Effects of NeemAzal-T/S on different developmental stages of rose aphid, Macrosiphum rosae

Abstract

Natural insecticides often do not provide a strong knock-down effect and have a lower efficacy than synthetic pesticides. For an effective application of natural insecticides, it is essential to know the product’s mode of action in detail. The efficacy of the commercial neem [Azadirachta indica A. Juss (Meliaceae)] product NeemAzal-T/S and its influence on stage-specific mortality, development, and reproduction of rose aphids, Macrosiphum rosae L. (Hemiptera: Aphididae), were determined in greenhouse trials. NeemAzal-T/S had an efficacy of 40% against M. rosae in standard efficacy trials with initial infestations between 100 and 270 aphids per plant. However, it has a significant impact on the survival of nymphs in the first to third instar as well as on juvenile development. Nymphs treated with NeemAzal-T/S exhibit a significant delay in molting to the second instar and most of them die before the first molt. Furthermore, reproduction of adult M. rosae females is reduced when aphids are exposed to sub-lethal concentrations of neem as first instars. Population growth is inhibited or delayed on rose plants treated with NeemAzal-T/S. The results indicate that applications of NeemAzal-T/S can be used to control rose aphids in integrated pest management (IPM) systems. Because this insecticide has no rapid knock-down effect and no effect on adult aphids, combinations with natural enemies of pest insects as well as with other insecticides are possibilities to enhance the efficacy.