Trichogramma acacioi (Hymenoptera, Trichogrammatidae) parasitism capacity at different temperatures and factitious hosts

Capacidade de parasitismo de Trichogramma acacioi em diferentes temperaturas e hospedeiros alternativos

SHORT COMMUNICATION

Dirceu Pratissoli^I; Adeney de Freitas Bueno^II; Regiane Cristina Oliveira de Freitas Bueno^III; José Cola Zanúncio^IV; Ricardo Antonio Polanczyk^I

^IDepartamento de Produção Vegetal, Centro de Ciências Agrárias, Universidade Federal do Espírito Santo, 29500-000 Alegre-ES, Brasil. [e-mail]; [e-mail]

^IIEmbrapa-Soja. Address for correspondence: Embrapa Arroz e Feijão, Rodovia GO-462, km 12, Zona Rural, Caixa Postal 179, 75375-000, Santo Antônio de Goiás-GO, Brasil. [e-mail] (author for correspondence)

^IIIBolsista Pós-doutorado Capes programa PNPD, Universidade de Rio Verde, FESURV, 75901-970 Rio Verde-GO, Brasil. [e-mail]

^IVDepartamento de Biologia Animal, Universidade Federal de Viçosa, 36571-000 Viçosa-MG, Brasil. [e-mail]

ABSTRACT

It was studied the parasitism capacity of Trichogramma acacioi on Anagasta kuehniella and Sitotroga cerealella eggs at different temperatures (15, 20, 25, 30 and 35 ± 1°C). The parasitism of T. acacioi varied with temperature and host. The highest parasitism (³80%) were observed during the first days after emergence in both hosts, at all tested temperatures. The accumulated parasitism varied with both host and temperature, being higher on A. kuehniella at 20°C, what shows good parasitoid species adaptation to this temperature. Thus, we conclude that the best host and best temperature to be used at mass-rearing of T. acacioi is A. kuehniella and 20ºC, respectively. Moreover, this Trichogramma species has great potential to be used in field releases at regions where average temperature is around 20ºC.

Keywords: Biological control; egg parasitoid; factitious host; mass-rearing.

RESUMO

Foi estudada a capacidade de parasitismo de Trichogramma acacioi em ovos de Anagasta kuehniella e Sitotroga cerealella em diferentes temperaturas (15, 20, 25, 30 e 35 ± 1°C). O parasitismo de T. acacioi variou com a temperatura e hospedeiro. O maior parasitismo (³80%) foi observado durante os primeiros dias após a emergência, em ambos hospedeiros e em todas as temperaturas estudadas. O parasitismo acumulado variou nas diferentes temperaturas e hospedeiros, sendo maior em A. kuehniella a 20ºC, o que mostra uma boa adaptação da espécie do parasitóide a essa temperatura. Assim, concluímos que o melhor hospedeiro alternativo e melhor temperatura para serem usadas em criações massais de T. acacioi é a A. kuehniella e 20ºC, respectivamente. Ainda, esta espécie de Trichogramma tem grande potencial para ser usada em liberações de campo em regiões onde a temperatura média está em torno de 20ºC.

Palavras-chave: Controle biológico; criação massal; hospedeiro alternativo; parasitóide de ovos.

Egg parasitoids from the genus Trichogramma have been recognized as an important biological control agent, being worldwide distributed and capable of parasitizing eggs of a great diversity of pests from the order Lepidoptera (Pratissoli et al. 2004). Studies about Trichogramma spp. have been carried out in more than 50 countries and mass releases done in around 32 millions of hectares every year (Smith 1996). A biological control program using parasitoids from the genus Trichogramma must follow several steps. Trichogramma species performance on different hosts and temperatures will show the best factitious host and temperature for mass-rearing, an important step of a program using Trichogramma (Parra & Zucchi 2004).

Pratissoli & Fornazier (1999) first recorded Trichogramma acacioi Brun, Moraes & Soares (1984) (Hymenoptera: Trichogrammatidae) on Nipteria panacea Thierry-Mieg (1892) (Lepidoptera: Geometridae) in Brazil. This parasitoid species is an option that might be used in biological control programs, however, there are very few researches on its biological characteristics. They might be greatly influenced by the different temperatures and hosts. Thus, this research was carried out aiming to evaluated the parasitism capacity of T. acacioi on Anagasta kuehniella Zeller (1879) (Lepidoptera: Pyralidae) and Sitotroga cerealella (Olivier, 1819) (Lepidoptera: Gelechiidae) eggs at different temperatures, aiming to acquire enough knowledge to choose the best factitious host and temperature for mass-rearing of this Trichogramma species.

The experiment was carried out in a factorial complete randomized design (2 hosts and 5 temperatures) at the Entomology Laboratory "Centro de Ciências Agrárias, Universidade Federal do Espírito Santo, Alegre, Espírito Santo, Brasil" at controlled conditions (70 ± 10% relative humidity, 14:10 L:D) and different temperatures (treatments): 15, 20, 25, 30 and 35 ± 1°C and 20 replications. Newly emerged females of T. acacioi were individualized in glass vials (3.5 x 0.5 cm) with a honey droplet that was internally placed in the inner wall of the vials as food source for the parasitoid.

Each replications was a single female that had 40 eggs of each factitious host species offered for parasitation. Eggs were replaced on a daily basis until the female death. The following parameters were evaluated: the number of parasitized eggs, accumulated percentage of parasitism and total number of parasitized eggs per female. The results were submitted to ANOVA and means were compared using Tukey test (P£ 0.05).

The highest parasitism of T. acacioi occurred during the first day at all tested temperatures and hosts, and parasitoid females stopped parasitizing S. cerealella eggs earlier than they stopped parasitizing A. kuehniella eggs, unless at 25°C (Fig. 1). The parasitoid lived until the 20^th day after emergence on eggs of A. kuehniella at 15ºC (Fig. 1) and laid eggs until the 15^th day at the rate of 1.51 parasitized egg per female (Figs. 1 and 2). Also at 15ºC, on S. cerealella eggs, the parasitoid survived 8 days, during which parasitized an average of 2.7 eggs/day/female (Figs. 1 and 2).

Females of T. acacioi were able to parasitize A. kuehniella eggs until the 15^th day after emergence at 20ºC. However, they lived 16 days (Figs. 1 and 2). The parasitism on S. cerealella occurred until the third day, whereas the longevity was 5 days. The daily parasitism rate per T. acacioi female was 5.3 and 8.23 eggs for A. kuehniella and S. cerealella, respectively (Fig. 1) at this temperature.

At 30ºC, females of the parasitoid lived for 8 days on A. kuehniella but were able to lay eggs until the 6^th day. The longevity and parasitism period were similar (5 days) on S. cerealella eggs. The daily parasitism rate per female was 6.4 and 10.4 eggs, for A. kuehniella and S. cerealella, respectively. Moreover, T. acacioi lived for 5 and 3 days at 35ºC on A. kuehniella and S. cerealella eggs, respectively. However, the parasitism period was 3 and 1 days whereas the parasitism rate was 3.7 and 4.1 eggs/day/female, respectively (Fig. 1).

It is important to consider that temperature influenced T. acacioi parasitism differently on A. kuehniella and S. cerealella eggs. Therefore, when parasitism was compared on both hosts, it was higher on A. kuehniella eggs at 20, 25, and 35°C and on S. cerealella at 15 and 30°C (Fig. 1). The accumulated parasitism reached 80% at 7, 9, 2, 3 and 1 days on eggs of A. kuehniella, and at 2, 2, 2, 2 and 1 days on S. cerealella eggs, at 15, 20, 25, 30 and 35ºC, respectively (Fig. 2).

The highest parasitism of T. acacioi on A. kuehniella eggs occurred at 20ºC and reached close to 70 eggs/female. Beyond that temperature there was a reduction in the parasitism rate. The lowest parasitism rates were registered for extreme temperatures (15 and 35ºC), whereas the maximum parasitism of T. acacioi on S. cerealella eggs was registered at 25ºC with 45.6 eggs/female. This value is similar to what was observed at 30ºC and is higher than the parasitism at 15, 20 and 35ºC (Fig. 3).

The findings presented in this paper are important for defining the best T. acacioi releasing strategy and mass-rearing control. On general, the contrast of parasitism for both alternative hosts at different temperature show that A. kuehniella is the best alternative host for mass-rearing of the parasitoid due to this longer lifespan and higher total parasitism at most of the tested temperatures (Figs. 1, 2 and 3). Furthermore,the highest total parasitism of T. acacioi was observed on A. kuehniella at 20ºC (Fig. 3) what was shown to be the best temperature and host for mass-rearing.

The parasitism period and total number of parasitized eggs were the lowest at 35ºC. The fact that the parasitism period of T. acacioi was higher at low temperature shows its survival capacity at those temperatures, which is consistent with the fact that this species occurred and was collect at 1000 m altitude where temperatures around 20ºC are common during the year. These results shows the importance of using a local Trichogramma strain whenever it is possible to ensure better chances for the biological control program to succeed since this species or strain will be more likely well adapted to the local climate. Moreover, the good performance of T. acacioi on lower temperature shows that this species might be successfully used in other areas where average temperature around 20ºC is common during the year.

Acknowledgments. To the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Coordenação e Aperfeiçoamento de Pessoal de Ensino Superior (CAPES), and Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG) for financial support. This paper was approved for publication by the Editorial Board of Embrapa Soja as manuscript number 023/2007.

Received 06/11/2007; accepted 18/11/2008

• Parra, J. R. P. & R. A. Zucchi. 2004. Trichogramma in Brazil: feasibility of use after twenty years of research. Neotropical Entomology 33: 271-281.
• Pratissoli, D. & M. J. Fornazier. 1999. Ocorrência de Trichogramma acacioi Brun, Moraes & Soares (Hym.: Trichogrammatidae) em ovos de Nipteria panacea Thierry-Mieg (Lep.: Geometridae), um geometrídeo desfolhador do abacateiro. Anais da Sociedade Entomológica do Brasil 28: 347-349.
• Pratissoli, D.; J. C. Zanuncio; U. R. Vianna; J. S. Andrade; E. M. Guimarães; M. C. Espindula. 2004. Fertility life table of Trichogramma pretiosum and Trichogramma acacioi on eggs of Anagasta kuehniella at different temperatures. Pesquisa Agropecuária Brasileira 39: 193-196.
• Smith, S. M. 1996. Biological control with Trichogramma: Advances, successes, and potencial of their use. Annual Review of Entomology 41: 375-406.

Trichogramma acacioi (Hymenoptera, Trichogrammatidae) parasitism capacity at different temperatures and factitious hosts

Capacidade de parasitismo de Trichogramma acacioi em diferentes temperaturas e hospedeiros alternativos

Publication Dates

• Publication in this collection
  04 May 2009
• Date of issue
  2009

History

• Received
  06 Nov 2007
• Accepted
  18 Nov 2008