It can be challenging to distinguish between species of morningglory, especially when small and in the cotyledon stage. Once true leaves emerge, it becomes easier. There are differences in herbicide effectiveness based on species. PPO-inhibiting herbicides (Ultra Blazer, Cobra, Storm) are effective on pitted morningglory but less so on entireleaf and ivyleaf morningglories. Control of tall morningglory seems to fall in between these. A major contributor is the pubescent nature of leaves (hairs.) This can affect coverage of the leaves by these contact herbicides.
In contrast, the herbicide 2,4-DB is more effective on tall/entireleaf/ivyleaf morningglories than it is on pitted morningglory. This herbicide essentially misses pitted morningglory.
Cadre/Impose performs the same on all species. Basagran does well across all species when weeds are small, as does paraquat.
In many fields, as we move through June, a mixture of PPO-inhibitors plus 2,4-DB will control the complex of morningglories present. Coverage with contact herbicides is critical.
Pitted morningglory (note the distinct cotyledons - other species have “blocky-shaped” cotyledons)
