Role of photosensitizer in control of mealybug and scale insects (Homoptera: Margarodidae and Diaspididae), in comparison with conventional insecticide

Abstract Background Two photosensitizer agents were used: rose bengal and eosin alone and mixed with soap. Two other chemical compounds were used: active cable oil and soap. All these materials were compared with malathion as a conventional insecticide. The Egyptian mealybug Icerya aegyptiaca attacking ornamental–medicinal plants (acalypha and rose shrubs) and the black Parlatoria scale Parlatoria ziziphus attacking sour orange were evaluated against the tested materials. Results The results obtained suggest that soap, rose bengal mixed, eosin mixed, malathion and active cable oil revealed potency in reducing the population of I. aegyptiaca by 57.24, 87.25, 75.62, 98.71 and 59.91%, respectively, on rose; and by 54.91, 82.64, 62.48, 96.67 and 48.13%, respectively, on acalypha shrubs; their potency on insects showed a significant difference on infested rose than on infested acalypha. The tested compounds revealed lower potency in reducing the population of P. ziziphus than malathion. Reduction percentages were 35.43, 40.39, 34.25, 91.81 and 28.21%, respectively. The accumulation potency of the tested compounds on two insects collectively, without regard to insect species, stages or infested plant species, was assessed at 51.49, 66.18, 55.86, 94.37 and 44.69, respectively. The obtained results confirmed that malathion was the most effective agent against both tested insects, followed by rose bengal mixed with soap, eosin mixed with soap, soap alone and active cable oil. Conclusions The obtained results showed that rose bengal (as a photosensitizers) mixed with soap can be used as a promising agent against all tested insects.