Early seedling management of Roundup Ready alfalfa is somewhat different than with regular alfalfa. In particular, it is important to spray Roundup Ready alfalfa when it reaches the third or fourth trifoliate leaf stage, regardless of whether weeds are a problem.
Of course, it makes sense to spray if you have weeds.— eliminating competition will help establish thicker, more productive stands more rapidly — but why spray if weeds are not a problem? Management of alfalfa varieties with Roundup Ready is different than management with Roundup Ready corn and soybeans. Not all RR alfalfa seedlings will be resistant to Roundup. For most varieties, about 5% of the seedlings will be susceptible to the herbicide. To avoid future problems with these plants dying after Roundup application, eliminate them while all plants are still very young.
During the seeding year, alfalfa stands naturally thin as more vigorous plants out-compete smaller plants. Surviving plants fill the gaps and become even more productive as competition is reduced. By removing Roundup susceptible plants as seedlings, the gaps will be filled easily by remaining Roundup resistant plants. If you wait until the stand is well established before making your first Roundup application, the gaps may not be as easily filled.
Bruce Anderson
Extension Forage Specialist
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