52 The Business of Ontario Agriculture Better Farming | November 2024 crops: the lynch fileS FORAGE DISEASES, WEEDS, & MORE Threats & management strategies for forage health. By Patrick Lynch This past year, I saw many firsts in forage production. With the aid of cellphones, FaceTime, and photographs, I witnessed forage production issues from frozen alfalfa in Alberta to strange weeds in the Maritimes. These issues were brought forward by several forage seed dealers that I work with. I keep brief notes on all these calls. Here is a list of some of them. Diseases Stemphylium was a new disease to me in the field. There were significant acres with this disease in northern Ontario. The symptoms include light brown lesions with a dark brown border, which sometimes is surrounded by a light-yellow halo. It is a cool and wet season disease. Generally, it appears in first-cut. This year, it was not noticed until late August. It was probably present earlier but wasn’t noticed until later. There is no known variety resistance to it. Early harvest is the only option. I checked with BASF, and they have no research on the effectiveness of Priaxor in treating this disease. Common leaf spot was present in significant acres in Ontario in 2024. The wet weather favoured this disease. The fungus overwinters in undecomposed leaves and leaf debris on the soil surface. In the spring, spores are discharged into the air. With the right conditions, next spring, we will see it again. The BASF product Priaxor was the first fungicide to be registered in Ontario to control common leaf spot. Lance WDG and Acapela are also registered to control common leaf spot. As we continue to push for higher yields, there will be more use of fungicides on forages. There were a number of fields where crown rot was evident. This disease is caused by heavy equipment driving over the alfalfa crowns and damaging the crown. Older fields have plants with bigger crowns, so they are more prone to this disease. The solution is to keep your alfalfa fields down for a short period of time. We are not going to see a reduction in the amount of damage to alfalfa crowns caused by heavy equipment. Weeds This year was especially challenging for weed control in new seedings. I had one call from a grower who seeded and planned to do a glyphosate burndown, but he said the plants had emerged in three days. This was extremely quick because of the ideal growing conditions after planting. Another weed control issue included wanting to spray alfalfa after the fourth trifoliate. There were a lot of acres where, due to weather, the weeds did not get sprayed in time. I intercepted one farmer who was told that if he clipped the weeds, he could go back and spray 2,4-DB even though the alfalfa plants were well beyond the fourth trifoliate. This product, 2,4-DB, is sold as Embutox, Caliber 625, and Cobutox 625. If he had sprayed, he would have severely damaged the alfalfa. 2,4-DB is the butyric form of 2,4-D. Young alfalfa plants cannot change the butyric form to the amine form. Weeds can make this change and it kills them. As alfalfa plants get older, they, too, can change the butyric form to the amine form. Chickweed has become a major weed concern in parts of Ontario. It seems to be particularly bad on dairy farms in Oxford County. With this weed, you have to control it before planting. It is very sensitive to glyphosate. If you try to use tillage in the spring to control it, you end up just moving the plants around, and they start to grow again. Two solutions for farmers are: 1) plant HarvXtra alfalfa and spray Roundup after the weeds and alfalfa emerge and then plant grass, and 2) plant alfalfa in August. That time of year, you have lots of time to control chickweed before planting. Volunteer wheat in summer seedings of alfalfa planted after winter wheat was a problem again this year. When planting alfalfa after winter Crown rot seen in an alfalfa plant. Patrick Lynch photo
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