Porphyric insecticides. 2. 1,10-Phenanthroline, a potent porphyric insecticide modulator

It is shown that in Trichoplusia ni, 1,10-phenanthroline, in addition to 2,2′-dipyridyl, exhibits potent contact porphyric insecticidal modulating properties. When sprayed with δ-aminolevulinic acid, 1,10-phenanthroline causes the larvae to accumulate massive amounts of protoporphyrin IX and lesser amounts of Zn-protoporphyrin IX in darkness and results in insect death in the light. In addition, ingestion of δ-aminolevulinic acid and 1,10-phenanthroline with the diet was extremely efficient in causing tetrapyrrole accumulation in darkness. This tetrapyrrole accumulation, in turn, was extremely efficient at producing insect death in the light, as evidenced by the low concentrations of δ-aminolevulinic acid (2 mM) and 1,10-phenanthroline (0.2 mM) that were sufficient to cause 100% larval mortality. Several substituted 2,2′-dipyridyls and 1,10-phenanthrolines were also shown to act in concert with δ-aminolevulinic acid in causing larval death in the light.