Andricus quercuslanigera
Asexual generation
[Hosts] The gall wasp is native to four live oak species in the subsection Virentes along the Gulf Coast of the southern United States and Mexico: Quercus virginiana, Quercus geminata, Quercus fusiformis, and Quercus oleoides. There are two other live oak spe- cies from which we do not know if the gall wasp has been found: Quercus sagraena (native to Cuba) and Quercus brandegeei (native to southern Baja, Mexico).
[Range] A. quercuslanigera has been documented on non-native, transplanted Q. virginiana in San Joaquin County, CA (Pujade-Villar et al. 2016) and the University of California–Davis Arboretum, Yolo County, CA (S.P.E., personal observation). There are other descriptions of specimens from various host associations that have been morphologically identified as A. quercuslanigera that may require further genetic analysis to solidify species identity. These include A. quercuslanigera potentially found on the netleaf oak, Q. rugosa, in a native portion of its range distributed throughout the temperate highlands of central Mexico (Serrano-Munoz et al. 2016). Q. rugosa also exists in small disjunct populations throughout south-central Arizona, southwestern New Mexico, and southwestern Texas (Little 1999), but the gall former has yet to be documented here. Furthermore, A. quercuslanigera has been reported to have shifted from native oak, Q. oleoides, to form galls on nursery live oak, Q. virginiana (native to southeastern United States and Texas), and pin oak, Q. palustris (native to the mid-western United States) in Tamaulipas and Nuevo Leon, Mexico, where it is classified as a pest species (Pujade-Villar et al. 2016).
[Gall] The previously described asexual generation of A. quercuslanigera develops within ‘fuzzy’ single chambered leaf galls located on the underside of new leaves on the midvein alone or in close proximity to other conspecific galls. The single chambered galls consist of a small inner capsule initially covered in short white hairs that eventually turn yellow to light brown and measure approximately 0.7–4.0 mm in final size but may often be interpreted as much larger due to the ‘fuzziness’ of a group of closely developing galls on the same leaf appearing as one large gall (Pujade-Villar et al. 2016; Fig. 1D–F). Galls are first visible beginning in late-August and continue to grow and mature by early-September to early-Decem- ber (Pujade-Villar et al. 2016, Serrano-Munoz et al. 2016, S.P.E., personal observation). Asexual females will begin emerging from late-September and continue through early-March. U
Wool covering an inner capsule of mature galls on underside of leaf along mid-vein (rarely on topside) final size 1.0–7.0 mm in diameter and 2–3 mm high (including the hairs); Wool creamy white, yellowing slightly when older; individual hairs making up the wool are straight and 0.5–2.0 mm in length; inner capsule is light brown and can be solitary or in clusters of 3–6 along midvein of leaf (Fig. 1A–F).
[Phenology] The mean date of emergence for the asexual generation was 18 January (±1 d), with the range of emergence spanning a 5-mo period from 9 September to 24 February (n = 1083) (Fig. 3).
Coinciding with spring leaf flush in mid-March to early April, the sexual generation, emerging from catkin galls (Fig. 4A), lay eggs into the lateral veins on the underside of newly flushed leaves (Fig. 4B). The fuzzy galls develop from mid- to late summer through the fall and winter (Fig. 4C and D), and asexual females emerge as adults beginning as early as September continuing through late February the following year (Fig. 4E) coinciding with catkin bud production. At that time, females oviposit into the unopened or newly opened bud of catkins (Fig. 4F). Galls on catkins grow rapidly in the spring, just as the catkins themselves do, with sexual adults emerging just weeks after asexual females initiate gall growth. Immediately following sexual generation adult emergence, males and females mate, and females oviposit into the newly growing leaves (Fig. 4E). The life history timing of each generation differs drastically (approximately 11 to 11(1/2) mo for the asexual generation and 2–4 wk for the sexual generation from oviposition to adult emergence).
