Distribution. Foxglove aphid occurs throughout the United States and southern Canada. As a pest, its effect is greatest in the eastern regions of the continent. Foxglove aphid is found almost world-wide, but is probably of European origin.
Host Plants. Although having a very wide host range, foxglove aphid is a pest principally of potato. In the northernmost potato-growing areas in eastern North America it is sometimes the dominant aphid species on this crop, but in other areas it is displaced by green peach aphid, Myzus persicae (Sulzer); potato aphid, Macrosiphum euphorbiae (Thomas); and buckthorn aphid, Aphis nasturtii Kaltenbach. Foxglove aphid also occurs on a few other vegetables including celery, chervil, lettuce, pea, and tomato, and also on alsike, red, and white clover. In Asia, but not North America, it frequently colonizes soybean. Fruit crops that on occasion support foxglove aphid include apple, raspberry, and strawberry. It may be found on such flowers as calla lily, cineraria, Easter lily, foxglove, gladiolus, pansy, salvia, tulip, and violet. Among the numerous weeds known to support foxglove aphid are bittersweet, Solanum dulcamara; buttercup, Ranunuculus spp.; cinquefoil, Potentilla spp.; common chickweed, Stellaria media; common plantain, Plantago major; dock, Rumex spp.; fall dandelion, Leontodon autumnalis; orange hawkweed, Hieracium aurantiacum; king devil, Hieracium floribundum; oxeye daisy, Chrysanthemum leucanthemum; pigweed, Amaranthus spp.; purslane, Portulaca oleracea; shepherdspurse, Capsella bursa-pastoris; and smartweed, Polygonum spp. The overwintering hosts of foxglove aphid in cold-winter climates are foxglove, which is the basis of its common name, and hawkweed species, which apparently are more important hosts. In Europe, additional overwintering hosts are known, but in North America, woody plant hosts are not required for overwintering by either the egg or adult stages.
Natural Enemies. The natural enemies of foxglove aphid are not well documented in North
America. Among the predators of foxglove aphid are the common lady beetles (Coleoptera: Coccinellidae), some lacewings (Neuroptera: Chrysopidae), flower flies (Diptera: Syrphidae), and the predatory midge Aphidoletes aphidimyza (Rondani). In Maine, several parasitoid species have been collected, including Aphi-dius nigripes Ashmead, Praon spp., Monoctonus sp., and Aphidius spp. (all Hymenoptera: Aphidiidae), and Aphelinus semiflavus Howard (Hymenoptera: Eulophi-dae) (Shands et al., 1965). In Europe, parasitoids reportedly exert good control of foxglove aphid (Robert and Rabasse, 1977), and this is likely the case in North America also. In addition, fungi affect these aphids.
Life Cycle and Description. Foxglove aphid can remain on its primary hosts, foxglove and hawkweed species, throughout the year. Alternatively, it can disperse during the summer to crops and weeds. In either case, the population peaks in August or September. In cold-winter climates such as Maine, overwintering occurs in the egg stage. In climates with warmer winters, such as New Jersey, aphids may overwinter as adults.
A brief treatment of foxglove aphid biology was found in Patch (1928). A morphological description was presented by Cottier (1953), and phenology and host plant relations by Wave et al. (1965). Developmental biology was given by MacGillivray and Anderson (1958). Foxglove aphid was included in the keys of Palmer (1952) and Blackman and Eastop (1984).
Aphid populations cause potato leaves to curl, especially if the leaves are young when attacked. Foxglove aphid apparently produces toxic saliva, as it causes plant deformity and stunting at lower densities than other potato-infesting aphids. This aphid also transmits numerous plant viruses.
Management of foxglove aphid has not been well-studied, probably because this aphid is usually only
Adult female foxglove aphid, winged form.
one component of the aphid complex, and often a minor component. The sampling and management techniques discussed in the sections on green peach aphid, potato aphid, and buckthorn aphid are likely applicable to foxglove aphid.
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