DISEASE

NAME
Bulb and Stem Nematode
Ditylenchus dispaci



Description
Pathogenic, there are different forms of this nematode with some only attacking foliage and others attacking the bulb. They are very small and not normally seen with the naked eye. Generally they are up to 3mm long and are 'eel-like` in shape with an unsegmented body with no legs or appendages.

Symptoms
The bulbs are attacked by nematodes that feed on the fleshy scales and may be seen as rotten rings when a cross section cut is taken at the neck, or as strips if cut longitudinally. The emerging foliage is distorted, twisted or thickened and in some cases with seedlings the foliage fails to appear. Established plants that become infected develop spongy brown areas on the bulb and the leaf or flower develops pale streaks causing the epidermal layer to blister or split.

     
Image by B. Sonsie

Source and Dispersal
Nematodes are dispersed physical means such as; planting infested bulbs, transfer or planting into infested soil and pieces of infested plant material being moved in or out of the garden. They infest a plant by moving within water along the leaf and entering through the stomate then travelling down to the bulb. In soil they move in a film of water between soil particles using special muscles in there elongated bodies.

Favoured Conditions
They prefer moist conditions and in warm climates they are found throughout the year.

Affected Plants
Many plants are attacked these include; Daffodils, Jonquils, Hyacinths and Onions. They also are found in beans, peas, lucerne, clover, oats and strawberries.

Non-chemical Control
Remove and destroy any badly infested bulbs or foliage and do not replant into infested soil. Infested bulbs may be lifted and stored in a cool dry place for several weeks then immersed in hot water 45 şC for up to 4 hours, then allowed to dry out. Implement crop rotation in infested soils using non-susceptible plants such as beetroot, cauliflowers, lettuce and spinach.

Chemical Control
The soil can be treated by watering in granules of fenamiphos.
Note
Always read the label for registration details and direction of use prior to application of any chemicals.