The red form of Tetranychus urticae Koch, the two-spotted spider mite, is known to cause damage to carnations. Previously, it was thought that the green form of the two-spotted spider mite did not damage carnations; however, in recent years, this has been rejected. Using two carnation breeding cultivars, Di-24 was damaged by the green form and Di-7 was not. The host plant acceptance, fecundity, survival rate and developmental time for the green form were investigated for each cultivar. The green form had high performance (host plant acceptance, fecundity, survival rate and developmental time) on Di-24 than on Di-7. The results of these experiments clearly show that a susceptible cultivar to the green form exists in carnations. The mechanism of host-range expansion of the green form may have involved changes to carnation cultivars.