A NEW GROUP OF PLANT-DERIVED NAPHTHOQUINONE PESTICIDES

A series of compounds with structures based on insecticidal/acaricidal naphthoquinones isolated from Calceolaria andina has been synthesised . A feature of the series is the lack of resistance shown by strains r esistant to established classes of pesticides. The importance for acti vity of the tetra-substituted carbon atom in the side-chain, as observ ed in the natural products, has been investigated. In analogues with a cyclic side-chains the position of the tetra-substituted carbon for op timum activity was dependent on the length of the sidechain. With cycl ic side-chains, activity was dependent on the size of the ring, the nu mber and position of the substituents therein. Activity of the compoun ds examined was particularly high against Bemisia tabaci and Tetranych us urticae in direct-contact tests, but was much lower than expected i n leaf-dip tests. A partial improvement based on formulation has been demonstrated.