Miguel Braganza
The attractively red-cheeked Sindhoora mangoes have arrived in town. Unlike Australia, where strict inter-state quarantine regulations govern the movement of plants and fruits, India has no such restrictions. As a result, South India—a hotspot for fruit fly infestations—has been a source of these pests spreading to other regions. In Goa, most people recognise fruit fly larvae as the ‘worms’ found in late-season Mussorad or Monserrate mangoes. However, in recent years, the early-season import of mangoes from South India has led to infestations even in prized varieties like Mankurad and Malges.
Fruit flies emerge from discarded rotten mangoes, mate, and lay eggs in ripening fruit, perpetuating their life cycle in Goa. To curb this problem, it is crucial that maggot-infested mangoes are not discarded in municipal solid waste bins but are instead buried in the ground—preferably after being crushed—to destroy the maggots before they can develop into adult flies.
The presence of fruit fly maggots in mangoes now begins earlier in the season, no longer waiting for the summer rains. Much like domestic tourism, the mango fruit fly now has an extended season! However, entomologists have found a clever way to break this cycle: a pheromone trap that exploits the male fruit fly’s natural instinct. These traps, available at Zonal Agriculture Offices (ZAO) for farmers and fruit-growing enthusiasts, use a specific pheromone to lure and capture male fruit flies, preventing them from mating.
The mango fruit fly (Bactrocera dorsalis) is related to other fruit fly species, but each species responds to a distinct pheromone. Pheromones are species-specific sex hormones—chemical signals that attract mates. For mango fruit flies, the key pheromones are methyl acetate or eugenol. It is essential to use the correct pheromone when purchasing a trap, as a generic attractant will not be effective.
Traps should be placed at chest height near mango trees about a month before harvest. The pheromone, soaked into a hardboard block or cotton wool pad, is suspended in a special trap or even a repurposed plastic bottle with holes. Drawn by the scent, male flies enter and remain inside. The pheromone lasts three to six months, while the trapped flies die within a week.
With no males to fertilise their eggs, female fruit flies die without reproducing. Even if they lay eggs in mangoes, these will not hatch, ensuring worm-free fruit without chemical insecticides or post-harvest treatments like hot water dips. Since fruit fly-free status is essential for mango exports, pheromone traps provide a sustainable solution for controlling infestations.
