Blankophor BBH as an enhancer of nuclear polyhedrosis virus in arborist treatments against the gypsy moth (Lepidoptera: Lymantriidae)

Doses of a commercial candidate formulation of gypsy moth nuclear polyhedrosis virus (LdMNPV) were applied with and without several concentrations of an enhancing adjuvant, Blankophor BBH, to individual trees against natural gypsy moth, Lymantria dispar (L.), populations. Amounts of Blankophor BBH adhering to foliage after application were measured at 1,322, 227, and 37 mu g/g dry weight of leaf for the 0.5, 0.1, and 0.02% treatments, respectively. The highest dose of the candidate formulation used without the adjuvant failed to increase significantly 1st-generation after-treatment LdMNPV mortality (direct infection caused by feeding on applied virus) above background levels, to reduce late season (instars 5 and 6) larval populations in treated trees or to provide significant foliage protection. However, Blankophor BBH added to the tank mix at concentrations of 0.5 or 0.1% (wt:vol) resulted in significantly increased levels of 1st-generation after-treatment LdMNPV, significantly reduced late-season larval populations, and significant levels of foliage protection, compared with untreated control trees. The resulting recommended tank mix (0.1% Blankophor BBH and 2x 10(10) PIBs per 75 liters final spray solution per tree) should give excellent foliage protection against gypsy moth at a cost of about $3 per tree.