Western flower thrips, Frankliniella occidentalis Pergande (WFT), is an important pest of most bedding plant species, including ivy geranium (Pelargonium peltatum L.; IG). The role of host plant nutrition on WFT population growth has rarely been studied. The response of WFT populations to two N (8 and 24 mM) by three P (0.32, 0.64, and 1.28 mM) fertilization treatments was studied in a greenhouse experiment with two IG cultivars having different levels of resistance to twospotted spider mite (Tetranychus urticae Koch), ‘Amethyst 96’ and ‘Sybil Holmes’. Plants were artificially inoculated with WFT four weeks after fertilizer treatments began. Inoculated and no-thrips control plants were destructively sampled at weeks six and eight. The number of nymph, pupae, and adult WFT were counted on three leaf strata (young, youngest fully-expanded, and old), and tissue N and P concentrations of the strata were determined. No-thrips control plants fertilized with different N x P treatments had similar dry weights but different tissue N and P concentrations. ‘Amethyst 96’ had less WFT than ‘Sybil Holmes’ (26 vs. 67, p < 0.0001). Total WFT was higher on plants fertilized with 0.64 and 1.28 mM P compared to 0.32 mM P (p=0.0049). More WFT were found on plants fertilized with 8 compared to 24 mM N (p=0.0056). However, N and P effects on different life stages of WFT were different. The interactions between cultivar and fertilization regime suggests that plant susceptibility was constant under different fertility management, and cultivar resistance has more impact on WFT populations than N and P status.
Species 1: Thysanoptera Thripidae Frankliniella occidentalis (western flower thrips)
Species 2: Geraniales Geraniaceae Pelargonium peltatum (ivy geranium)
Keywords: cultural control
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