In the past we have examined different components (i.e., sunlight protectants, virus enhancers) that would be essential in a viral pesticide formulation. In this study, we investigated the effects of silicon-containing materials (bentonite, diatomeaceous earth, kaolin) on the activity of the gypsy moth nucleopolyhedrovirus LdMNPV, as well as the effect of these materials on the viral enhancement activity of a fluorescent brightener Tinopal LPW. Bentonite (1%), diatomaceous earth (1%), and kaolin (1%) had little effect upon the activity of LdMNPV. Moreover, the addition of bentonite, diatomaceous earth or kaolin to LdMNPV/Tinopal had little effect upon the enhancement activity of Tinopal LPW.