Nectar feeders should be cleaned and disinfected every two days, as already described. Be sure to rinse the nectar feeder after it has been immersed in the bleach-water solution. Many people feed suet all year, but sun-warmed suet can cause infected follicles and loss of facial feathers. It can mat feathers, reducing insulation and waterproofing. Use suet only from October through April or May, depending on the temperatures.
Birds eat granules or eat prey that have been exposed to chemicals.
If you use any chemicals, use only as directed. Even then, many are lethal to wildlife. Rethink your use of these substances. Choose plant species that are resistant to diseases and pests. Let the many wildlife species that eat insects be your insect control.