Garlic Bulb Mite
Rhizoglyphus echinopus
📖 Description
Rhizoglyphus echinopus — the Garlic Bulb Mite — is a microscopic astigmatid mite pest of garlic and other bulb crops in India, with economic significance centred on the garlic seed-production and storage systems of Madhya Pradesh (Mandsaur, Ratlam, Ujjain — India’s largest garlic belt producing ~40% of national output), Rajasthan (Kota, Jhalawar, Baran), Gujarat (Junagadh, Amreli), and Uttar Pradesh (Mathura, Agra). India is the world’s second-largest garlic producer (~1.3 million tonnes from ~0.25 million ha), and garlic seed quality is a critical determinant of yield — infested seed garlic produces weak, patchy stands that yield 30–50% less than mite-free seed. The mite’s life cycle is adapted to both field and storage environments — eggs hatch in 4–6 days; larvae (6 legs) feed for 2–3 days; protonymphs (8 legs) feed for 3–4 days; deutonymphs (8 legs) feed for 3–4 days; adults live 30–60 days and lay 200–400 eggs. The total life cycle takes 12–18 days at 25 °C, allowing rapid population build-up. The mite’s most distinctive adaptation is the hypopus — a resistant deutonymphal stage with a flattened body, hardened cuticle, and ventral sucker discs that allow attachment to insects, birds, or farm equipment for dispersal. The hypopus can survive without feeding for 6+ months, withstands desiccation and fumigation, and is the primary means by which the mite survives between crops in stored garlic. Beyond direct feeding damage, R. echinopus is an important vector of garlic viruses — Garlic Common Latent Virus (GCLV), Garlic Virus A (GarV-A), and Shallot Latent Virus (SLV) are all transmitted through mite feeding on basal plate tissue. Once acquired, these viruses persist in the garlic crop for life (garlic is vegetatively propagated, so viruses accumulate over generations), causing chronic yield decline of 20–40% per generation — Indian garlic yields have plateaued at 5–6 t/ha partly due to virus accumulation in seed stocks. Management is challenging because mites are concealed inside clove sheaths and the hypopus stage is resistant to most acaricides — the most effective approach combines hot water treatment of seed garlic, certified virus-free planting material, 2-year crop rotation, dry storage, and threshold-based acaricide application. The Indian Council of Agricultural Research’s Directorate of Onion and Garlic Research (ICAR-DOGR, Pune) maintains virus-free garlic foundation stock through meristem tip culture and thermotherapy, and certified seed from this programme is the most reliable prevention measure available to Indian growers.
⚠️ Symptoms to watch for
- Mites feed on the basal plate and root primordia of garlic cloves, both in the field and in storage. In the field, infested plants show stunting, yellowing of leaf tips, and poor root development — symptoms easily confused with nutrient deficiency or Fusarium basal rot. Bulbs form undersized, with loose skins and decayed basal plates. In storage, mites tunnel into cloves through the basal plate, causing sunken brown lesions, desiccation, and secondary bacterial/fungal rots. Heavy storage infestations can destroy 30–60% of seed garlic over a 4–6 month storage period, making cloves unplantable. Affected cloves, when planted, produce weak seedlings with poor emergence (often <50% emergence). Mites also vector several garlic viruses (Garlic Common Latent Virus, Garlic Virus A, Shallot Latent Virus) — virus-infected crops show chronic yield decline of 20–40% per generation.
🩹 Treatment
- Pre-plant dip of garlic cloves in dicofol 18.5 EC at 2 ml/L for 10 minutes — kills mites inside clove sheaths. Apply dicofol 18.5 EC at 2.5 ml/L as a foliar + basal drench at 30 and 60 days after planting. Apply propargite 57 EC at 2 ml/L — contact acaricide; effective against all stages. Apply etoxazole 10 SC at 1 ml/L — chitin synthesis inhibitor; excellent against eggs and immature stages. Apply wettable sulphur 80 WP at 5 g/L — low-toxicity acaricide; effective under warm humid conditions. For storage treatment, fumigate seed garlic with aluminium phosphide (Celphos) 1 tablet per tonne for 72 hours — kills all stages including hypopus. Hot water treatment of cloves at 50 °C for 30 minutes — kills mites without affecting germination.
🌿 Organic treatments
- Hot water treatment — soak cloves at 50 °C for 30 minutes; kills all mite stages including hypopus; standard quarantine treatment. Wettable sulphur 80 WP — 5 g/L; low-toxicity acaricide; OMRI-listed. Neem seed kernel extract (NSKE) 5% — repels mites; azadirachtin disrupts development. Beauveria bassiana (1×10⁹ CFU/g) at 5 g/L — entomopathogenic fungus; effective against soil-dwelling stages. Garlic + chilli + ginger extract (3% each) — traditional Indian repellant. Sun-drying of harvested bulbs for 7–10 days — desiccation kills mites on outer sheaths. Crop rotation with non-Allium crops (cereals, legumes) for 2 years — breaks mite lifecycle. Avoid storing garlic in humid godowns (relative humidity >70% favours mite population build-up).
🧪 Chemical treatments
- Dicofol 18.5 EC (Kelthane) — 2.5 ml/L; contact acaride; effective against all stages; 7-day PHI. Propargite 57 EC (Omite) — 2 ml/L; mitochondrial ATP synthase inhibitor; contact; effective against all stages. Etoxazole 10 SC (Barako) — 1 ml/L; chitin synthesis inhibitor; excellent against eggs and nymphs; translaminar. Abamectin 1.9 EC — 0.5 ml/L; glutamate-gated chloride channel activator; translaminar; effective against concealed mites in clove sheaths. Fenpyroximate 5 SC — 1 ml/L; mitochondrial complex I inhibitor; contact. Hexythiazox 5.45 EC — 1 ml/L; chitin synthesis inhibitor; effective against eggs and nymphs. Aluminium phosphide (Celphos) — 1 tablet per tonne of garlic; fumigant; kills all stages including hypopus; use only by licensed pest control operators. Rotate acaricide mode-of-action groups to prevent resistance.
🛡️ Prevention
- Use certified mite-free seed garlic — source from ICAR-DOGR or NHRDF-certified nurseries. Hot water treatment of cloves at 50 °C for 30 minutes before planting — standard quarantine practice. Practise 2-year crop rotation with non-Allium crops — breaks the mite lifecycle. Plough fallow fields deeply in May–June to expose and kill soil-dwelling mites. Store garlic in well-ventilated dry godowns (relative humidity <70%, temperature 25–30 °C). Inspect stored garlic monthly; remove and destroy infested bulbs immediately. Fumigate storage godowns with aluminium phosphide before loading new crop. Avoid planting garlic in fields that grew Allium crops in the previous 2 years. Use raised beds with drip irrigation (avoid flood irrigation that promotes mite-spread through water). Plant windbreaks around garlic fields to reduce mite migration from neighbouring Allium fields. Maintain 500 m isolation from previous-year garlic fields.
🪴 Affected plants
- Garlic (Allium sativum — primary host). Also on onion (Allium cepa), tulip (Tulipa species), lily (Lilium species), hyacinth (Hyacinthus orientalis), gladiolus (Gladiolus species), and iris (Iris species). In India, the pest is most damaging in garlic seed-crop and storage systems of Madhya Pradesh (Mandsaur, Ratlam, Ujjain — India's largest garlic belt), Rajasthan (Kota, Jhalawar, Baran), Gujarat (Junagadh, Amreli), and Uttar Pradesh (Mathura, Agra).
🦋 Natural predators
- Hypoaspis miles (predatory mite — Laelapidae; feeds on bulb mite eggs and nymphs in soil; commercially reared by NBAIR Bangalore). Gaeolaelaps aculeifer (predatory mite — soil-dwelling; feeds on all stages). Stratiolaelaps scimitus (predatory mite — soil-dwelling; effective in storage). Predatory nematodes (Steinernema feltiae — infects mites in moist soil). Entomopathogenic fungi (Beauveria bassiana, Metarhizium anisopliae — effective against soil-dwelling stages). Rove beetles (Staphylinidae — generalist predators in soil). Springtails (Collembola — compete with mites for decaying organic matter). Natural enemies are most effective in field soils with high organic matter — storage environments are too dry for predatory mites and rely on fumigation for control.
🌱 Host plants
- Garlic (Allium sativum — primary host). Onion (Allium cepa), shallot (Allium cepa var. aggregatum), leek (Allium porrum). Ornamental bulb crops — tulip (Tulipa), lily (Lilium), hyacinth (Hyacinthus), gladiolus (Gladiolus), iris (Iris). Some grass species serve as secondary hosts in field rotation.
🔄 Lifecycle
- Egg → Larva (6 legs) → Protonymph (8 legs) → Deutonymph (8 legs — feeding stage) OR Hypopus (8 legs — resistant dispersal stage) → Tritonymph → Adult.
- Females lay 200–400 eggs in clusters of 20–80 in the soil or inside the garlic bulb sheath.
- Eggs hatch in 4–6 days.
- Larvae (6 legs) feed for 2–3 days.
- Protonymphs (8 legs) feed for 3–4 days.
- Deutonymphs (8 legs) feed for 3–4 days, OR under adverse conditions (crowding, food shortage, low humidity) moult into the resistant hypopus stage.
- Hypopus can survive 6+ months without feeding and disperses by attaching to insects or farm equipment.
- Tritonymph (8 legs) feeds briefly for 1–2 days.
- Adults live 30–60 days; females begin oviposition 3–5 days after the final moult.
- Total cycle 12–18 days at 25 °C; 15–25 generations per year in storage, 5–8 generations per year in field conditions.
📅 Season
- Field activity September–March (rabi garlic crop in Madhya Pradesh, Rajasthan, Gujarat, Uttar Pradesh) — mites most active during the bulb-filling stage (December–February).
- Storage activity year-round, with peak populations in March–June (post-harvest storage of seed garlic in humid pre-monsoon conditions).
- Hypopus stage most common in May–July (warm dry conditions trigger hypopus formation).
- Field populations crash during the southwest monsoon (July–September) — waterlogging kills all stages except hypopus.
🔎 Appearance
- Microscopic, glossy, pearly-white mite 0.5–0.9 mm long with a smooth, oval body and eight reddish-orange legs (typical of astigmatid mites).
- Body is somewhat flattened dorsally, with long body setae (hairs).
- Mouthparts are chewing-type, adapted for feeding on bulb tissue.
- Larvae have six legs; nymphs have eight legs.
- Eggs are oval, white, 0.15 mm, laid in clusters of 20–80 in the soil or in the garlic bulb sheath.
- Hypopus (dispersal stage) — a resistant deutonymph with a flattened body and ventral sucker discs — attaches to insects or survives in stored bulbs for 6+ months without feeding.
💥 Damage level
- Severe
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent
- South Asia
- cosmopolitan. In India: Madhya Pradesh (Mandsaur
- Ratlam
- Ujjain
- Neemuch)
- Rajasthan (Kota
- Jhalawar
- Baran
- Bundi)
- Gujarat (Junagadh
- Amreli
- Rajkot
- Jamnagar)
- Uttar Pradesh (Mathura
- Agra
- Aligarh)
- Maharashtra (Nashik
- Pune
- Ahmednagar)
- Punjab (Hoshiarpur
- Jalandhar)
- Karnataka (Dharwad
- Belagavi). Pest is cosmopolitan — found in all garlic-growing regions of the world; particularly damaging in temperate storage systems with high humidity.
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