Temporal and spatial differences in gall induction on Haloxylon by Aceria haloxylonis (Acari: Eriophyidae) in the Gurbantünggüt Desert

Abstract

Flower-like galls have been observed on Haloxylon ammodendron and H. persicum in the Gurbantünggüt Desert in northwest China. The galls were induced by Aceria haloxylonis, a new species of Eriophyidae. The galls began as small protuberances at the base of new stems and on small branches. As they matured, the galls changed color from green to dark brown. Some galls on H. persicum became red. At maturity, the galls and the infected branches became desiccated. Adult females of A. haloxylonis overwintered in galls or in branch crevices of H. ammodendron and H. persicum. There were more galls on H. ammodendron than on H. persicum. Several ecological factors influenced gall number, including terrain, tree size, branch direction and slope aspect. H. ammodendron trees in gravel desert had more galls than trees at sand dune edges. Trees in the interdune space had the fewest galls. Large H. ammodendron trees had significantly more galls than small trees. Branches on the south side of the tree had more galls than branches on the north, east, and west sides. Terrain * tree size had significant interaction on gall number on H. ammodendron. H. persicum trees on low sand dunes had more galls than trees on high sand dunes and trees on sunny slopes had more galls than trees on shady slopes. There were more galls on large H. persicum trees than on medium-sized trees. Few galls were observed on small H. persicum trees. The number of galls on H. persicum was significantly affected by terrain, tree size and slope aspect. The terrain * slope aspect interaction and tree size * terrain interaction were also significantly. This study is important for the conservation and recovery of the ecological environment in the Gurbantünggüt Desert.