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Aulacorthum solani Kaltenbach

Aulacorthum solani is commonly referred to as foxglove aphid or glasshouse potato aphid. Known as one of the most agriculturally important pests affecting potatoes since the 1960’s (Wave et al. 1965), in recent years it has gone from an occasional pest to a major pest of many agricultural and greenhouse crops, including pepper (Down et al. 1996, Sanchez et al. 2007), lettuce  (Palumbo 2003, Lee et al. 2008a), and many ornamental plants (Jandricic et al. 2010). It is also an important pest of soybean in Japan and Korea, but is not known from this crop in North America (Kim et al. 1991; Takada et al. 2006).

Originally described from potato (Solanum tuberosum) (Blackman and Eastop 1984), Digitalis purpurea L. (common foxglove) and Hieracium spp. (common perennial hawkweed) are the important primary hosts for A. solani in North America (Patch 1928, Wave et al. 1965). However, A. solani is known to overwinter and produce sexuals on several other plant species (Hille Ris Lambers 1947, Hille Ris Lambers 1949), and thus has a wide variety of primary hosts throughout its distribution (Blackman and Eastop 1984). Aulacorthum solani is also able to use a large variety of plants as secondary hosts, and is a reported pest on 95 different plant species from 25 families (Kim et al. 1991), including mono- and dicotyledonous, herbaceous and woody plants (Blackman and Eastop 1984, Blackman and Eastop 1994, Blackman and Eastop 2006).

Identifying characteristics of A. solani are as follows. Apterous (un-winged) adult females vary in color from pale green to yellow (Damsteegt and Voegtlin 1990) and have a body length of 1.8-3.0 mm. They have 6 segmented antennae, with dark apices. The tubercles are well developed and their inner faces are parallel. The cornicles are pale with dark tips, gradually tapering but with a distinct large apical flange and 2 rows of reticulations. The cauda is pale and elongate. Alate (winged) females are yellow-green with a brown head, and a dark thorax and abdomen that has pale to dark transverse bands. The body shape is similar to wingless females, but is 2.0-3.0 mm long (Miller and Stoetzel 1997). In practice, A. solani is easily distinguished from other aphid species due its i) larger body size, ii) dark joints of the antennae and legs, iii) parallel tubercles, iv) the usual presence of darker green patches at the antennal bases (Gill and Sanderson 1998), and v) its overall “shiny” appearance (Murphy and Shipp, 2006).

Along with the usual damage to plants caused by aphids (e.g. plant yellowing and wilting, defoliation, decreased yeilds, growth of sooty molds from honeydew excretion, etc.) A. solani also secretes salivary toxins that can cause vein yellowing in leaves, severe twisting and curling of plant tissue, and local tissue necroses (Miles 1990, Sanchez et al. 2007). Thus, tolerance for this aphid in ornamental crops may be lower compared to other aphids due to its tissue-distorting feeding damage. Like other aphids, they are also able to transmit various plant viruses. Currently, 45 different plant viruses are known to be transmitted by this aphid (Miller and Stoetzel 1997), including leaf roll and mosaic viruses (Wave et al. 1965).

Natural enemies of this pest are similar to other aphid species, and include parasitic wasps in the genus Aphidius and Aphelinus, as well as predators such as ladybugs, lacewings, syrphids and the predatory midge Aphidoletes aphidimyza. Unlike many pest aphid species, A. solani does not currently have serious resistance to commonly applied pesticides.