In this section:
Frequently Asked Questions
Remember
Seed tests indicate the disease status of a seed-lot whilst antifungal seed treatments provide protection against fungal infection. Both seed testing and treatment are recommended in your integrated disease management strategy.
Seed test results - your questions answered
Disease outbreaks depend on the interaction of three factors:
- the pathogen (the fungus or bacteria which causes the disease) must be present;
- a susceptible host (eg crop plants);
- environmental conditions that encourage the disease to develop and spread.
The interaction between these three factors is often called the ‘disease triangle’.
Disease outbreaks require all of these factors to occur together. It is hard to accurately predict disease outbreaks as infection can come from several sources, eg seed, stubble and soil. This has resulted in growers questioning the validity of seed tests.
Q. I tested my seed. It was negative but I still saw some disease in the crop.
A. Seed tests help minimise the risk of disease outbreaks occurring from infected seed. But the test does not aim to achieve nil tolerance. Seed with a negative result can still carry a very low level of disease. Sowing tested seed minimises the risk of disease outbreaks but cannot eliminate this risk totally.
Other sources of infection are also important for many diseases including volunteers, crop residues and neighbouring crops. This is why seed tests are only one part of your overall disease management strategy.
Q. The seed test recommended that I should not use the seed. I sowed the seed anyway and I didn't see any disease. Was the seed test wrong?
A. The seed test was not wrong, rather you were lucky with the season. Seed tests assess the risk of outbreaks when conditions favour the disease, but weather conditions have a big impact on how much
disease will develop in a crop. In some seasons conditions do not favour disease outbreaks and even crops grown from infected seed will prosper.
Q. My crop was inspected and there was no disease. I had the seed tested and it was positive. Is the seed test too sensitive?
A. Seed tests measure the level of infection in the crop at harvest. Paddock inspections generally occur several weeks prior to this. When inspected, disease symptoms may not have been obvious, however, conditions before harvest may have encouraged the disease to develop.
The sensitivity of the test is set at a level that balances reasonable risk against cost and benefit.
