Development of New Herbicide Options for Weed Control in Potato Production

 

 

Corey V. Ransom, Charles A. Rice, and Joey K. Ishida

Malheur Experiment Station

Oregon State University

Ontario, OR, 2004

 

 

Introduction

           

Weed control in potatoes is essential for production of high yielding marketable tubers.  Herbicide options in potato production are limited.  Outlook^®, Spartan^®, and Chateau^® (previously Valor^®) demonstrate great promise for use in potato.  Spartan and Chateau represent a mode of action that is not currently used in potatoes and offer excellent hairy nightshade control.  Outlook (dimethenamid-p) has the same mode of action as Dual^® but controls a wider spectrum of weeds.  Trials were conducted to evaluate new herbicides for weed control in potatoes.  The results of our research have been provided to herbicide companies, the IR4 program, and state regulators in support of additional herbicide registrations in potatoes.  Spartan was registered for use in potato in 2004 and Outlook is registered for use in potato in 2005.  Chateau is also registered for use in potato and will be available in limited quantities for commercial evaluation for 2005.  The registration of these herbicides gives producers additional tools for controlling weeds and may increase economic returns through improved weed control.

 

Materials and Methods

 

Three trials were conducted at the Malheur Experiment Station to evaluate new herbicides for weed control efficacy and crop tolerance in potatoes: Spartan alone and in 2- and 3-way tank mixtures; comparisons of standard 2-way tank mixtures with Chateau or Matrix^® added in 3-way tank mixtures; and Outlook in 2- and 3-way tank mixtures.  In fall 2003, 50 lb nitrogen (N) and 100 lb phosphorus (P)/acre was applied prior to bedding in all trial areas.  On October 17, 2003, Telone II^® (20 gal/acre) and Vapam^® (20 gal/acre) were applied and the ground was bedded.  Potatoes were planted April 27, 2004 in an Owyhee silt loam soil with pH 7.6, 2.7 percent organic matter content, and a cation exchange capacity of 19.  ‘Russet Burbank’ seed pieces were planted every 9 inches in 36-inch-wide rows.  Seed pieces were treated with Tops-MZ^® plus Gaucho^®.  Experimental plots were 4 rows wide and 30 ft long.  Plots were sidedressed with 102 lb N, 4 lb P, 9 lb potassium (K), 8 lb sulfate, 32 lb elemental sulfur (S), 5 lb zinc (Zn), and 1 lb boron (B)/acre on May 3 and rehilled on May 11.  Preemergence herbicides were applied with a CO₂-pressurized backpack sprayer delivering 20 gal/acre at 30 psi and incorporated with approximately 0.5 inch of sprinkler irrigation on May 13.  Petiole samples were taken and sent for nitrate analysis on July 13.  On July 16, 25 lb N/acre was applied through the sprinkler.  Aerial fungicide applications included Bravo^® and Ridomil Gold^® on June 12, Headline^® (12 oz/acre) on June 26, Topsin-M^® (20 oz/acre) plus liquid sulfur (6 lb/acre) on July 17, and Headline (12 oz/acre) plus liquid sulfur (6 lb/acre) on August 8.  In addition, 1.5 lb P and 0.2 lb Zn/acre were added to the July 17 fungicide application. 

 

Visual potato injury and weed control were evaluated throughout the growing season and tubers were harvested from the center two rows of each plot on September 13-15.  Potatoes were graded for yield and size on September 20-27.

 

Herbicide screening for activity on dodder

Herbicides were screened in a petri dish assay to determine effects on dodder germination and elongation.   Dodder seeds were scarified using sandpaper and 10 seeds were placed in each petri dish.  Each dish was treated with 6 ml of water containing herbicides at rates equivalent to what would be applied in the field.  Dodder germination was counted 4 and 5 days after treatment (DAT), and dodder shoot length was measured 5 DAT. 

 

Results and Discussion

 

Spartan alone and in 2- and 3-way tank mixtures

Control of all weeds present in this trial was 93 percent or greater by treatments with Spartan alone or combined with other herbicides (Table 1).  Spartan caused potato injury on June 9, consisting of interveinal chlorosis and necrosis on one set of leaves, and injury tended to be greater with higher rates of Spartan (Table 1).  No differences in potato yield were observed between herbicide treatments, suggesting that the injury was transient (Table 2). 

 

Comparisons of standard 2-way tank mixtures with Chateau or Matrix added in 3-way tank mixtures

The 2-way tank mixtures provided the same level of control as 3-way tank mixtures including either Chateau or Matrix (Table 3).  The exception was the combination of Prowl^® plus Eptam^®, where pigweed control was increased with the addition of Matrix.  The 3-way combination of Prowl, Eptam, and Chateau had lower pigweed and barnyardgrass control than most other treatments.  Plots treated with Chateau exhibited severe injury on May 26 (Table 3).  Injury symptoms included stunting and crinkling of newly emerged shoots and leaves.  Rainfall events at the time of potato emergence may have increased the contact of Chateau with the emerging foliage.  Some treatments were still causing significant injury on June 9.  In one instance, the combination of Prowl, Eptam, and Chateau yielded lower than Prowl plus Eptam (Table 4).  This could have been a result of the early injury when Chateau was in the tank mixture. 

 

Outlook in 2- or 3-way tank mixtures

Outlook combined with Prowl or Sencor^® in 2-way tank mixtures or with both in a 3-way tank mixture provided 96 percent or greater control of all weeds (Table 5).  Potato yields were not different among herbicide treatments (Table 6).

 

Herbicide screening for activity on dodder

Only Nortron^® suppressed dodder germination compared to the untreated check (Table 7).  However, all herbicides except Chateau shortened shoot length compared to the untreated check.  Nortron caused the greatest reduction followed by Kerb^®, Prowl, Spartan, and Dacthal^®.  Nortron and Kerb are not registered for use in potato.  The fact that Prowl and Spartan reduced dodder shoot growth suggests they may be useful in managing dodder in potatoes.  In this trial, both Prowl and Spartan rates were higher than those registered for use in potato.  Additional research needs to be done with Prowl and Spartan rates that are used in potato production.

Table 1.  Effect of Spartan^® alone and in combinations on crop injury and weed control in potato, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.

		Potato injury		Weed control†
				Pigweed‡	Common lambsquarters	Hairy nightshade	Kochia	Barnyard grass
Treatment*	Rate	5-26	6-9
	lb ai/acre	---------------------------------------------------------%------------------------------------------------------------
Untreated check	--	-	-	-	-	-	-	-
Spartan	0.094	0	14	100	100	100	100	98
Spartan	0.14	5	20	100	100	100	100	94
Spartan	0.187	3	20	100	100	100	100	98
Spartan + Prowl	0.094 + 1.0	3	14	100	100	100	100	93
Spartan + Prowl	0.14 + 1.0	6	18	100	100	100	100	100
Spartan + Dual Magnum	0.094 + 1.33	0	11	100	100	100	100	100
Spartan + Dual Magnum	0.14 + 1.33	6	21	100	100	100	100	100
Spartan + Outlook	0.094 + 0.84	3	11	100	100	100	100	100
Spartan + Outlook	0.14 + 0.84	11	15	100	99	100	100	100
Spartan + Eptam	0.094 + 3.94	3	13	100	100	100	100	97
Spartan + Eptam	0.14 + 3.94	4	21	100	100	100	100	99
Spartan + Prowl + Eptam	0.094 + 1.0 + 3.94	3	7	100	100	100	100	99
Spartan + Prowl + Dual Magnum	0.094 + 1.0 + 1.33	0	11	100	100	100	100	100
Spartan + Prowl + Outlook	0.094 + 1.0 + 0.84	9	5	100	100	100	100	100
LSD (P = 0.05)	--	NS	9	NS	NS	NS	NS	NS

*Herbicide treatments were applied preemergence on May 13, 2004.

^†Weed control evaluations were taken September 2.

^‡Pigweed species were a combination of Powell amaranth and redroot pigweed.

Table 2.  Effect of Spartan^® alone and in combinations on potato yield and quality, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.

		Potato yield†
		U.S. No. 1					Total No. 2	Total marketable	Total yield
Treatment*	Rate	4-6 oz	6-12 oz	>12 oz	Total	Percent
	lb ai/acre	-------------------- cwt/acre --------------------				%	------------- cwt/acre -------------
Untreated check	--	106	113	15	234	65	5	239	359
Spartan	0.094	90	316	62	467	75	70	537	616
Spartan	0.14	102	293	79	474	78	58	532	606
Spartan	0.187	87	316	86	488	77	70	558	623
Spartan + Prowl	0.094 + 1.0	91	289	46	427	73	71	497	583
Spartan + Prowl	0.14 + 1.0	91	298	69	457	74	87	544	609
Spartan + Dual Magnum	0.094 + 1.33	91	287	51	429	72	88	516	584
Spartan + Dual Magnum	0.14 + 1.33	77	306	65	447	75	71	518	592
Spartan + Outlook	0.094 + 0.84	81	290	65	435	74	76	511	586
Spartan + Outlook	0.14 + 0.84	85	295	64	444	73	82	525	601
Spartan + Eptam	0.094 + 3.94	93	296	54	443	74	80	522	598
Spartan + Eptam	0.14 + 3.94	81	319	85	484	78	68	552	617
Spartan + Prowl + Eptam	0.094 + 1.0 + 3.94	102	311	64	476	76	71	547	624
Spartan + Prowl + Dual Magnum	0.094 + 1.0 + 1.33	97	275	39	411	72	83	493	572
Spartan + Prowl + Outlook	0.094 + 1.0 + 0.84	90	290	66	446	75	67	513	590
LSD (P = 0.05)	--	NS	53	37	74	6.8	26	72	63

*Herbicide treatments were applied preemergence on May 13, 2004.

^†Potatoes were harvested September 13 to 15.  Total marketable yield = total number ones + total number twos.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3.  Comparison of standard 2-way tank mixtures with Chateau^® or Matrix^® added in 3-way tank mixtures for potato crop injury and weed control, Malheur Experiment Station, Oregon State University, Ontario, OR, 2004.

		Potato injury		Weed control†
Treatment*	Rate			Pigweed‡	Common lambsquarters	Hairy nightshade	Kochia	Barnyard grass
		5-26	6-9