seed head gall fly
Diptera: Tephritidae
Biological Control Links Photos: [spotted knapweed]
[larva/galls] [galls/knapweed seeds] [Urophora affinis]
Photo
by: Bob Richard, USDA-APHIS-PPQ.
Origin: Native of Europe. (10)
Life Cycle: In summer the adult, female gall fly lays her eggs upon the knapweed flower buds, among the developing stamens. She can lay one egg per seed head, or more. The eggs hatch within three to four days (1) and live off of the floret of the plant all summer and fall. The insect overwinters as a larvae in a gall in the seedhead and pupates in early spring. The adults emerge timed with flower budding of knapweed in late spring/summer. The adult form of the gall fly lives about fifteen days after the emerging. The gall fly can produce two generations before a new year is up. (3)
Over Wintering State: In the over wintering stage the gall fly spends time as a mature larva in the seed heads of the plant. (3)
Egg Stage: After mating the female flies to a half grown bud and lays her eggs. The eggs hatch in three to four days. (3) She can lay up to 366 eggs but the average is around 130 eggs. Each bud can hold close to 14 eggs. (10)
Larva Stage: The larva is a white color and has a brown anal plate. (1)
Pupa: The larvae pupate in the galls within the seed heads in early to mid spring. (3 )
Adult Stage: The adults emerge from pupa in spring and summer timed so that they can lay their eggs on flower buds. (3)
Damage to Host: The larva will feed on seeds and damage them and cause galls in the seed head that stress the plant. (2) For ever gall formed 1.9 seeds are damaged in the seed head. There are reports of the U. quadrifasciata, with U. affinis, killed 95% of the seed heads in two British Columbia sites. These flies are most effective when combined with other bio-agents and including the root borers. These flies them selves do not control knapweed spread in Montana. (3)
Host Impact: The adults lay their eggs in the developing stamens. Then when the larva hatches and eats the floret of the plants flower. This effects the plant so it can't grow as well, spread seed or come back the next year as well. (3)
Release Habitats: The best places to release is where
they can
adapt and survive. They
mostly
live in the Midwest and western states. Some of this states are
Arizona,
California, Colorado, Idaho, Michigan, Minnesota, Montana, Nebraska,
North
Dakota, South Dakota, Utah, Washington, Wisconsin, and Wyoming.
Some
eastern states are Indiana, Maryland, New York, Pennsylvania, Vermont,
New Hampshire, Massachusetts, Rhode Island, Connecticut, and New
Jersey.
They are well adapt to sunny areas rather than shaded
sites.
The area you are releasing the flies on should be an area that
won't
be disturbed in at the least the next ten years. The best
time is in the spring. (3) We find these where ever knapweed
occurs in Montana and do not need to release them any more. They
can disperse them selves just fine now. (Mr. Breitenfeldt)
How to collect: To collect the larvae you can hand
pick
the heads of spotted or diffuse knapweed in fall, winter or early
spring.
Store these in a refrigerator until early spring and then set them out
in tied bouquets so they can pupate and the adults can emerge at the
proper
egg laying time. This is the most efficient way.
Also, you can sweep net the seed heads for adult
flies in the spring and summer. Release these quickly onto new
sites.
(10)
We find these where ever knapweed occurs in Montana
and do not need to
release them any more. They can disperse them selves just fine
now.
(Mr. Breitenfeldt)
Comments: Part of the floret well be ruined by the
larva.
Because of this the gall forms a nutrient sink and the whole plant is
effected. U. quadrifasciata can be obtained from almost any
knapweed plant in Montana. They fly great
distances to get to the knapweed patches. They spread
into the U.S. from releases in Canada. This is not the best
defense
against knapweed but it is still a well known agent that somewhat helps
control the weed. (10) These seed head feeders in
combination with the root borers is a good one-two punch that is
working well (but slowly) on many sites in Montana! (Mr.
Breitenfeldt)
Links:
1) http://www.bioimages.org.uk/HTML/R32172.HTM
2) http://www.maes.msu.edu/nwmihort/cff_gallfly.html
3) http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/
4) http://ag.montana.edu/warc/biocontrol_agents_of_knapweed.htm
5) http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/urophora_quad.html
6) http://www.invasive.org/browse/detail.cfm?imgnum=1350080
7) http://ucsub.colorado.edu/~honors/theses/s98/gregory.html
8) http://cedarcreek.umn.edu/insects/album/029061003ap.html
9) http://www.for.gov.bc.ca/hfp/noxious/Bioagents/Short/u3.htm
10) http://www.invasive.org/eastern/biocontrol/13Knapweed.html
Bibliography
(1) Lang, R.F., USDA-APHIS-PPQ, Bozeman Biocontrol Facility, Forestry Sciences Laboratory, Montana State University, Bozeman, MT 59717-0278.last up date August 28, 1998. online:
http://www.nysaes.cornell.edu/ent/biocontrol/weedfeeders/urophora_quad.html
(2) The Appearance of Two Non-Pest Tephritids in Michigan
Orchardsunknown, last up date
Tuesday ,January 02, 2000, Forest Practices
Branch
online:
http://www.for.gov.bc.ca/HFP/PUBS/INTEREST/Bioagent/diffuse.htm
(3) Bill Klein, weed feeders table of Content,
skleinw@pilot.msu.edu
Last Revised: 3-5-99 online:
http://www.maes.msu.edu/nwmihort/wingband.html
(4) Dr. Jeff Stewart, Section Head, Crop Sciences Section,
Agriculture
and Agri-Food Canada Lethbridge Research Central, Box 3000 5403 - 1st
Avenue
Lethbridge, Alberta, CanadaT1J4B1.last up date 2000 12 28, online:
http://res2.agr.ca/lethbridge/weedbio/agents/aurocard.htm
By: Mary Beth Sacry 3/15/02.
Updated by: Ian MacMurdie 2/9/05
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