Bhupinder Pall Singh Khambay

A nematicidal metabolite from Verticillium chlamydosporium.

A bioassay-directed fractionation of cultures of the fungus, Verticillium chlamydosporium, demonstrated nematicidal activity, due mainly to phomalactone. Compared with aldicarb, the lethal activity against Meloidogyne incognita was less, but its activity in suppressing root invasion was similar. The extract also contained monorden

Effects of selected botanical insecticides on the behaviour and mortality of the glasshouse whitefly Trialeurodes vaporariorum and the parasitoid Encarsia formosa

Toxicity and behavioural bioassays were used to assess the lethal and sub‐lethal effects of two naphthoquinones from the Chilean plant Calceolaria andina L. (Scrophulariaceae), two products derived from Azadirachta indica and pyrethrum on the glasshouse whitefly, Trialeurodes vaporariorum Westwood, and the parasitoid Encarsia formosa Gahan. The potential use of these botanicals in an Integrated Pest Management (IPM) programme is discussed. Pyrethrum was the most toxic botanical tested, but it was toxic to both the whitefly and parasitoid. The naphthoquinones showed potential for inclusion into an IPM programme if, by formulation, the toxicity towards the whitefly could be increased and the deterrent activity towards E. formosa adults decreased. Overall, the A. indica‐derived products had the most potential for use in an IPM system for the control of whitefly, which includes E. formosa as a biocontrol agent.

The potential of natural naphthoquinones as the basis for a new class of pest control agents - an overview of research at IACR-Rothamsted.

Abstract Two pesticidal naphthoquinones from Calceolaria andina (Scrophulariaceae) both contain a key structural feature not previously investigated in this group of compounds. Structure–activity studies have led to the identification of analogues with commercial levels of activity. The primary mode of action in insects is by inhibition of complex III of the mitochondrial respiratory chain. Species specificity has been attributed to differences in the sensitivities of the target sites and whether the hydroxy group at position 2 is acylated. However, in comparative assays with some commercial insecticides, these compounds exhibited unexpectedly poor dose-transfer to insects from leaf surfaces when formulated as emulsifiable concentrates. Volatilisation and degradation were identified as key factors and performance improved with well-chosen formulations.

An insecticidal mixture of tetramethylcyclohexenedione isomers from Kunzea ambigua and Kunzea baxterii

A mixture of isomers, all 4-[1-(5,7-dihydroxy-6-methyl-4-oxo-2-phenyl-chroman-8-yl)-3-methyl-butyl]-5-hydroxy-2,2,6,6-tetramethyl-cyclohex-4-en-1,3-diones, which comprises a pair of epimers, each of which is a pair of conformers, has been isolated from the hexane extract of the aerial parts of Kunzea ambigua and K. baxterii (Myrtaceae). The mixture exhibits moderate insecticidal activity in comparison with natural pyrethrum extract.