May 18, 2007

With wet spring conditions in many parts of Nebraska, producers may be pressed to adjust their intended herbicide program. Each year questions arise on the limits of using preemergence herbicides on emerged corn. In 2006, Alex Martin assembled a table of these products, which we have updated for this year.Table 1lists a number of commonly used premergence herbicides labeled for broadcast application after corn emergence, along with crop and weed stage or height information. This list is not comprehensive. If your herbicide choice is not listed inTable 1, check the label for use restrictions.

If the product you are using contains atrazine, adding a crop oil concentrate can enhance control. Atrazine is primarily translocated upward in the plant (xylem mobile). When a foliar application is made, atrazine behaves more like a contact herbicide.

If you planted glyphosate-resistant corn, tank mixing glyphosate with one of the preemergence herbicides will improve total weed control, especially if weeds are larger than you had anticipated. If you tank mix glyphosate with a preemergence product in this situation, adding 17 lbs/100 gallons of AMS will improve its performance. The same will apply to tank mixing Liberty on Liberty Link corn varieties, however, you will want to use 3 lb/ac AMS (1.5 lb/ac if tank mixing with Lumax or Lexar).

Remember, applying preemergence herbicides with a liquid nitrogen carrier is not advised. Unacceptable crop injury will occur.

Lowell Sandell
Extension Educator, Weed Science, Lincoln

Table 1. Preemergence herbicides that can be applied postemergence in corn.
Herbicide		Active Ingredient(s)	Crop Stage		Weed Stage
	Aatrex/atrazine	Atrazine	0-12"		1.5" G
	Bicep II Magnum/Cinch ATZ	S-metolachlor, atrazine	0-5"		2-leaf G&B
	Bicep II Lite Magnum/Cinch ATZ Lite	S-metolachlor, atrazine	0-5"		2-leaf G&B
	Bicep II Magnum FC	S-metolachlor, atrazine	0-5"		2-leaf G&B
	Bullet	Alachlor, atrazine	0-5"		2-leaf G&B
	Callisto1	Mesotrione	0-30"		0-5" B
	Camix1	S-metolachlor, mesotrione	0-12"		0-3" B
	Degree	Acetochlor	0-11"		unemerged
	Degree Xtra	Acetochlor, atrazine	0-11"		2-leaf G&B
	Dual Magnum	S-metolachlor	0-5"		unemerged
	Dual II Magnum/Cinch	S-metoloachlor	0-5"		unemerged
	Dual + atrazine	S-metolachlor, atrazine	0-5"		2-leaf G&B
	Expert1,2,3	S-metolachlor, glyphosate	0-12"		weeds < 6"
	FieldMaster*,2	Acetochlor, atrazine, glyphosate	0-11"		weeds < 6"
	G-MAX Lite	Dimethenamid,阿特拉津	0-12"		1.5" G&B
	Guardsman Max	Dimethenamid,阿特拉津	0-12"		1.5" G&B
	Harness/Confidence	Acetochlor	0-11"		unemerged
	Harness Xtra/Confidence Xtra	Acetochlor, atrazine	0-11"		2-leaf G&B
	Hornet WDG	Flumetsulam, Clopyralid	0-20"		2-6"G&B
	Keystone	Acetochlor, atrazine	0-11"		unemerged
	Keystone LA	Acetochlor, Atrazine	0-11"		unemerged
	Lasso	Alachlor	0-5"		2-lea fB
	Lasso + Atrazine	Alachlor, Atrazine	0-5"		2-leafG&B
	Lasso + Banvel	Alachlor, dicamba	0-3"		2-leaf B
	Lightning (IMI corn)	Imazethapyr, Imazapyr	corn < 8 leaf		weeds < 3"G&B
	Lumax/Lexar1	阿特拉津,S-metolachlor mesotrione	0-5"		0-3" B
	Marksman	Atrazine, Dicamba	0-8"		0-4"B
	Me-Too-Lachlor II	Metolachlor	0-40"		2-leaf B
	Outlook	Dimethenamid	0-12"		unemerged
	Penimax/Prowl	Pendimethalin	0-24"		1" G
	Harness/Confidence	Acetochlor	0-11"		unemerged
	Prowls + atrazine	Pendimethalin, atrazine	up to 2-leaf		up to 2-leaf
	Prowl H2O	Pendimethalin	0-30"		1"G
	Stalwart Xtra	Metolachlor, atrazine	0-5"		2-leaf G&B
	Surpass	Acetochlor	0-11"		unemerged
	Topnotch	Acetochlor	0-11"		unemerged
	Trizmet二世	Atrazine, Metolachlor	0-5"		2-leafG&B
	1Severe injury may occur if Callisto is applied postemergence to corn crops that have been treated with Counter or Lorsban. Do not tank mix with any organophosphate or carbamate insecticide. Do not cultivate within seven days of application. 2Do not tank mix this product with any other herbicide when applied postemergence. 3Do not mix this product with complex fertilizer mixtures such as 10-34-0 or flowables. Use only water or liquid nitrogen carrier. * Apply this product to Roundup Ready corn only. G = Grass B = Broadleaf