Browsing by Author "Melo, Rui"
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- Duração do desenvolvimento de Mythimna unipuncta, Xestla c-nigrum, Agrotis ipsilon, Heliothis armigera, Peridroma saucia, Spodoptera littoralis (Lep.: Noctuidae) e Pieris brassicae azorensis (Lep.: Piralidae).Publication . Melo, Rui; Oliveira, Luísa; Tavares, JoãoA influência dos factores abióticos sobre o desenvolvimento de espécies de Lepidópteros, nomeadamente no estado larvar, foi e será objecto de numerosos estudos, contribuindo assim para o conhecimento dos seus limites teóricos, duração/velocidade de desenvolvimento e percentagem de mortalidade no estado larvar. Analisou-se, em condições controladas, a duração do desenvolvimento de cada fase do ciclo de vida das diferentes espécies em estudo. Estes Lepidópteros foram seleccionados de acordo com os níveis de abundância registados nas armadilhas luminosas. Para cada espécie, observou-se diferentes tipos larvares (5, 6, 7 e 8). Nas espécies Mythimna unipuncta (HAW.), Agrotis ipsilon(HUF.), Xestia c-nigrum (L.) e Heliothis armigera (HBN.) a duração do desenvolvimento dos diferenles tipos larvares foi significativarnente diferente. 0 desenvolvimento total foi significativamente diferente nas especies M. unipuncta, X. c-nigrum e A. ipsilon. A proporção verificada para as tipos larvares dependeu da alimentação e, provavelmente da sua informação genética.
- Especificidade do parasitóide Apanteles militaris (Hymenoptera: Braconidae) em relação ao hospedeiro Mythimna unipuncta (Lepidoptera: Noctuidae)Publication . Oliveira, Luísa; Melo, Rui; Tavares, JoãoApanteles militaris (Walsh) é o mais importante parasitóide larvar de Mythimna unipuncta (Haworth) em todas as ilhas dos Açores. Pretendendo-se saber do modo de actuação deste parasitóide larvícola, procedeu-se ao estudo semanal da sua abundância e à do seu hospedeiro natural. Numa tentativa de compreender onde se encontra este parasitóide durante o Invermo, realizámos ensaios de parasitismo, em condições controladas, utilizando como hospedeiro larvas de Noctua pronuba L., Peridroma saucia (Hb), Xestia c-nigrum (L.), Spodoptera litoralis B., Agrotis ipsilon (Hüf.), Heliothis armigera (Hb.), Sesamia nonagrioides (Lef.), Autographa gamma (L.) e Pieris brassicae azorensis Rebel. Estes Lepidópteros foram seleccionados por existirem nos biótopos que são ocupados por M. unipuncta, apresentarem uma densidade importante nas condições ambientais dos Açores ou por serem hospedeiros de parasitóides pertencentes ao mesmo género. Para além de M. unipuncta, apenas S. nonagrioides e A. gamma apresentaram uma percentagem muito reduzida de larvas efectivamente parasitadas, 10 e 12,5%, respectivamente. Assim, a população açoreana de A. militaris apresenta uma grande especificidade em relação ao seu hospedeiro natural.
- Host Age of Pseudaletia unipuncta (Lepidoptera; Noctuidae) and parasitic capacity of Glyptapanteles militaris (Hymenoptera; Braconidae)Publication . Oliveira, Luísa; Melo, Rui; Tavares, JoãoSuccessful use of Glyptapanteles militaris (Walsh) to control the polyphagous pest Pseudaletia unipuncta (Haworth) depends on knowledge of the host-parasite relationship. In this study, we determined the suitability of different P. unipuncta instars for oviposition by G. militaris females, and we evaluated the parasitoid performance on each host instar (L1 to L6). The following parameters were measured: percentage of larvae parasitized from which parasitoids emerged; percentage of host mortality; percentage of hosts that pupated after being stung by the parasitoid; egg-larval developmental time; pupal period; total developmental time; mean number of cocoons per host; mean number of parasitoid larvae that emerged from a host larva but failed to spin a cocoon; number of parasitoid larvae that failed to emerge from each host; total number of parasitoid larvae per host; parasitoid sex ratio and emergence rate of adult progeny. All host instars were stung by female parasitoids, but cocoons were never obtained from L6. The proportion of parasitized larvae increased from L1 to L6 then declined steeply, reaching no parasitism for L6, with a significant difference between L1 and L3, L4. Conversely, the proportion of host larvae that pupated decreased from Ll to L3, increased for L4 and L5, and slightly declined for L6. Significant differences were observed between L5, L6 and the other 4 instars. Similar results were observed for the proportion of larva killed before emergence of the parasites, with a significant difference between L6 and L2, L3. Host instar at the time of parasitization significantly affected egg- larval and total developmental time, the total number of parasitoid larvae per host, and the emergence rate of adult progeny. These results indicate that the 2nd, 3rd, and 4th instars of P. unipuncta were more suitable for G. militaris parasitism, because these instars provide a high percentage of hosts that will be successfully parasitized and they also produce large numbers of parasitoids per host.
- Influence of photoperiod on biology of Apanteles militaris (Hymenoptera; Braconidae)Publication . Oliveira, Luísa; Melo, Rui; Tavares, JoãoThe effects of photoperiod on development time, longevity and progeny of Apanteles militaris (Hymenoptera: Braconidae) were investigated using Mythimna unipuncta (Lepidoptera: Noctuidae) as host. Three groups of parasitized host larvae were exposed to 15.5±0.5°C of temperature, 75±0.5 of R.H. Each group was submitted to a different photoperiod, 8:16, 12:12 and 16:8 (L:D). Significant differences were found in the egg-larvae development time, pupal period and in the total development time. The adults longevity was higher and significantly different between 8:6 (L:D) and the others photoperiods. Concerning the progeny, the mean total and the mean number of cocoons per host did not differ significantly. However, the mean number of parasitoids that emerged from host larva but failed to spin a cocoon was significantly different between 8:6 and 16:8 (LD). Length of photophase did not significantly affect parasitoid sex-ratio but the emergence of adult progeny was different between 8 and 16 hours light.
- Influence of the host larval density on the parasitic capacity of Apanteles militaris (Walsh) (Hymenoptera, Braconidae).Publication . Oliveira, Luísa; Melo, Rui; Tavares, JoãoThe relationships between Apanteles militaris and the number of host's larvae of Mythimna unipuncta (Haworth) (Lep., Noctuidae) that can be parasitized, was the subject of this study. One parasitoid female parasitizes one, two, four, six or ten larvae of M. unipuncta during 24 hours. There was a relationship between the total number of larvae and the number of parasitized hosts. A significant difference was found among the progeny. The number of hosts per parasitoid did not significantly affect the sex ratio and the progeny adult emergence.
- Response of Glyptapanteles militaris (Walsh) (Hymenoptera: Braconidae), a Larval Parasitoid of the Armyworm, Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae), to Different TemperaturesPublication . Oliveira, Luísa; Melo, Rui; Tavares, JoãoThe effect of four different temperatures (15, 20 25 and 30°C), on biological parameters of the Azorean population of Glyptapanteles militaris (Walsh) was studied, using Mythimna unipuncta (Haworth) as the host. Thirteen biological parameters of the were analyzed: percentage of hosts that died without producing parasitoids; percentage of larvae parasitized from which parasitoids emerged; percentage of hosts surviving to pupate after the parasitoid's sting; egg-larval development time; pupal period; total developmental time; adult longevity; total number of larvae per host; number of larval parasitoids that fail to emerge from each host; mean number of parasitoids that emerged from host larva but failed to spin a cocoon; mean number of cocoons per host; parasitoid sex-ratio; and finally emergence rate of adult parasitoid progeny. The percentage of hosts that died without producing parasitoids increased with increasing temperature. Developmental times significantly decreased with increasing temperature. The mean number of cocoons per host; mean number of parasitoids that emerged from each host larva but failed to spin a cocoon; and total number of larvae per host were higher when the temperature was lower. Parasitoid sex ratio and emergence rate of adult progeny were not affected by the temperatures tested.