Weather could increase risk from seed-borne diseases, says NIAB

Seed-borne diseases in untreated wheat, oilseed rape and field beans could be more troublesome than usual next season after wet spells at critical times this year, says NIAB.

So seed health tests will be vital, reckons pathologist Jane Thomas.

“The results enable growers to know whether the seed is suitable for use and whether it’s healthy enough to go in the ground.” In some cases, particularly with farm-saved seed, the results help to make informed decisions on seed treatments, she says.

In wheat, earlier conditions favoured Microdochium nivale, which causes seedling blight.

“I think it’s going to be important this year for farmers to get their seed tested to see how high the levels of microdochium are,” says Dr Thomas. “The good news is that it is quite easy to control with seed treatment.

“If levels are above 10% infection, then treatment really does need to be applied.” Very high levels, say 70-80%, are probably best shunned for seed.

It is important to check for bunt and essential if sowing untreated seed in organic systems, she adds.

Recent warm humid weather may have encouraged alternaria in oilseed rape. Purplish-brown spots developing rapidly on the pods could mean seed will have been infected, and badly affected seed may not emerge, warns Dr Thomas.

With the field bean area expected to rise, all growers should be on their guard against seed-borne stem nematodes and ascochyta disease.

“If growers plan to save field bean seed this year, it is really important that they get them tested for stem nematode. We have had several reports of infestations in the field this year, and those infestations will get on the seed. If infected seed is sown again, problems with the crop are highly likely.”