An EFAO member called the office last week to see if staff could recommend someone who might have some insight to the causes and solutions for rust on wheat? Apparently this has become an issue for organic growers in Southwestern Ontario. Any information or contact info for someone who might be able to help out would be greatly appreciated!
I’ve never tried to control it before as I never grew wheat on a very large scale. It’s so weather dependent since Wheat Rust is fungal in nature, so wet and warm weather will help it establish, and wind will help it proliferate (through airborne spores) across the field. The only thing I can suggest is to make sure to use rust-resistant varieties of wheat, and maybe make sure you have a good windbreak to limit the spread. Apart from that, I’m not sure if there is an organic-approved fungicide that could be applied, if you would even want to do that in the first place (because who wants to revert to using fungicides in ecological farming, certified or otherwise?!), but that could be worth looking into.
OMAFRA has a bit of info on this as well:
http://www.omafra.gov.on.ca/english/crops/pub811/14cereal.htm
There’s some research to suggest that adequate levels of copper and plant-available silicon in the soil can help prevent fungal diseases like rust in cereal crops. As Denis pointed out, there’s a genetic component to resistance too. Remember that rust will impact the photosynthetic capacity of the plant, limiting growth and yield, but it won’t have a direct impact on grain quality (unlike fusarium).
One potential solution is a copper sulfate spray, but it is much more effective as a preventative or early treatment option. Copper sulfate is pretty acidic, so it will burn leaves, especially in warmer weather. The usual recommendation is to apply it as “Bordeaux mixture”, which reduces (but doesn’t eliminate) the phyto-toxicity. Here are details from OMAFRA (for apple orchards):
“When preparing Bordeaux mixture, dissolve 1kg of copper sulfate in 1000 L water in the spray tank following label directions. Turn on the mechanical agitator. Premix the hydrated spray lime in a bucket with enough water to make a slurry and pour the lime slurry through a 0.3 mm screen into the spray tank. Mix the lime and copper sulfate for about 15 minutes before spraying, and keep the agitator running while spraying. The objective is to make a 1:6:1000 Bordeaux mixture (1kg of copper sulfate: 6 kg hydrated lime: 1000 liters of water) and apply as a dilute spray at a rate of 3000 L/ha. Do not use as a concentrate.”
Organic growers are also required to monitor copper levels in the soil to prevent excess copper accumulation, so anybody interested in doing this had best have a conversation with their certification body in advance. Copper sulfate is also highly-toxic in its raw form, so if you’re handling it, either as a soil amendment or as a fungicide, pay very close attention to the handling instructions.
Some Ontario growers are experimenting with EcoTea Foliar, a liquid biological amendment designed to colonize the leaf surface with plant-beneficial microbes that out-compete pathogens for space and resources, induce the plant’s own defense mechanisms, and can have a direct impact on disease-causing organisms. One farmer noted a significant difference in the incidence and development of rust in wheat fields that received a foliar application in late May versus those that were left untreated. This was well before rust started appearing, which is really the ideal time. Other farmers tried spraying EcoTea once rust appeared, hoping to limit its spread and provide additional support to the effected plants - we may have to wait until harvest to determine if this approach had a positive impact.
Great input @rob!
You’re making me wonder if, under organic/ecological methods, a whey-based spray would be helpful as used by some organic apple orchards to combat fungal diseases (like scab). I believe the principle is to essentially promote the colonization of the surface of the leaves/fruit with beneficial fungi before harmful fungi have a chance to establish. The result is that once the harmful fungi come in to try and establish themselves, the “space” has already been taken by the beneficial fungi. Food for thought!
I don’t see any rust on my wheat field. I sprayed a mixture of “sillica” and molasses and have great luck with it. Most of my neighbors have major rust problems.
Cheers Bernd