RESUMO
The intrinsic rate of increase of a parasitoid related to its hosts play an important role in biological control programs. In this work, fertility of the parasitoid Aphidius colemani Viereck was evaluated on Aphis gossypii Glover by means of a fertility life table. To determine the immature mortality, the development time and the sex ratio, 12 mated females of A. colemani (24h old), and 240 nymphs of A. gossypii (3 days old) were used. To evaluate fertility 15 mated females (24h old) were used. For each parasitoid female, 300 nymphs were offered in the 1st day, 250 nymphs in the 2nd day, 200 nymphs in the 3rd day, 150 nymphs in the 4th day, 100 nymphs in the 5th day and 50 nymphs in the other days. Immature mortality of A. colemani was 22.1%, development time of males and females were 12.0 and 11.8 days, respectively, and sex ratio was 0.6. The females of A. colemani laid 420 eggs and had longevity of 5.9 days. The net reproduction rate (R(o)) was 194.81 females and the intrinsic rate of increase (r(m)) was 0.384 females/females/day. The finite rate of increase (lambda) was 1.48 females/day, the mean length of a generation (T) was 13.74 days and the time to duplication the population (TD) was 12.60 days. The parasitoid A. colemani had a great potential of population growth on A. gossypii as a host and could be an effective biological control agent of this aphid.
Assuntos
Afídeos/parasitologia , Himenópteros/fisiologia , Controle Biológico de Vetores/métodos , Animais , Feminino , Fertilidade , Mortalidade , Ninfa/parasitologia , Reprodução , Fatores de TempoRESUMO
Aphidius colemani Viereck is among the main natural enemies used for biological control of Aphis gossypii Glover. The objective of the present study was to evaluate the development of A. colemani and the alterations caused by the parasitism in the host A. gossypii in different temperatures and to estimate the thermal requirements of the parasitoid. The experiments were carried out in controlled environmental chambers at 16, 19, 22, 25, 28 and 31 +/- 1 degrees C, 70 +/- 10% RH, and 12h photophase. Second-instar nymphs of A. gossypii were parasitized once and kept individually in glass tubes (2.5 cm x 8.5 cm), containing leaf disc of cucumber (2 cm) and 1% water/agar solution. The development time of A. colemani, from oviposition to mummies (11.9, 9.8, 7.7, 6.4 and 6.4 days) and from oviposition to adult (19.4, 16.2, 12.6, 10.5 and 10.7 days) decreased with the increase of the temperature from 16 degrees C to 25 degrees C. The rates of mummies and the emergence of the parasitoid, and its longevity also decreased with the increase of the temperature. Mummies were not produced at 31 degrees C. The lower temperature threshold of A. colemani was 5.94 degrees C and its thermal constant was 200 degrees-day. The alterations caused by the parasitoid in the A. gossypii host were minimized at 31 degrees C, where 98% of the host did not show symptoms of parasitism and produced nymphs. The temperature of 22 degrees C was optimal for the development time of A. colemani.
Assuntos
Afídeos/parasitologia , Himenópteros/crescimento & desenvolvimento , Temperatura , Animais , Feminino , MasculinoRESUMO
A taxa intrínseca de crescimento populacional de um parasitóide relacionada ao hospedeiro tem papel importante em programas de controle biológico. Este trabalho avaliou a fertilidade de Aphidius colemani Viereck sobre Aphis gossypii Glover, por meio de tabela de vida de fertilidade. Na avaliação da mortalidade de imaturos, desenvolvimento e razão sexual de A. colemani foram utilizadas 12 fêmeas, acasaladas, com 24h de idade e 240 ninfas de A. gossypii (com três dias de idade). Na avaliação da fertilidade foram utilizadas 15 fêmeas. O número de ninfas do pulgão oferecidas durante o ciclo de vida do parasitóide foram oferecidas: 300 ninfas no 1° dia, 250 ninfas no 2°, 200 ninfas no 3°, 150 ninfas no 4°, 100 ninfas no 5° dia, e 50 ninfas nos dias subseqüentes. A mortalidade de imaturos de A. colemani foi de 22,1 por cento. O desenvolvimento de machos e fêmeas foi de 12,0 e 11,8 dias, respectivamente e a razão sexual de 0,6. As fêmeas de A. colemani depositaram 420 ovos e tiveram longevidade de 5,9 dias. A taxa líquida de reprodução (Ro) foi de 194,81 fêmeas, a taxa intrínseca de crescimento populacional (r m) de 0,384 fêmeas/fêmea/dia, a razão finita de aumento (lambda) de 1,48 fêmeas/dia, tempo médio entre gerações (T) de 13,74 dias e o tempo de duplicação da população (TD) de 12,60 dias. A. colemani apresenta alto potencial de crescimento populacional, tendo como hospedeiro A. gossypii, podendo ser um agente efetivo de controle biológico deste afídeo.
The intrinsic rate of increase of a parasitoid related to its hosts play an important role in biological control programs. In this work, fertility of the parasitoid Aphidius colemani Viereck was evaluated on Aphis gossypii Glover by means of a fertility life table. To determine the immature mortality, the development time and the sex ratio, 12 mated females of A. colemani (24h old), and 240 nymphs of A. gossypii (3 days old) were used. To evaluate fertility 15 mated females (24h old) were used. For each parasitoid female, 300 nymphs were offered in the 1st day, 250 nymphs in the 2nd day, 200 nymphs in the 3rd day, 150 nymphs in the 4th day, 100 nymphs in the 5th day and 50 nymphs in the other days. Immature mortality of A. colemani was 22.1 percent, development time of males and females were 12.0 and 11.8 days, respectively, and sex ratio was 0.6. The females of A. colemani laid 420 eggs and had longevity of 5.9 days. The net reproduction rate (Ro) was 194.81 females and the intrinsic rate of increase (r m) was 0.384 females/females/day. The finite rate of increase (lambda) was 1.48 females/day, the mean length of a generation (T) was 13.74 days and the time to duplication the population (TD) was 12.60 days. The parasitoid A. colemani had a great potential of population growth on A. gossypii as a host and could be an effective biological control agent of this aphid.