Influence of photoperiod on Orius thyestes Herring (Hemiptera: Anthocoridae) reproduction and longevity

Influência do fotoperíodo na reprodução e longevidade de Orius thyestes Herring (Hemiptera: Anthocoridae)

BIOLOGICAL CONTROL

Influence of photoperiod on Orius thyestes Herring (Hemiptera: Anthocoridae) reproduction and longevity

Influência do fotoperíodo na reprodução e longevidade de Orius thyestes Herring (Hemiptera: Anthocoridae)

Alessandra R. Carvalho; Vanda H.P. Bueno; Elizabeth C. Pedroso; Leonardo I. Kon; Alexandre J.F. Diniz; Robson J. Silva

Lab. Controle Biológico, Depto. Entomologia, Univ. Federal de Lavras. Campus Universitário UFLA, C. postal 3037 Lavras, MG, [e-mail]

ABSTRACT

Several species of Orius Wolff are used in biological control of thrips in protected cultivations in temperate regions, but some of them show reproductive diapause, compromising the efficiency of these agents of biological control. There are no reports on the biology of the neotropical species Orius thyestes Herring under different environmental conditions. The purpose of this work was to investigate the influence of photoperiod on reproduction and longevity of this predator. Nymphs were kept in petri dishes in climatic chambers at 28 ± 1°C, 70 ± 10% RH and under the photoperiods of 12L:12D, 11L:13D, 10L:14D e 09L:15D. The mating adults were kept in petri dishes with Bidens pilosa L. Asteraceae inflorescences as oviposition substracts and eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) as food. The pre-oviposition and oviposition periods, fecundity and longevity were evaluated and O. thyestes did not show reprodutive diapause in all photoperiod conditions established. The mean number of eggs obtained per female decreased with the reduction of the photophase, with a difference (P < 0.05) between the values obtained in 12h and 9h of photophase. Longevity of females and males under 9h photophase was shorter (P < 0.05) than in all other photoperiods tested. The knowledge of the biology of the natural enemy under different conditions allows to optimise the mass rearing and to predict the performance of the predator in different photoperiods which may occur along the year and in greenhouses.

Key words: Predator, fecundity, photophase, behavior, biological control

RESUMO

Várias espécies de Orius Wolff são utilizadas no controle biológico de tripes em cultivos protegidos em regiões temperadas, entretanto algumas delas apresentam diapausa reprodutiva, comprometendo a atuação desses agentes de controle biológico. Não existem relatos sobre a biologia da espécie neotropical Orius thyestes Herring em diferentes condições ambientais. Este trabalho objetivou verificar a influência do fotoperíodo na reprodução e longevidade desse predador. Ninfas foram individualizadas em placas de Petri e mantidas em câmaras climatizadas a 28 ± 1°C, UR de 70 ± 10% e nos fotoperíodos de 12L:12E, 11L:13E, 10L:14E e 09L:15E. Os adultos foram acasalados em placas de Petri contendo inflorescência de Bidens pilosa L. Asteraceae como substrato de oviposição e ovos de Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) como alimento. Foram avaliados os períodos de pré-oviposição e oviposição, fecundidade e longevidade de fêmeas e machos. Em nenhuma das condições de fotoperíodos avaliadas O. thyestes apresentou diapausa reprodutiva. O número médio de ovos por fêmea diminuiu proporcionalmente ao número de horas de luz, com diferença (P < 0,05) entre os valores obtidos em 12h e 9h de luz. A longevidade de fêmeas e machos do predador sob fotofase de 9h foi menor (P < 0,05) que as longevidades observadas nos demais fotoperíodos testados. O conhecimento sobre a biologia do inimigo natural em diferentes condições permite otimizar a criação massal e prever o desempenho do predador em diferentes fotoperíodos que podem ocorrer ao longo do ano e no interior das casas de vegetação.

Palavras-chave: Predador, fecundidade, fotofase, comportamento, controle biológico

To understand the mechanisms that influence diapause induction is important for rearing procedures and storage of natural enemies and for inoculative and inundative releases (Ruberson et al. 1991).

Insects react in several ways to photoperiod according to its geographical location, and examples are known for those of the Heteroptera. In general, the critical day lenght for diapause induction declines with latitude (Beck 1980, Danks 1987). Musolin & Numata (2003) found influence of day lenght on the life-cycle of Nezara viridula (L.): short days induces diapause, changes in adult coloration from green to brown and increase of pre-mating and pre-oviposition periods.

In protected cultivation, photoperiod variation is a common and necessary practice to induce flowering on several ornamental plants where thrips are of economic importance (Arruda et al. 1996), and may affect their natural enemies on site. Under this system of cultivation, heteropterous of genus Orius Wolff are widely used on biological control of thrips in Europe, United States and Canada (van den Meiracker 1994, van Lenteren 2000), where reproductive diapause studies are made. Gillespie & Quiring (1993) found a decrease of approximately 3h in the critical day lenght when comparing Orius tristicolor (White) from Canada (49°N) and from California (38°N).

Tommasini & Nicoli (1996) found that strains of Orius laevigatus (Fieber) from North Italy tend to enter reproductive diapause while southern strains of this species can be used on thrips control in autumn and winter. Thus, low latitude strains may be of great value to biological control in greenhauses on high latitude regions (van den Meiracker 1994).

In Brazil, Argolo et al. (2002) did not detect diapause in Orius insidiosus (Say) when submitted to constant photophases from 9h to 14h. Silveira & Bueno (2003) did not observe sensibility of this predator to alternate photoperiods between pre-imaginal and adult phases. On the other hand, O. insidiosus has its reproduction altered by short photoperiods in temperate countries, resulting in reproductive diapause (Kingsley & Harrington 1982, Ruberson et al. 1991, van den Meiracker 1994).

There are no known studies referring to the influence of photoperiod on Orius thyestes Herring, since it was previously found only in Colombia and Mexico and more recently in Brazil (Silveira et al. 2003). Thus, this study aimed to knowm the influence of several constant photoperiods in the reproduction and longevity of O. thyestes under laboratory conditions, in order to optimize its mass rearing and utilization in biological control programs of thrips on crops in greenhouses.

Material and Methods

Rearing of O. thyestes was carried out in the Laboratório de Controle Biológico of the Departamento de Entomologia da UFLA with field collected specimens on amaranth (Amaranthus sp.) in Lavras, MG, Brazil (21°14'S, 44°59'W). Eggs of Anagasta kuehniella (Zeller) (Lepidoptera: Pyralidae) were placed every other day as food and farmer's friend inflorescence (Bidens pilosa L.) as oviposition substrate.

Single fourth- and fifth-instar nymphs of O. thyestes were placed in petri dishes (5 cm diameter) containign eggs of A. kuehniella and wet cotton, and sealed with plastic film. All specimens used in this study originated from a laboratory rearing maintained over six generations. After emergence and mating of the adults, they were placed in petri dishes containing farmer's friend inflorescence surrounded by wet cotton using distilled water and A. kuehniella eggs. The inflorescence used as oviposition substrate was desinfected with ± 0.12% sodium hypochlorite solutions to avoid the occurrence of fungi and bacteria which could interfere with the development of the eggs and nymphs; the upper part of the inflorescences were removed to prevent individuals from feeding on pollen which could interfere on their biology (Kiman & Yeargan 1985). Food and oviposition substrates were substituted daily. Experiments were conducted in climatic chambers at 28 ± 1ºC and 70 ± 10% RH. Thirty replicates of the following photoperiods were evaluated: 9L:15D, 10L:14D, 11L:13D e 12L:12D.

Each oviposition substrate was carefully evaluated every day under stereoscopic microscopy for egg counting untill female death. Death males were not replaced as females oviposit even at their absence (Askari & Stern 1972). Females and males were evaluated for pre-oviposition and oviposition periods, fecundity and longevity.

Data were submitted to the homogeinity variance test and transformed to Öx before the analyses of variance. Means were compared using the Tukey's test at 5% of probability.

Results and Discussion

Females of O. thyestes found in Lavras did not show reproductive diapause in all tested photoperiods, since 100% oviposited before the eight day of life. According to Ruberson et al. (1991) and van den Meiracker (1994), species of Orius enter reproductive diapause when the pre-oviposition period exceeds 14 days. For Tommasini (2003), the pre-oviposition period is an indicator on how adult populations react to external stymuli.

The tested photoperiods did not interfere (P < 0.05) with the pre-oviposion and oviposition periods of O. thyestes when compared to each other (Table 1). Argolo et al. (2002) observed a longer pre-oviposition period of O. insidiosus submitted to 11h of photofase and found a direct relation between the number of hours of light and the oviposition period of the predator.

The pre-oviposition (1.4 days) and oviposition (9.1 days) of O. thyestes under 12h-photofase (Table 10) were shorter than the periods reported by Carvalho et al. (2005), (3.5 e 17 days, respectively). This difference may be explained by the presence of males together with females for 15 min only per day, as compared to this experiment where they were kept together with the females until death.

A significant (P < 0.05) reduction on the mean number of eggs/female/day under 10h (4.6) was observed as compared to 12h (5.9) (Table 1), with no significant differences among the remaining values obtained.

As for the 12L:12D photoperiod, the results are similar to those obtained by Carvalho et al. (2005), where O. thyestes deposited a mean of 5.8 eggs/female/day. Significant difference (P < 0.05) was found for egg number/female between 9h and 12h of light only. Argolo et al. (2002) also found no influence of different photofases on O. insidiosus fecundity, but the number of eggs/female was higher than the observed for O. thyestes (Table 1), varying from 162.0 eggs at 09L:15D to 195.2 eggs at 12L:12D.

Mean female and male longevity of O. thyestes was similar among the 12L:12D, 11L:13D and 10L:14D photoperiods, but was significantly shorter (P < 0.05) at 09L:15D (Table 1). In general, males live from 36% to 49% less than females (Table 1). These results confirm those of Mendes et al. (2003) who found a significant reduction of 6.7 days on O. insidiosus females when kept full time with males. But Carvalho et al. (2005) found no difference between male and female longevity of O. thyestes when mated every seven days, with longevity equal to 20.5 and 20.9 days for males and females, respectively. According to Askari & Stern (1972), females of O. insidiosus are always receptive to males but may become stressed and have their life spam reduced.

Comparing O. thyestes to O. insidiosus (Argolo et al. 2002), longevity of O. insidiosus is greater than in O. thyestes in both sexes (Table 1) on all tested photoperiods, longevity varying from 53 to 41 days in adults of O. insidiosus.

Results indicate that O. thyestes found in Lavras have no reproductive diapause and the tested photoperiods do not interfere with longevity, but fecundity may be reduced. These data may be used to optimize mass rearing of the predator and predict its performance under the several photoperiods that may occur during the year in different localities and in greenhouses. Further studies should focus on photoperiod and temperature interactions.

Acknowledgments

To the "Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)" for the scholarships and financial support to the project.

Received 12/V/05.

Accepted 17/I/06.

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Publication Dates

• Publication in this collection
  21 Sept 2006
• Date of issue
  Aug 2006

History

• Accepted
  17 Jan 2006
• Received
  12 May 2005