Citrus Psyllid
Diaphorina citri Kuwayama
📖 Description
Citrus Psyllid (Diaphorina citri) is one of the most serious sap-sucking pests and disease vectors of citrus across the Indian subcontinent and worldwide. Diaphorina citri is native to the Indian subcontinent (India, Pakistan, Sri Lanka) — but has spread to all citrus-growing regions worldwide where it vectors ‘Candidatus Liberibacter asiaticus’ — the bacterium that causes Citrus Huanglongbing (HLB — also called Citrus Greening Disease — the most destructive disease of citrus worldwide). HLB has destroyed citrus industries in many countries — including Florida (USA), Brazil, China, and parts of India. India is one of the world’s largest citrus producers (over 4 million tonnes annually) with major growing belts in Maharashtra (Nagpur — famous for Nagpur mandarin — HLB has destroyed many Nagpur mandarin orchards), Andhra Pradesh, Telangana, Punjab (kinnow mandarin — Punjab is India’s largest kinnow producer), Rajasthan, Madhya Pradesh, Karnataka (Coorg — Coorg mandarin), Assam (Khasi mandarin), and the Northeast. India is particularly renowned for its diverse citrus genetic resources — including Nagpur mandarin, Coorg mandarin, Khasi mandarin, Assam lemon, Andhra acid lime, and many other varieties — but HLB threatens these genetic resources. The pest is unusual among citrus pests because (a) it is the most efficient known vector of ‘Candidatus Liberibacter asiaticus’ — the bacterium that causes Citrus Huanglongbing (HLB — the most destructive disease of citrus worldwide — HLB is incurable, once a tree is infected it cannot be cured and the tree dies within 5-8 years), (b) the psyllid reproduces rapidly on tender citrus shoots (flush growth) — females lay 200-800 eggs on tender shoots and leaves, with nymphs developing over 10-15 days and adults living 30-60 days, (c) the pest causes characteristic ‘curling and distortion’ of tender leaves due to a toxin in the saliva (similar to other psyllids), (d) HLB symptoms include asymmetric ‘blotchy mottle’ yellowing of leaves (characteristic HLB symptom), stunting of trees, dieback of twigs, small lopsided fruits with bitter taste, fruit drop, and tree death within 5-8 years of infection, (e) the pest has 10-15 overlapping generations per year in tropical India — allowing year-round population buildup, and (f) the pest is most damaging during ‘flush’ periods (when tender new shoots are emerging — psyllids concentrate on flush growth and are most susceptible to systemic insecticides during these periods). IPM with HLB-free certified nursery trees (most critical — buy only from certified nurseries that test for HLB), Tamarixia radiata biological control (the single most effective biological control agent for Diaphorina citri — native to India/Pakistan — naturally present in many Indian citrus areas; commercially available in many countries — limited commercial availability in India through NBAIR), Cryptolaemus montrouzieri predator releases, yellow sticky trap monitoring, neem-based sprays, need-based insecticide rotation (Buprofezin, Acetamiprid, Spirotetramat — selective and safe to natural enemies), systemic insecticides during ‘flush’ periods, weed host management (curry leaf control), roguing of HLB-symptomatic trees, area-wide psyllid management, and orchard replanting with HLB-tolerant varieties provides effective control. The pest is a particular concern for Indian citrus growers because (i) India is one of the world’s largest citrus producers and HLB is the most destructive disease of citrus worldwide — any widespread HLB outbreak would be economically devastating, (ii) HLB is present in most Indian citrus-growing regions — particularly severe in Nagpur mandarin belt (Maharashtra), where HLB has destroyed many orchards, (iii) HLB causes 50-100% yield loss in infected orchards and complete orchard loss within 5-8 years — HLB is incurable, once a tree is infected it cannot be cured, (iv) the psyllid is native to India — but its natural enemy Tamarixia radiata is also native to India/Pakistan, providing opportunities for effective biological control, (v) citrus is a major fruit crop in India supporting small and marginal farmers — pest-induced yield losses directly affect farmer income, (vi) India is particularly renowned for its diverse citrus genetic resources — including Nagpur mandarin, Coorg mandarin, Khasi mandarin, Assam lemon, Andhra acid lime — HLB threatens these genetic resources, and (vii) much Indian citrus farming is done by small and marginal farmers with limited access to IPM knowledge and HLB-free certified nursery trees.
⚠️ Symptoms to watch for
- Direct feeding damage: sap-sucking on tender citrus shoots and leaves; characteristic 'curling and distortion' of tender leaves (caused by toxin in saliva — similar to other psyllids); yellowing of leaves, stunting of new shoots, dieback of twigs; reduced plant vigour; reduced fruit yield (20-40% reduction in severely infested orchards). Honeydew deposition leads to sooty mold growth on leaves (reduces photosynthesis). Virus transmission (most serious consequence): Diaphorina citri is the vector of 'Candidatus Liberibacter asiaticus' — the bacterium that causes Citrus Huanglongbing (HLB — also called Citrus Greening Disease — the most destructive disease of citrus worldwide). HLB symptoms: yellowing of leaves (asymmetric 'blotchy mottle' — characteristic HLB symptom), stunting of trees, dieback of twigs, small lopsided fruits with bitter taste, fruit drop, tree death within 5-8 years of infection (HLB is incurable — once a tree is infected, it cannot be cured). Crop loss: 50-100% yield loss in HLB-infected citrus orchards; complete orchard loss within 5-8 years; ₹500-1000 crore annual loss to Indian citrus industry. HLB is present in most Indian citrus-growing regions — particularly severe in Nagpur mandarin belt (Maharashtra), where HLB has destroyed many orchards.
🩹 Treatment
- Install yellow sticky traps @ 20/ha for monitoring adult activity (psyllids attracted to yellow), spray neem oil 1% + 5 g/L soap on colonies (focus on tender shoots and leaf undersides — repeat at 10-15 day intervals), release Tamarixia radiata parasitoids @ 100/ha (parasitoid — the single most effective biological control agent for Diaphorina citri — introduced from India to many countries and now used worldwide for biological control; native to India/Pakistan — naturally present in many Indian citrus areas), conserve native ladybird beetles and predatory bugs, prune and destroy heavily infested shoots and HLB-symptomatic branches (critical — once a citrus tree is infected with HLB it cannot be cured, the tree must be removed to prevent secondary spread), apply imidacloprid 17.8 SL @ 0.3 ml/L (systemic — reaches all plant parts including tender shoots where psyllids feed), apply thiamethoxam 25 WG @ 0.2 g/L (systemic), apply dimethoate 30 EC @ 1 ml/L (systemic — effective against psyllids).
🌿 Organic treatments
- Release Tamarixia radiata @ 100/ha (parasitoid — the single most effective biological control agent for Diaphorina citri — native to India/Pakistan — naturally present in many Indian citrus areas; commercially available in many countries — limited commercial availability in India through NBAIR), release Cryptolaemus montrouzieri ladybird predator @ 50/ha (predator — feeds on psyllid nymphs), release Chrysoperla carnea @ 50,000/ha (lacewing predator), spray neem oil 1% + 5 g/L soap on colonies (deters feeding and reproduction), apply Verticillium lecanii @ 5 g/L (entomopathogenic fungus — effective against nymphs), apply Beauveria bassiana @ 5 g/L (entomopathogenic fungus), spray NSKE 5% (neem seed kernel extract — azadirachtin-based), spray fish oil rosin soap 25 g/L, prune and destroy heavily infested shoots, conserve native ladybird beetles (Menochilus, Coccinella) and predatory bugs (Orius, Geocoris), apply essential oil blends (peppermint, lemongrass — repel adults), intercrop with non-host trees (reduces psyllid spread), Rogue out and destroy HLB-symptomatic trees immediately (most critical — once a citrus tree is infected with HLB it cannot be cured, the tree must be removed to prevent psyllids from acquiring the bacterium and transmitting it to healthy trees), use HLB-free certified nursery trees (most important preventive measure — buy only from certified nurseries that test for HLB).
🧪 Chemical treatments
- Imidacloprid 17.8 SL @ 0.3 ml/L (systemic — reaches all plant parts including tender shoots where psyllids feed), Thiamethoxam 25 WG @ 0.2 g/L (systemic), Acetamiprid 20 SP @ 0.2 g/L (systemic — relatively safe to predators), Acephate 75 SP @ 0.75 g/L (systemic — effective against psyllids), Dimethoate 30 EC @ 1 ml/L (systemic), Diafenthiuron 50 WP @ 1 g/L (contact and stomach), Buprofezin 25 SC @ 1 ml/L (insect growth regulator — kills nymphs, safe to predators), Spirotetramat 240 SC @ 0.5 ml/L (systemic — reaches all plant parts including new growth, highly effective against psyllids), Chlorpyriphos 20 EC @ 2 ml/L (broad-spectrum — use sparingly to conserve natural enemies), Lambda-Cyhalothrin 5 EC @ 0.5 ml/L (pyrethroid — use sparingly to conserve natural enemies). Note: Apply systemic insecticides during 'flush' periods (when tender new shoots are emerging — psyllids concentrate on flush growth and are most susceptible to systemic insecticides during these periods). Rotate modes of action to slow resistance. Avoid spraying during flowering to protect pollinators. Observe withholding period before harvest. Use selective insecticides (Buprofezin, Acetamiprid, Spirotetramat) to conserve natural enemies — particularly Tamarixia radiata parasitoid. Note that insecticides can reduce psyllid populations but CANNOT cure citrus trees already infected with HLB — prevention through psyllid management and use of HLB-free planting material is the only effective strategy.
🛡️ Prevention
- Use HLB-free certified nursery trees (most important preventive measure — buy only from certified nurseries that test for HLB — HLB can be transmitted through infected nursery material), plant HLB-tolerant citrus varieties (no completely HLB-resistant citrus varieties are available — but some varieties show partial tolerance), inspect incoming nursery trees for psyllids and HLB symptoms before planting (reject infested or HLB-suspect trees), destroy weed hosts and alternative hosts (curry leaf — Murraya koenigii — is an important alternative host for Diaphorina citri and HLB bacterium — control curry leaf around citrus orchards), install yellow sticky traps @ 20/ha for monitoring, use balanced fertilization (avoid excess nitrogen which favours psyllid population buildup — but ensure adequate nutrition for tree health), practice intercropping with non-host trees (reduces psyllid spread), conserve natural enemies (Tamarixia radiata parasitoid — the single most effective biological control agent for Diaphorina citri — native to India/Pakistan — naturally present in many Indian citrus areas; Cryptolaemus montrouzieri ladybird predator; Chrysoperla lacewings; predatory bugs), release Tamarixia radiata @ 100/ha where not yet established (parasitoid — the single most effective biological control — native to India/Pakistan — commercially available in many countries — limited commercial availability in India through NBAIR), avoid broad-spectrum insecticides (kill Tamarixia parasitoids and Cryptolaemus predators — disrupt biological control and trigger psyllid outbreaks), use selective insecticides when pesticide application is necessary (Buprofezin, Acetamiprid, Spirotetramat — safe to natural enemies), apply systemic insecticides during 'flush' periods (when tender new shoots are emerging — psyllids concentrate on flush growth and are most susceptible to systemic insecticides), Rogue out and destroy HLB-symptomatic trees immediately to prevent secondary spread (most critical — once a citrus tree is infected with HLB it cannot be cured, the tree must be removed to prevent psyllids from acquiring the bacterium and transmitting it to healthy trees), implement area-wide psyllid management (all citrus orchards in a region should be treated simultaneously — prevents re-infestation from untreated orchards), implement strict nursery certification programmes (HLB-free nursery trees are essential — Government of India has established citrus nursery certification programmes), practice citrus orchard replanting with HLB-tolerant varieties (replace old HLB-infected orchards with new tolerant varieties — most sustainable long-term strategy), implement Integrated Pest Management (IPM) that prioritises biological control (Tamarixia radiata) and HLB-free planting material over chemical control.
🪴 Affected plants
- Citrus (all Citrus species — particularly sweet orange, mandarin, acid lime, lemon, grapefruit, pummelo); also feeds on curry leaf (Murraya koenigii — Indian curry leaf tree — an important alternative host), orange jasmine (Murraya paniculata), and other Rutaceae. India is one of the world's largest citrus producers (over 4 million tonnes annually — particularly renowned for Nagpur mandarin, Coorg mandarin, Khasi mandarin, Assam lemon, Andhra acid lime) with major growing belts in Maharashtra (Nagpur — famous for Nagpur mandarin), Andhra Pradesh, Telangana, Punjab, Rajasthan, Madhya Pradesh, Karnataka (Coorg — Coorg mandarin), Assam (Khasi mandarin), and the Northeast. Citrus is a major fruit crop in India.
🦋 Natural predators
- Tamarixia radiata (parasitoid — the single most effective biological control agent for Diaphorina citri — native to India/Pakistan — naturally present in many Indian citrus areas; commercially available in many countries; introduced from India/Pakistan to Florida, Brazil, Reunion, and many other citrus-growing regions where it provides effective biological control — one of the most successful classical biological control programmes in citrus), Diaphorencytrus aligarhensis (parasitoid — native to India/Pakistan — limited commercial availability), Cryptolaemus montrouzieri (ladybird predator — the 'mealybug destroyer' — also feeds on psyllid nymphs), Menochilus sexmaculatus (ladybird), Coccinella septempunctata (ladybird), Chrysoperla carnea (lacewing predator), Syrphid Fly Larvae (hoverflies — feed on nymphs), Predatory Bugs (Orius, Geocoris — feed on nymphs and adults), Spiders (capture adults), Entomopathogenic Fungi (Verticillium lecanii, Beauveria bassiana — infect nymphs and adults).
🌱 Host plants
- All Citrus species (sweet orange — Citrus sinensis, mandarin — Citrus reticulata, acid lime — Citrus aurantifolia, lemon — Citrus limon, grapefruit — Citrus paradisi, pummelo — Citrus maxima), Murraya koenigii (curry leaf — important alternative host), Murraya paniculata (orange jasmine), other Rutaceae
🔄 Lifecycle
- Adult female lays 200-800 eggs on tender citrus shoots and leaves (eggs attached by a short stalk to plant tissue — only laid on tender new growth 'flush').
- Egg incubation 2-4 days.
- Nymph passes through 5 instars over 10-15 days; nymphs are flat, oval, yellowish-orange with waxy filaments and tubercles — feed on tender shoots.
- Adult lifespan 30-60 days (lays 200-800 eggs — females mate multiple times).
- Total life cycle 15-25 days at 25-30°C; 10-15 overlapping generations per year in tropical India.
- Pest persists year-round on citrus and alternative hosts (curry leaf — Murraya koenigii).
- HLB bacterium transmission: psyllid acquires bacterium by feeding on infected tree for 30+ minutes; bacterium multiplies in psyllid body; psyllid transmits bacterium to healthy tree by feeding for 30+ minutes; once acquired, psyllid remains infective for life (bacterium persists in psyllid body — 'persistent transmission').
📅 Season
- Year-round in tropical India; peaks Mar-Jun (warm dry pre-monsoon — most favourable for psyllid reproduction, and citrus flush growth is maximum during this period) and Sep-Nov (post-monsoon second flush period).
- Pest activity is lowest during the peak monsoon (Jul-Aug) when heavy rain washes off nymphs and the cool dry winter (Dec-Feb) when citrus flush growth is minimum.
🔎 Appearance
- Adult is a small, brownish-grey psyllid (family Psyllidae — jumping plant lice) with mottled grey-brown wings held tent-like over body; body wedge-shaped with characteristic 45-degree angle resting posture (abdomen tilted upward at 45 degrees — diagnostic for Diaphorina citri); antennae 10-segmented with black tips; large prominent eyes; powerful hind legs for jumping (gives 'jumping plant louse' name).
- Nymphs are flat, oval, yellowish-orange, with conspicuous waxy filaments and tubercles around body margin — distinct from adults by flattened appearance, waxy filaments, and occurrence on tender citrus shoots.
- Eggs are yellowish-orange, oval, attached by a short stalk to tender citrus shoots and leaves.
- Distinct from other psyllids by 45-degree resting posture and occurrence on citrus.
💥 Damage level
- Moderate
🔁 Reproduction rate
- Fast
🗺️ Geographic regions
- Indian Subcontinent (native range — India
- Pakistan
- Sri Lanka)
- South Asia
- Southeast Asia
- East Asia
- Middle East
- Africa
- Pacific
- Americas (introduced — now cosmopolitan in tropical and subtropical citrus-growing regions worldwide)
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