Presence of the Aphid, Chaetosiphon fragaefolii, on Strawberry in Argentina

Seasonal abundance of the strawberry aphid complex under different agronomic practices in the outskirts of La Plata, Argentina was studied on strawberry, Fragaria x ananassa Duchesne (Rosales: Rosaceae). Aphid densities were low in strawberry fields in which insecticides and fungicides were used. In addition to Aphis gossypii, Aphis fabae, Mysus persicae and Macrosiphum euphorbiae, the aphid, Chaetosiphon fragaefolii (Cockerell) (Homoptera: Aphididae), was recorded for the first time in this horticultural area. Life history and some demographic parameters were calculated for C. fragaefolii. The mean duration of nymphal stages was 10.44 days, the oviposition period was 11.8 days, and the mean number of nymph/female/day was 2.4 ± 0.3. Demographic parameters analyzed included the net reproductive rate Ro = 14.55 ± 0.096 nymph/female, generation time T=16.91 ± 0.035 days, and the intrinsic rate of increase rm = 0.158 ± (0.004). No parasites were found associated with C. fragaefolli. The pathogenic fungus, Entomophthora planchoniana Cornu (Zygomycetes: Entomophthorales) was the main mortality factor. Although aphids are not the main pests in strawberry fields, C. fragaefolii can be a serious problem because it can transmit several virus diseases of strawberry. Greater knowledge of life history traits and mortality factors of this species is needed in order to design appropriate control strategies

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

<div><p><i>Hyadaphis foeniculi</i> (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 <i>H</i>. <i>foeniculi</i> 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 (<i>r_m</i>), gross reproduction rate (<i>GRR</i>), net reproduction rate (<i>R₀</i>), finite increase ratio (λ), generation time (<i>GT</i>), the time required for the population to double in the number of individuals (<i>DT</i>), and the reproduction value (<i>RV_x</i>)) of the fennel pest <i>H</i>. <i>foeniculi</i>. The values of lx (survival of nymphs at age <b>x</b>) 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 <b>x</b>) increased from 15 to 25°C and fell at 28 and 30°C. The net reproduction rates (<i>R₀</i>) of populations of <i>H</i>. <i>foeniculi</i> 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 (<i>r_m</i>) (day) ranged from 0.0033 (15°C) to 0.1995 (28°C). The highest values of <i>r_m</i> were recorded at temperatures of 28°C and 30°C. The <i>r_m</i> values were a good fit to the models tested, with R² > 0.91 and R²_adj > 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 <i>r_m</i> values observed, with R² > 0.91 and R²_adj > 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 <i>H</i>. <i>foeniculi</i>. Parameters relating to the age-specific fertility table for <i>H</i>. <i>foeniculi</i> 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.</p></div