Leaf colour has been proposed to signal levels of host defence to insect herbivores, but we lack data on herbivory, leaf colour and levels of defence for wild host populations necessary to test this hypothesis. Such a test requires measurements of leaf spectra as they would be sensed by herbivore visual systems, as well as simultaneous measurements of chemical defences and herbivore responses t...

Naturally occurring parasitoids may provide sufficient control of aphid pests in fields undisturbed by insecticides. Yet the efficacy of these parasitoids may be strongly influenced by characteristics of their hosts and by the availability of alternative hosts in neighbouring crops. In the present study, parasitoid guild structure was compared in two aphid species, Brevicoryne brassicae and Lip...

O controle de insetos fitófagos como o pulgão da couve Brevicoryne brassicae (Linnaeus, 1758) (Insecta: Hemiptera: Aphididae) geralmente é realizado com inseticidas químicos, que pode causar danos ao ambiente e à saúde humana, bem selecionar resistentes a pesticidas. Dessa forma estabelece-se necessidade pesquisar desenvolver métodos alternativos para couve. Nesse sentido, utilização extratos v...

The population dynamics of major brassica pests and occurrence of their natural enemies were monitored weekly for a period of 9 months on cabbage (var. Copenhagen Market) at a research station plot (no pesticides applied) and a farmer’s field (weekly application of Permethrin 10 EC or Dimethoate 40 EC) in Central Kenya. Pest infestations occurred within 14 days after the seedlings were transpla...