A previous study showed that feeding of adult banded cucumber beetle, Diabrotica balteata LeConte, and development of the female reproductive system were strongly inhibited by a diet of fresh Valmaine (Val) romaine lettuce, Lactuca sativa L., relative to Tall Guzmaine (TG). Leaf surface chemicals have been shown not to be involved in the resistance of Val. In this study, leaves of TG and Val were freeze-dried and incorporated into an artificial diet to evaluate whether the chemicals within the lettuce leaves were responsible for resistance to D. balteata feeding. The amount consumed and mature eggs produced were not significantly different when adults were given either a choice or no choice of TG or Val diets. However, latex from TG and Val strongly inhibited D. balteata feeding on a favorite food, lima bean leaves, when applied to leaf surfaces. Latex from Val turned brown faster than that from TG, and flowed for a longer period of time before ceasing. Localized induced resistance to feeding was found in Val but not in TG after plants were previously damaged for 48 h. Therefore, we propose that localized inducible resistance and physical defenses in latex may account for resistance in Val to D. balteata.