Andricus quercuslaurinus (sexgen)

Andricus quercuslaurinus (agamic)

Andricus quercuslaurinus Melika & Pujade-Villar, new species

Gall (Figs 37-38). Juicy integral monolocular leaf galls are located on the central vein, rarely on leaf petiole, causing a vein swelling. The fully grown gall is 13 mm long and 5.6 mm wide. Generally one gall per leaf occurs, rarely more; up to six galls per leaf were detected. In this case the separate galls are fused and it seems that the galls are multilocular. During the gall development, the colour of the surrounding leaf tissues changes from green to brown-yellow and the vein swelling is enlarging. As the cynipid larva matures, the main vein changes to purple colour. The central larval chamber is oval. When the gall matures, the tissues become hard. Adults emerge from early May to early July.

Biology. Alternate asexual and sexual generations are known, both inducing galls on Quercus laurina (Section Lobatae of Quercus, red oaks), which is distributed in Mexico, Guatemala and El Salvador (Govaerts & Frodin 1998). In the state of Hidalgo of Central Mexico, severe outbreaks of this newly described cynipid species cause the death of thousands of trees in natural stands of Q. laurina. The decline and death of trees is due to the twig and stem swellings caused by asexual galls. For Mexico, this is the first reported cynipid gallwasp capable to kill trees of different ages and sizes. A local infestation took place in a private forest in 2003 and the severe outbreak remained active until summer of 2009 without any signals of reduction of harmful impact, in spite of intensive management applied. There is no doubt that this species could expand its distribution and jeopardize the survival of Q. laurina in other parts of Mexico.

Distribution.  Currently  known  from  the  type  locality only: México, Estado de Hidalgo

Andricus quercuslaurinus Melika & Pujade-Villar, new species 

Gall (Figs 17-18). The complete growth and development of the gall until mature stage requires at least 30 months. Asexual females lay eggs in twigs about 1-3 cm in diameter, in late spring and early summer of the first year. In late winter or early spring of the second year, the diameter of the infected twig is rapidly increasing. At this stage, developing galls are spherical, contiguous contact between them deforms the branch, galled tissue reaches up to 40 cm long and 3.5 cm wide. Surface of the galled tissue is smooth and light green. In the summer of the third year, many of the larval chambers acquire a “horn shaped” form, and some are projecting through the exterior surface of the gall; many of these chambers are expulsed and fall down to the ground. By the end of the third year, pupae are formed and during late January and February of the next year adults emerge.

Biology. Alternate asexual and sexual generations are known, both inducing galls on Quercus laurina (Section Lobatae of Quercus, red oaks), which is distributed in Mexico, Guatemala and El Salvador (Govaerts & Frodin 1998). In the state of Hidalgo of Central Mexico, severe outbreaks of this newly described cynipid species cause the death of thousands of trees in natural stands of Q. laurina. The decline and death of trees is due to the twig and stem swellings caused by asexual galls. For Mexico, this is the first reported cynipid gallwasp capable to kill trees of different ages and sizes. A local infestation took place in a private forest in 2003 and the severe outbreak remained active until summer of 2009 without any signals of reduction of harmful impact, in spite of intensive management applied. There is no doubt that this species could expand its distribution and jeopardize the survival of Q. laurina in other parts of Mexico.

Distribution.  Currently known  from  the  type  locality only: México, Estado de Hidalgo

New species of oak gallwasp from Mexico (Hymenoptera: Cynipidae: Cynipini)-a serious pest of Quercus laurina (Fagaceae)