Fluorescent Brighteners Can Enhance or Inhibit the Nucleopolyhedrovirus of the Diamondback Moth (Lepidoptera: Plutellidae)²

The nucleopolyhedrovirus of the diamondback moth, Plutella xylostella (L.), (PxMNPV) was the most potent of three viruses tested against this insect. The potency of PxMNPV could be increased by the addition of certain diaminostilbene disulfonic acid-derived fluorescent brighteners, including Blankophor P167® at a concentration of 1%. Other fluorescent brighteners, including Blankophor HRS® at 1%, reduced the activity of PxMNPV, though lower concentrations of Blankophor HRS (0.25 to 0.5%) enhanced activity. In contrast, Blankophor HRS at 1% enhanced the nucleopolyhedrovirus of the celery looper, Anagrapha falcifera (Kirby), (AfMNPV) against the diamondback moth. Similar results were found in the corn earworm, Helicoverpa zea (Boddie), and the beet armyworm, Spodoptera exigua (Hübner), which are also susceptible to both PxMNPV and AfMNPV. Consumption of foliage treated with Blankophor HRS (0.5 to 1.0%) did not differ from that of foliage treated with similar concentrations of Blankophor P167. These results indicate a negative effect of higher concentrations of Blankophor HRS on PxMNPV, rather than on the host insect.