Characterizing Resistance to Tetranychus urticae in Tomato

Five tomato lines selected for resistance to the two-spotted spider mite, Tetranychus urticae Koch, were studied to characterize the nature of their resistance. Highly resistant PI 251303, moderately resistant ‘Anahu’ and ‘Kalohi,’ and low-resistant ‘Roma’ and T-526 were tested by 3 different procedures to define the nature of resistance. Detached leaf disks rimmed with tanglefoot were inoculated with teneral female mites and counts Were obtained on mites that died on the leaf, as a measure of antibiosis; mites that were trapped in the tanglefoot, as a measure of repellency; and oviposition, as a measure of food acceptibility and fecundity. High numbers of mites feeding on PI 251303 were either killed or repelled into the tanglefoot, and there was direct acaricidal action attributable to leaf hair exudate. This was velified by topical application of the exudate to mites. Fewer numbers of mites inoculated on leaf disks from the other lines either died or were trapped in the tanglefoot as compared with PI 251303.