Cucurbit Fruit fly:  Lifecycle, Nature of Damage, Management

Scientific Name: Bactrocera cucurbitae
Order: Diptera
Family: Tephritidae 

Cucurbit fruit fly is very serious and major pest of cucurbit crops, which occurs throughout the  growing areas. Adult fly are 4 to 5 mm long having a wing expanse of 11 to 13mm and 14 to 16 mm  in males and females respectively. Adult fly has reddish brown body with transparent and shiny  wings, bearing yellow-brown streaks. The pest is active almost all season; however, peak  infestation occurs in summer.  

Nature of damage of Cucurbit Fruit Fly

• Adult female flies select soft and young fruits for oviposition by puncturing the rind with their sharp ovipositor. Such damaged fruits show signs of brown resinous substance at the  sites of oviposition punctures due to discharge of fruit juice through punctures. 
• After hatching maggots feed on the pulp of fruits as well as on the immature seeds and cause  premature dropping of fruits. 
• Infested fruits rot and are not fit for sale or human consumption. 
• Infested fruits show internal decay, give out foul smell and numerous maggots are seen when  cut open. 

Life cycle of Cucurbit Fruit fly

 This insect remains active throughout the year if hosts are continuously available.  The total days required to be adult is 12 to 28 days. The developmental stages are 2 days for egg,  4-9 days for larvae and 7 -11 days for pupae. The adult female lay eggs inside the fruits by  puncturing it with its sharps ovipositor mostly in evening. The female releases gummy secretion  on the puncture which makes the entrance water-proof. Within about a week the eggs hatch into  the maggots which start to bore the pulp. The attack fruit decay because of secondary bacterial  infection. The mature larva comes out of the rotten fruits and may bury inside the soil as pupae.  Pupation mainly occurs in the soil around 2 inches below from the ground surface. Sometimes,  larva may remain inside the fruit where it pupate and transform themselves into winged adults.  There may be 8-10 generation a year. 

Management of Cucurbit Fruit Fly

• Follow clean cultivation, collect and destroy infested fruits. 
• Deep ploughing to expose hibernating stages of fly. 
• To prevent egg laying by adult, set up fly traps (pheromons trap) in the field with 1% Cue  lure or Methyl Eugenol or Cintronella oil or Vinegar or Acetic acid or Lactic acid or  ammonia liquid or Vanilla or Pollard mixture. 
• Cover developing young fruits with paper or polythene cover or muslin cloth.
• Grow Maize plants as trap crop in rows at a distance of 8-10cm in cucurbit field as flies rest  on such tall plants. 
• Use extract of neem fruit, tobacco or zinger to repel female flies. 
• Parasitoid Fopius arisanus introduced in the IPM program.  
• Male sterile technique is accomplished through irradiation, chemo – sterilization.
• Use protein bait (protein derived from corn, wheat or the other sources).
• Soil incorporation of Cabaryl 10 % dust can be done in fruit fly endemic areas to control fruit  fly. 
• Spray Malathion @ 2 ml/litre of water at fortnightly intervals.