Coffee Green Scale
Coccus viridis
Sap-Sucking Insects Moderate Risk 2.5–4.0 mm
📖 Description
Coccus viridis, the coffee green scale, is a soft scale (Coccidae) of probable South American origin that has become pantropical. It is the single most economically important scale pest of Robusta coffee in India, with outbreaks most frequent on 1–3-year-old bushes under heavy shade and high humidity. The scale feeds on phloem sap and excretes copious honeydew, which supports sooty-mould growth that further reduces photosynthesis. Its tight mutualism with ants — particularly the crazy ant Anoplolepis gracilipes and the red imported fire ant in some regions — protects scales from natural enemies and accelerates colony expansion. Without effective biological control, coffee green scale can reduce Robusta yields by 15–25 % over a season.
⚠️ Symptoms to watch for
- Yellow speckling on upper leaf surface above feeding sites, premature leaf drop, dieback of tender shoots, sticky honeydew on lower leaves with attendant sooty mould, and reduced berry set. Heavy infestation on young coffee causes bush stunting and delays first bearing by 1–2 years. Ant trails along stems and leaf petioles are a reliable indicator of an active scale colony.
🩹 Treatment
- Conserve Coccinellid predators and parasitoids — they normally keep Coccus viridis below economic thresholds. Prune and burn heavily infested suckers and water sprouts. Spot-spray neem oil 1 % or fish oil rosin soap 25 g/L on crawler stages. If infestations exceed 5 scales/leaf on young coffee, apply buprofezin 25 SC @ 1.25 ml/L (insect growth regulator, safe to predators) or spirotetramat 240 SC @ 0.4 ml/L (translaminar, controls both scales and root-feeding stages).
🌿 Organic treatments
- Neem oil 1 % emulsion; fish oil rosin soap 25 g/L; release of Cryptolaemus montrouzieri (Australian ladybird) at 10 beetles/infested bush; spray of Verticillium lecanii 1×10^8 cfu/mL @ 5 g/L during humid months; pruned sucker destruction.
🧪 Chemical treatments
- Buprofezin 25 SC @ 1.25 ml/L; spirotetramat 240 SC @ 0.4 ml/L; imidacloprid 17.8 SL @ 0.3 ml/L (only on non-bearing young coffee); acephate 75 SP @ 1 g/L (avoid during flowering).
🛡️ Prevention
- Maintain balanced shade (30–35 %) — too much shade favours scale. Prune lower suckers and water sprouts that act as scale reservoirs. Control ants (which tend and protect scales) with chlorpyrifos trunk bands or sticky banding. Avoid excessive nitrogen on young coffee — soft, nitrogen-rich tissue is most colonised. Inspect nursery plants before field planting.
🪴 Affected plants
- Coffee (Robusta and Arabica), citrus, mango, guava, pepper, oleander, and many ornamentals. In India it is the dominant scale pest of Robusta coffee in the Western Ghats of Karnataka, Kerala, and Tamil Nadu.
🦋 Natural predators
- Coccinellid predators (Cryptolaemus montrouzieri, Scymnus coccivora, Pullus spp.), green lacewing larvae, predatory thrips, parasitoid wasps (Coccophagus cowperi, Aneristus ceroplastae, Encyrtus infelix), and entomopathogenic fungi (Lecanicillium lecanii, Fusarium coccophilum).
🌱 Host plants
- Coffee (Coffea canephora, C. arabica), citrus, mango, guava, black pepper (training vine on shade trees), oleander, croton, and many ornamental shrubs.
🔄 Lifecycle
- Females reproduce parthenogenetically, producing 100–600 crawlers each over 3–4 weeks.
- Crawlers settle along midribs and tender shoots, moult three times (females) or four times (males, rare) over 6–8 weeks, and reach reproductive maturity in 30–45 days.
- Multiple overlapping generations per year (4–6 in Indian coffee tracts).
📅 Season
- Population peaks during post-monsoon (October–December) and early dry season (January–March) in Indian coffee tracts.
- Heavy rains dislodge crawlers and crash colonies.
🔎 Appearance
- Oval, flat, pale green to yellowish-green soft scale with a characteristic black-bordered, U- or H-shaped black marking on the dorsum.
- Fully mature females are sessile, dorsally convex, and lack a visible covering scale; legs and antennae are reduced but still present.
- Early instars (crawlers) are pale yellow, mobile, and settle along leaf midribs and tender shoots where they secrete honeydew.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Moderate
🗺️ Geographic regions
- Indian Subcontinent (Western Ghats
- North-East hill tracts)
- Southeast Asia
- East Africa
- Central and South America
- Pacific Islands.
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