Foxglove Aphid: Lifecycle, Damage, and Identification

Common Name: Foxglove Aphid   

Scientific Name: Aulacorthum solani    

Order and Family: Hemiptera  

The Foxglove aphid, Aulacorthum solani, a member of the Hemiptera family, thrives in the cooler regions of North America and is a notable pest in greenhouses. Although the green peach aphid, Myzus persicae, often dominates, the Foxglove aphid stands out as a key secondary pest. Recognizing the Foxglove aphid, understanding its life cycle, and implementing specific control strategies are essential for successful management in greenhouse settings. 

LIFE CYCLE & REPRODUCTION RATE 

The Foxglove aphid, Aulacorthum solani, has a similar life cycle to other Aphid species. It undergoes four molts, leaving behind white molted skins known as exuviae that indicate its presence. Unlike other aphids that thrive in warmer temperatures, the Foxglove aphid is more prolific in cooler temperatures, producing almost twice as many offspring as at 18-20°C. Females reproduce asexually, giving birth to live young who are already pregnant, allowing rapid population growth. The eggs can survive the winter and hatch in large numbers in the spring. Due to the mostly constant temperature in the greenhouse, asexual reproduction is most common. The population then consists of females only. These females produce live offspring. The nymphs start feeding on plant saps immediately after birth. The Foxglove aphid reaches the adult stage after seven to ten days and lives an average of two weeks.  

KEY IDENTIFYING CHARACTERISTICS 

Foxglove aphids, Aulacorthum solani, are larger than green peach or melon aphids, measuring about 1.8 to 3 mm in length. Their size can vary with temperature. They have an oval-round body shape, long legs, and antennae. Short cornicles are also a characteristic feature. These aphids typically display a light green color but can vary, showing hues ranging from green to orange to pink. They are distinguishable by their somewhat shiny appearance compared to other aphids. A key identifying trait of the Foxglove aphid is the presence of two large, dark-green spots near the tips of their abdomen, located at the base of their cornicles. These spots are particularly noticeable in adults and can be seen clearly with a hand lens. Another unique feature is the black banding on their legs and antennae, which is absent in other common greenhouse aphid pests. Foxglove aphids can be either winged or wingless. The winged adults tend to be browner and have various black markings. When the aphid population becomes overly dense, the newly born aphids are born with wings, aiding their movement to other plants and facilitating the spread of the population. 

HOST PLANTS 

The Foxglove aphid, notable for its wide host range, is a versatile pest infesting both dicot and monocot plants. It is known to target over 95 species across 25 families. Particularly in greenhouse environments, this aphid demonstrates a high degree of polyphagy, attacking almost every plant vulnerable to the green peach aphid and the melon aphid. Initially considered a minor pest in greenhouses, A. solani has evolved into a major concern for growers worldwide. The aphid's adaptability to various plants has contributed to its successful spread across the globe. 

DAMAGE 

The Foxglove aphid, known for its ability to spread multiple plant viruses, causes significant damage to plants. Its toxic saliva induces leaf curling and twisting, leading to stunted growth and deformities. The aphid's feeding habits, which involve extracting copious amounts of sap, result in the secretion of excess sugar in the form of honeydew. This honeydew not only makes plants sticky but also encourages the growth of black sooty mold, further damaging crops and reducing their marketability. Additionally, the Foxglove aphid contributes to plant wilting and the yellowing of leaves. Its capacity to transmit approximately 40 plant viruses, including the Cucumber mosaic virus and the Lettuce mosaic virus, significantly aggravates its impact on plant health.