Parasitismo de Aphidius colemani Viereck (Hymenoptera: Aphidiidae) em diferentes densidades de Myzus persicae (Sulzer) (Hemiptera: Aphididae)

Abstract

-This research aimed to determine the functional response of parasitoid Aphidius colemani Viereck, by determining the number of mummies of Myzus persicae (Sulzer) formed and its sexual ratio at densities of 20, 40, 60 and 80 2 nd -and 3 rd -instar nymphs on sweet-pepper leaves, at temperature of 21±1ºC. The functional response was also evaluated by calculating the number of attacks of the parasitoid on the host and its search behaviour on leaf discs of sweet-pepper leaves (43mm) in a Petri dish (50mm). The temperature of 23±1ºC and the densities of zero, four, eight, 16 and 32 nymphs of M. persicae were used. A. colemani's functional response was of type II, not only for number of mummies formed (12.4; 22.7; 33.0 and 31.6) but also for number of attacks (0; 4.1; 6.8; 13.2; and 19.2), with a gradual increase in the number of host density and reaching a plateau. The average sexual ratio was 0.57 and showed no significant influence in host density (P≤0.05). The number of contacts made by parasitoid's antennae onto their hosts (encounters) increased gradually with higher host densities, with an abrupt increase in the highest density (32 hosts), indicating an increase in searching behaviour of the parasitoid. The time of the first visit of A. colemani has not varied with the host density. In the presence of hosts it lasted from 1526.9 to 1638.0 seconds; in the absence of host, the parasitoid stayed on the leaf disc for a short time (340.1 seconds).

The density of females of Palmistichus elaeisis Delvare and LaSalle (Hymenoptera: Eulophidae) affects their reproductive performance on pupae of Bombyx mori L. (Lepidoptera: Bombycidae)

“…On the other hand, the percentage of parasitism and the emergence of Aphidius colemani Viereck (Hymenoptera: Aphididae) were similar with different densities of Myzus persicae (Sulzer) (Hemiptera: Aphididae). This suggests that M. persicae does not present any nutritional or physiological barriers for the development of A. colemani (Sampaio et al 2001). B. mori might have an efficient defense mechanism against P. elaeisis because the emergence of this parasitoid was observed only from 18:1 and higher densities of the parasitoid per pupae of this host.…”

“…The density of parasitoids per host affects the parasitoid offspring (Thomazini andBerti Filho 2000, Matos Neto et al 2004), the sex ratio (Choi et al 2001), the parasitism capacity (Sampaio et al 2001), the duration of the life cycle, the size of the body, and the longevity of the imagines (Silva-Torres and Matthews 2003). To minimize the cost and labor and to maximize the production of parasitoids in mass rearing programs, it is, therefore, necessary to study the density of the parasitoids in relation to the host (Sagarra et al 2000a).…”

Densidade de fêmeas de Palmistichus elaeisis Delvare & LaSalle, 1993 (Hymenoptera: Eulophidae) para sua reprodução em pupas de Anticarsia gemmatalis Hübner, 1818 (Lepidoptera: Noctuidae)

“…A densidade de parasitoides por hospedeiro pode afetar a produção de descendentes (Pereira et al, 2010b), a razão sexual da prole (choi et al, 2001), a capacidade de parasitismo (saMPaio et al, 2001), a duração do ciclo, o tamanho do corpo e a longevidade de parasitoides (silva-torres;Matthews, 2003). Isso indica a necessidade de se aprimorar as metodologias de criação massal de parasitoides em laboratório visando conhecer, principalmente, a densidade ideal em relação ao hospedeiro para se minimizar o custo com mão de obra e maximizar a produção (saGarra et al, 2000).…”

Trichogramma pretiosum (Hymenoptera: Trichogrammatidae) Parasitism of Trichoplusia ni (Lepidoptera: Noctuidae) Eggs Under Different Temperatures

“…The density of female parasitoids per host can affect parasitism (Sampaio et al 2001), progeny sex ratio (Chong & Oetting 2006, 2007, life cycle length, and the longevity of the offspring .…”