however, there is still additional information being collected”. The cases in 2012 were therefore likely acute poisonings where bees were killed from short term exposure to lethal doses of an insecticide. It is important to note that they have found no cases of off-label use by growers. It is also important to note that, though the analysis indicates the presence of clothianidin (active ingredient in Poncho), thiamethoxam (active ingredient in Cruiser) breaks down to metabolites that include clothianidin. Virtually all corn seed sold in Ontario is treated with some form of the insecticides in question.
Many factors may have contributed to these incidences. Environmental conditions and planting practices during the 2012 planting season may play a significant role. Unfortunately, without being present in each field at the time of planting to collect data, there may never be conclusive evidence as to route(s) of exposure to bees. However, results indicate that honey bees were somehow exposed to corn seed insecticides. So how can a bee come into contact with a seed insecticide during planting?
One of the more likely routes is dust. Research from Purdue University and other jurisdictions in Europe have found evidence that dust coming from the exhaust of high pressure air-assisted corn planters contained particles of neonicotinoid (eg. Poncho or Cruiser) seed insecticides. Many factors can contribute to the contamination of the dust including abrasion of the seed from the planter lubricant (eg. talc), quality and formulation of the polymer seed coating (sticker), and rough handling of the seed bags causing chaffing of the seed coat. Planting on dry, windy days may also help to carry the “fugitive dust” greater distances. Bees can come into contact with the contaminated dust while flying across the field during planting or from the dust settling on water sources or nearby flowers that they are foraging on.
What can corn producers do to help reduce the risk of bee kills when planting? The following are actions that should help reduce the production of contaminated dust during planting, and consequently (hopefully) reduce the exposure of bees to this dust. There is no guarantee that these actions will prevent bee kills from happening during planting. Many of these are best management practices that growers should be following anyway, given they are applying pesticides when planting treated seed.
Strengthen communication with local beekeepers. Honey bees can forage up to 5km from their hives. Take an active role in finding out where the nearest hives are to your fields and let the local beekeepers know when you plan to plant. There may be steps that they can take to protect their hives during planting. Contact information for the local beekeepers’ association in your area can be found on the Ontario Beekeepers’ Association website at:
Time of planting. Keep in mind that during dry spring conditions, dust will travel further on windy days. If there is an opportunity to plant in the early morning or evening on windy days, when bees are less likely to be foraging, it may also help to reduce the risk of exposure.
Manage dandelions and other flowering weeds in and around fields, prior to planting. The warm March, followed by a very cold April of 2012 may have resulted in dandelions being the predominate flowering plant for bees to forage on during corn planting. Managing flowering weeds in and along field perimeters prior to planting may help to reduce the likelihood of bees foraging around your field at the time of planting.
Minimize the amount of insecticide seed treatment used. Growers planting corn on corn with moderate to high populations of corn rootworm should consider planting a Bt corn rootworm hybrid. Transgenic control has been proven to be more effective than using a high rate of seed insecticide. In addition, not every grower in the province has soil insect pest problems. It is time to get back to integrated pest management. Evaluate your fields and determine if soil pests are present at threshold levels. Even if they were in the past, it doesn’t mean they are now, especially if insecticide seed treatments have been used in the same field over multiple years. If the soil pests are not at threshold and impacting yield, a seed insecticide is not necessary. Most companies can accommodate orders for non-insecticide treated seed, as long as the orders are done well in advance. Test non-insecticide treated seed to see how they do on your farm. For information on how to monitor for soil insects and determine thresholds, refer to the Soil Insects and Pests section of the OMAFRA Publication 811, Agronomy Guide for Field Crops at: http://www.omafra.gov.on.ca/english/crops/pub811/13general.htm#soilpests
Limit the amount of seed lubricant (eg. Talc) used at planting. The amount of lubricant needed varies by planter. There has been a tendency to err on the “safe side” for planter performance, and apply at the upper end of the label rate. Experience from some growers would suggest that in low humidity situations, little to no talc is required. Follow label recommendations. A build-up of talc on the blower exhaust indicates overuse. Take precautions to reduce the risk of inhaling talc, which can have serious health effects. Fortunately, there are promising new lubricants being developed that could greatly reduce the amount of dust produced.
Exhaust dust towards the center of the field. When planting the outside rounds along the perimeter of the field, blow the air in. If your planter exhausts air towards the right side, plant in a counter-clockwise direction. This will help direct the dust into the field rather than directing the dust onto the vegetation and water sources near the field’s edge.
Modifying planters with deflectors. Deflecting exhaust air directly at or into the ground will reduce the distance the contaminated dust is able to travel. Deflectors have been mandated in parts of Europe to reduce dust implications. In North America, deflectors need to be tested for their impact both on planter performance and on efficacy to reduce dust concerns. Stay tuned.
Again, following all of these recommendations does not guarantee that there will not be future bee kill incidences at planting. These are the best suggestions we can offer based on the information available to date. We will continue to modify these recommendations as more information is made available, and research and technology is developed to address the issue. Updates will be provided on the Field Crop News site at: http://fieldcropnews.com/