Population dynamics, natural enemies of lepidopteran pests in maize area of Sakarya and Duzce provinces, and their alternative control along with factors affecting some biological features of trichogramma species

In this study, the populations of Ostrinia nubilalis Hbn. (Lep.: Crambidae), Helicoverpa armigera Hbn. (Lep.: Noctuidae), and Mythimna unipuncta Haw. (Lep.: Noctuidae) were monitored in maize fields in the Sakarya and Düzce during 2021 and 2022. The natural enemies associated with these species were also identified. Additionally, Trichogramma evanescens West. (Hym.: Trichogrammatidae) and Bracon hebetor Say. (Hym.: Braconidae) were released in maize fields to assess their effectiveness in the biological control of these species. In laboratory conditions, the parasitism rate, development period, adult longevity, and functional response of T. evanescens, T. brassicae (Bezdenko), T. pintoi (Voegele), and T. turkestanica (Meyer) were determined on Ephestia kuehniella Zeller (Lep.: Pyralidae) eggs at different temperatures. Furthermore, the host preference of T. brassicae in parasitizing different host eggs was observed. In the Düzce and Sakarya, the larvae of O. nubilalis reached their peak population from mid-August to early September in the first crop and from late August to mid-September in the second crop. Larvae of H. armigera peaked in the first crop from late July to early August, while in the second crop, they peaked from mid-September to the end of September. The larvae of M. unipuncta reached their peak population in the first crop from August, and in the second crop, from mid-September to the end of September. Furthermore, ten predators from the orders Coleoptera, Hemiptera, and Neuroptera, as well as nine parasitoids from the orders Diptera and Hymenoptera, were identified as associated with these target species. Biocontrol studies revealed that O. nubilalis were effectively suppressed when T. evanescens were released either alone or in combination with B. hebetor. However, the release of T. evanescens alone did not adequately control H. armigera, but its effectiveness increased when combined with B. hebetor. On the other hand, neither parasitoid demonstrated efficacy in controlling M. unipuncta. Laboratory studies indicated that Trichogramma adults exhibited the longest longevity at 18 °C and the shortest longevity at 32 °C. The highest parasitism rate of E. kuehniella eggs by the parasitoids was observed at 32 °C, while the lowest rate occurred at 18 °C. The shortest development period was observed at 32 °C, whereas the longest development period was observed at 18 °C. Furthermore, Trichogramma species exhibited a type III functional response. In preference studies, T. brassicae showed a preference for E. kuehniella eggs, followed by P. interpunctella Hbn. and G. mellonella L. (Lep.: Pyralidae) eggs, respectively.