Redtop
(Agrostis gigantea Roth)

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Table of Contents

1. History
2. Life Cycle
3. Distinguishing Characteristics
4. Control in Corn
5. Control in Soybeans
6. Control in Winter Wheat

History

A member of the grass family. Not a particularly common weed in Ontario, but is quite competitive because of its perennial nature when established in field crops.

Life Cycle

Perennial, reproduces by horizontal underground stems (rhizomes) and by seed.

Distinguishing Characteristics

Usually grows in clumps with thick white rhizomes that are shallowly buried in the soil. Unlike quackgrass, redtop does not have auricles. The ligule is membraneous. When redtop starts flowering, the inflorescence (flowerhead) is green, but gradually spreads out and takes on a reddish tinge that gives red top its namesake.

Redtop Pictures
Each thumbnail image links to a larger image

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Herbicide Control in Field Corn

Post Emergent Control

Any of the post-emergent group II grass herbicides will provide good control of redtop in field corn.

 

Table 1. Redtop control in corn with post-emergent herbicides.

Active Ingredient	Trade Name	% Control
foramsulfuron	OPTION 35 DF	98
nicosulfuron/rimsulfuron	ULTIM	97
nicosulfuron + primisulfuron/dicamba	SUMMIT EXTRA	91
nicosulfuron	ACCENT	89
primisulfuron/dicamba	SUMMIT	76

Source:

Dr. Peter Sikkema, Ridgetown College, University of Guelph.

Number of Trials:

Table 1 is based on 1 field trial in Ontario.

Herbicide Rates:

Rates used in this trial are listed in OMAF Publication 75 - Guide to Weed Control.

Weed Stage:

Redtop had 1 to 5 leaves (5 to 30 cm in height) at the time of application.

What has been your experience?

We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

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Herbicide Control in Soybeans

Post-Emergent Control in Soybean

Glyphosate applied post-emergent to "Roundup Ready" soybeans provides the best control of redtop. If growing conventional soybeans, Venture or Select provides supression of redtop (Table 1).

Table 1. Redtop control in soybean with post-emergent herbicides.

Active Ingredient	Trade Name	% Control
glyphosate	glyphosate	93
clethodim	SELECT	75
fluazifop-p-butyl	VENTURE L	75
sethoxydim	POAST ULTRA	68
quizalofop-p-butyl	ASSURE II	63
fenoxaprop-p-ethyl	EXCEL SUPER	13

Source:

Dr. Peter Sikkema, University of Guelph.

Number of Trials:

Table 1 is based on 1 field trial in Ontario.

Herbicide Rates:

Rates used in this trial are listed in OMAF Publication 75 - Guide to Weed Control.

Weed Stage:

Red Top had 3 to 8 leaves (5 to 60 cm in height) at the time of application.

What has been your experience?

We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

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Herbicide Control in Winter Wheat

No field trials have evaluated redtop control in winter or spring cereals.

What has been your experience?
We want your feedback. Let us know what you have experienced with these or other products, as well as any other effective management strategies.

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