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Posts tagged “Rubus

Blackberry Seed Gall

Galls, abnormal plants growths caused by many agents including insects, are formed during the growing season on the buds, leaves, roots and branches of plants as a response to chemicals or physical irritation. These galls serve as shelters and a source of food for their inhabitants. Blackberry is host to numerous gall-making insects, including mites, midges and gall wasps, and their temporary homes (galls) are more obvious now that Blackberries have lost their leaves. The Blackberry Seed Gall is caused by a cynipid gall wasp, Diastrophus cuscutaeformis. This wasp gets its species name from the resemblance of the galls it forms to the fruit of Dodder or Cuscuta, a parasitic plant. A cluster of small, globular, seed-like galls within which the gall wasp larvae live are pressed together in a lump surrounding the cane. Each of these 1/10th-inch diameter chambers bears a spine, and together they create a reddish-brown hairy mass.12-3-13 blackberry gall IMG_0555


Blackberry Knot Gall

12-28-10      Blackberry Knot Gall

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Winter is a good time to look for galls (abnormal plant growths caused by different agents, including insects, fungi, mites and bacteria) such as the blackberry knot gall, which is much more noticeable when there are no leaves to hide it. Whereas many galls are inhabited by a solitary insect, the blackberry knot gall contains many individual chambers, each containing the larva of the tiny wasp Diastrophus nebulosus. During the spring and summer months, this little wasp deposits eggs into the ridged stems of blackberry which stimulates the plant’s tissue into abnormal growth along the stem. This particular colonial gall can be six inches in length, although two or three inches is more typical (the more eggs that are laid, the larger the gall).  The eggs hatch and the larvae overwinter inside the gall. Adult wasps emerge in the spring and chew their way out of the gall, leaving tiny holes along the gall’s lumpy ridges. In the first photograph you can see where a hungry predator has worked its way into two of the larval chambers.  In the second, multiple chambers and larvae are exposed (sacrificed for the sake of knowledge, but popular food for chickadees on a very cold morning).