First Report of Smynthurodes betae (Hemiptera: Aphididae) on Phelipanche ramosa (Orobanchaceae)

Summary The bean root aphid, Smynthurodes betae Westwood (Aphididae: Eriosomatinae: Fordini) is reported for the first time feeding on haustoria of branched broomrape, Phelipanche ramosa, (Orobanchaceae) a cropparasitic plant. Field surveys conducted in Poland revealed infestations of P. ramosa by nymphs and adult apterous females of a secondary-host generation of S. betae in 1 locality in Sandomierz County, near Szewce, Poland. Numerous nymphs of S. betae fed on broomrape sap, resulting in poor growth or dead shoots, and 10 to 20% of the total population of broomrape was infested. Potential use of this insect as a biological control method for invasive broomrapes requires further study.

Smynthurodes betae Westwood (Hemiptera: Aphididae: Eriosomatinae: Fordini), also known as bean root aphid, is a host-alternating aphid species with a 2-yr life cycle. Its primary host is Pistacia spp. (Anacardiaceae), on which it creates leaf galls. Secondary hosts occur in many genera and families of plants, principally Asteraceae, Fabaceae, and Solanaceae (Blackman & Eastop 2008). Smynthurodes betae feed on roots, often in ants' nests (Lasius spp.; Hymenoptera: Formicidae). On both primary and secondary hosts it may be a serious pest, inflicting direct harm through induction of persistent leaf galls on Pistacia and by sucking the sap of secondary hosts and causing root deformations. Its occurrence is not restricted to areas of its primary host's occurrence (Mediterranean region); permanently parthenogenetic (anholocyclic) populations also occur in various parts of the Northern Hemisphere that are characterized by moderate climate (Capinera 2001).
Holoparasitic plants of the family Orobanchaceae parasitize the roots of both wild and cultivated hosts. Several species are serious agricultural pests (weeds). One of the most damaging weeds is the branched broomrape, Phelipanche ramosa (L.) Pomel (syn. Orobanche ramosa L.) (Orobanchaceae), an obligate root parasite that causes significant losses in a variety of crops, especially tomatoes and tobacco. It is native to Eurasia and North Africa, but has been introduced in many other areas of the world.
Field surveys conducted in Poland in Sep and Oct 2017 revealed infestations of P. ramosa by larvae and adult apterous females of a secondary-host generation of S. betae in 1 locality in Świętokrzyskie Voivodeship, Sandomierz County, near Szewce (50.6166°N, 21.6166°E, 145 masl). Here, P. ramosa parasitized roots in a 2-ha area of tomato crops containing about 2,000 shoots. Infestation with S. betae was observed on the underground parts of broomrape shoots, on both haustoria and tubers, by digging plants from the soil (Fig. 1). Numerous larvae fed on broomrape sap, resulting in weakened or dead shoots (Fig. 1). A single plant was parasitized by over 50 S. betae nymphs, and 10 to 20% of the total population of plants were infested. Distinguishing characteristics of S. betae include (a) globular body shape; (b) diameter about 2 mm; (c) short appendages; (d) whitish to yellowish color; (e) slightly waxy covering; and (f) the young nymphs are flattened and olive-green (Fig. 2).
DNA was extracted using a DNeasy Blood & Tissue Kit by Qiagen (Venlo, Netherlands) and a standard barcode sequence of mitochondrial cytochrome c oxidase subunit I (COI) was amplified using the primers LCO1490 and HCO2198. The Neighbor-Joining phylogenetic tree showed that the newly sequenced COI region of S. betae (GenBank accession no. MG581930) was 99% similar to other S. betae sequences found in GenBank (EU701910.1, KR045151.1).
So far, only a few insects have been reported to feed on Orobanche (Orobanchaceae), (e.g., Phytomyza orobanchia Kaltenbach (Diptera: Agromyzidae), which is very promising as a biological control agent of broomrape (Linke et al. 1990 (Holman 2009). To the best of our knowledge, this is the first report of S. betae parasitizing P. ramosa. Further observations on the potential use of this insect as a control method for P. ramosa might be useful, because poor growth and necrosis have been observed in broomrape. Use of natural enemies appears to be a promising approach for suppression of root parasitic plants (Klein & Kroschel 2002;Qasem 2010). Recent observations have shown that the melon aphid (Aphis gossypii Glover [Hemiptera: Aphididae]) may be a biological control method for broomrape, because it was found to completely stop the growth and flowering of broomrape plants (Borkowski & Dyki 2008).

Summary
The bean root aphid, Smynthurodes betae Westwood (Aphididae: Eriosomatinae: Fordini) is reported for the first time feeding on haustoria of branched broomrape, Phelipanche ramosa, (Orobanchaceae) a cropparasitic plant. Field surveys conducted in Poland revealed infestations of P. ramosa by nymphs and adult apterous females of a secondary-host generation of S. betae in 1 locality in Sandomierz County, near Szewce, Poland. Numerous nymphs of S. betae fed on broomrape sap, resulting in poor growth or dead shoots, and 10 to 20% of the total population of broomrape was infested. Potential use of this insect as a biological control method for invasive broomrapes requires further study.