INSECTS AND C. TARAXACI (DIPTERA: ) - SISTER SPECIES WITH SIMILAR MORPHOLOGY BUT DIFFERENT POPULATION DYNAMICS

DIETHER P. PESCHKEN, 217 Lockwood St., Winnipeg, MB R3N 1S1 email: [email protected] Introduction (Figure 1). The larvae produce The purpose of this paper slightly raised, round, yellowish- is to report on the population green or reddish to red blister development of the midge galls, about five millimeters in Cystiphora sonchi as compared diameter. (Figures 2, 3) From to that of the Cystiphora taraxaci. the underside, they appear As far as I know these light grey in the early stage of do not have an official common development, and contain one name, and I will call them “sow- or two whitish larvae which may thistle midge” and “dandelion be seen through a thin layer of midge” respectively. cells that lack chlorophyl (Figure 4). Female sow-thistle midges 3 The sow-thistle midge oviposits produce single-sexed broods. only on sow-thistle (Sonchus) species.1 Females oviposit Originally imported from Europe into leaves via the stomatal by Agriculture Canada, the sow- openings of the lower epidermis.2 thistle midge was released as a biological control agent to help

Figure 1. Sow-thistle midge laying an egg through stomatal opening on the underside of leaf of perennial sow-thistle. -R. DeClerck-Floate

71 (4) December 2013 183 Figure 2. Yellowish-green blister galls on top surface of a leaf of the perennial sow-thistle produced by the larvae of the sow- t h i s t l e m i d g e ( s e e i n s i d e f r o n t c o v e r f o r c l o s e - u p c o l o u r i m a g e ) -D. Peschken Saskatchewan, Manitoba, Quebec and Nova Scotia starting in 1981.4,5 The spread rapidly and is now very widely distributed in the three prairie provinces. It is also established in Nova Scotia, maybe in New Brunswick but not in British Columbia and Quebec. It has spread into Minnesota (personal observation).

In 1987, at Outlook, Saskatchewan, Figure 3. Reddish blister galls on leaves could be found that top of a leaf of the perennial sow- were completely covered with thistle produced by the larvae of galls. Up to 700 were counted the sow-thistle midge. (see inside on one leaf but with many galls front cover for close-up colour coalescing that an accurate count image) D. Peschken could not be made (Peschken unpublished). This level of control weedy sow-thistle species infestation could not be found in in British Columbia, Alberta, subsequent years. For example,

184 Blue Jay Figure 4. Blister galls of the sow-thistle midge as seen on the underside of a leaf of the perennial sow-thistle. - D. Peschken in 1991, the maximum count on the dandelion midge.6 one leaf was 265 and the average In July 1980, Murray Maw was much less. A similar midge (formerly at the Regina Research population collapse occurred in Station, Agriculture Canada) Alberta.5 Perennial sow-thistle collected blister galls from was not controlled anywhere in dandelion (Taraxacum officinale) Canada. at Holbein, Saskatchewan. Adults

that emerged from these galls The larvae of the sow-thistle were identified asCystiphora sp., midge have been commonly possibly canadensis. In 1989, parasitized by the parasitic I discovered numerous blister wasps sp. near galls on dandelion near Nipawin, atticus and to a lesser extent Saskatchewan (Figure 5), very by 3 other parastic wasps, similar to those on perennial Neochrysocharis formosa sow-thistle. Females reared (Westwood), Chrysonotomyia from these galls could not be sp. (Hymenoptera: Eulophidae) differentiated from those of the and Zatropis sp. near justica sow-thistle midge.4,7 By means of (Hymenoptera: Pteromalidae) in the male genitalia, the midge was Alberta and Saskatchewan.5 A. identified as the dandelion midge, sp. near atticus and Chrysotomyia which had not been reported in sp. also parasitize the larvae of Canada.6 It is assumed to have

71 (4) December 2013 185 Figure 5. Reddish-green blister galls on a dandelion leaf produced by the dandelion midge. D. Peschken

been accidentally introduced into to Humboldt and Tisdale. Galls Canada from abroad. were found on 17 out of 31 sites. The insect may have occurred The dandelion midge occurs over a larger area to the N, E and widely in Europe and was W, although no galls were found found in Kashmir.6 It oviposits S of Tisdale. To determine any only on species of the genus population change, I conducted Taraxacum.6, 7, 8 The sow-thistle further surveys in 2007 and 2012. and dandelion midges both produce several generations per Method year. On 11 and 12 Aug 2007, six sites along Highway six between In 1989 and 1992, the distribution the Qu’Appelle River and Melfort, of the dandelion midge was two sites up to 50 km south of surveyed by searching for galls Tisdale, and 12 sites in an area on dandelions at intervals of defined by Melfort, Choiceland, 20-30 km along roadways in White Fox, Nipawin and Tisdale north-central Saskatchewan.6 were surveyed, roughly in the The survey was limited to the same survey area as in 1989 area from Carrot River in the E and 1992. On 20-22 July 2012, to Prince Albert in the W, and S 32 sites in the area defined by

186 Blue Jay Figure 6. Sites surveyed in 2007 and 2012, indicating the presence or absence of the dandelion midge. Melfort, Choiceland, White Fox, I surveyed each site for five - ten Nipawin and Tisdale were again minutes for consistency. The surveyed. The sites were located presence of perennial sow-thistle along highways or gravel roads. and galls was also noted and

71 (4) December 2013 187 served as an indication that use have decreased, at least in the of insecticides did not cause the area that was surveyed. Thus, absence of galls of the dandelion this might be an example that midge. the population of an accidentally introduced biological organism Results and Discussion remained at a low density or In 2007, galls of the dandelion even declined. midge were found on only one dandelion plant on each of One reason for the different two sites, with 16 and 38 galls, population dynamics might be the 21 and 24 km south Nipawin difference in plant architectures respectively (Figure 6). Galls of the two host plants species. of the sow-thistle midge were Dandelion leaves form a found on all sites. In 2012, galls relatively low and dense basal of the dandelion midge were rosette, while perennial sow- found on only one site, on two thistle has an open growth form dandelion plants, with 15 and and becomes 30 - 150 cm high. eight galls respectively, 3.9 km It is possible that the low-growing south of Nipawin. Perennial sow- dandelion is the preferred micro- thistle occurred on 30 of the 32 habitat for the parasitic wasps sites, and galls of the sow-thistle that prey on both midges, and midge, often quite numerous, on that the dandelion midge is 26 sites. Thus, the low incidence therefore more vulnerable to of the dandelion midge is not due parasitic attack. to insecticides. Acknowledgments The two midges are sister I thank the anonymous reviewer species. They are morphologically and the editor of Blue Jay, my almost identical. Both midges daughters, Ms. Susan and Wiebke occur over wide regions in Peschken, for many helpful Europe and Asia and their host suggestions and comments. I am plants are frequent weeds in grateful to Jeff Keith, Saskatchewan the Canadian prairie provinces Conservation Data Centre, for But the two midge species differ producing the map for Figure 6. in their population dynamics. According to previous surveys, 1. Peschken DP (1982) the sow-thistle midge spread Host specificity and biology rapidly in the three western of Cystiphora sonchi (Dip.: provinces since its release. But Cecidomyiidae), a candidate for the dandelion midge seems to the biological control of Sonchus

188 Blue Jay species. Entomophaga 27 (4): Cystiphora taraxaci (Kieffer. 405-416. 1888) (Diptera: Cecidomyiidae) in North America. The Canadian 2. DeClerck R, Steeves, TA Entomologist: 125 913-918. (1988). Oviposition of the gall midge Cystiphora sonchi (Bremi) 7. Neuer-Markmann B, Beiderbeck (Diptera:Cecidomyiidae) via R (1990) Biology and host range of the stomata of perennial sow- the gall midge species Cystiphora thistle (Sonchus arvensis L.). taraxaci under growth chamber The Canadian Entomologist 120: conditions (Diptera: Cecidomyiidae). 189-193. Entomologia Generalis 15: 209-216.

3. McClay AS (1996) Unisexual 8. Skuhrava M & Skuhravy V broods in the gall midge (1973) Gallmücken und ihre Cystiphora sonchi (Bremi)) Gallen auf Wildpflanzen. Die (Diptera: Cecidomyiidae) The Neue Brehm Bücherei 314ö Canadian Enomomologist 128 : Wittenberg. 775-776.

4. Peschken DP, McClay AS, Derby JL, DeClerck R. (1989) Cystiphora sonchi (Bremi) (Diptera: Cecidomyiidae), a new biological control agent established on the weed perennial sow-thistle (Sonchus arvensis L.) (Compositae) in Canada. The Canadian Entomologist 121: 781-791.

5. McClay AS, Peschken DP (2002) Sonchus arvensis L. Perennial sow-thistle (Asteraceae). In: Biological Control Programmes in Canada, 1981-2002. Mason, PG, Huber JT. Editors, CABI Publishing, Wallingford, p. 416-424.

6. Peschken DP, Gagne RJ, Blister galls on perennial sow- Sawchyn KC (1993) First record thistle. - D. Peschken of the dandelion leaf-gall midge

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