Susceptibility of previously damaged strawberry plants to mite attack

Using radioactive labelling techniques on two cultivars of strawberry (Fragaria grandiflora Duch.) and on the two-spotted spider mite (Tetranychus urticae Koch) which fed on them, differential feeding was monitored. Leaves of the susceptible cultivar Georg Soltwedel previously damaged by mites were more attractive for spider mites than leaves of undamaged plants. The opposite was observed when the resistant cultivar Macherauch's Frühernte was investigated. The results are discussed according to the induced resistance hypothesis.