Spiral Gall
14th July 2009, Tuesday
Looking closely at Black Poplar trees at Castle Water today, there was a gall on a leaf stalk that I had not seen before. Research at home revealed how this was formed.
As a leaf starts growing a female aphid, Pemphigus spirotheacae, feeds on the plant’s sap, causing a distortion of the leaf stalk into a ribbon which spirals around the feeding site. With the aphid inside, the coils tighten, but do not fuse! She produces up to 30 daughters inside, which in turn produce grand-daughters (no males required). In August the spiral loosens and the adults leave the safety of their home and lay eggs on the bark of their host. These eggs hatch into males and females and, after mating, the fertilised eggs are laid on the bark and over-winter.
Wild Hastings
wildRye
