Population parameters and Parasitism of Ganaspidium utilis (Beardsley) (Hymenoptera: Eucoilidae), a Parasitoid of Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) in Laboratory

• Main Authors: Lekhnath Kafle, 卡雷納
• Other Authors: Po-Yung Lai
• Format: Others
• Language: en_US
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/44283276465210991566

碩士 === 國立屏東科技大學 === 熱帶農業暨國際合作研究所 === 93 === This study was aimed at determining the biological attributes, functional response, mutual interference and searching efficiency of Ganaspidium utilis (Beardsley), a parasitoid of Liriomyza trifolii (Burgess), under the laboratory conditions at 17±2o, 25±2o and 29±2oC. The immature stage of G. utilis could be divided into egg, 4 discernible larval instars as well as prepupal and pupal stages. Superparasitism and encapsulation of eggs or first instar larvae of G. utilis inside the parasitized larvae of L. trifolii were observed. The developmental time of G. utilis was longest (32.85±0.86 days) at 17±2oC and shortest (14±0.44 days) at 29±2oC. The developmental time between a male and a female G. utilis under the tested temperatures was not significantly different. The longevity of G. utilis decreased as the density of G. utilis per container increased. The overall fecundity and sex ratio of the offspring of G. utilis were also affected by the variation in density and temperature. Mutual interference between G. utilis adults searching for hosts was clearly demonstrated and the searching efficiency increased as the density of G. utilis increased. The longevity of a G. utilis male and female was not affected by temperature under all densities, but the mean longevity was affected by the temperature across densities. When more than 3 pairs of G. utilis adults were provided with 50 L. trifolii larvae for parasitization, inverse relationships were observed on the ability of a female to find and attack suitable L. trifolii larvae. The number of the male progeny produced was almost the same as the female progeny under all temperatures. Results of the mutual interference study show that at the host density of 50 L. trifolii larvae per container, 3 G. utilis females were able to parasitize more than 50% of leafminer larvae at 25±2o and 29±2oC. However, at 17±2oC, the majority of L. trifolii larvae were not able to complete their life cycle due to the low temperature. Therefore, only 1 G. utilis female was able to prevent L. trifolii larvae and pupae from reaching adulthood at 17±2oC. Results of the population parameter analysis showed that 25±2°C was the most favorable temperature for G. utilis to multiply in laboratory conditions. The temperatures at 17±2° and 29±2°C caused lower net reproduction rate of G. utilis than 25±2°C. The mean generation time, finite rate of increase and population-doubling time of G. utilis had an inverse relationship with temperature; however, the intrinsic rate of increase of G. utilis showed a positive relationship with temperature. A type II random parasitoid equation (RPE) was used to estimate instantaneous search rate and handling time. The instantaneous search rate increased as temperature increased. At 29±2oC, the maximum number of larvae parasitized was 6.4 per day. This decreased to 6 larvae parasitized at 25±2oC. At 17±2oC, there was no significant increase of parasitization with the increase of the host density. However, estimated numbers of L. trifolii larvae parasitized per day were higher than the observed numbers of L. trifolii larvae parasitized per day across the temperatures. The estimated handling time was lowest at 17±2oC and highest at 25±2oC. The type II functional response curves were demonstrated when 8 different densities of L. trifolii larvae were exposed to a female G. utilis for parasitization. If the initial number of L. trifolii exposed to 1 G. utilis female exceeded 20 larvae at 25±2o or 29±2oC per container, the number of L. trifolii parasitized would be proportionally smaller than that of L. trifolii successfully reaching adulthood. According to its population parameters and parasitism, demonstrated in this study, G. utilis has a good potential to be an effective natural enemy for the control of L. trifolii