Activity of Xanthene Dyes Against Black Cutworm Larvae12

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Abstract
The activity of 3 xanthene dyes (rose bengal, erythrosin B, and phloxin B) against 3rd-6th instars of Agrotis ipsilon (Hufnagel) was investigated in the laboratory. Toxic dyesensitized photooxidation reactions occurred after larvae ingested dye impregnated diet and were exposed to one of 3 levels (9200, 4400, or 1500 lux) of flourescent light intensity. At a concentration of 5 × 10−3 M, ingestion of rose bengal resulted in the highest level of mortality, followed by phloxin B and erythrosin B. The 3 dyes were most effective at the 2 highest light intensities. Mortality in 5th–6th instars as a function of dietary concentration of rose bengal and illumination time showed that LT50 values decreased with increasing dietary concentration. Relative toxicity of rose bengal was described by means of a pseudo 2nd-order rate constant of photooxidation (k2).