Grainswest - Winter 2024

Winter 2024 grainswest.com 39 Menzies does encounter reports of fields that have 25 to 35 per cent loss due to smut. The visual clues are often not spotted until it’s too late. As well, because there are multiple types of smut, it’s important to note which type you’re dealing with in a field (see sidebar). Smut does not drastically affect or delay crop growth, so it is near impossible to detect until late anthesis. “During late anthesis, go and walk through the field, if you have smut you’ll see it,” he said. If present, grain heads will be replaced with masses of black teliospores. Walking through an infected field, these will blacken one’s pants. To calculate the loss is quite simple, as well. The infection rate typically equals yield loss. Twenty per cent infection? Twenty per cent yield loss. If your grain is substantially downgraded or outright rejected by an elevator, it can be sold as animal feed. Livestock can process smutted grain with minimal to zero associated health risks, said Menzies. Fortunately, smut is easier to manage than other fungal diseases. Smut seed treatment fungicides are readily available to farmers, noted Menzies. Though outbreaks can have a frightening appearance, he added, the appearance is almost always worse than the actual infection rate. He has inspected fields that at first glance appear to be 90 per cent infected but turn out to be just 10 to 35 per cent affected. To determine the level of infection, Menzies advises you check three or four areas in a given field. Construct a square metre with rope or PVC pipe and get to work. Count 1,000 or 2,000 heads. “While you’re counting, keep track of the number of those heads that are smutted, and that will give you your level of infection.” Twenty smutted heads, or two per cent, is a bad number, but one in a thousand, would be deemed trace level infection. The three chemistries typically used against smut are difenoconazole, carbithiin and triazoles. Perhaps the most used fungicide is Group 7 product carboxin, which has high efficacy. There are documented cases of fungicide tolerance or resistance to this product in smut, though. Despite this, Menzies said it remains a very good option and resistance cases are minimal. He does remind farmers to rotate fungicide modes of action when possible and apply only when necessary. If you skip the application of a $200 per acre fungicide seed treatment because you’re only losing $100 per acre by the smut, he said, you’re still ahead $100. In addition to seed treatments, farmers can guarantee a quality product by purchasing certified seed, which is tested for smut. “Really, the problem usually arises because farmers use their own seed to re-seed,” he said. “If you’re going to do that, you have to monitor your crop the year before.” This will eliminate a surprise occurrence of smut. “If you have high levels of smut, you probably shouldn’t use that crop, or you should use a fungicide seed treatment on that seed. Re-using seed is probably the number 1 culprit for having smut issues. It just gradually builds up.” WHICH TYPE OF SMUT DO YOU HAVE? Prairie farmers must be mindful of six smut types CORN: Large growths, or galls, form from the inside out of a mature ear of corn. The discoloration is often bluish-blackish, sometimes with a burnt appearance. In certain countries such as Mexico, smutted corn is a delicacy and contains more protein than non-infected cobs. WHEAT: Loose smut infects wheat plants during flowering. Infection can be transmitted by insects, rain droplets or wind. As the disease matures, infected plant heads blacken. Spores blow away or fall off and grain is left headless. BARLEY, TRUE LOOSE SMUT: Similar to wheat, brown or black heads replace healthy grain kernels. True loose smut does not affect a barley plant’s ability to germinate. Typically, flowering spikes are not visible once they’ve been replaced with fungal spike spores. These will rub off on your pants during in-field scouting. BARLEY, FALSE LOOSE SMUT: Typically visible at the heading stage, this smut is characterized by dusty, black-brown heads. Largely identical in appearance to true loose smut, under a microscope, its unique teliospores are oblong. COVERED SMUT IN OAT, BARLEY AND RYE: Covered smut on all three cereals typically emerges as hard, dark brown or black galls. They can be covered in a white-grey outer shell, which differs from other smut types. These galls stay on the plant longer than other types.