WESTERN FLOWER THRIPS (THYSANOPTERA, THRIPIDAE) EFFECTS ON CHRYSANTHEMUM CULTIVARS - PLANT-GROWTH AND LEAF SCARRING IN NONFLOWERING PLANTS

The effects of exposure of 12 cultivars of Dendranthema grandiflora Tz velev and one cultivar of D. pacifica Tzvelev to 20 adult females of t he western flower thrips, Frankliniella occidentalis (Pergande), were studied in two no-choice experiments. Thrips damage resulted in large reductions in plant length and leaf area to all genotypes. The values of the damaged leaf area were significantly different among genotypes (range, 0 to >500 mm(2) scarred area per plant), and the pattern and t he location of the scarring was also different. This damage, however, was not related to the induced reductions in plant growth. For all 13 genotypes tested, the thrips population declined within 4 wk.