Biology
Eggs are laid on young thistle leaves and shoots, typically
in the spring about mid March to April. Eggs are laid singly
or in small clusters of three or four and hatch in 3-4 days.
Young larvae mine in the young shoots. Older larvae feed inside
of the plant stem and tunnel up or down in the stem. The plant
is damaged by the feeding and flower and seed production is
disturbed. Multiple larvae may infest a single stem. Pupation
occurs in the root probably in the springtime. Adult flies
are black with yellow hairs and are over ˝ inch long.
History
This fly is native throughout Europe. It was originally imported
from Italy and released in Maryland in 1990. Only a single
pupa has been recovered from a research site in Maryland.
It has not been recovered from research or release sites in
Oregon, Washington, or Texas.
Status
In 1995, 135 flies were released at Hereford in Deaf Smith
County. Additional releases were made in Gillespie and Menard
Counties in Texas. No establishment has been documented in
Texas.
Management
Adults could be collected with a sweep net in early spring.
Larvae or pupae could be collected in stems in the fall of
the year.
Weeds Affected
Musk thistle, Carduus nutans complex; Italian thistle,
Carduus pycnocephalus; and plumeless thistle, carduus
accentthoides. Cirsium crassicaule is a marginally
suitable host.
Literature
Rees, N. M., J. L. Littlefield, W. I. Bruckart, and A. Baudoin.
1995. Cheilosia corydon. In Biological Control of Weeds
in the West. Western Society of Weed Science.
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