Rose galls

Rose gall inducers (Diplolepis sp. and Liebelia sp.) are hymeopterous insects, taxonomically belonging to the family Cynipidae (Hymenoptera: Cynipoidea). They induce galls on several wild rose species. In the Western Palearctic six species of rose gall inducers are known. Of these, the most common is Diplolepis rosae. Its surface structure is “hairy” and it is known under several different common names like bedeguar gall, mossy rose gall or Robin’s pincushion. The species D. mayri, which causes similar galls to the before named, but differs significantly from it by the surface structure and can also occur on the same host at the same time. The surface of the latter species is covered with spikes.

Another rose gall inducer is D. spinosissimae. Its gall has a cushion form, protruding on both sides of leaves. The spiked pea gall (D. nervosa) has several distinct spikes on the surface of its globular galls or some ridges in other cases. The smooth pea gall (D. eglanteriae) has also globular galls with is surface bearing never ridges or spikes, its color may be yellow or red. D. fructuum is distributed in South-Eastern Europe and Asia Minor, it can be found in Turkey and on the east coast of the Black Sea. Gall chambers are formed in fruits. The seeds, which, as a result of their growth, dislodge the fruits by unfurling them.

Regarding the number of chambers rose galls can be divided into two groups: those which induce a single chamber (unilocular) and those which induce galls from several to many chambers. In this first group can be included the spiked (D. nervosa) and the smooth (D. eglanteriae) pea galls. D. spinosissimae is inducing typically galls compound by only a few chambers, while gall with several to multiple chambers are caused by D. rosae, D. mayri and D. fructuum.

In these galls develop not only the larvae of the rose gall inducer (see below at left a D. rosae female) but also the larvae of several parasitoid species. The larvae of these species are primarily predators of the larvae of the gall inducers, but they may be the parasitoids of each other also. Such parasitoid species is Torymus bedeguaris (a female in the middle below) or Glyphomerus stigma (a female at right below).

Other parasitoid species from the community are: Pteromalus bedeguaris (female, left below), Orthopelma mediator (female, mid below), Exeristes roborator (female, right below).

In addition to parasitoids, there is another family member of the Cynipidae family. The inquiline Periclistus brandtii (female left below) can induce galls only in galled plant tissues. Thus they cause several (up to 5-6 ) smaller chambers inside the D. rosae gall chamber.

Also in the galls of D. spinosissimae (female middle up) may develop the larvae of various parasitoid species. Similarly, different parasitoid species may be present in the smooth pea gall (D. eglanteriae), and even one of the inquiline species, Periclistus caninae, may also be present in these small chambers. One of the smallest species in this community is Stepanovia eurytomae (female up to the right) which larvae fed gregariously on their hosts.

 

The spiked pea gall wasp (Diplolepis nervosa) (female upper left, gall middle) is also attacked by several parasitoid species like Torymus microstigma. Diplolepis japonica (female upper right) is distributed in Japan, the eastern shores of China, and Primorsky Krai (Russian Federation).