ROTATION, ROTATION, ROTATION
It’s location that matters most in real estate, but for disease management it’s rotation that pays dividends. Well, that’s not entirely true; there are those pesky wind-and seed-borne diseases that could care less what crop was grown the year previously. But for diseases that live in the soil or on crop residue, a solid rotation timing interval of non-host crops is an integral part of disease avoidance and management.
Don’t take my word for it, take Faye Dokken-Bouchard’s. She’s the Saskatchewan Ministry of Agriculture’s plant-disease specialist, and she wants you to know that a tight rotation is nearly as bad as no rotation at all in some cases.
Let’s look at ascochyta of lentil. The recommendation is to have at least three and preferably four years in between lentil crops in order to whittle down the viable inoculum in the soil. Dokken-Bouchard says if you’re leaving one year in between, you may as well just grow lentil on lentil.
“A one-year break isn’t any better than no break at all.”
She adds that though they share a name, ascochyta of chickpea and ascochyta of field pea are different strains and therefore safe to grow in between lentil crops.
Beyond decreasing inoculum in the soil, ideal rotations extend the useful life of other forms of disease management. That means those resistant varieties we know and love and our handy fungicides will be effective much longer if other disease avoidance practices are employed.
Getting back to our discussion on ascochyta of lentil, Dokken-Bouchard notes that for years it wasn’t showing up in seed tests, but that changed last year (2009). “There was ascochyta detected on lentil seed last year, but no indications of a major outbreak,” she says.
That means the resistant varieties and fungicides did the job in 2009, but what if that seed is then planted in another field? Or if the field that seed came from produces another lentil crop this year? One prominent pulse breeder calls this “fungus breeding.” Over time, the disease will mutate to overcome the selection pressure we’re putting on it with fungicides and resistant varieties and could become a major threat once again. It’s that simple. Proper rotations are a must.
SEED TEST AND SCOUT
Germination tests are well and good, but if you’re spending the money on them, it’s not a bad idea to ask the lab to run disease and vigour tests as well. Lentil, and all pulses really, should have the full disease-spectrum test. If tests come back with a five per cent ascochyta infection rate, a seed treatment is recommended. If tests show a higher than 10 per cent infection rate, find a new seed source, Dokken-Bouchard says.
“Even with a resistant variety, higher levels of infection still pose a risk,” she says, not to mention that it’s never a good idea to knowingly seed disease spores.
Ascochyta is active early on in the season and affects yield right through flowering and podding, at which point it stops stealing yield and starts eating at quality. “If the weather favours disease development, you may end up spraying three times — once to protect the leaflets, later to protect the stems and then finally to protect the pods,” she says.
This wide window of attack means that scouting early and often with an eye to the weather is critical to managing the disease. With lentil, start scouting prior to flowering, at about the eight-to 10-node stage. Focus on the high-risk areas of the field, those with dense canopy, but try and keep your scouting random. Zigzagging is better than checking in straight lines. Scout high-risk fields first, and scout more often if weather favours disease development.
ATTACK OF THE SCLEROTIAEATING MONSTERS!
Let’s take a step back from ascochyta and talk about another nasty disease — sclerotinia. Not as economically significant in Saskatchewan, sclerotinia has become the bane of some Manitoba farmers’ existence. One major problem with sclerotinia is that it’s not terribly choosy about what plant it lives on and attacks. Several crops, including canola, sunflower, beans and peas, are susceptible to the disease. Unlike ascochyta strains that each attack only one to a few crops, the sclerotinia strain is the same for all. That doesn’t make rotating away from a host crop all that easy.
It’s this lack of choosiness that has essentially removed certain crops as options for some Manitoba growers. In the case of sunflowers, there aren’t any really great control products for head rot (caused by sclerotinia) and that makes an infested field off limits, sometimes indefinitely.
That may have been so, until now.
As editor of Grainews I get to meet some pretty neat people and also get a sneak peek at what’s coming down the pipe in terms of new products. Late last month I was invited to chat with Garth Render with UAP Canada about its new product, Contans. This product is what I’m going to call a next-generation pesticide. It’s actually a fungus, one that loves to chow down on sclerotia (the overwintering stage of sclerotinia. Sclerotia go on to cause infection later in the season). The Contans active ingredient occurs naturally in the soil, just not at levels high enough to make much of a difference in our monoculture, tight rotation production system.
This product is a bit different in several ways. It’s a fungus, is up for organic approval (but as of press time, that wasn’t set in stone) but it’s being sold to very conventional farmers. And seeing as it’s not a chemical, Contans provides a whole new mode of action and one more pesticide rotation option.
But the differences don’t stop there. Contans is alive and therefore must be handled with care. Similar to inoculants, but perhaps a bit higher maintenance, Contans will need to be kept cool and used relatively quickly.
What impressed me the most, and what might be difficult for some to wrap their heads around, is that this product actually kills off the sclerotia. It will literally sanitize a field if applied in enough quantity and given enough time to work. There’s the key word — time. While Contans seems effective, the fungus goes dormant outside of 5 C and 30 C, and needs roughly 90 days to knock back the sclerotia bodies where it’s applied. Those farmers looking for a fix this spring should think ahead — an application now or in the fall on wheat fields means a cleaner field for canola next year.
Contans isn’t a fix-all product, nor is it cheap, but it does appear to be very effective and could mean the difference between losing rotation options and preserving them. And who doesn’t like diversification?
IN THIS ISSUE
This issue of Grainews is not only focused on disease management, but also on the ever-expanding world of precision agriculture.
Scott Garvey has done a bang-up job of scoping out if buying a used GPS system is worth it (page 17), how to connect all your farm GPS units and data using a cellular network (page 12) and what you need to know about implement guidance (page 15).
Warren Bills answers your toughest precision-farming questions on page 14, including what the pros and cons are of satellite and airplane imagery for use in precision applications.
I managed to find time to write an article bridging both themes: using precision equipment to vary fungicide rates (page 16). Bobbie Bratrud offers a reason for stagnant flax yields (hint: pasmo) on page 11, and Gerald Pilger gives us the rundown on fusarium head blight in Alberta and a wheat variety that may help in the fight against this disease and quality robber.
WHEAT AND CHAFF ONLINE
For all you Internet-savvy folks out there, my webmaster-type people tell me that my blog is up and running on the Grainews website. Given that we’re heading into the busy season for you and the not-so-busy season for me, I’m hoping to use the blog as a means of quickly sharing the neat stuff I come across at all the crop tours and field days I’ll be at.
The blog, a virtual edition of Wheat and Chaff, is another place to share ideas, ask for solutions to problems or for me to post new product announcements and that sort of thing. If you’ve got a spare second in the next while (I know, I know, I won’t hold my breath), check it out at http://bloggn.grainews.ca/lyndsey.You should be able to access it from the main site as well, at www.grainews.ca.
Well, that’s it for the month of April. Those of you who didn’t start two weeks early (or who had a more average spring) will be rolling out the seeding equipment any day now. Remember to stay safe, rest when you can, seed for target plant populations not just by pounds or bushels per acre and, especially in canola, slow it down a little. Cheers!
Lyndsey Smith Editor, Grainews