Porphyrins and related compounds as photoactivatable insecticides. I. Phototoxic activity of hematoporphyrin toward Ceratitis capitata and Bactrocera oleae.

The photodynamic sensitizer hematoporphyrin (HP) IX was efficiently accumulated by Ceratitis capitata (Mediterranean fruit fly) and Bactrocera oleae (olive fly) when the insects were fed with a sugar/protein bait containing micromolar amounts of porphyrin. Hematoporphyrin appeared to be mainly accumulated in the midgut, Malpighian tubes, adipose tissue and cuticle and was gradually cleared from the organism in a 24-48 h time interval. Exposure of the HP-fed flies to light mimicking the solar spectrum caused a decrease in the survival whose extent was modulated by the HP concentration in the bait, the irradiation fluence rate and the total light dose. For 8 mumol/mL HP in the bait 100% mortality during 1 h exposure to light was obtained using a fluence rate of 1220 microE s-1 m-2 for C. capitata and 2080 microE s-1 m-2 for B. oleae. The latter fly was somewhat less photosensitive than C. capitata possibly owing to the smaller amount of ingested HP and/or darker pigmentation. Studies are in progress in order to extend these investigations from the laboratory to the field scale.