Isolation of Phagostimulative Substances from the Host Plant of the Colorado Potato Beetle12

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Abstract
Substances which stimulate feeding of the Colorado potato beetle, Leptinotarsa decemlineata (Say), were isolated from potato leaf powder and fresh potato leaves. An agar-cellulose medium was used to evaluate the stimulative effect of leaf fractions. Sucrose, isolated from potato leaf powder, was found to be partially responsible for the stimulative effect of the powder on feeding. A phospholipid fraction obtained from fresh potato leaves also showed stimulative effects. A feeding stimulant present in the lead acetate precipitate of fresh potato leaves was isolated and identified as chlorogenic acid. Tests with several related phenolic acids showed that only chlorogenic acid can elicit the feeding response. Preference experiments, using a lettuce-disc assay, indicated the presence of a botanically restricted stimulant. This stimulant was partially purified from an alcoholic extract of fresh potato leaves. It is suggested that this specific stimulant could be a phenolic flavonoid or related compound.