Skip to content

Citrus psylla (Diaphorina citri) and HLB vector control Photo: Aarav Mishra · CC BY-NC 4.0 · source ↗

Citrus psylla (Diaphorina citri) and HLB vector control

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the single most important pest of sweet orange and mandarin in India because it transmits Candidatus Liberibacter asiaticus, the bacterium responsible for citrus greening or huanglongbing (HLB). HLB is incurable in the field and progressively kills affected trees; long-term productivity of orchards in the YSR Kadapa belt (YSR Kadapa Citrus Belt) and the Marathwada Mosambi tract depends on keeping the vector below damaging levels.

Identification

Adult psyllids are 3-4 mm long, mottled brown, and characteristically sit head-down at a 45-degree angle on young leaves and shoots. Eggs are golden-yellow, almond-shaped and laid on the tips of new flush. Nymphs are flat, yellow-orange with prominent red eyes and secrete white waxy filaments from the abdomen. Honeydew and black sooty mould on flushes are a secondary indicator. Heavy nymphal feeding distorts and stunts new leaves.

Hosts and life cycle

The pest is restricted to Rutaceae. In India it builds heavily on sweet orange (Mosambi, Sathgudi) (Citrus Mosambi Sweet Lime), Nagpur mandarin, Kinnow, acid lime, curry leaf (Murraya koenigii) and the ornamental Murraya paniculata. The female lays 300-800 eggs over her lifespan. Eggs hatch in 4-6 days; five nymphal instars complete in 13-20 days; adults live 30-45 days. ICAR-CCRI Nagpur reports 9-10 overlapping generations per year in central India, with peaks coinciding with the ambia, mrig and hasta flushes.

Damage and economic impact

Direct feeding damage by itself is modest, but the pest's role as the obligate vector of HLB makes it economically devastating. HLB-affected trees show blotchy mottle leaves, lopsided fruit with aborted seeds, and progressive twig dieback; productive life is reduced from 25-30 years to 7-10 years. Once an orchard's psylla population is left unmanaged, HLB incidence in CCRI surveys has reached 70-80% in 6-7 years.

Management

ICAR-CCRI Nagpur recommends a vector-suppression package:

  • Plant indexed material: source budwood and saplings only from indexed, virus-free mother blocks (CCRI Nagpur, NRCC Tirupati).
  • Rogue infected trees: identify and remove HLB-positive trees promptly; without this, vector control alone has limited effect.
  • Monitor new flush: yellow sticky traps at 10-15 per hectare; visually inspect new flushes during ambia and mrig flushing.
  • Chemical control on flush: imidacloprid 17.8% SL at 0.3 ml/L or thiamethoxam 25% WG at 0.2 g/L sprayed on emerging flush; soil drench of imidacloprid 0.6 ml/L on young trees for 4-6 weeks of systemic protection. Rotate mode-of-action groups to avoid resistance.
  • Biological: conserve naturally occurring parasitoids Tamarixia radiata and Diaphorencyrtus aligarhensis, and the coccinellid predators Curinus coeruleus and Chilocorus nigritus.
  • Sanitation: remove water shoots, curry leaf and Murraya paniculata hosts inside the orchard.

See also: Citrus Mosambi Sweet Lime, YSR Kadapa Citrus Belt, Citrus Gummosis, Phytophthora Foot Rot Citrus.

Sources

  1. Citrus psylla and Huanglongbing. ICAR-CCRI Nagpur.
  2. Asian citrus psyllid. CABI Plantwise Knowledge Bank.