Stem nematode – Dictylenchus dipsaci
Stem nematode lives in the plant tissue and can withstand severe desiccation, being, dispersed with dried seeds from one site to another. It also lives in the soil and can survive several years without a host crop. Hosts include beans and oats but will also infect sugar beet, peas, maize, strawberries and many weeds.

Infected plants become swollen or distorted, later becoming dark brown in colour. This dark colouration usually starts at the stem base and stops at a leaf node. Infestations in the podding area result in infested seed. Heavily infested seeds have a blemished, darkened and cracked seed coat. One seed can carry 10 000 nematodes and is capable of infested clean soil.

A seed test exists for stem nematode. Results are indicated as either present or absent although more detailed scoring is available from PGRO and NIAB. Uninfected land should not be planted with seed at any level of infection. Where infection has been present in the past, low scores can be planted whilst moderate scores are fine if pulses or oats will not be planted in the same field for four years. High counts (equivalent to 3% in the PGRO test) should not be planted.

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