Identification and Natural Parasitism of Trichogramma Species on Ostrinia nubilalis Hübner (Lepidoptera: Noctuidae) Eggs in Düzce, Turkey
2017
Kutuk, Halil
Small corn fields are intertwined within hazelnut orchards as main crops in Düzce province, located in the Black Sea Region of Turkey. In recent years, the fall webworm, Hyphantriacunea (Drury) reached outbreak levels in hazelnut orchards and chemical agents represented the primary means used to control the population of H. cunea in those orchards. Frequent pesticide spraying against H. cunea may have an adverse effect on beneficial insects and may also disrupt biological control of the European corn borer (ECB), Ostrinia nubilalis (Hübner) by Trichogramma species. Trichogramma specimens collected from corn fields of Düzce provinces in the West Black Sea region in Turkey were identified as T. brassicae Bezdenko based on morphological and molecular characteristics. As a result of this study, natural occurrence of the parasitoid, T. brassicae is still important in successfully suppressing the ECB population in Düzce province of Turkey. It seems that this wasp species adapts well to corn fields. Two years following the initial incidence of parasitism, T. brassicae parasitized more than 90% of the eggs of ECB. A second generation borer attack had not caused stalk or tassel breakage and/or boring into the ear shanks in 2014 and 2015. In both years, larvae were extremely sparse. It would appear that T. brassicae was responsible for the total collapse of the host population. Parasitization of host eggs by T. brassicae in 2014 and 2015 were correlated with the time of collection (r=0.71 and 0.26, respectively). Reasons for the high incidence of parasitism by T. brassicae possibly may have been overwintering survival and alternate hosts of T. brassicae being available prior to August.
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