Melon aphid performance on chrysanthemum as mediated by cultivar, and differential levels of fertilization and irrigation

Population parameters of the melon aphid, Aphis gossypii Glover, were compared for insects grown on six cultivars of chrysanthemum, Dendranthema grandiflora Tzvelev ('Fontana', 'Iridon', 'Pink Lady', 'Splendor', 'White Diamond', and 'White View Time') fertilized with 3 different levels of nitrogen (80, 160 and 240 mg N/l) and 2 levels of irrigation (high 300 ml and low 210 ml every other day). Fecundity, longevity, and survivorship of aphids were significantly affected by the cultivar treatment, but were not affected by irrigation or fertilizer treatments or by any combination of interactions among cultivar, fertilizer and irrigation. Significantly fewer aphids survived on the cultivar 'Pink Lady' (populations reduced by 20.8%) than any other cultivar examined. Intrinsic rates of increase r _m , finite rates of increase (R ₀), and population doubling times (DT) for aphids were different among fertilizer levels and cultivars, but were not different among irrigation levels. There were no significant fertilizer by irrigation interaction effects upon r _m , R ₀, or DT. The highest rate of fertilizer applied (240 mg N/liter) adversely affected the intrinsic rate of increase of melon aphids; however, aphid intrinsic rate of increase was weakly correlated with foliar soluble protein levels (r=0.989, P=0.0954). Foliar soluble protein levels were not associated with fertilization treatment. Melon aphids perform consistently better on the cultivars 'White Diamond', 'Fontana', and 'Splendor', relative to those aphids growing on 'Iridon', 'Pink Lady', or 'White View Time'. In general, melon aphids performed best on 'White Diamond' and poorest on 'Pink Lady'.