Aphid, turnip

The alarm pheromones of aphids often are sesquiterpenes such as ( )-3-famesene (71) and germacrene A (72) (Bowers, 1985). Upon release of these compounds, aphids drop from the plant on which they have been feeding. The compounds are very labile and break down in only a few minutes. This is important to prevent the aphids from being in a constant state of alarm (Bowers, 1985). Although this sesquiterpene elicits response in many species of aphids, the turnip aphid Lipaphis (Hyadaphis) erysimi responds only weakly. Addition of plant-derived isothiocyanates to p-famesene has a synergistic effect and greatly enhances the effect of P-famesene (71) (Dawson et al., 1987 Harbome, 1989). 

Dawson, G. W., D. C. Griffiths, J. A. Pickett, L. J. Wadhams, and C. M. Woodcock, Plant-derived synergists of alarm pheromone from turnip aphid, Lipaphis (Hyadaphis) erysimi (Homo-ptera, Aphididae), J. Chem. EcoL, 13, 1663-1671 (1987). 

The EU ban on neonicotinoids from December 2013 means that seed dressings containing clothianadin, imidacloprid and thiomethoxam can no longer be used for the control of cabbage stem hea beetle (CSFB) or the peach-potato aphid, a vector of turnip yellows virus. Fohar apphed pyrethroids ate now the only control for CSFB, but resistance is now widespread. 

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