Plant Doctor Archive

Narcissus fly attacks

COULD you please tell me how to combat the narcissus fly? Every year I lose some of my best hippeastrums to them.

SOME gardeners have lots of trouble with bulb flies, because once they're in your garden the cycle continues. As the foliage on your bulbs dies down, the female lays eggs on the leaf bases, on the neck of the bulb or in the soil nearby. The maggots hatch and burrow into the bulb, causing rot.

One control method is to make it difficult for the fly to lay its eggs on the bulb. As the leaves start dying back, cover the bulb with several centimetres of soil.

Commercial growers sometimes lift bulbs as soon as the leaves have died and submerge them in water at 43°C for three hours to kill eggs and larvae, but this is probably impractical at home. Alternatively, apply a soil insecticide such as Liquid Diazinon or Soil Insect Killer to the soil around the bulb as the leaves start dying down.

Reproduced with permission from the former Weekend Gardener magazine. The views expressed here are not necessarily those of the RNZIH.