By Harry Brook
As of March 4 this year, strychnine for control of Richardson's ground squirrels (RGS) can no longer be sold to the public. By March 4, 2023, farmers and ranchers will no longer be allowed to use strychnine for control of RGS. So, what are the alternatives to control this pest?
Richardson's ground squirrels, also known as gophers, are a prolific pest on the prairies. They can be very destructive on field crops, showing a particular liking to canola seedlings. They are a grazing animal and will compete with livestock for forages on hay land and pasture. Under dryer conditions they become more of a problem as a shortage of growth on pastures drives them into annual crop areas.
The ideal time for any control measure is prior to grass greening up. The males come out first, showing up in late February until mid-March, with females coming out two weeks later. Mating occurs shortly after females emerge, so this is the time to control the next generation. It takes a little more than three weeks for the next generation to be born and four weeks for the new gophers to emerge and feed. Control options are best when done early.
Other methods, besides strychnine also need to be done early. Zinc phosphide pellets, used primarily to control grain insects, are also registered for the control of RGS. However, to use these products, a written fumigation management plan must be in place. Make sure there is RGS in the burrow, prior to application. Gophers forage during the day but return to their burrows just before sunset. Each burrow can have one or two pellets added, then soil or newspaper added to plug the burrow. To access these pellets, applicants must have a valid Farmer Pesticide Certificate with the appropriate endorsement.
Of course, there is always biocontrol. However, badgers, which consume gophers, only make a bigger mess in the field. Hawks, crows, ravens, skunks, fox and coyotes also feed on gophers. The predation is mostly on the males and they usually do little to reduce overall populations.
Another poison bait is Rozol, an anti-coagulant. To be effective, gophers must consume it more than once over two or three days. They may still be consuming it and continue feeding even after eating a fatal dose. Using a bait station can work, if done early enough and if close enough to the area where the RGS are active. It should be checked frequently to ensure bait is available.
Significantly more effort is required if using Rocon foam. This foam can asphyxiate the gophers and consists of white mustard powder, which creates a foam when applied. It is time consuming, but well suited for urban areas and small infestations. Then there are the tried-and-true methods of control in rural settings. These are trapping and shooting. It helps if there are adolescents looking to help out as this usually only works in relatively small, concentrated areas. In the U.S., some people have resorted to using a vacuum truck to suck up underground rodents. That would only work in heavy, solid soils. In crop fields, cultivation can work to cause the gophers to relocate to less tilled soils.
There are no perfect control measures for RGS. We can’t eradicate them but they can be kept at a manageable level by using some of the above methods. All of them take more effort and time than our old solution, strychnine. However, strychnine was removed as a pest product due to non-target species being killed. Our remaining control methods are less damaging to other species and we have to adapt. Richardson's ground squirrels are going to be with us for a long time to come. It is always better to keep populations low rather than deal with a population explosion.