Yellow Nutsedge Nutlet Viability in Response to Fumigation

Malheur Experiment Station

Oregon State University

Ontario, OR, 2006

Introduction

Yellow nutsedge has become a major problem weed in agricultural land in the Treasure Valley, especially in fields planted to onion. Control of yellow nutsedge is difficult because reproduction is mainly by rhizomes and tubers (nutlets) and nutlet production is intense. Control of yellow nutsedge will partly rely on nutlet destruction by fumigation. Growers and others have suggested that Telone^®®C-17 could enhance the control of nutsedge if applied prior to Vapam. Others have suggested that Dual Magnum^® could be applied following Vapam to enhance nutsedge control. Consequently, all three products were tested alone and in combination for their effectiveness in reducing nutlet viability. 

Materials and Methods

The trial was conducted in a field severely infested with yellow nutsedge, approximately 2 miles from the Malheur Experiment Station. On September 1, 2006, the field was furrow irrigated. The field was disked on September 7. The experimental design was a randomized complete block with four replicates. Each plot was 16 ft wide and 60 ft long. On September 8, 3 core (4.25 inch diameter) samples, 1 ft apart were taken in the plot center. The core samples were divided into 2 depths: 0- to 12-inches and 12- to 16-inches. The nutlets from each sample were separated by washing and sieving. The nutlets were counted and weighed. Nutlets were placed in open plastic bags in a dark cooler at 40°F. The treatments were seven fumigants or fumigant combinations and an untreated check (Table 1).

On September 12, Telone C-17 was shanked in to the respective plots at 23 gal/acre (238 lb ai/acre). Telone C-17 was shanked in at 18-inch depth using equipment with shanks 20 inches apart.

On October 6, Vapam was shanked in to the respective plots at 50 gal/acre (213 lb ai/acre). Vapam was shanked in at 10- to 12-inch depth and 5- to 6-inch depth using equipment with shanks spaced 5 inches apart.

On October 26, Dual Magnum was broadcast on the soil surface to the respective plots at 2 pt/acre (1.9 lb ai/acre). Following the Dual Magnum application, the field was disked twice. On October 27, the field was plowed to a 10-inch depth by Simplot Growers Solutions to thoroughly mix the Dual Magnum into the treated plots. Dual Magnum is not a registered treatment for plow down preceding onion. It was tested here only as a potential treatment for future registration. The use of this treatment does not constitute a recommendation to use this product.

On November 14, the field was roller harrowed twice. Core samples were taken on October 20, in the same number, size, and depth as before fumigating. The nutlets were counted and weighed. Nutlets were placed in open plastic bags in a dark cooler at 40°F.

On December 8, 100 visually healthy prefumigation nutlets from each plot were put in petri dishes between two layers of filter paper and 6 ml of water was added. The petri dishes were sealed with plastic wrap and placed in a dark, walk-in cooler at 80°F. On December 11, the first of four counts was made of sprouted nutlets in all petri dishes of the prefumigation samples. After counting, the sprouted nutlets were discarded, the petri dishes were resealed and placed in the cooler. The last count was made on January 2. From January 8 to 10, nutlets from the postfumigation samples were placed in petri dishes as described previously. On January 16 the first of three germination counts was made on the postfumigation samples as described previously. The last postfumigation count was made on January 23. In the spring of 2007, the field will be furrowed, irrigated, and nutsedge emergence will be counted.

Results and Discussion

The field had substantially more nutlets in the 0- to 12-inch depth than at the 12- to 16-inch depth. All treatments, except Dual Magnum alone, significantly reduced nutlet viability at the 0- to 12-inch depth (Table 1). Vapam alone or combinations of Vapam with Telone C-17 or Dual Magnum resulted in the largest decrease in nutlet viability at the 0- to 12-inch depth. There was no significant difference in nutlet viability between fumigant treatments at the 12- to 16-inch depth.

All these treatments will be evaluated in the field in the spring of 2007. We expect the treatment effects will show more pronounced differences in the spring because we will be able to evaluate nutlet emergence over larger areas, rather than the small 4-inch soil cores evaluated to date. Dual Magnum may be more effective in the spring, since it is a sprout inhibitor.

Dual Magnum is not a registered treatment for plow down preceding onion. It was tested here only as a potential treatment for future registration. The use of this treatment does not constitute a recommendation to use this product.

Table 1. Nutlet counts and germination in response to fumigation. Malheur Experiment Station, Oregon State University, Ontario, OR, 2006.

^aNot a registered application method.

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