Chemical Characteristics of Chrysanthemum Cause Resistance to Frankliniella occidentalis (Thysanoptera: Thripidae)

Abstract

Western flower thrips, Frankliniella occidentalis (Pergande), performance on intact chrysanthemums, Dendranthema grandiflora Tzvelev, was compared with that on the sap of squeezed chrysanthemums to examine the importance of plant chemical characteristics. Seventy-six percent of the variation in resistance of intact chrysanthemum cultivars could be explained by the variation in resistance of leaf sap. Thus, the chemical composition of chrysanthemum leaves was a significant factor in resistance to F. occidentalis. Because similarities in resistance were found between Rower sap, leaf sap, and intact, nonflowering chrysanthemums, we suggest there is a chemical resemblance among Rowers and leaves causing thrips resistance in chrysanthemum. Grafts were made between a resistant and susceptible cultivar (cultivars 2 and 15, respectively). A resistance factor was transported from the resistant scion to the susceptible stock, further indicating that chemical compounds play a major role in chrysanthemum resistance to thrips. Relative growth and survival of F. occidentalis larvae was correlated with larval longevity and the resulting feeding damage on intact chrysanthemum cultivars. Thus, growth and survival during the 1st few days can be used as a quick measure of thrips resistance in chrysanthemum.