One elicitor-based fungicide that has achieved full registration as a pesticide is UPL’s Iodus, which is currently registered for use in winter wheat.
The product contains the active laminarin which is extracted from seaweed but behaves differently to seaweed extracts typically found in biostimulants, says Greg Hanna, technical specialist and trials manager for UPL. This molecule tricks plants into thinking they are already under attack from disease.
Mr Hanna says: “Normally when a plant comes under attack from a pathogen it will take around 48 hours to mount its natural defence processes.
“Using laminarin ahead of disease transmission, you’re telling the plant to arm its defences before a pathogen attack so you don’t have that 48-hour window where the pathogen can get in without too much resistance from the crop.”
Laminarin is said to offer multiple lines of defence – it signals for increased lignification to create a thicker cell wall that is harder for the pathogen to penetrate. Secondly, it promotes the release of phytoalexins and proteins produced by the plant that attack a fungal pathogen. If present in good numbers, these will fight back and cut down on the pathogen’s ability to create a reservoir of infection in the crop, says UPL.
“Phytoalexins can almost be thought of as a multisite response because they will bind at different sites on a pathogen and interact in a number of ways. We’ve seen good data on reducing the rates of other chemistry and getting a good return on investment and strengthening some of the chemistry under pressure.”
Iodus is best used in a preventative scenario and is positioned to be sprayed at T0. Although only leaf 4 is present as an immediate target, the flag leaf and leaf 2 are bound within the stem but not yet visible, making it a good point to prime the plant, says Mr Hanna.
“You’ve got all the structures and organs that the plant’s going to need going forward.
“Because laminarin triggers systemic resistance, you’re not just priming the cells you hit with the spray, the reaction is cascaded through all cells and plants and the whole plant is switched on in terms of defence. You’ve effectively protected leaf 1, 2 and 3 before they were ever vulnerable to pathogen attack.”
Whether the product needs to be applied alongside other fungicides will depend on the target disease and how high pressure the scenario.
Unlike some biofungicides, elicitors can generally be tank mixed with other products because they are less susceptible to damage from chemistry, says Mr Hanna.
“We’ve seen Iodus perform well with other fungicides, but it depends on the pathogen you’re going after. For septoria, it performs very well on its own. However, for yellow rust we see a bit of efficacy, but not at a level that could be relied upon, so that’s where we’d suggest mixing with a triazole or a strobilurin.”
Laminarin’s mode of action has potential against a number of diseases and can trigger elicitation in a wide range of crops. Registration trials for further arable crops are ongoing.