[Syrphidae] Syrphid Introduction
jopagr at comcast.net
jopagr at comcast.net
Thu Jun 18 15:00:17 BST 2009
I was interested in the proposal to import Carringia calcarata as a syrphid predator of the woolly apple aphid (Eriosoma lanigerum). As a long-ago graduate student I made some field studies of the aphid, and even now, in my retirement years as a stubborn aphidologist, have some continuing interest in its habits.
E. lanigerum can be found on other plants, such as Pyracantha spp., so we need to know whether C. calcarata would be necessarily attracted to the "perfumes" of apple or to the aphid itself...and at what time of the year and under what environmental conditions. E. lanigerum may indeed have a refuge on Pyracantha (and perhaps some Crataegus spp. plants for all I know). (Whether those on Pyracantha would fly back to elm, then back to apple, we hardly know; there are, of course, some questions raised by California scientists as to which populations of "E. lanigerum" are migrating and to what.)
I am reminded of the program of introducing the Asian ladybird beetle (Harmonia axyridis) to control aphids on pecan trees in several USA states. This particular beetle was favored because it would fly higher than the native ones, and therefore would be effective on the aphids in the higher portions of the tree canopies. There were a few unwelcome side effects: large populations wintering inside vulnerable vacant homes and some commercial facilities; but especially the apparent willingness of the beetle (in larval or adult, I cannot say) to feed on the NATIVE ladybird beetle larvae.
Someone should make sure that C. calcarata larvae will not feed on our native syrphid larvae--or, for that matter, the coccinellid larvae. Perhaps we should also wonder whether C. calcarata will be attacked by the aggressive Asian ladybird beetle larvae. Perhaps, with regional habitat differences, it would be wise to see whether other behavioral changes could take place.
John Graham, Ph.D.
jopag at comcast.net
18 June 2009
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