Bean nematode brings big headaches

29 May 1998




Bean nematode brings big headaches

BEAN stem nematode is causing crop problems across the country, prompting a rethink of rotations and seed sources.

In a normal year, PGRO plant pathologist Anthony Biddle expects to see only one case of stem nematode damage. This year he has seen seven in three weeks.

One grower affected is Jeff Elston who manages 930ha (2,300 acres) at Gidding and Upton Farms near Huntingdon, Cambs. He first spotted problems with the late-October planted Punch in early February.

"Most plants were 15-20cm or 6-8in tall. But patches of stunting started to appear. We noticed stem lesions and sent samples to PGRO to confirm what we thought was ascochyta. Only then did we find it was stem nematode."

Some plants have grown away from the damage. But others have died completely, leaving open patches in the crop. A 4t/ha (32 cwt/acre) crop will be a good result, says Mr Elston. Average bean yield on the farm is 5t/ha (40 cwt/acre).

Source of infestation is not clear. Mr Biddle says initial infestation is usually seed borne, but the pest survives in the soil for over five years.

The affected field at Gidding and Upton Farms last grew beans four years ago. Seed was bought from Dalton Seeds at Eye. "Im not sure if the seed was nematode tested, but well make sure it is in future", says Mr Elston.

Tony Dalton of Dalton Seeds says every seed lot is tested for nematodes. "But not all companies do this by any means – it is not a certification requirement," he points out. If growers are home-saving he suggests seed should be nematode and ascochyta tested, a point echoed by Mr Biddle.

Beans ruled out

Once fields are infested beans are ruled out of the rotation. "We recommend at least a ten year break following infestation," says Mr Biddle.

Both spring and winter beans are affected and other hosts include bulbs, strawberries, dead nettles and oats.

Growers are urged to check crops for damage. If nematode is suspected send plant samples to the PGRO for checking, says Mr Biddle. "Early identification is of prime importance so growers dont plant seed and spread the problem around the whole farm," he advises. PGRO services are free to levy payers.

Stem nematode symptoms

Stunted plants

Wavy/distorted stems

Twisting and swelling usually at top of plant

Fleshy distorted leaves

STEMNEMATODE SIGNS

&#8226 Stunted plants.

&#8226 Wavy/distorted stems.

&#8226 Twisting and swelling usually at top of plant.

&#8226 Fleshy distorted leaves.

Bean nematode has hit Punch winter beans hard on Jeff Elstons Huntingdon farm. Growers are urged to check for symptoms (inset) and to consider routine seed testing.


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