The effect of aphid prey quality on searching behaviour of Adalia bipunctata and its susceptibility to insecticides

After consumption of one individual of a suitable prey, such as Phorodon hu muli (Schrank) (Aphididae), Adalia bipunctata L. (Coleoptera, Coccinellidae ) adults changed from extensive to intensive searching behaviour. However, after the consumption of one individual of three other aphid species: Aphis fabae Scop., Aphis craccivora Koch or Aphis spiraephaga Muller, which are unsuitable prey, this coccinellid remained immobile for 12-76 min and did n ot switch to intensive search after moving off. Adult A. bipunctata fed an unsuitable prey, A. fabae, for 2 weeks were 2-4 times more susceptible to p yrethroid insecticides (permethrin, deltamethrin, fenpropathrin, esfenvaler ate, alfa-cypermethrin and bioresmethrin) and insect growth regulators (dif lubenzuron, triflumuron, fenoxycarb, flufenoxuron, teflubenzuron) than thos e fed a suitable prey, P. humuli. The searching behaviour of coccinellids could thus be another criterion for determining the suitability of aphids as prey. The fact that the nutrition al quality of aphids can affect the susceptibility of predatory coccinellid s to insecticides should be borne in mind in integrated pest management pro grams.