Globular galls on Haloxylon (Centrospermae: Chenopodiaceae) induced by gall midges, and the corresponding parasitoids in China

Abstract

The concealed gall inducers represent a significant challenge for both study and control within the realm of pest management. Gaining an understanding of the natural enemies that influence gall inducer populations is essential for the development of effective integrated pest control strategies. Haloxylon spp. are dominant xerophyte species that possess substantial ecological importance due to their roles in shelter provision and sand fixation. This study aimed to determine the main gall inducers that induce globular galls on both H. ammodendron and H. persicum and the parasitoid complex associated with them. Totally, two species of gall inducers and four species of parasitoids were obtained from the globular galls. Suaediola sp. was recorded as the predominant gall inducer, exhibiting biannual generational turnover. Both Torymus sp. and Mesopolobus quadrimaculatus were primary solitary koinobiont ectoparasitoids of gall midges, while only Platygaster sp. was endoparasitoid. Torymus sp. established dominance among the parasitoids, demonstrating a predilection for attacking first instar larvae. We also found that temperature variations significantly influenced the emergence and lifespan of the insects recorded from the galls, with a consistent trend of shortened wasp lifespan correlating with increasing temperature. According to these results, we conclude Torymus sp. could have an important potential to control gall inducers within closed galls and, therefore, should be considered for inclusion in the integrated pest management programs of Haloxylon forests in China.