Foxglove Aphid
Aulacorthum solani
📖 Description
Aulacorthum solani — the Foxglove Aphid — is one of the most damaging insect pests of India’s protected cultivation (polyhouse/greenhouse) industry, with economic significance centred on the high-value vegetable and ornamental polyhouses of Pune (Shirwal, Baramati, Talegaon), Bengaluru (Hoskote, Doddaballapur, Anekal), Hyderabad (Shamirpet, Medchal), and the Kashmir Valley (Srinagar, Pulwama). India has approximately 25,000 ha of protected cultivation, with tomato, capsicum, and cucumber accounting for ~50% of polyhouse vegetable area and ornamentals (rose, gerbera, carnation) for ~40%. The pest is native to Europe but has spread worldwide through the international horticultural trade — it was first reported in Indian polyhouses in the 2010s and has since become the dominant polyhouse aphid in Maharashtra and Karnataka, displacing the native Myzus persicae (peach-potato aphid) and Aphis gossypii (cotton-melon aphid) in many protected cultivation systems. The polyhouse microclimate (warm 20–28 °C, humid 60–80% RH, sheltered from rain) is ideal for A. solani — populations can multiply 30-fold per generation and complete 15–20 generations per year, all year-round (parthenogenetic reproduction — males are rare in polyhouses). The pest’s biology makes it particularly damaging in polyhouses: (1) rapid parthenogenetic reproduction — a single female founds a new population; (2) concealed feeding inside curled leaves and growing tips — protected from contact insecticides; (3) wide host range (>95 plant species) — survives on polyhouse weeds between crops; (4) high insecticide resistance — the polyhouse biotype has documented resistance to organophosphates, pyrethroids, and carbamates in Pune polyhouses; and (5) efficient virus vectoring — both non-persistent (CMV, AMV) and persistent (PVY) transmission of over 40 plant viruses. The economic impact is severe: heavy infestations can reduce tomato fruit yield by 30–50% and render 40–70% of capsicum fruits unmarketable due to sooty mould contamination of honeydew. Virus transmission can cause complete crop loss — CMV-infected tomato and capsicum plants produce no marketable fruit. Management in Indian polyhouses is best achieved through IPM combining biological control (preventive Aphidius colemani parasitoid wasp releases), physical exclusion (insect-proof netting, double-door airlocks), monitoring (yellow sticky traps), threshold-based flonicamid or pymetrozine application (selective aphicides that preserve beneficials), strict sanitation, and balanced nutrition. The National Committee on Plasticulture Applications in Horticulture (NCPAH) and ICAR-NBAIR jointly promote this IPM approach for Indian polyhouse growers, with Aphidius colemani as the cornerstone biological control agent.
⚠️ Symptoms to watch for
- Adults and nymphs feed on phloem sap, causing leaf curling, distortion, and stunting of new growth. On tomato and capsicum, feeding causes characteristic downward leaf curling with yellowing of leaf margins. On foxglove, feeding causes flower spike distortion and reduced seed yield. Honeydew excretion promotes sooty mould growth on leaves and fruits — reducing photosynthesis and market value. The greater economic impact is the transmission of over 40 plant viruses, including Cucumber Mosaic Virus (CMV), Potato Virus Y (PVY), Tomato Aspermy Virus (TAV), and Alfalfa Mosaic Virus (AMV) — both non-persistent (CMV, AMV) and persistent (PVY) transmission. Heavy polyhouse infestations can reduce tomato fruit yield by 30–50% and render 40–70% of capsicum fruits unmarketable due to sooty mould contamination.
🩹 Treatment
- Apply imidacloprid 17.8 SL at 0.3 ml/L — systemic neonicotinoid; long residual activity. Apply thiamethoxam 25 WG at 0.4 g/L — systemic neonicotinoid. Apply acetamiprid 20 SP at 0.4 g/L — systemic; less bee-toxic than other neonicotinoids. Apply flonicamid 50 WG at 0.4 g/L — selective aphicide; preserves beneficials. Apply pymetrozine 50 WG at 0.4 g/L — selective aphicide; feeding inhibitor. Apply diafenthiuron 50 WP at 1 g/L — mitochondrial ATP synthase inhibitor. Apply azadirachtin 1% at 2 ml/L — antifeedant. Release Aphidius colemani parasitoid wasps at 2 per sq m — most effective biological control for polyhouse aphids. Release Chrysoperla zastrowi sillemi lacewing larvae at 5 per sq m. Use yellow sticky traps at 8–12 per 250 sq m polyhouse. Avoid pyrethroids (broad-spectrum, kill beneficials).
🌿 Organic treatments
- Azadirachtin 1% (NeemAzal) — 2 ml/L; antifeedant and growth disruptor; OMRI-listed. Neem seed kernel extract (NSKE) 5% — repels aphids. Verticillium lecanii (Lecanicillium lecanii, 1×10⁹ CFU/g) at 5 g/L — entomopathogenic fungus specific to aphids and whiteflies; highly effective under polyhouse humid microclimate. Beauveria bassiana (1×10⁹ CFU/g) at 5 g/L — entomopathogenic fungus. Garlic + chilli + ginger extract (3% each) — traditional Indian repellant. Yellow sticky traps at 8–12 per 250 sq m polyhouse — mass-trap alates. Release Aphidius colemani parasitoid wasps at 2 per sq m — most effective biological control; commercially reared by NBAIR Bangalore. Release Chrysoperla zastrowi sillemi lacewing larvae at 5 per sq m. Release Hippodamia variegata ladybird beetles at 2 per sq m. Avoid broad-spectrum insecticides — they kill natural enemies and trigger aphid population resurgence.
🧪 Chemical treatments
- Imidacloprid 17.8 SL (Confidor) — 0.3 ml/L; neonicotinoid; systemic; long residual (21–28 days); 7-day PHI. Thiamethoxam 25 WG (Actara) — 0.4 g/L; neonicotinoid; systemic. Acetamiprid 20 SP (Mospilan) — 0.4 g/L; neonicotinoid; systemic; less bee-toxic than imidacloprid. Flonicamid 50 WG (Fulfill) — 0.4 g/L; selective aphicide; feeding inhibitor; preserves beneficials. Pymetrozine 50 WG (Plenum) — 0.4 g/L; selective aphicide; feeding inhibitor; IRAC Group 9B. Diafenthiuron 50 WP (Polo) — 1 g/L; mitochondrial ATP synthase inhibitor; effective against all stages including eggs. Spirotetramat 240 SC (Movento) — 0.4 ml/L; lipid synthesis inhibitor; systemic; excellent against nymphs. Avoid pyrethroids (lambda-cyhalothrin, deltamethrin) — broad-spectrum, kill beneficials and trigger aphid resurgence. Rotate IRAC groups to prevent resistance.
🛡️ Prevention
- Inspect all incoming planting material under 10x magnification — polyhouse introductions are the most common source of new aphid infestations. Maintain polyhouse integrity — repair screens (50-mesh insect-proof netting on vents), seal doorways with double-door airlock systems. Use yellow sticky traps at 8–12 per 250 sq m polyhouse from crop establishment to monitor alate (winged) aphid migration. Release Aphidius colemani parasitoid wasps preventively at 2 per sq m — most effective biological control for polyhouse aphids; commercially reared by NBAIR Bangalore. Maintain strict sanitation — remove and destroy all crop debris, weeds, and volunteer plants inside and immediately outside the polyhouse (aphids survive on weed hosts between crops). Rogue out virus-infected plants immediately — the aphid vectors over 40 plant viruses. Avoid overhead irrigation (aphids thrive in humid microclimate); use drip irrigation. Apply threshold-based insecticide sprays (10 aphids per plant) rather than calendar sprays — preserves natural enemies. Rotate polyhouse crops — avoid continuous solanaceous cultivation; rotate with non-host crops (leafy greens, herbs) for 1–2 cycles to break the aphid lifecycle. Maintain balanced nutrition — excess nitrogen promotes soft, aphid-susceptible growth.
🪴 Affected plants
- Foxglove (Digitalis purpurea — primary host, gives the aphid its common name). Also on tomato (Solanum lycopersicum), capsicum (Capsicum annuum), cucumber (Cucumis sativus), lettuce (Lactuca sativa), eggplant (Solanum melongena), potato (Solanum tuberosum), rose (Rosa hybrida), tulip (Tulipa), lily (Lilium), calceolaria (Calceolaria), and many ornamentals. In India, the pest is most damaging in polyhouses of Pune (Shirwal, Baramati), Bengaluru (Hoskote, Doddaballapur), Hyderabad (Shamirpet), and the Kashmir Valley (Srinagar, Pulwama).
🦋 Natural predators
- Aphidius colemani (braconid parasitoid wasp — the most effective biological control agent for polyhouse aphids; commercially reared by NBAIR Bangalore; release rate 2 per sq m). Aphidius matricariae (braconid parasitoid wasp — used for Myzus persicae but also effective on A. solani). Aphelinus abdominalis (aphelinid parasitoid wasp — effective on larger aphids). Chrysoperla zastrowi sillemi (green lacewing — predator of aphid nymphs; release rate 5 larvae per sq m). Hippodamia variegata (ladybird beetle — predator; release rate 2 per sq m). Coccinella septempunctata (7-spot ladybird — predator). Syrphus corollae (hoverfly — predatory larvae). Aphidoletes aphidimyza (predatory midge — commercial biocontrol agent; effective under polyhouse conditions). Entomopathogenic fungi (Lecanicillium lecanii, Beauveria bassiana — effective under humid polyhouse microclimate). Natural enemies are highly effective in polyhouses where broad-spectrum insecticides are avoided.
🌱 Host plants
- Foxglove (Digitalis purpurea — primary host). Polyhouse vegetables — tomato (Solanum lycopersicum), capsicum (Capsicum annuum), cucumber (Cucumis sativus), lettuce (Lactuca sativa), eggplant (Solanum melongena), potato (Solanum tuberosum). Polyhouse ornamentals — rose (Rosa hybrida), tulip (Tulipa), lily (Lilium), calceolaria (Calceolaria), carnation (Dianthus caryophyllus). Weed hosts inside polyhouses — Solanum nigrum, Datura stramonium, Sonchus oleraceus.
🔄 Lifecycle
- Egg (rare in polyhouses — parthenogenetic reproduction predominates) → Nymph (4 instars) → Adult.
- In polyhouses, reproduction is entirely parthenogenetic (viviparous) — females give birth to live female nymphs without mating.
- Each female produces 50–80 nymphs over her 20–30 day adult lifespan.
- Nymphs feed and moult 4 times over 7–10 days, reaching maturity.
- Total cycle 10–14 days at 25 °C; 15–20 overlapping generations per year in polyhouse conditions (year-round activity).
- In field conditions (where present), the aphid alternates between primary host (foxglove, Digitalis) for overwintering eggs and secondary hosts (tomato, capsicum, potato) for summer parthenogenetic generations — but in Indian polyhouses, the parthenogenetic phase is continuous year-round.
📅 Season
- Year-round activity in polyhouses (controlled environment) — peak populations during March–June (warm pre-monsoon period when polyhouse temperature reaches 28–32 °C) and October–December (post-monsoon warm period).
- Lower activity July–September (southwest monsoon — polyhouse cooling reduces temperature).
- Field populations (where present) peak March–May and October–November.
🔎 Appearance
- Medium-sized, pear-shaped aphid 1.8–3.0 mm long.
- Colour varies from pale yellow-green to yellowish-brown or dirty green, often with a darker green or brown stripe down the dorsal midline.
- The body is somewhat shiny, with long, dark, tubular siphunculi (cornicles) on the dorsal abdomen — distinctly longer than the cauda (tail plate), a key identification feature.
- Antennae are longer than the body, with dark tips.
- Legs are pale with dark apices on the tibiae and tarsi.
- Winged forms (alates) have a dark thorax and longer wings.
- Nymphs resemble adults but are smaller and wingless.
- The polyhouse biotype is markedly more insecticide-resistant than the field biotype.
💥 Damage level
- Severe
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- cosmopolitan. In India: polyhouses of Maharashtra (Pune — Shirwal
- Baramati
- Talegaon; Nashik — Sinnar
- Niphad)
- Karnataka (Bengaluru — Hoskote
- Doddaballapur
- Anekal; Mysuru)
- Telangana (Hyderabad — Shamirpet
- Medchal)
- Tamil Nadu (Hosur
- Coimbatore)
- Jammu & Kashmir (Srinagar
- Pulwama)
- Himachal Pradesh (Solan
- Mandi). Pest is native to Europe — first reported in Indian polyhouses in the 2010s; has since spread to all major polyhouse belts through infested planting material.
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