Fluorescent brighteners improve Anticarsia gemmatalis (Lepidoptera : Noctuidae) nucleopolyhedrovirus (AgMNPV) activity on AgMNPV-susceptible and resistant strains of the insect

Fluorescent (optical) brighteners are known for their characteristics of pr otecting baculoviruses against deactivation by ultraviolet (UV) light and e nhancing the activity of these agents as microbial insecticides on hosts an d semipermissive hosts. These substances were evaluated in combination with the velvetbean caterpillar, Anticarsia gemmatalis Hubner, multiple-embedde d nucleopolyhedrovirus (AgMNPV). The first trial involved 4 fluorescent bri ghteners (Blankophor BBH, Blankophor HRS, Blankophor RKH, and Tinopal LPW) obtained from the United States. The second trial was conducted with 11 flu orescent brighteners (Tinopal UNPA-GX, Tinopal DIMS, Tinopal CBS, Leukophor DUE, Leukophor BSBB, Hostalux KS-N, Hostalux ETBN, BRY 10 D2 100, BRY 10 D 2 150, Uvitex BHT, and Uvitex NFW) available in Brazil in combination with the AgMNPV to determine the degree of enhancement of viral activity. These brighteners were also evaluated with regard to AgMNPV protection against de activation by UV light. Combinations of the virus with selected fluorescent brighteners were tested against both AgMNPV-susceptible and resistant stra ins of A. gemmatalis. In the first trial, brighteners obtained from the Uni ted States promoted increases in AgMNPV activity from 5.2-fold (Blankophor HRS) to 76.6-fold (Blankophor REM) and reduced the mean time to death by 2. 8 to 3.5 days. In the second trial, the most effective brightener (Tinopal UNPA-GX) reduced the LC50 in A. gemmatalis larvae from 7083 occlusion bodie s (OBs)/ml (virus alone) to 77.8 OBs/ml (approximate to 90-fold). When 4 se lected brighteners were tested in combination with the AgMNPV in resistant insects, the LC,, was reduced by ca. 10,000-fold (Leukophor DUE) to ca. 62, 000-fold (Tinopal UNPA-GX), in comparison to the LC50 of 3.7 x 10(7) OBs/ml observed for the virus alone. Therefore, mortality of highly resistant A. gemmatalis larvae to the AgMNPV increased dramatically when the virus was c ombined with some fluorescent brighteners. UV protection measured by origin al activity remaining (OAR) varied from <30% OAR (Uvitex NFW) to >90% OAR ( Tinopal UNPA-GX and BRY 10 D2 100). All efficacious brighteners were stilbe ne disulfonic acid derivatives and, when used alone, none showed negative e ffects against A. gemmatalis larvae. (C) 2001 Academic Press.