HOST PEST RELATIONSHIPS BETWEEN THE 2-SPOTTED SPIDER-MITE (ACARI, TETRANYCHIDAE) AND STRAWBERRY CULTIVARS WITH DIFFERING LEVELS OF RESISTANCE

A greenhouse study was conducted to investigate the host-pest relation ships of seven cultivars of strawberry, Fragaria spp., that differed i n resistance to the twospotted spider mite, Tetranychus urticae Koch. Plants were infested with a homogeneous density of females per unit of leaf area. Mite population development and plant damage were monitore d on a weekly basis for 6 wk on initially infested and subsequently co lonized leaves. Cultivars differed in their support of mite population s and in sensitivity to mite damage from the second to the fifth week of the experiment. 'Floridabelle' showed antibiotic and antixenotic ch aracteristics by supporting the lowest population density and showing lower damage values than other cultivars. 'Totem' demonstrated high le vels of tolerance by withstanding higher populations than other cultiv ars with damage comparable to that of resistant clones. 'Canoga' and ' Profumata di Tortona' showed hypersensitive responses to relatively lo w populations. 'Rainier', which supported high populations and demonst rated high overall damage values, was susceptible. 'Chandler' and 'Sel va' demonstrated resistance patterns which were intermediate. Resistan ce to the twospotted spider mite appears to be qualitative because it is conditioned by different mechanisms among cultivars.