galls of the silk button gall wasp, neuroterus numismalis, on underside of a sheet of pedunculate oak, quercus robur, bavaria, ger

abnormal andricus apple background bavaria botanical botany branch brown button closeup cynipid cynipidae damage disease forest gall galliwasp galls ger german green growth hymenoptera infected infection insect leaf leaves macro natural nature neuroterus numismalis oak parasite parasitic pedunculate plant quercus robur sheet silk summer tree underside wasp wasps wild wildlife woodland woods