RESISTANCE TO WESTERN FLOWER THRIPS IN GREENHOUSE CUCUMBER - EFFECT OF LEAF POSITION AND PLANT-AGE ON THRIPS REPRODUCTION

Three greenhouse cucumber (Cucumis sativus L.) accessions, previously selected for low levels of damage after infestation with Frankliniella occidentalis (Pergande), were tested for resistance against F. occide ntalis in a no-choice greenhouse experiment at the mature plant stage. The three accessions showed a strong reduction in thrips damage compa red to the susceptible control. The effects of leaf position and plant age of the four cucumber accessions on the reproduction of F. occiden talis were determined in a leaf disc assay. Leaf position had a signif icant effect on thrips reproduction, whereas plant age, within the tes t range, had not. In general, reproduction was higher on young leaves. Reproduction as measured on leaf discs from certain leaf positions wa s strongly correlated with resistance of mature plants in the greenhou se, and can therefore be used as a quick test to screen cucumber acces sions for resistance against thrips.