Relationships of the Gall Midge Asphondylia miki Wachtl (Diptera, Cecidomyiidae) with Its Host Plant, the Alfalfa Medicago sativa, and Ectoparasitoids of Its Larvae and Pupae (Hymenoptera, Eulophidae) in the Forest-Steppe of the Middle Volga Region

Abstract

The gall midge Asphondylia miki Wachtl (Diptera, Cecidomyiidae) was studied in crops of alfalfa (Medicago sativa ssp. × varia) in 2018–2022 in the forest-steppe of Samara Province. Galls were counted from the beginning of their formation to the end of the crop growing season in plots 0.1 to 1 m² in area. The data were processed using ANOVA. The gall midge had two annual generations in the alfalfa fields sown in spring and in the perennial crops; when alfalfa was sown in summer, A. miki produced one generation during the first year. The pupae overwintered in galls, and adults of the overwintered generation emerged in April. The highest rate of damage to alfalfa by A. miki larvae (40–68% of generative shoots) and the highest density of galls (500–830 ind./m²) were observed during the first year of the summer-sown crop, when the flight peak coincided with the alfalfa budding phase; the seed loss was considerable (13–81%). On average, parasitoid wasps destroyed the larvae and pupae of A. miki in 60% of its galls in the summer-sown crops not treated with chemical pesticides. The gregarious ectoparasitoid Sigmophora brevicornis (Eulophidae), mainly infesting larvae, accounted for about 77% of the identified parasitoid specimens. The males and females in the S. brevicornis population had similar body coloration and belonged to three phenotypes: the lightest brownish yellow, yellowish brown, and dark, which comprised 53, 28, and 19% of the specimens, respectively.