Fertiliser application affects susceptibility of chrysanthemum to western flower thrips - abundance and influence on plant growth, photosynthesis and stomatal conductance.

by Fred T. Davies Jr., Chuanjiu He, Amanda Chau, Jay D. Spiers, and Kevin M. Heinz

We report the influence of plant fertility, principally nitrogen (N) levels, on plant growth, gas exchange and herbivore abundance in chrysanthemum (Dendranthema grandiflora Tzvelev 'Charm') infested with western flower thrips [WFT: Frankliniella occidentalis (Pergande)]. Four levels of a commercial, soluable fertiliser "15-16-17" (elemental analysis: 15N-6.7P-14.1K) were tested at: 0, 38, 75 and 375 mg 1-1 N [0N, 35N, 75N, 375N], which represented 0%, 10%, 20%, and 100% of the recommended N-fertilisation rate, respectively. Adult and immature WFT were most abundant at the highest fertility level (375N). At moderate (38N and 75N) to high fertility (375N), WFT infestation depressed plant vegetative and reproductive growth, and altered carbohydrate partitioning. WFT-infested plants had reduced flower bud dry mass (DM) and flower bud number compared to uninfested plants. While WFT infestation reduced leaf area and leaf mass, the specific leaf area (SLA; i.e., leaf thickness) was not affected. However, high fertility plants had greater reproductive and vegetative biomass, greater leaf elemental levels (N, P, Ca, Mg, B, Fe, Mn, Cu, and Zn) and a higher SLA (i.e. thinner leafs) than low fertility (0N) plants. Leaf stomatal conductance (gs) was more sensitive to WFT damage than net photosynthesis (Pn). WFT damage caused a reduction in Pn in young and physiologically mature leaves at the highest fertility level, whereas gs was reduced in young, physiologically mature and older basal leaves of plants damaged by WFT at moderate to high fertility. WFT infestation had no effect on leaf macro- and micro-elements, ethylene production or chlorophyll levels. WFT damage reduced vegetative and reproductive growth primarily through reduced Pn and gs.

Journal of Horticultural Science and Biotechnology, Vol. 80(4), pp. 403-412, 2005.