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It is better to be a month early when applying preemergence herbicides for summer
annual grass control than it is to be a day late. They have begun to emerge so don’t
wait. It is important to know which grass(s) that you have but that is not possible
without prior knowledge when making preemergence applications. There are more than
25 annual grass species that are found here during the summer although only about
10 are common. Most of these look very similar at early growth stages and identification
can be difficult. There is a tendency to lump them all together and call them water
grass, jungle rice barnyard grass or several other names. There are differences
between them, however, and it is important to accurately identify them at early
growth stages. This is important because many of them respond differently to herbicides
and have different growth habits. For example, sprangletop is only controlled by
the highest rates of Select (clethodim) and generics of this herbicide and missed
by all of the other selective postemergence herbicides like Poast and Fusilade and
sandbur is tolerant to all of them. By the same token, sandbur and sprangletop can
over winter, come back from crowns and not be controlled by preemergence herbicides
applied in the spring while most other summer annual grasses die in the winter and
the seed can be controlled with herbicides in the spring. There are just 6 genera
and 12 species of summer annual grass that are common here. These include echinochloa
(water grass and barnyard grass), leptochloa (red sprangletop and mexican sprangletop),
eriochloa (southwestern cupgrass and prarie cupgrass), cenchrus (field sandbur and
red sandbur), setaria (green foxtail and yellow foxtail), and chloris (feather finger
grass and truncate finger grass). A power point presentation can be found by clicking
on
Summer Annual Grass ID which contains pictures and descriptive characterics
of each of these species.
To contact Barry Tickes go to: btickes@ag.arizona.edu.
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For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
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