Augusta K. Doetzer

Desenvolvimento, longevidade e reprodução de Trissolcus basalis (Wollaston) e Telenomus podisi Ashmead (Hymenoptera: Scelionidae) em condições naturais durante a entressafra da soja no sul do Paraná

Investigou-se o desenvolvimento, a longevidade e a reproducao de Trissolcus basalis (Wollaston) e Telenomus podisi Ashmead mantidos em condicoes naturais durante a entressafra da soja de 1999 a 2001 no sul do Parana, a fim de se conhecer como esses parasitoides sobrevivem durante o outono e inverno em regioes subtropicais. Adultos de T. basalis e T. podisi emergiram durante o outono e inverno de ovos parasitados a 18oC entre abril e junho. A longevidade dos adultos em condicoes naturais foi superior a oito e sete meses, para T. basalis e T. podisi respectivamente, demonstrando que os parasitoides hibernam no estagio adulto. O indice de sobrevivencia das femeas ate o final do inverno foi superior a 85% e a mortalidade acentuou-se significativamente apos o inicio da primavera. Femeas dos parasitoides mantidas por ate seis meses em condicoes naturais parasitaram ovos de E. heros apos sua transferencia para 25oC e a progenie constou de machos e femeas, demonstrando a ocorrencia da copula durante o outono e o inverno. A temperatura durante o desenvolvimento dos estagios imaturos afetou significativamente o potencial dos adultos hibernantes, regulando sua longevidade e capacidade reprodutiva apos a dormencia. Parasitoides desenvolvidos em temperaturas mais elevadas (inicio do outono) foram mais bem sucedidos no processo de hibernacao, apresentando maior longevidade e parasitando mais ovos hospedeiros apos a sua transferencia para 25oC, em relacao a femeas que nas fases imaturas passaram por temperaturas mais baixas (final do outono).

Capacidade reprodutiva e longevidade de Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) parasitando lagartas de Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae)

A capacidade reprodutiva de Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) foi estudada em laboratorio (20 ± 1oC; 12 horas de fotofase) utilizando-se como hospedeiros lagartas de segundo instar de Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae). Femeas expostas a cinco lagartas por dia viveram em media 8,4 dias, enquanto que femeas criadas na ausencia de hospedeiro viveram em media 20,6 dias. Femeas de G. muesebecki parasitaram em media 20,8 lagartas durante a vida, produzindo um total de 666,8 descendentes. O parasitismo diario foi de 3,6 hospedeiros por femea no primeiro dia apos a emergencia e manteve-se acima de dois hospedeiros por femea ate o oitavo dia. Ate cinco lagartas foram parasitadas por femea em um periodo de 24 horas.

Effect of temperature on the development and progeny production of Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) parasitizing larvae of Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae)

The developmental time of Glyptapanteles muesebecki (Blanchard) parasitizing the armyworm Pseudaletia sequax Franclemont, and the number of pupae/host were determined at six constant temperatures ranging from 14° to 30°C. The egg + larval stages lasted from 17.8 days at 26° and 29°C to 56.4 days at 14°C, while the pupal stage ranged from 6.4 days at 29°C to 34.5 days at 14°C. G. muesebecki required 291.9 degree-days (DD) above the lower threshold of 8.9°C to complete the egg + larval development, while the pupae required 107.0 DD above 11.1°C. Development from egg to adult was completed after 397.4 DD above the lower threshold of 9.6°C. The number of pupae/host was not significantly different between 18°° and 26°C, and ranged from 86.9 at 22°C to 92.1 at 18°C. At the lower (14°°C) and upper (29°C) threshold temperatures, this number was significantly lower, averaging 27.6 and 19.8 pupae/host, respectively. Moreover, at 14° and 29°C the proportion of parasitized caterpillars was significantly lower than in the range between 18° and 26°C and at the lower temperature there was no synchronism in the pupation of parasitoids from the same host. At 30°C, the host larvae died before the emergence of the parasitoids. At 18, 22 or 26°C, the development and progeny production of G. muesebecki was not affected in the laboratory after five consecutive generations.

Efeito do parasitismo por Glyptapanteles muesebecki (Blanchard) no consumo e utilização do alimento por Pseudaletia sequax Franclemont

Food consumption and utilization for unparasitized larvae of Pseudaletia sequax Franclemont (Lepidoptera: Noctuidae) in relation to parasitized larvae with Glyptapanteles muesebecki (Blanchard) (Hymenoptera: Braconidae) was evaluated in laboratory, using kikuyo grass (Pennisetum clandestinum) as larval food. Parasitized larvae consumed significantly less foliage than unparasitized ones, although the larval stage of parasitized larvae was longer than the healthy ones. Parasitized larvae which had seven instars produced more parasitoids and consumed significantly more foliage than parasitized larvae which had six instars. Relative consumption rate (RCR), relative metabolic rate (RMR) and approximate digestibility (AD) were significantly higher in parasitized larvae, but the relative growth rate (RGR) and the efficiency of ingested (ECI) and digested (ECD) food were higher in unparasitized larvae. G. muesebecki regulates growth and development of P. sequax through the number of eggs laid. The values obtained for the number of pupae/host were positively correlated with food consumption and final weight of the host. The development time of the parasitoid was also positively correlated to the number of pupae/host.

Host Instar Preference of Peleteria robusta (Wiedman) (Diptera: Tachinidae) and Development in Relation to Temperature

The effect of four temperatures on the development of the larval endoparasitoid Peleteria robusta (Wiedman) as well as its preference for different instars of the host, the armyworm Mythmina(Pseudaletia) sequax Franclemont were evaluated. Females of P. robusta laid more than one egg outside the cuticle of the caterpillars, however only one parasitoid developed and pupated within the host. Females of P. robusta successfully parasitized the fourth- to sixth-instars of M. sequax, with preference for the fourth and fifth instars of the host. No parasitoids emerged from caterpillars exposed to P. robusta females between the first and third instars. The development of P. robusta to the adult stage was completed in the range between 15oC and 30oC, and the incubation period lasted less than 24h in all temperatures evaluated. Successful parasitism, as indicated by percentage of adult emergence, was significantly higher at 20oC (56.2%) and 25oC (70.0%), as compared to 15oC (29.5%) or 30oC (9.5%). Developmental time from oviposition to adult emergence ranged from 23.8 days at 30oC to 90.3 days at 15oC. At 20oC and 25oC, developmental time was significantly shorter for males as compared to females. The thermal constant for the egg + larval stages was 266.9 degree-days (DD) above a lower threshold of 6.7oC; the pupal stage required 235.5 DD above 9.7oC; and the development from oviposition to adult emergence was completed in 457.5 DD above a lower limit of 9.3oC. Together with other parasitoids already described, P. robusta is another member of a complex of species that may have considerable importance in the natural control of the wheat armyworm.

Biology of Microplitis mediator Haliday (Hymenoptera: Braconidae) parasitizing the wheat armyworm Mythimna (Pseudaletia) sequax Franclemont (Lepidoptera: Noctuidae)

The larval endoparasitoid Microplitis mediator Haliday is described for the first time in the Neotropical Region, parasitizing the wheat armyworm Mythimna (Pseudaletia) sequax Franclemont. Females successfully parasitized the four first instars of the host, with a significant preference for the second and third, in relation to either the first or fourth instars. No parasitoids emerged from caterpillars parasitized in the fifth and sixth instars. Development of M. mediator was determined at four constant temperatures between 15°C and 30°C. The duration of the egg-larval stages varied from 32.3 days at 15°C to 8.0 days at 30°C. The pupal stage lasted 24.3 and 5.1 days at 15°C and 30°C, respectively. Development of the parasitoid from oviposition to adult emergence required the total of 251.3 degree-days (DD) above the threshold of 10.3oC. At 20°C, longevity of females was significantly shorter when kept in oviposition activity (16.8 ± 1.81 days) in comparison to females kept without hosts (29.7 ± 1.83 days). Parasitoid females remained reproductively active until one day before death, and parasitized an average of 60.6 ± 8.40 second instar hosts during their adult life, with an average of 3.9 parasitized caterpillars/day.

Efeito da temperatura no desenvolvimento de Euplectrus ronnai Brèthes (Hymenoptera, Eulophidae) parasitando lagartas de Pseudaletia sequax Fraquelemont (Lepidoptera, Noctuidae) e consumo alimentar do hospedeiro

Estudou-se em laboratorio o efeito de cinco temperaturas constantes (15 °, 17 °, 21°, 25 ° e 29 ° C) na duracao das fases imaturas de Euplectrus ronnai (Bretlies) sobre lagartas de Pseudaleria sequax Franclcmont. O parasitoide completou o desenvolvimento em todas as temperaturas. A menor mortalidade (13 %) ocorreu a 25 ° C e a maior (48%) a 15 ° C. Obteve-se uma relacao linear entre o tempo de desenvolvimento de E. ronnai e a temperatura na faixa entre 15 e 29 ° C. A temperatura base (Tl) e a constante termica (K) foram estimadas atraves da equacao de regressao linear; a Tb foi de 11.4° C para a fase ovo-larval e 12,3 ° C para a fase pupal. A constante termica para a fase ovo-larval e pupal foi de 109,5 e 102,4 graus-dia (CD), respectivamente, e 211,4 CD durante todo o periodo de desenvolvimento. A temperatura mais adequada para o desenvolvimento de E. ronnai , em termos de sobrevivencia e de velocidade de desenvolvimento foi 25 ° C. O consumo alimentar de lagartas parasitadas foi avaliado em laboratorio, utilizando-se folhas capim quicuio ( Pennisetum clandestinum Hochstetter) como alimento. Lagartas parasitadas consumiram cerca de 95 % menos alimento que lagartas nao parasitadas, mesmo quando os ovos do parasitoide foram retirados logo.