The preparation VIRIN-ZSP w/v. is a water solution containing polyhedra of the nuclear polyhedrosis virus of the common spruce sawfly, with a titer of 1x109 polyhedra/ml. This biological preparation is intended for use in coniferous forests. The preparation is used in the field of forest protection and is designed to combat insect pests such as the common spruce sawfly. The water solution is convenient to apply and provides effective protection of plants from pests due to the action of specific viral particles.