PEST

NAME
Lesser Bulb Fly
Eumerus tuberculatus

ORDER
Diptera

Description of the Pest
The small blackish green adult fly grows to 8mm long with white markings on the body and thorax. The eggs are laid in the neck or damaged areas of the bulb or in the adjoining soil, and a single bulb may contain up to twenty larva. The plump larva is a clear yellowish colour up to 7mm long with two small wart-like growths on both sides and a horny out growth on its bottom. The young larvae travel inside the scales then tunnel into the bulb.

The Greater Bulb Fly(Eumerus tuberculatus) adult has a bumblebee-like appearance and lays eggs on the leaves and the neck of the bulb. There are usually only one or two larvae that infest the bulb. Both of these flies are of European origin and were introduced into North America and Australia.

     

Life Cycle
These insects have a Holometabolouslife cycle, ie. When metamorphosisis observed during the pupalstage.

Period of Activity
Normally the adult female fly lays the eggs after the foliage has died down, revealing the neck of the bulb. This usually occurs late in the season.

Damage Caused
The bulbs are eaten out by the larvae causing rot and may be difficult to detect, until the bulb is cut open. On inspection the larvae tend to congregate towards the top of the bulb, but the whole bulb appears to be damaged. Bulbs that are infested grow poorly and generally fail to flower. The tunnels that are made by the larvae allow fungal and bacterial infections to enter the bulb causing a secondary problem.

Larvae

Susceptible Plants
Bulbous plants such as Narcissusspecies, Daffodil are most susceptible but Jonquil; Hyacinthusand Amaryllisspecies are attacked.

Cultural Control
Bulbs should be covered with a layer of soil as the foliage dies off to prevent the fly having access. Suspect bulbs may be lifted and heat treated at 43şC for three to four hours to kill the larva.

BiologicalControl
No known biological control.

Chemical Control
No satisfactory chemical control.