Disholcaspis quercusvirens sexual generation

Small bud galls developed beneath bud scales (Fig. 1E) and were located on the branches at the base of a petiole, hidden between young leaves (Fig. 1F). Bud galls were 2.5 ± 0.02 mm in length and 1.1 ± 0.01 mm in width. They likely were initiated by asexual wasp oviposition (i.e., November–January), and remained on trees until May. Bud gall tissue was soft and spongy and continued to grow and harden until the bud scales fell off the galls. The tips of young bud galls, sometimes red in color (Fig. 1E), were visible in early- to mid-March. Emergence of D. quercusvirens ended by mid-April, and parasitoid emergence continued until all bud galls fell off the trees in May. Bud galls were fragile after hardening, and, similar to the D. cinerosa system (Frankie et al. 1992), could be easily dislodged after adult emergence or inclement weather.

Galled (2.8 ± 0.1 mm length, 1.7 ± 0.08 mm width) and nongalled (2.5 ± 0.1 mm length, 1.6 ± 0.05 mm width) buds collected on 9 March 2009 did not significantly differ in length (F = 1.70; df = 1; P = 0.1983) or width (F = 2.44; df = 1; P = 0.1251). Live oak buds collected on 9 March 2009 ranged in development from dormant to green-tipped.

Sexual generation pupae (Fig. 3B) were present in bud galls by 11 March 2009, and 65% of the bud galls collected on 16 March contained white pupae. First adult emergence (Fig. 3C and D) occurred on 21–23 March 2009 from laboratory rearings, and emergence continued through ≈21 April 2009.

In total, 480 bud galls were collected from 4 April to 14 May 2008, at the end of the sexual D. quercusvirens emergence period. Parasitoids comprised 99.1% and D. quercusvirens comprised 0.9% of the specimens reared (Table 1). Parasitoids reared from these bud galls included a species of Aprostocetus, Baryscapus, and Pediobius (Eulophidae); Brasema auratus (Ashmead) (Eupelmidae); and Acaenacis lausus (Walker) (Pteromalidae). The most abundant species was B. auratus. No inquilines were reared from the bud galls; a feature shared with some other small and structurally simple oak cynipid galls (Stone et al. 1995, Schönrogge et al. 2000).

From 19 March to 14 May 2009, 3,884 bud galls were collected. These bud galls had a more diverse parasitoid complex (Table 1), which included a species of Aprostocetus, Baryscapus, and Pediobius (Eulophidae); B. auratus and Brasema gemmarii (Ashmead) (Eupelmidae); Sycophila and an unknown species (Eurytomidae); Ormyrus hegeli (Girault) (Ormyridae); and A. lausus (Pteromalidae). Only one specimen was reared from each bud gall (e.g., bud galls were monothalamous), as observed in other small sexual-generation oak cynipid galls (e.g., Stone et al. 1995, Schönrogge et al. 2000). The most abundant parasitoid in 2009 was A. lausus, and it was reared also from bullet galls in 2007. Pteromalid wasps in cynipid galls are typically parasitoids, and their larvae feed on the eggs or larvae of their hosts (Krombein et al. 1979, Askew 1984). O. hegeli (Girault) (Ormyridae) was also reared from both bud galls in 2009 and bullet galls in 2007.

The parasitoid species Brasema ficigerae (Ashmead), Eupelmus quercus Ashmead, Eurytoma querciglobuli rubra Bugbee, Eurytoma studiosa Say, Torymus elegantissimus (Ashmead), Torymus fagopirum (Provancher), and Torymus lissus (Walker) were previously reared from the bullet galls of D. quercusvirens (Krombein et al. 1979), but were not found in the current study. Eurytoma and Tetrastichus (Eulophidae) can feed on developing larvae of D. perniciosa in bullet galls (Seibert 1993). It is assumed that the parasitoids reared from the D. quercusvirens bud galls also fed on the gall maker larvae or pupae.

- Jessica Bird, George Melika, James Nicholls, Graham Stone, Eileen Buss: (2013) Life History, Natural Enemies, and Management of Disholcaspis quercusvirens (Hymenoptera: Cynipidae) on Live Oak Trees^©

Reference: https://academic.oup.com/jee/article/106/4/1747/805904?login=false