Growers have long used conventional chemistry to control key foliar diseases. But bio-fungicides are increasing and these use different strategies to help reduce pathogens.
And there are two particularly noteworthy methods: systemic acquired resistance (SAR); induced systemic resistance (ISR). But what are these and how can they help strengthen your integrated pest management (IPM) programme?
Making use of Darwin
Plants evolve ways to defend themselves against pathogens and growers can steal these evolutions to prime plants for resistance. Contact with pathogenic and non-pathogenic microorganisms triggers a wide range of defence mechanisms – both systemic and local to the plant.
The biological differences between SAR and ISR are down to the source of the trigger or attacking organism.
SAR is a virus-, fungi- or bacterial-activated defence characterised by a local increase in salicylic acid (SA) and the transcription of pathogenesis-related (PR) genes.
ISR uses jasmonic acid (JA) and ethylene (ET) mediated signalling to fire defence responses in distant tissue. In nature, this tends to be caused by rhizobacteria in the roots.
(There is a third systemic response from plants that chewing insects activate – but this is yet to be harnessed and used in plant protection in the UK.)
Vaccination, vaccination, vaccination
That may sound heavy on the science but the principle is powerful: using a plant’s natural defence is innovative and effective; it improves the overall efficacy of an integrated pest management programme.
The active ingredient within a product inducing SAR and ISR works like a vaccine – producing a physical and biochemical defence within the plant. Specific receptors recognise the ingredient on a plant cell (pathogen recognition receptors).
Once these bind, signals cascade through the cell, then from cell to cell, producing molecules such as SA, JA and ET.
At the genetic level, the signalling cascade fires defence genes that make pathogen recognition proteins and phenolic compounds with protective properties.
How to use SAR and ISR in your programme
These genetic-level changes prompt a wide range of physical alterations so the plant’s cells become stronger, creating a protective barrier alongside the phenolic compounds and PR proteins. This is useful in an IPM programme as they give a range of resistance to and protection from several diseases.
Think of it as having a plant that is now a semi-resistant variety. Now you can increase the time between applications of conventional chemistry, reduce the overall quantity of active ingredients applied and reduce residues in the crop. And it is just as effective.
Growers need to place products that use SAR and ISR responses carefully in a programme, alongside other control methods, for the greatest benefit.
The Fargro technical team can support growers upgrading their IPM programme through SAR and ISR products with advice and assistance. For more details about how to utilise SAR and ISR in your crops get in touch with the Fargro technical team.