We do not see any reason why you can't spray Bifen IT and Hi-Yield Atrazine together. For more information on application and dilution, please refer to the product labels of each product.
Bifen IT cannot be applied to hay intended to be consumed by animals. We would recommend to use Evergreen Pyrethrum. Be sure to wait a week or two after application to harvest.
Bifen IT has a residual of 90 days indoors and 30 days outdoors. Repeat application should only take place if there are signs of renewed insect activity and must not exceed one application per 7 days.
Please view the product label for listed insects and more information.