Mark VanGessel, Extension Weed Specialist; mjv@udel.edu
Weed emergence has begun, with seedlings from many species already up. A 4-year study in Georgetown DE, has demonstrated giant foxtail, common ragweed, and common lambsquarters are consistently the first species to begin emerging. Historically, at least 25% of the seedlings from these species will emerge by May 5. On the other hand, pigweed species (including Palmer amaranth), morningglory, and common cocklebur do not start emerging until the soils are warmer. Historically by May 5, less than 5% of their seedlings will emerge.
Fields with glyphosate-resistant common ragweed need to include herbicides that will provide effective burndown control.