The genus Cuscuta L. (Convolvulaceae), commonly known as dodder, includes about 200 obligate stem-parasitic species. Several of these (about 15–20) are aggressive parasitic weeds that have significant impact on economically important crops, especially in temperate and tropical regions of the world (Costea et al. 2015). Cuscuta lupuliformis Krock. (Convolvulaceae) occurs from central Asia (Mongolia, China) to western Europe (reaching Germany, Netherlands) (USDA 2019). In Poland, this species is primarily found in valleys of large rivers where it most frequently parasitizes Salix spp. (Salicaceae) (Wayda 1999).

Field surveys conducted in Poland from Jul to Sep 2018 revealed the presence of larval Melanagromyza cuscutae Hering (Diptera: Agromyzidae) feeding on C. lupuliformis. Melanagromyza cuscutae is known to be monophagous on Cuscuta spp. Specimens (over 100, dominated by females) were collected in 10 localities in the Lesser Poland Uplands, Sandomierz County, in Sandomierz and surrounding areas along the Vistula River valley (50.6514292°N, 21.7278589°E to 50.6840489°N, 21.7874561°E, 137 to 148 masl). Three males and 6 females were deposited in the private collection of the second author. Approximately 10 ha of alluvial forests, scrubs, flood embankments, and wasteland were observed to be infested with thousands of C. lupuliformis shoots that parasitized various plant species, especially Salix spp. (Fig. 1A, B). Melanagromyza cuscutae larvae were observed mining in flowers and fruits of the dodder, but rarely in shoots (Fig. 1C). Numerous larvae also were observed feeding on ovaries, resulting in damage, necrosis, and reduced seed production of this parasitic plant. In these areas, 30 to 60% of the total dodder populations were infested in sample areas from those habitats previously mentioned. Several infested plants with fly pupae were taken to the laboratory and reared in an incubator at 21 to 23 °C, where adults emerged after 2 to 3 wk.

Papp & Černý (2015) provide taxonomic characters and male genitalic illustrations that allow for differentiation of M. cuscutae from other central European Agromyzidae. The principal diagnostic features of M. cuscutae are as follows: (a) abdomen with a metallic greenish shine; (b) frons not significantly projected above the eyes; (c) eyes bare; (d) orbital setulae reclinate; (e) presence of 2 anterior and 2 posterior fronto-orbital setae; (f) margin and fringe of squamae black; (g) halter black (Figs. 1, 2).

So far, M. cuscutae has been reported from several Cuscuta spp., such as Cuscuta europaea L., C. lupuliformis, Cuscuta campestris Yunck, Cuscuta reflexa Roxb., Cuscuta approximata Bab., Cuscuta hyalina Roth, and Cuscuta planiflora Ten. (all Convolvulaceae) (Tóth et al. 2004 and references therein). Melanagromyza cuscutae occurs in Japan, South Asia (India, Myanmar, Pakistan), Central Asia (Kazakhstan), and Europe (Czech Republic, Germany, Hungary, Slovakia, Italy, Ukraine) (Papp & Černý 2015). To the best of our knowledge, this is the first report of M. cuscutae from Poland and north of the Carpathians, a fact that significantly expands its range northward. Previously, the nearest records of M. cuscutae in this area are from Germany, Slovakia, and the Czech Republic (Papp & Černý 2015, Tóth et al. 2004).

Melanagromyza cuscutae is a fly whose larvae mine the ovaries and stems of its host, and there have been attempts to use this species as a means of biological control in other Cuscuta infested areas (Baloch et al. 1967). Papp & Černý (2015) note that M. cuscutae have no significant economic importance, but this may not be true because larval feeding causes significant reduction of seed in its invasive host. However, Chalcidoidea wasps have been reported to emerge from M. cuscutae pupae in previously parasitized dodder, most of which still await identification (Piwowarczyk et al. unpublished). Spencer (1973) previously noted that wasps reared from this fly include specimens of Opius Wesmael, Dacnusa Haliday, Bracon Fabricius (all Braconidae), Eucoilidae, and Eupelmus Dalman (Eupelmidae). Bruchophagus Ashmead (Eurytomidae) also was listed by Spencer (1973) and earlier by Baloch et al. (1967), but this is a genus of phytophagous species (Burks 1957) and should be excluded as potential parasitoid of Melanagromyza. Moreover, Bouček (1961) stated that Sphegigaster cuscutae Ferrière (Pteromalidae) is a primary parasitoid of M. cuscutae. The high degree of parasitoidism is known to be one of the important factors limiting M. cuscutae as a biocontrol agent (Spencer 1973).

We would like to thank Justyna Kasińska (Kielce University of Technology) for the SEM photographs, Karol Zubek (Jan Kochanowski University) for stereomicroscope photographs, and previous reviewers for their valuable comments on our manuscript.

Fig. 1.

Melanagromyza cuscutae Hering parasitizing Cuscuta lupuliformis Krock; C. lupuliformis extensively infecting host, Salix sp. (A), fruits of C. lupuliformis (B); Melanagromyza cuscutae: larva in fruit of C. lupuliformis (C), lateral view (D), dorsal view (E), anterolateral view (F), pupae in SEM (G, H).

Fig. 2.

Melanagromyza cuscutae details: female ovipositor sheath (A); female sternites, ventral (B); male sternites, ventral (C); male genitalia (D); male phallapodeme genitalia (E); male phallus, ventral genitalia (F).