Generalist Pollinators and Soybeans
By Sam Custer
OSU Extension, Darke County 

We had three calls in the Extension Office in the last two weeks regarding bee swarms and the need to collect and move them.  If you have a swarm you need moved from your home or farm you can call us for necessary information. 

As we get close to soybeans flowering across the state (growth stages R1-R2), we need to bring up an important issue related not specifically to honey bees, but to pollinators in general (albeit honey bees in soybeans is still a concern).  Although soybeans are a self-pollinated crop, generalist pollinators such as bumblebees and other solitary bees do visit soybean fields regularly during the crop’s flowering stage.  These pollinators will also visit other nearby sites, offering pollinating services to other plants including flowers and if present, vegetable crops.  Research out of Iowa State University indicates that many generalist pollinators make regular visits to soybeans and are at danger from insecticide sprays; researchers at the OARDC have recently joined these studies. 

Luckily, there are few insect pests that reach economic levels during flowering in Ohio; almost all occur during pod development or seed fill stages (R3-R5).  Thus, when following an IPM strategy, little insecticide should be sprayed at flowering because a treatment application, as we all know, should only be applied when needed, when a threshold is reached, and not applied as a preventive application.  

However, we are aware that many growers are adding insecticides to spray tanks when applying fungicides for plant health purposes and even late applications of herbicides because: “Well, I’m going over the field anyway so I thought I’d add an insecticide for insurance purposes! The insecticide is relatively cheap and soybeans are worth so much!” As we have always stated, we do NOT recommend this practice, and feel an IPM approach is much better for everyone and everything, including the environment and in this case, pollinators. We NEVER recommend an insecticide application unless there is a need.  And with the recent information and concern about generalist pollinators, this caution is even more important.  To illustrate this potential problem, just two weeks ago there was a significant bumblebee kill in Oregon, when over 50,000 bumblebees were killed by an insecticide sprayed (in this case a material called Safari) on linden trees in a parking lot during a time period when the trees were in flower and being visited by bumblebees (read just one of the many articles that were written about this: http://guardianlv.com/2013/06/pesticide-causes-largest-mass-bumble-bee-death-on-record/?dm_i=1ANQ,1MG0A,6LPXAW,5N4VO,1 ).  This was with an insecticide that had the warning about being highly toxic to bees on its label and the need to NOT spray flowering plants or trees! 

Growers and applicators should remember, having read the label, that most insecticides have a statement about spraying around bees and on blooming crops. The typical statement is: “This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are actively visiting the treatment area”.   Ohio goes further in that the Ohio Department of Agriculture addresses this concern under Regulatory Divisions & Programs, Plant Industry Division, Pesticide Regulations, Law and Statues, Plant Industry 901:5. 

901:5-11-02 restrictions 

 (B) No person shall: 

 (15) Apply or cause to be applied any pesticide that is required to carry a special warning on its label indicating that it is toxic to honey bees, over an area of one-half acre or more in which the crop-plant is in flower unless the owner or caretaker of any apiary located within one-half mile of the treatment site has been notified by the person no less than twenty-four hours in advance of the intended treatment; provided the apiary is registered and identified as required by section 909.02 of the Revised Code of Ohio (http://codes.ohio.gov/orc/909.02), and that the apiary has been posted with the name and telephone number of the owner or responsible caretaker. 

 (16) Apply pesticides which are hazardous to honey bees at times when pollinating insects are actively working in the target area; however, application of calyx sprays on fruits and other similar applications may be made. 

We continue to advise that growers and applicators maintain good communications with bee keepers near their fields to prevent and limit unintended problems. A listing of registered apiaries can be obtained from the Ohio Department of Agriculture. The list can be requested via e-mail to the address apiary@mail.agri.state.oh.us 

Applicators should avoid spraying when bees are active in the field with flowering crops or weeds. Other times to avoid spraying are from 10:00 a.m. to 7:00 p.m. or when temperatures are above 65 degrees F. On extremely hot days, bees may be active later into the evening. 

Follow label precautions that relate to drift and be aware of the potential risk to neighboring crops or areas. Filter strips or other conservation areas that border fields may have flowering plants with foraging bees. Bees have a long range and can forage up to two and one-half miles from the apiary. 

The source for much of this information is Ron Hammond and Andy Michel, OSU Extension Entomologist Specialists. 

For more detailed information, visit the Darke County OSU Extension web site at www.darke.osu.edu, the OSU Extension Darke County Facebook page or contact Sam Custer, at 937.548.5215.