ERGOT reared its ugly black head this past season to haunt and plague wheat production in most areas of our province. Could all the crop residue that direct seeding accumulates on the soil surface have been a factor in unleashing this newest pestilence? The question being voiced is, "Should we encourage more tillage to help reduce the risk of another such infestation next year?"
To honestly answer this question you must first understand a bit more about ergot and the processes that caused all those toxic black bodies in many wheat samples. Ergot is not a new disease, it has in fact been around for hundreds perhaps even thousands of years. The black ergot bodies are produced by a fungus. It is this stage of the fungus that over winters and under wet soil conditions in the spring produces tiny mushroom like structures that produce spores. (There are similarities to the black sclerotia produced by the sclerotina stem rot of the canola pathogen that producers have become so familiar with in the last few years.) These spores infect the florets of grasses, winter cereals and early seeded crops. Within 5 days the florets produce a sticky ooze containing more spores which can be spread by insects, and rain splash to other florets. Eventually this ooze is replaced by the black ergot body where the seed would normally be.
The conditions that favor the ergot fungus are: wet soil conditions in the spring and early summer, wet conditions during grass and cereal flowering, and longer flowering periods. Wet, cool and cloudy weather can cause flowers to remain open longer and be more susceptible to infection. Poor fertility and or herbicide injury often keeps flowers open longer. Non-uniform cereal crops provide more hosts for the continuation of the oozing stage causing more spores to be released. Copper deficiency can also cause flowers to remain opener longer letting more spores enter.
Penny Pearse, plant disease specialist with Sask. Ag. & Food, says that this year has been one of those years when environmental and crop maturity conditions coincided to get wide spread ergot infestation. Besides the wet weather favoring the fungus it also favored the increase of small insect populations to spread these sticky spores. Weather played a much greater role in the ergot outbreak this year than all of the reduced tillage we have been practising. It has been many years since we have had such a major infestation. The risk of all these weather factors lining up so closely again next year is low. But still many of these ergot bodies now have ended up falling on the soil surface. What can we do to avoid the infestation they might cause next year?
Firstly, ergot bodies in contrast to the sclerotia bodies of sclerotina stem rot of canola survive in the soil for only 1year so rotating away from cereal crops for a year is very effective in reducing ergot production. The problem we could face next growing season if weather conditions favor spore production is the spores produced by these ergot bodies moving by wind onto adjacent cereal fields. Since part of the disease cycle often includes grasses a second method of reducing ergot infestation is mowing grass stands in ditches etc. next to susceptible crops before they head or flower.
Thirdly, do all you can to ensure uniform stands including using seed with high germination, seeding at consistent depths, high seeding rates, and using a balanced fertilizer program. If you have copper deficient soil the addition of copper will reduce ergot infestation. Copper deficiencies are most commonly found on light loam or sandy or peaty land.
Fourthly, if an infestation is observed at harvesting time, the highest levels of infestations are most likely to occur close to grassed areas so storing these areas of the field separately may reduce down grading on the rest of the production. Also leaving these areas standing as long as possible may increase the chance of wind shaking the ergot bodies out of the heads.
A fifth way to reduce ergot infestation is to bury ergot bodies 1.5 inches deep . This will keep spores from being released. This of course does not have very good fit with direct seeders. Pearse suggests that to produce spores these ergot bodies need wet soil and under a direct seeding system the bodies are so close to the surface that the chance of having sufficient moisture for spore release is less than if the bodies were buried at a shallow depth.
The general consensus among researchers on crop disease under direct seeding is that good rotations have a bigger impact on reducing disease than your tillage system whether it is a conventional system, a minimum tillage system, or zero till. Randy Kutcher plant pathologist with the Melfort Research Station concurs with this commenting that his observations on sclerotina in canola are that there was no statistical difference in occurrence of the disease under these tillage scenarios. He suggests that this may apply to ergot as well.
If you are direct seeding or contemplating beginning direct seeding following a good rotation and a balanced fertility program should be adequate protection against diseases.