Arable

Fusarium fears make home-saved seed testing vital

Wednesday 22 August 2012 11:16
Sowing wheat

Testing and treating home-saved seed may prove crucial this autumn, as high incidence of fusarium ear blight increases the risk of seedling blight, while a prolonged wet harvest could hit germination levels.

Therefore, some form of testing makes perfect sense and this coming season could be one where growers who historically don't use a treatment reconsider their policy. "Seed treatments are a good insurance policy, offering good value and a high level of protection," says Harper Adams University College plant pathologist Simon Edwards.

"In general, Barley is less affected by fusarium and germination tends not to suffer," adds Gordon Bristow, chief analyst at testing firm Seedlab 100. "However, for anyone home-saving seed this season, I recommend carrying out a germination test, even for barley."

This view is mirrored by Jane Thomas, head of pathology at NIAB TAG. "Oats and barley are not immune from fusarium and michrodochium, but the risk from serious infection is higher in wheat.

"Getting seed stock tested is important and most seed will need treating this autumn. This will be difficult for organic farmers and growers who historically use untreated seed. For these growers, seed testing is a must so that levels of infection can be determined," says Dr Thomas.

"For those who are home-saving seed, cleaning can significantly reduce the level of infected grains in the sample. Removing all the small, pink and shrivelled grains will reduce the percentage of infected grains, as these grains are likely to have the highest level of infection," adds Dr Thomas.

Jon Tisdall, managing director of CYO Seeds, agrees. "Produce as bold a sample of seed as possible, shrivelled grains will have highest incidence of disease. With home-saved seed, growers have full control over the cleaning process and using gravity separators will enhance the sample.

"If you don't clean and treat seed properly, michodorium nivale and F graminearum can cause seedling blight and reduce plant populations. Later-sown crops planted in cooler conditions are most at risk," adds Dr Thomas.

What tests?

"If you are a grower who cannot or chooses not to sow treated seed, a disease test will at least confirm what you are dealing with. You can do an agar test to identify which strains of diseases are present, including fusarium, seed blight, and septoria. If less than 10% of the seed is infected you can use the seed untreated."

Germination tests are a good measure of seed quality. A sample of 200 seeds is germinated under optimum conditions to establish a germination rate. The main drawback is it takes about one week to carry out the test in cereals and up to four weeks in some grasses.

"If you can't wait 7-10 days for a germination test, you could consider using a tetrazolium test. Here seed is tested in tetrazolium solution to identify which seeds are alive and capable of germination under ideal conditions."

The tetrazolium test is effective at establishing whether seed samples have been affected during the drying process, reducing seed viability. Heat damage can occur over time making it difficult to gain an accurate picture.

Seed vigour testing can provide a picture of the likely germination rate the grower will experience in the field. Vigour testing mimics poor conditions enabling growers to see how seed will perform under less than ideal conditions.

Once tests have established the diseases and the level of infection, growers need to select the product that suits their needs. Most treatments have penetrative and systemic modes of action to control soil and seed-borne diseases.

"In trials work we found a range of general purpose seed treatments to be effective against fusarium and microdochium, with Beret Gold (fludioxonil) showing the best all round performance. But, users should check product labels as not all treatments are effective against both pathogens." Other options include Redigo Deter (clothianidin) and Kinto (prochloraz and triticonazole).

Sowing top tips: 
Simon Edwards, Harper Adams University College professor of plant pathology, offers his top tips for sowing:
  • Growers planning on sowing untreated seed should have a germination and disease test to establish risks
  • Clean seed to extract shrivelled and infected grains and produce a bold sample
  • Both cleaning and seed treatments have the ability to elevate germination results significantly
  • Seed treatments will control seed and soil-borne diseases
  • Avoid poor seed-bed conditions when using highly infected seed
  • Crops can compensate for poor emergence by increased tillering. A 50% reduction in emergence will often have no yield loss at harvest

 

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