Objective

The objective of this trial was to compare two formulations of citrus oil (d-limonene) at three rates with three commercial standards (Worry Free Moss & Algae Control, Garden Safe Moss & Algae Killer, and Lilly Miller Moss-Out) sprayed at 2x label rate to determine bentgrass tolerance to these products.

Materials and Methods

The trial was initiated on February 20th at the Lewis-Brown Horticulture Farm in Corvallis, Oregon. The trial site was a stand of different varieties of colonial bentgrass which was planted several years ago and was growing on a silty clay loam soil with a pH near 6.0.

The weather on the date of application was foggy in the morning and overcast until 1 p.m. The products were applied between 2:20 pm and 3:45 pm. The sun was out during the application of all the products. The temperature and relative humidity at 2:20 pm was 53 degrees Fahrenheit and 71%, respectively.

All treatments were applied with a CO2-powered plot sprayer with a 5 foot boom using TeeJet 80015 flat fan nozzles spraying 2 gallons per 1,000 square feet. All products were applied at a spray volume of 6 gallons per 1,000 square feet by spraying each plot three times.

Because of cold temperatures and adequate rainfall, the plots were neither mowed nor irrigated during the duration of the trial.

The trial was set up as a randomized complete block design with three replications using a plot size of 5 X 5 (25 square feet).

Visual turf injury ratings were made on February 23 (3 DAT), February 27 (7 DAT), March 5 (14 DAT), March 18 (4 WAT), and April 18 (8 WAT). The data for each rating date were subjected to analysis of variance (ANOVA) and differences between means were determined by LSD at the 5% level.

The treatments applied were as follows:

Trt # Products Rate (oz)
Product per 1,000
Spray Volume
Gallons per 1,000
1 Moss-1 70 % ai (d-limonene) 11 6
2 Moss-1 70 % ai (d-limonene) 22 6
3 Moss-1 70 % ai (d-limonene) 33 6
4 Moss-2 70 % ai (d-limonene) 11 6
5 Moss-2 70 % ai (d-limonene) 22 6
6 Moss-2 70 % ai (d-limonene) 33 6
7 Lilly Miller Worry Free Moss & Algae* 64 6
8 Garden Safe Moss & Algae Killer (22%)* 160 6
9 Lilly Miller Moss-Out (9.75 % iron)* 128 6
10 Untreated na na

* The active ingredient in the Worry Free Moss & Algae Control product is 15% sodium lauryl sulfate and 6% citric acid. The active ingredient in Garden Safe is potassium soap of fatty acids. The active ingredient of Moss-Out is ferric sulfate.

Results

With the exception of treatments 3 and 8, all the treatments had at most only minor leaf tip burn which recovered within 28 days. Although the leaf burn was severe in the case of treatments 3 & 8 (Moss-1 at the 33 oz rate & Garden Safe Moss & Algae Killer), no turf death occurred and the turf showed only minor injury after 28 days after treatment (See turf injury data and photos on page 3). There was no turf injury observable 8 weeks after treatment.

Table 1: Turf Injury Ratings

      Injury Ratings 1 - 9; 1 - no injury
Trt # Products Rate (oz)
Product per 1,000
2/23/08
3 DAT* Avg
2/27/08
7 DAT Avg
3/5/08
14 DAT Avg
3/18/08
4 WAT* Avg
4/18/08
8 WAT Avg
1 Moss-1 70 % ai (d-limonene) 11 1 1 1 1 1
2 Moss-1 70 % ai (d-limonene) 22 1.7 1.7 1.5 1.2 1
3 Moss-1 70 % ai (d-limonene) 33 6.3 6.3 5 1.3 1
4 Moss-2 70 % ai (d-limonene) 11 1 1 1 1 1
5 Moss-2 70 % ai (d-limonene) 22 1 1 1 1 1
6 Moss-2 70 % ai (d-limonene) 33 3.3 3.3 3.3 2 1
7 Worry Free Moss & Algae Control 64 1 1 1 1 1
8 Garden Safe Moss & Algae (22%) 160 7.3 7.3 6.3 3 1  
9 Lilly Miller Moss-Out (9.75 % iron) 128 3 3 3 1 1
10 Untreated na 1 1 1 1 1
    LSD @ .05 0.65 0.65 0.73 0.6 na

* DAT = days after treatment; WAT = weeks after treatment