Francisco S. Fernandes

The Biology and Thermal Requirements of the Fennel Aphid Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae)

The relationship between the insect development rate and temperature was established very early and represents an important ecological variable for modeling the population dynamics of insects. The accurate determination of thermal constant values and the lower and upper developmental thresholds of Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) on fennel (Foeniculum vulgare Miller (Apiales: Apiaceae)) crops would obviously benefit the effective application of control measures. This paper is a study of the biology and thermal requirements of H. foeniculi. Winged insects were collected from fennel crops at the Embrapa Algodão in Campina Grande, Paraíba. Nymphs (age ≤24 h) produced by winged insects were subjected to constant temperatures of 15, 20, 25, 28, 30 or 33°C, a photophase of 12 h and a relative humidity of 70±10%. The results of the study showed that at temperatures between 15 and 30°C, H. foeniculi nymphs were able to develop normally. The four instars were found at all temperatures tested. However, temperatures of 3 and 33°C were lethal to the nymphs. The nymph stage development time varied from 5 (30°C) to 19 (15°C) days. The influence of temperature on the development time is dependent on the instar. The base temperature (Tb) and the thermal constant (K) for the nymph stage were estimated at 11.2°C and 107.5 degree-days, respectively. The shortest nymph development stage was observed at 30°C, and the highest nymph viability (85.0%) was observed at 28°C. This information can be used for developing phenological models based on the temperature and development rate relationships so that outbreaks of H. foeniculi in the fennel crop can be predicted, therefore improving the application of control programs targeting this fennel pest.

Feeding of fall armyworm, Spodoptera frugiperda, on Bt transgenic cotton and its isoline

Studies on insect food intake and utilization are important for determining the degree of insect/plant association and host species’ resistance, and also for helping design pest management programs by providing estimates of potential economic losses, techniques for mass breeding of insects, and identifying physiological differences between species. We studied the feeding and development of fall armyworm, Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae), on transgenic (Bt) and non‐transgenic (non‐Bt) cotton. The larvae of S. frugiperda fed on Bt cotton had a longer development period (23.0 days) than those fed on non‐Bt cotton (20.2 days). Survivorship of S. frugiperda larvae fed on Bt cotton (74.1%) was lower than that of larvae fed on non‐Bt cotton (96.7%). Pupal weight of larvae fed on Bt cotton (0.042 g) was lower than that of larvae fed on non‐Bt cotton (0.061 g). The cotton cultivar significantly affected food intake, feces production, metabolization, and food assimilation by S. frugiperda larvae. However, it did not affect their weight gain. Intake of Bt‐cotton leaf (0.53 g dry weight) per S. frugiperda larva was lower than the intake of non‐Bt‐cotton leaf (0.61 g dry weight). Larvae fed on Bt‐cotton leaves produced less feces (0.25 g dry weight) than those fed on non‐Bt‐cotton leaves (0.37 g dry weight). Weight gain per S. frugiperda larva fed on Bt‐cotton leaves (0.058 g dry weight) was similar to the weight gain for larvae fed on non‐Bt‐cotton leaves (0.056 g dry weight). The cotton cultivar significantly affected the relative growth, consumption, and metabolic rates, as well as other nutritional indices: the figures were lower for larvae fed on Bt‐cotton leaves than for larvae fed on non‐transgenic cotton leaves.

Assessment of Fennel Aphids (Hemiptera: Aphididae) and their Predators in Fennel Intercropped with Cotton with Colored Fibers

ABSTRACT The fennel aphid, Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) is a major pest of fennel, Foeniculum vulgare Miller in northeast region of Brazil. We hypothesize that intercropping can be used as an alternative pest management strategy to reduce aphid yield loss in fennel. Thus, we investigated the severity of fennel plant damage in relation to infestation by the fennel aphid and predation by Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) (spotless lady beetle), green lacewing, Chrysoperla cornea (Stephens) (Neuroptera: Chrysopidae), and Scymnus spp. (Coleoptera: Coccinellidae) in sole fennel plots and plots of fennel intercropped with cotton with colored fibers. The fennel aphid populations in nontreated plots were significantly larger in sole fennel plots than in intercropped plots. The highest densities of C. sanguinea, green lacewings and Scymnus spp., associated with the suppression of fennel aphid populations was found in fennel in the intercropping systems. Fennel aphids reduced the fennel seed yield by 80% in the sole fennel plots compared with ≈30% for all intercropping systems. The results obtained in this research are of practical significance for designing appropriate strategies for fennel aphid control in fennel-cotton intercropping systems. In summary, intercropping fennel with cotton with colored fibers apparently promoted biocontrol of fennel aphid in fennel.

Feeding Damage from Cotton Aphids, Aphis gossypii Glover (Hemiptera: Heteroptera: Aphididae), in Cotton with Colored Fiber Intercropped with Fennel

ABSTRACT Intercropping is a traditional agronomic practice, and when properly managed, it can significantly contribute to pest control. The current study investigates the severity of plant damage related to infestation by the cotton aphid, Aphis gossypii Glover (Hemiptera: Heteroptera: Aphididae) and its predation by spotless ladybird beetle, Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae) and green lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and parasitism by Lysiphlebus testaceipes (Cresson) (Hymenoptera: Aphidiidae) in sole cotton plots and in plots of cotton intercropped with fennel. Cotton aphid populations were significantly higher in sole cotton plots than in intercropping plots for plots that were not treated with insecticide. The percentages of losses in cotton seed yield were higher in the sole cotton plots than in the four intercropping systems (one row of cotton for two rows of fennel, one row of cotton for three rows of fennel, two rows of cotton for one row of fennel, and three rows of cotton for two rows of fennel). The losses in cotton seed yield were significantly lower in the intercropping system with three rows of cotton interspersed with two rows of fennel than in the other intercropping systems. Spotless ladybird beetle and green lacewing densities were significantly higher in the intercropping system with three rows of cotton interspersed with two rows of fennel than in the other intercropping systems. These results are of practical significance in designing appropriate strategies for cotton aphid control in cotton-fennel intercropping systems.

Effects of Photoperiod on Reproduction and Longevity of Podisus nigrispinus (Heteroptera: Pentatomidae)

ABSTRACT Effects of photoperiod on reproduction and longevity of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) were assessed under seven different photophases (10, 11, 12, 13, 14, 15, and 16 h) at a constant 28 ± 1°C temperature and 70 ± 10% RH in the laboratory. Photoperiod affected the longevity of P. nigrispinus females. The highest longevity (24.10 d) occurred with a 15-h photoperiod, compared with longevity of 9.75 d at 12-h photoperiod. The preoviposition period of P. nigrispinus was influenced by the photoperiod. The preoviposition period of P. nigrispinus was longer for the 16-h photoperiod (7.25d) than for the 12- (4.06d), 13- (4.00 d), and 14-h (3.68d) photoperiod. The postoviposition period, the number of egg clutches per female per day, and the interval between egg clutches were not affected by the photoperiod. The postoviposition period ranged from 1.46 d (at 14 h of light) to 3.71 d (at 11 h of light). The number of egg clutches per female per day varied between 0.19 (at 11 h or 14 h of light) and 0.40 (at 15 h of light). The interval between egg clutches ranged from 1.29 d (at 14 h of light) to 2.07 d (at 11 h of light). The variation in the number of eggs and egg clutches per female of P. nigrispinus in relation to their age varied according to the photophase to which they were exposed. The fecundity of P. nigrispinus females was higher in 15 h of light. These informations serve as a valuable ecological variable in modeling population dynamics of P. nigripinus, both in the field and in the laboratory, thereby contributing to the success of A. argillacea control programs.

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

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 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 rm 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 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.

Feeding and Dispersal Behavior of the Cotton Leafworm, Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), on Bt and Non-Bt Cotton: Implications for Evolution and Resistance Management

The host acceptance of neonate Alabama argillacea (Hübner) (Lepidoptera: Noctuidae) larvae to Bt cotton plants exerts a strong influence on the potential risk that this pest will develop resistance to Bt cotton. This will also determine the efficiency of management strategies to prevent its resistance such as the “refuge-in-the-bag” strategy. In this study, we assessed the acceptance of neonate A. argillacea larvae to Bt and non-Bt cotton plants at different temperatures during the first 24 h after hatching. Two cotton cultivars were used in the study, one a Bt DP 404 BG (Bollgard) cultivar, and the other, an untransformed isoline, DP 4049 cultivar. There was a greater acceptance by live neonate A. argillacea larvae for the non-Bt cotton plants compared with the Bt cotton plants, especially in the time interval between 18 and 24 h. The percentages of neonate A. argillacea larvae found on Bt or non-Bt plants were lower when exposed to temperatures of 31 and 34°C. The low acceptance of A. argillacea larvae for Bt cotton plants at high temperatures stimulated the dispersion of A. argillacea larvae. Our results support the hypothesis that the dispersion and/or feeding behavior of neonate A. argillacea larvae is different between Bt and non-Bt cotton. The presence of the Cry1Ac toxin in Bt cotton plants, and its probable detection by the A. argillacea larvae tasting or eating it, increases the probability of dispersion from the plant where the larvae began. These findings may help to understand how the A. argillacea larvae detect the Cry1Ac toxin in Bt cotton and how the toxin affects the dispersion behavior of the larvae over time. Therefore, our results are extremely important for the management of resistance in populations of A. argillacea on Bt cotton.

Within-plant distribution of cotton aphid (Hemiptera: Aphididae) in cotton cultivars with colored fibers

We describe the vertical and horizontal distribution of the cotton aphid Aphis gossypii Glover within a cotton plant in two cotton (Gossypium hirsutum Linnaeus) cultivars (BRS Safira and BRS Rubí) with colored fiber over the time. Measurements of aphid population dynamics and distribution in the cotton plants were recorded in intervals of seven days. The number of apterous or alate aphids and their specific locations were recorded, using as a reference point the location of nodes on the mainstem of the plant and also those on the leaves present on branches and fruit structures. The number of apterous aphids found on the cultivar BRS Safira (56,515 aphids) was greater than that found on BRS Rubí (50,537 aphids). There was no significant difference between the number of alate aphids found on the cultivars BRS Safira (365 aphids/plant) and BRS Rubí (477 aphids/plant). There were interactions between cotton cultivar and plant age, between plant region and plant age, and between cultivar and plant region for apterous aphids. The results of this study are of great importance in improving control strategies for A. gossypii in the naturally-colored cotton cultivars BRS Safira and BRS Rubí.

Estimating the development of the fennel aphid, Hyadaphis foeniculi (Passerini) (Hemiptera: Aphiididae), using non-linear models.

BACKGROUND Non-linear models making it possible to predict agricultural pest outbreaks and optimise control tactics are of primary importance for integrated pest management. The development period for immature stages of the fennel aphid Hyadaphis foeniculi (Passerini) (Hemiptera: Aphididae) at constant temperatures was modelled in order to determine mathematical functions for simulating the aphids development. Non-linear models were used to describe the relationship between temperature and development rates of H. foeniculi subjected to constant temperatures. RESULTS The models used were found to be good fits for estimating H. foeniculi development rates as a function of temperature, with the exception of the Davidson model. The development time of H. foeniculi nymphs ranged from 2.73 days (first instar) to 6.18 days (fourth instar) at 15 °C, from 2.57 days (first instar) to 4.52 days (fourth instar) at 20 °C and from 1.53 days (first instar) to 2.05 days (fourth instar) at 28 °C. CONCLUSION These models provide important tools for better elucidation of the relationship between temperature and development rates in H. foeniculi. The results could be used for predicting the occurrence of the various immature stages of H. foeniculi in the fennel crop in Brazil, making it possible to predict more accurately the best periods for implementing pest control.

Feeding and Life History of Alabama argillacea (Lepidoptera: Noctuidae) on Cotton Cultivars Producing Colored Fibers

ABSTRACT Quantitative analysis of the consumption and use by herbivore pests of the host plant is a common tool used for studying the interaction between insects and plants. Our goals were to quantify cotton leafworm, Alabama argillacea (Hübner) (Lepidoptera: Noctuidae), larval consumption rate in three cotton, Gossypium hirsutum L., cultivars that produce colored cotton fibers, and the effects of the consumption rate on A. argillacea pupal weight in greenhouse conditions. Larvae consumed a maximum of 0.69–1.03 g of leaf tissue over a 24-h period in all cultivars tested. Total consumption by A. argillacea larvae was highest when fed with ‘BRS 200’ leaves (2.89 g) and the lowest when fed with leaves from ‘BRS Safira’ (2.26 g). The regression analysis showed significant relationships between the quantity of leaf tissue consumed and pupal weights for each cotton cultivar. A. argillacea larvae fed on BRS 200 demonstrated a longer developmental period (14.84 d) than larvae fed on ‘BRS Rubi’ leaves (11.62 d) or BRS Safira (11.14 d). We concluded that BRS Safira presents the best quality food source for A. argillacea, BRS 200 is the worst, and BRS Rubí is intermediate. The longer developmental times of A. argillacea on BRS 200 may allow longer windows of opportunity for the use of biological control agents to reduce the damage caused by this pest and also would complete less generations per phenological cycle of the cotton crop.