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Nodding Thistle Gall Fly - Urophora solstitialis
State Rank Reason (see State Rank above)
Urophora solstitialis was introduced from Italy into the United State of America (USA; Maryland) in 1993 as a biocontrol agent to control non-native thistles and create the balance between a plant species with their natural predator (Winston et al. 2012). The establishment of Urophora solstitialis in the USA is not confirmed (Winston et al. 2012). A conservation status rank is not applicable (SNA) because Urophora solstitialis is a non-native insect in Montana that is not a suitable target for conservation activities.
General Description
Nodding Thistle Gall Fly (Urophora solstitialis) is an insect, specifically a type of gall fly in the Family Tephritidae.
ADULTS: Brownish-black with a yellow head and yellow legs. On each wing is a ‘VII’-shaped marking. They grow to 5 mm long. Source: Winston et al. 2012
LARVAE: White, barrel-shaped bodies, and with a dark brown anal plate. They grow to 4 mm long. Source: Winston et al. 2012
Range Comments
Nodding Thistle Gall Fly is native to Europe and central Asia (Winston et al. 2012).
Habitat
HOST PLANTS
Nodding Thistle Gall Fly feeds on Musk Carduus nutans) and (Spiny Plumeless (Carduus acanthoides) Thistles (Winston et al. 2012).
Ecology
DAMAGE TO PLANTS [Adapted from Winston et al. 2012]
Nodding Thistle Gall Fly predates on Musk and Spiny Plumeless Thistles.
Larvae feeding on plant tissue reduces seed production for Musk and Spiny Plumeless Thistles. As larvae feed, hardened galls develop around them and act as metabolic sinks which diverts resources away from normal plant development.
ANIMAL-ANIMAL INTERACTIONS
Nodding Thistle Gall Fly may be outcompeted by the biocontrol insect, Thistle Seedhead Weevil (Rhinocyllus conicus) (Winston et al. 2012).
Reproductive Characteristics
LIFE CYCLE [Adapted from Winston et al. 2012]
Nodding Thistle Gall Fly has up to two generation per year. Larvae overwinter in galls which pupate in early spring. Adults emerge in late spring when thistles have bolted. Adults deposit eggs in developing flower heads. Larvae hatch and feed on seeds and tissue in the flower head’s receptacle. As larvae feed, galls harden around them. Multiple larvae can be found in a single flower head. Larvae develope through three stags (instars). Most larvae overwinter in their 3rd instar. Larvae that mature early may pupate in early summer as a 2nd generation.
Management
BIOLOGICAL CONTROL [Adapted from Winston et al. 2012 and 2016; NRCS 2019)
A fair amount of preliminary work and an array of factors must be considered when developing a biocontrol plan for controlling thistles. Readers are encouraged to consult the "Useful Links" and cited literature in this profile.
The establishment of Nodding Thistle Gall Fly is unknown; therefore, it is unavailable for collection in Montana.
Melissa Maggio-Kassner is the coordinator for the Montana Biological Weed Control Project. She can be reached at (406) 258-4223 or
mmaggio@missoulaeduplace.orgUseful Links:Montana Invasive Species websiteMontana Biological Weed Control Coordination Project Field Guide for Biological Control of Weeds in Montana Montana Department of Agriculture - Noxious WeedsMontana Weed Control AssociationMontana Weed Control Association - Weed District ContactsMontana Fish, Wildlife, and Parks - Noxious WeedsMontana State University Integrated Pest Management ExtensionWeed Publications at Montana State University Extension - MontGuides
Stewardship Responsibility
References
- Web Search Engines for Articles on "Nodding Thistle Gall Fly"
- Additional Sources of Information Related to "Insects"
