Lesser Bulb Fly – Emerus tuberculatus

Lesser Bulb Fly (Emerus tuberculatus) Common Name: Lesser Bulb Fly Latin Name: Emerus tuberculatus Appearance: Egg:   Lesser bulb fly eggs are very little (0.72 by 0.24 mm), thin, and somewhat pointed on one end. They are frequently arranged in tiny groups. Larva: The maggots of the lesser bulb fly range in size from 0.75 mm to 7 to 10 mm and are white to grayish-yellow, depending on the quality of the host bulb. They are more slender and somewhat flattened than the narcissus bulb fly (2.5 mm broad and 1.8 mm high). The breathing tube is brick red or brown, with a fleshy protrusion on either side. Pupa:  The pupa grows within the final larval skin, which hardens into a robust protective covering 6 to 8 mm long, 3 mm broad, and 2.8 mm high (the puparium). However, when the maggot pupates in soil, the puparium becomes fully coated with small soil particles. Adult: Lesser bulb flies are dark blue insects with a metallic golden sheen that range in size from 5 to 9 mm (they appear black at a distance). On the abdomen, three pairs of grayish-white crescents with yellowish hairs at the tip. The thorax features two whitish lines that run longitudinally. The hind legs feature broad segments that appear to be designed for leaping. Territory: Lesser bulb flies were brought into the United States from Europe. These insects can be found everywhere narcissus is growing. Host plant: Lesser bulb flies can cause damage to onion, narcissus, and hyacinth plants. Shallots, garlic, iris, lilies, parsnips, potato tubers, amaryllis, cabbage roots, Calla elliottiana, Eurycies, Galtonia, Gladiolus, Scilla, Sprekelia formosissima, and vallota are among the other hosts. Damages caused by Lesser Bulb Fly: In certain environments, smaller bulb flies have affected up to 25% of some species of narcissus and 10% of hyacinths. The maggots tunnel in by scraping away the bulb tissue. Infested bulbs begin to rot, and their interiors fill with a semi-liquid substance. The bulb may be fully destroyed or damaged so that only stunted leaves emerge the next year. Life history and habits: Maggots spend the winter in the bulbs. The maggots migrate to the soil surface and pupate in the spring. In April and May, the first generation of flies emerges. The second generation appears midsummer, followed by a tiny third generation in late summer. Female lesser bulb flies descend along soil fissures and deposit eggs at, on, or under the dead skin that covers the bulbs. The maggots develop after approximately 30 days and pupate inside the final larval skin. Adult flies hatch from puparia. Some smaller bulb flies may live for up to 36 days if a nectar source is present and temperatures are not extreme.