Temperature-Dependent Fecundity and Life Table of the Fennel Aphid Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae)

Abstract

Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) is a cosmopolitan species and the main pest of fennel in northeastern Brazil. Understanding the relationship between temperature variations and the population growth rates of H. foeniculi is essential to predict the population dynamics of this aphid in the fennel crop. The aim of this study was to measure the effect of constant temperature on the adult prereproductive period and the life table fertility parameters (infinitesimal increase ratio (rm), gross reproduction rate (GRR), net reproduction rate (R0), finite increase ratio (λ), generation time (GT), the time required for the population to double in the number of individuals (DT), and the reproduction value (RVx)) of the fennel pest H. foeniculi. The values of lx (survival of nymphs at age x) increased as the temperature rose from 15 to 28°C and fell at 30°C, whereas mx (number of nymphs produced by each nymph of age x) increased from 15 to 25°C and fell at 28 and 30°C. The net reproduction rates (R0) of populations of H. foeniculi increased with temperature and ranged from 1.9 at 15°C to 12.23 at 28°C for each generation. The highest population increase occurred with the apterous aphids at 28°C. The rate of population increase per unit time (rm) (day) ranged from 0.0033 (15°C) to 0.1995 (28°C). The highest values of rm were recorded at temperatures of 28°C and 30°C. The rm values were a good fit to the models tested, with R2 > 0.91 and R2adj > 0.88. The models tested (Davidson, Sharpe and DeMichele modified by Schoolfield et al., Logan et al., Lamb, and Briere et al.) were very good fits for the rm values observed, with R2 > 0.91 and R2adj > 0.88. The only exception was the Davidson model. Of the parameters studied, the reproductive capacity was higher in the apterous aphids, with the unique exception of daily fecundity at 28°C, which was higher in the alate aphids of H. foeniculi. Parameters relating to the age-specific fertility table for H. foeniculi were heavily influenced by temperature, with the highest biotic potential and population growth capacity found at 34°C. Therefore, the results obtained in this study could be of practical significance for predicting outbreaks of fennel aphids and improving the management of this aphid in fennel crops.

Fig 1. Prereproductive period (Mean ± SEM) for apterous morphs of H. foeniculi at different temperatures.

Means with common lower case letters are not significantly different, the Student-Newman-Keuls test (P = 0.05). Standard error of the mean (SEM) is represented above each bar.

Fig 2. Effect of temperature on prereproductive period (y = 5.61–0.24x² + 0.003x, F = 38.91, df = 2, 2, P = 0.0251, R² = 0.9412), longevity (4.93x² - 0.10x - 41.08, F = 97.69, df = 2, 2, P = 0.0101, R² = 0.9816), nymph/female (-16.63x³ + 0.87x² - 0.01x + 104.49, F = 157.33, df = 3, 1, P = 0.0467, R² = 0.9409), and nymph/female/day (-1.86x³ + 0.08x² - 0.001x + 13.10, F = 157.33, df = 3, 1, P = 0.0467, R² = 0.9120) for apterous morphs of H. foeniculi. d = day.

Fig 3. Relationship between age class (d) and age-specific daily fecundity (mx) and age-specific survival (lx) for apterous morphs of H. foeniculi at 15, 20, 25, 28 and 30°C.

Age class = 1 d.

Fig 4. Reproductive value for apterous morphs of H. foeniculi as a function of temperature: 15°C (0.1939–0.1392x³ + 0.0337x²–0.0022x, F = 4.38, df = 3, 6, P = 0.0588, R² = 0.6870); 20°C (0.0551 + 0.0093x² - 0.0006x, F = 4.38, df = 3, 6, P = 0.0588, R² = 0.6058); 25°C (0.3634–0.0254x, F = 43.29, df = 1, 12, P = 0.0001, R² = 0.7829); 28°C (0.2712–0.0194x, F = 45.61, df = 1, 10, P = 0.0001, R² = 0.8003); and 30°C (y = 0.3082–0.0308x, F = 64.93, df = 1, 8, P = 0.0001, R² = 0.8903).

Fig 5. Fitting nonlinear models to the observed values of the increase rate (r _m) for apterous morphs of H. foeniculi as function of temperature (°C).

Observed (dots) and predicted data (dashed line).