Alldown™, a natural organic non-selective herbicide, was screened for efficacy in turfgrass and compared to Roundup. Three studies with this material were conducted at the Iowa State University Horticulture Research Station north of Ames, IA. The experimental area for Study I was established 'Majestic' Kentucky bluegrass. Studies II and III were conducted in the same plots in established 'Vantage' bluegrass. The soil in these areas was a Nicollet (fine-loamy, mixed, mesic Aquic Hapludoll) with an organic matter content of 3.9%, a pH of 6.5, 3 ppm P, and 77 ppm K.

The experimental design for all studies was a randomized complete block. There were three replications with no barrier rows between replications. Individual plot size was 5 x 5 ft and there were six treatments including an untreated control. For Study I, Alldown™ was applied at the label rate of 22 ml product/25 ft² (10 gal/A) and at 22, 44, 66, and 88 ml/plot (Table 1). Alldown™ application rates were increased to 88, 110, 132, and 154 ml product/plot for Studies II and III (Tables 2 and 3). Roundup was applied at the label rate for comparisons in all three studies.

The two lowest rates of Alldown™ for Study I were applied with a boom equipped with a single #8500 TeeJet flat fan nozzle because of the low volume of liquid. All other materials were applied using a boom equipped with three TeeJet #8006 flat fan nozzles. A carbon dioxide backpack sprayer was used at 30-35 psi.

Treatments for Study I were applied on May 26. It was 70º F and sunny with no wind. Study II was begun on June 24 under sunny skies with no wind and a temperature in the mid 80's. Conditions were ideal for application of materials for Study III on July 27. It was 85º F and partly sunny with a light southeast wind.

Efficacy of the materials was recorded as the percentage of dead turf per plot. The first data were taken 24 hours post treatment and subsequent data were taken weekly until Alldown™ -treated turf had recovered (Tables 1-3).

Data were analyzed using the Statistical Analysis System (SAS, Version 6.12) and the Analysis of Variance (ANOVA) procedure. Means were compared with Fisher's Least Significant Difference (LSD) test.

Twenty-four hours post application, turf treated with the highest rate of Alldown™ in Study I was > 70% dead (Table 1). By June 2, the Alldown™-treated turf was beginning to recover while the Roundup-treated turf was >85% dead.

Less than 30 minutes post application, Alldown™ -treated turf in Study II was turning brown and dying. On June 25, twenty-four hours post application >95% of Alldown™ -treated turf was dead (Table 2). By July 7, Alldown™ -treated turf was beginning to recover while the Roundup-treated turf was 85% dead. After July 14, Alldown™ -treated turf had recovered and was indistinguishable from untreated turf.

Similar results were observed following treatment for Study III. The Alldown™ -treated turf began to brown within 30 minutes following application. Data taken on July 28, show that at 24 hours post treatment turf treated with Alldown™ at 110, 132, and 154 ml was „95% dead (Table 3). By August 24, the Alldown™ -treated turf had recovered.

Materials applied on May 26, 1999

Materials applied on June 24, 1999

Materials applied on July 27, 1999