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 (r(m)), gross reproduction rate (GRR), net reproduction rate (R-0), finite increase ratio (lambda), 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 degrees C and fell at 30 degrees C, whereas mx (number of nymphs produced by each nymph of age x) increased from 15 to 25 degrees C and fell at 28 and 30 degrees C. The net reproduction rates (R-0) of populations of H. foeniculi increased with temperature and ranged from 1.9 at 15 degrees C to 12.23 at 28 degrees C for each generation. The highest population increase occurred with the apterous aphids at 28 degrees C. The rate of population increase per unit time (r(m)) (day) ranged from 0.0033 (15 degrees C) to 0.1995 (28 degrees C). The highest values of r(m) were recorded at temperatures of 28 degrees C and 30 degrees C. The rm values were a good fit to the models tested, with R-2 > 0.91 and R-adj(2) > 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 R-2 > 0.91 and R-adj(2) > 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 degrees 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 degrees 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.