Investigation on the parasitism level of Ostrinia nubilalis (Hub.) eggs related to different densities of released Trichogramma brassicae Bezd. in corn
2010
Shirazi, J. | Taghizadeh, M. | Dadpour, H. | Attaran, M. R. | Zand, S.
Biological control of ECB has been practiced by release of mass reared Trichogramma wasps for years in the world as well as Iran. Due to rapid growth of corn plants, it seemed that the fixed amount of parasitoid released might not compensate for increasing plant surface to be searched thoroughly. Therefore, a study was conducted to compare the rate of parasitism of host eggs by T. brassicae, a dominant parasitoid of ECB eggs in Iran, in conventional method (1 g parasitoid/h) with a method in which number of parasitoid needed per release is calculated based on the plant surface area. The study was conducted in corn plantations of Mazndaran (North) and Moghan (North West) of Iran. Eight to 16 plots of 50 m2 of field corn with 10 m distance from each other were selected. A day before treatments, the surface of 30 leaves from 10 randomly selected plants were measured. At the release day, 10 to 20 egg cards (each contained 30 fresh eggs of Sitotroga cerealella) were uniformly installed in each plot. Two days later, the egg cards were recovered and proportions of parasitized and lost cards and number of parasitized eggs on each were recorded. The data showed that the maximum parasitism rate in conventional and second methods was 43.93 % and 25 %, respectively, in Mazandaran without significant difference. In Moghan, the rate of parasitism ranged from 60 to 90% during 3 years of release, being significantly different in the first year of experiments. However, it can be concluded that the amount of wasps released in both the treatments was not enough to control the prevailed populations of ECB in studied locations.
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