Lack of interaction between the milky disease bacterium Paenibacillus popilliae and stilbene-derived optical brighteners in Japanese beetle larvae

Abstract

Optical brighteners cansynergistically enhance nucleopolyhedrovirusinfectivity to lepidopteran larvae by blockingthe sloughing of infected primary midgut cellsand inhibiting the formation of the peritrophicmembrane in the hosts. Because of similaritiesin the route of infection, we investigatedwhether optical brighteners would also enhanceinfection with the milky disease bacterium,Paenibacillus popilliae, of Japanesebeetle, Popillia japonica, larvae. Thelarvae were kept in soil mixed with P.popilliae spore preparations and the opticalbrighteners Blankophor BBH, P167, or RKH withperennial ryegrass provided as food. Noenhancing effect of any of the opticalbrighteners on P. popilliae infection wasobserved at a concentration of 0.1% (w/w). Rather, when mixed into the soil at 0.02, 0.1,or 0.5% (w/w) BBH reduced P. popilliaeinfection at the highest rate.