I first spotted
these…
unusual galls on an…
As usual, I ‘googled.’
I tried the terms ‘gall’ ‘oak’ ‘stem’ etc. and got many results, none of which
included these galls. I submitted these images to Bug guide (http://bugguide.net/). The oak was
identified as a Blackjack Oak (Quercus
marilandica). The gall was not identified and placed in the ‘unidentified
galls’ category. I also expanded my searches to include ‘Quercus marilandica’
and/or ‘Blackjack Oak’ with no success.
Recently, I
discovered the ‘Plant Identification’ group on Facebook
This is a closed
group but I was granted access very quickly. At first, it didn’t occur to me to
submit the oak to this group but when I did I got an almost-immediate response
from Mr Charles Davis, who provided me not only with the correct identification
for this oak, but also the identification of the gall, and a reference to a
publication describing oak galls including this one.
The oak is Quercus falcata, known as the Southern
Red Oak/Spanish Oak. The gall is caused by the cynipid gall wasp, Amphibolips acuminata.
When I ‘googled’
‘gall’ ‘Quercus falcata,’ I got two results for this gall – both in Bug Guide. The
first is for the observation provided by Mr. Davis (http://bugguide.net/node/view/1081451/bgpage) in which the host plant and the
causal agent is identified. The second result is for another ‘unidentified
gall’ on ‘Quercus marilandica’ (http://bugguide.net/node/view/1078120/bgimage). A comment on this record is that the
host oak is ‘Quercus falcata,’ not ‘Quercus marilandica.’
The publication that
Mr. Davis referred me to is a Google Books reproduction of an article entitled
‘Species of Amphibolips and
their Galls’ in the Bulletin of the American Museum of Natural History from
1909. Interestingly, the article states that the specimens were collected from…
‘twigs of the black jack oak ‘Quercus
marylandica (sic)’ Mr. Davis noted that this was very likely a mis-identification
of the host species by the entomologists collecting the gall. This seems a
reasonable assumption considering that in the case of the second observation
and mine, the leaves of the young oaks were also misidentified as Q. marilandica.
So... ‘my’ galls have
now been successfully identified as occurring on a Southern Red Oak (Q. falcata) and being caused by a
cynipid wasp, Amphibolips acuminata.
Southern Red Oaks
occur throughout the southeastern United States, from Delaware to eastern Texas.
This species has been documented in relatively few counties in Georgia. This
observation was made in Barrow County that is not included in this distribution
map; this species may be distributed more widely in this state than has been
documented.
Observations of
this gall appear to have been made widely in the eastern/southeastern United
States. A newsletter from the South Carolina Association of Naturalists, some
of whose members observed this gall attached to a ‘black jack oak’ (another
misidentification?). They ultimately received an identification from Dr. George Melika, Head of the Central
Plant Pest Diagnostic Laboratory in Budapest, Hungary, who noted that
observations of these galls had been
made ‘…along the Eastern
Coast of USA, from Florida, Georgia up to Virginia and even Washington DC. It
is present in PA also.’
The wasp, Amphibolips acuminata, that produces
these galls is a tiny wasp related to the wasp (Amphibolips confluenta) that produces the more frequently
encountered Oak Apple galls on Quercus
sp., Q, coccinea, Q. rubra,
Q. falcata, Q. marilandica,
and Q. texana.
Special note: I
would not have identified this gall if it had not been for the invaluable
assistance provided by Mr. Charles Davis on the Facebook ‘Plant Identification’
group (
https://www.facebook.com/groups/156706504394635
). Consider joining this group if you have plants you wish to identify.
Reference sources:
Facebook Group:
Plant Identification
USDA Plant Database: Quercus falcata (Southern Red Oak)
Bug Guide: Amphibolips
acuminata
Bug Guide: Unidentified gall
Bug Guide: Unidentified gall
- Page 53.
Amphibolips acuminata
- Page 66. Plate XI, illustrations 4,5.
South Carolina
Association of Naturalists. Newsletter, May 2013.
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