A short description is given of 19 laboratory, 12 semi‐field and 5 field methods to test the side‐effects of pesticides on beneficial organisms. The methods were developed according to standard guidelines by members of the Working Group ‘Pesticides and Beneficial Organisms’ of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS); 28 members in nine countries participated and the beneficial organisms (natural enemies of insects and mites) included: 6 Hymenoptera, 4 Coleoptera, 2 Diptera, 1 Neuroptera, 1 Heteroptera, 3 Acari, 1 Aranea, 1 entomopathogenic fungus (Hyphomycetes). There is agreement that a combination of laboratory, semi‐field and field tests is needed to show the side‐effects of pesticides on beneficial organisms and that the beneficials chosen for the test should be relevant to the crop on which the pesticide is to be used.

Chemical factors have an important role in the host plant/insect relationship. Yet insects are living in a complex environment consisting not only of host plants, but also of many non‐host plants. The latter also release chemical signals that may be perceived by insects.We show here how a non‐host plant (chestnut) affects the sugar beet moth's reproduction. The chestnut compounds inhibit mating and egg‐laying behaviour and mask the chemical stimulating effect of the beet on oogenesis and oviposition. In this way they act in laboratory conditions by reducing the reproductive potential of an oligophagous insect, and in field conditions they lower population density.These results reveal the possible role of non‐host plant compounds, and their identification will open new prospects in pest management by manipulating the behaviour of insects.RÉSUMÉACTION D'UN EXTRAIT DE PLANTE NON HȮTE SUR LA REPRODUCTION D'UN INSECTE PHYTOPHAGE OLIGOPHAGE: LA TEIGNE DE LA BETTERAVE SCROBIPALPA OCELLATELLA BOYD. (LEPIDOPTERA GELECHIIDAE)Les signaux chimiques émis par la betterave attirent la femelle pondeuse pour le choix d'un support de ponte, stimulent l'ovogènese, stimulent les accouplements et la ponte.L'extrait aqueux de feuilles de châtaignier, plante non hôte, inhibe les accouplements et la ponte; pulvérisé sur une betterave, il masque l'action stimulante de la plante‐hôte sur l'ovogénèse et la ponte. Pulvérisé sur des parcelles de betterave dans la nature, l'extrait de châtaignier entraîne une diminution de près de la moitié de la densité de population.Dans les communautés végétales naturelles de nombreuses espèces de plantes sont intimement mélangées. Les signaux chimiques émis par les plantes non hôtes peuvent masquer la plante‐hôte qui n'est pas perçue et n'est pas découverte. Ces signaux chimiques peuvent aussi diminuer le potentiel de reproduction et modifier la dynamique de population de l'insecte phytophage. L'étude des substances présentes dans les plantes non hôtes doit ouvrir de nouvelles perspectives dans la protection des plantes cultivées.