The decision to carry out the treatment this spring has been taken by local authority and public health partners.
The treatment of the river has been carried out for many years to reduce the number of Blandford Flies emerging during the spring.
Only one targeted treatment is needed based on the specific lifecycle of the insect and it is carried out on a scientific basis.
Before treatments began there was a significant nuisance caused by these insects, which can give a nasty bite.
Roger Frost, Environmental Health Manager from North Dorset District Council, said: “This work is being undertaken to continue to control the number of flies emerging from the river in the spring, which has the potential to cause a nuisance at this time of year. The treatment has been successful over the years.”
The treatment will be carried out by Bournemouth University’s Global Environmental Solutions, Department of Life and Environmental Sciences.