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Redgram pod fly (Melanagromyza obtusa) Photo: Digvijaysinh Padhiyar · CC BY-SA 4.0 · source ↗

Redgram pod fly (Melanagromyza obtusa)

Pod fly, Melanagromyza obtusa (Diptera: Agromyzidae), is a concealed-feeding pest of redgram (Cajanus cajan), blackgram, greengram and other pulses. Across Karnataka, Maharashtra, Telangana and Andhra Pradesh redgram tracts, ICAR-IIPR (Kanpur) and ICAR-NCIPM report pod-fly damage of 10-60 percent of grains in long-duration redgram if scouting and management are missed. Together with the Helicoverpa pod borer (Pod Borer Pulses) it forms the dominant pod-stage pest complex.

Identification and symptoms

The adult is a small, shiny dark-brown to black fly about 2-3 mm long. Eggs are inserted into developing green pods through a small puncture. The maggot is white, legless, and feeds inside the developing grain, hollowing it from inside without an external feeding hole. On harvest the damage shows up as shrivelled, partially-eaten, blackish grains that fail to germinate and are downgraded at the mandi. Unlike Helicoverpa damage, there is no large external bore-hole on the pod wall.

Hosts and lifecycle

Hosts include redgram (the primary host), blackgram, greengram, cowpea, soybean and lablab. Eggs are laid singly on green pods. Larval development takes 10-15 days inside the developing grain. Pupation occurs in the pod itself, with the adult cutting a small exit hole. The lifecycle from egg to adult is 18-25 days, and 6-8 overlapping generations can occur in a long-duration redgram crop. Carry-over occurs on alternate pulse hosts and self-sown plants.

Economic impact

Pod fly damage is concealed and is not visible until pod maturity. ICAR-IIPR multi-location trials report 10-25 percent grain damage in medium-duration redgram and up to 60 percent in long-duration types such as Maruti (Maruti Redgram) and LRG-41 (Lrg 41 Redgram) in seasons of high pest pressure. Short-duration types such as ICPL 87119 (Asha) (Icpl 87119 Asha Redgram) escape part of the pod-fly window through earlier maturity.

Management

  • Resistant/escape varieties: short-duration redgram such as ICPL 87119 (Asha) escapes the pod-fly window; ICPL 332WR and ICPL 87 have shown moderate field tolerance.
  • Scouting: dissect 50 random green pods per acre at 50, 60 and 70 days after flowering; threshold action is 2-3 larvae per 100 pods.
  • Cultural: avoid staggered sowing within a field; rogue out volunteers and alternate-host weeds.
  • Bio-control: conserve Euderus agromyzae and other parasitoids by avoiding broad-spectrum sprays before podding.
  • Chemical: spray at peak flowering and again at 50 percent podding with profenofos 50 EC (2 ml/L), thiodicarb 75 WP (1 g/L), indoxacarb 14.5 SC (0.5 ml/L), or emamectin benzoate 5 SG (0.4 g/L). Rotate modes of action across sprays to delay resistance. Coragen (chlorantraniliprole) controls pod borer but is weaker on pod fly.
  • Pheromone traps: pheromone trapping (Pheromone Traps) is more effective for Helicoverpa than for pod fly; combine with scouting for the latter.

See also: Pod borer of pulses (Helicoverpa), ICPL 87119 Asha redgram, Maruti redgram, LRG-41 redgram, IPM in vegetables.

Sources

  1. Pod fly Melanagromyza obtusa. ICAR-Indian Institute of Pulses Research, Kanpur.
  2. Pulse pod fly management. ICAR-National Centre for Integrated Pest Management.