When leafy spurge's yellow flowers begin to bloom, landowners can evaluate the effectiveness of their control program, says Paul Johnson, SDSU Extension agronomy field specialist.
Johnson said the only way to get spurge under control is “to be on it every year and get the root reserves depleted so the plants will start to die.”
"A cold winter helps to take out the spurge when the root reserves have been depleted," Johnson said. "As soon as the yellow flowers are out it is time to start spraying."
Johnson says the control window is only about one month before there will be viable seed in the plant.
"If you also have thistles in with the spurge you may want to wait a little until thistles are at bud to make sure you get good coverage and control on both of the weeds," he said.
But again, Johnson says be careful not to wait too long.
"Waiting too long only allows the root reserves to build back up in the plant, and then you will not make any progress on getting rid of the plants. Instead, they will come back stronger than ever," he said.
Based on SDSU test plots in Moody County a new compound called Perspective looks like it should be as good as Tordon in controlling leafy spurge, but Johnson says this compound has fewer use-restrictions; and it is more environmentally friendly.
"It should be able to be used in more areas that have a shallow ground water problem," he said. "This is the first new product that has effect on thistles and spurge that has been developed in the last 40 years."
At present, Perspective is not labeled on any areas that are cropped or hayed, Johnson says until more labeling is done, it will be limited on where it can be used. Also some grass injury will need to be tolerated with its use.
"Usually the grass will recover the next year," he said. "And, I always want readers to know that use of the product's names does not imply endorsement. Information is based on SDSU research and observations."
Before use, landowners need to verify information on current product labels prior to application.