2013: Blue Oak with an Enormous Load of Galls In early September, 2013, in Del Puerto Canyon, west of Patterson, CA, some friends and I stumbled on the biggest population of Andricus crystallinus galls I've ever seen. The blue oaks (Quercus douglasii) were so loaded with galls that the trees appeared a dark pinkish red color from a distance even though the leaves are bluish green (and do not change color even when they drop in the fall). While Andricus crystallinus was the most numerous gall, there were also many other galls, including those made by Andricus gigas, Antron quercusechinus (= Cynips quercusechinus), Andricus atrimentus, Disholcaspis canescens, Liodora pattersonae (= Andricus pattersonae), and Besbicus multipunctatus (= Cynips multipunctatus). It seems 2013 has been a banner year for A. crystallinus. I've seen higher-than-usual numbers of their galls in other locations with blue oaks. However, none of those other locations have had numbers as high as the trees in Del Puerto Canyon, and in a few locations it was actually hard to find any of these galls. It will be interesting to see how many A. crystallinus galls are on the Del Puerto Canyon trees next year.
NOTE: All of the images below will enlarge if you click on them.
Note the rusty red/pink color of this blue oak, caused by an immense number of galls. The dominant gall is Andricus crystallinus. Andricus crystallinus closer up. Many have pinkish hairs, and some don't. It's not known why some don't. Antron quercusechinus galls were also quite numerous. There were also many Andricus gigas galls. Andricus gigas galls closer up. Two Andricus gigas galls, one with an exit hole. Andricus atrimentus, fall generation. The flat, yellowish gall is Liodora pattersonae (= Andricus pattersonae). Besbicus multipunctatus (= Cynips multipunctatus) gall in the middle of many Andricus crystallinus galls. Another Besbicus multipunctatus (= Cynips multipunctatus) gall, with a parasitoid wasp on it. There were many, many wasps flying around the galls and the tree. Due to their constant activity and small size, it was hard to know what they all were but the majority seemed to be parasitoids. Disholcaspis canescens gall with parasitoid wasps. These Disholcaspis canescens galls have ants farming aphids on them. More Andricus crystallinus galls, plus at least 3 other species visible if you look closely (Andricus gigas, A. atrimentus, Liodora pattersonae [= Andricus pattersonae]). The galls were falling onto the ground and turning the ground pinkish red. These galls have fallen onto a spider web.