UNITED STATES ENVIRONMENTAL PROTECTION AGENCY 

WASHINGTON D.C., 20460 

MAY 21 2015 

OFFICE OF CHEMICAL SAFETY 

AND POLLUTION PREVENTION 

MEMORANDUM 

SUBJECT: Non-Agricultural Use & Usage Report for the Herbicide Isoxaben (PC Code # 

125851} in Support of Risk Mitigation & Preliminary Interim Decision 

FROM: 

THRU: 

TO: 

Summary 

Liabeth Yohannes, Biologist 

Science and Information Analysis Branch 

Biological and Economic Analysis Division (7503P) 

Steve Jarboe, Team Leader A..7~ Science Information and ~ B;~cif' Biological and Economic Analysis Division (7503P) 

Christina Scheltema, Chemical Review Manager 

Risk Management and Implementation Branch 

Pesticide Reevaluation Division (7508P) 

Isoxaben is undergoing registration review by the Pesticide Reevaluation Division (PRD). The 

Biological and Economic Analysis Division (BEAD) conducted an analysis of isoxaben's nonagricultural usage and labeled maximum application rates for non-agricultural uses in support of 

risk mitigation and preliminary interim decision. lsoxaben (PC Code 125851) is a soil-applied 

pre-emergent herbicide used for control ofbroadleafweeds. Based on data presented in this 

document, isoxaben usage makes up a small fraction of herbicides used in the professional turf, 

ornamental and consumer markets and has a maximum single application rate of 1.0 lb a.i./acre. 

Background 

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) authorizes EPA to register 

pesticides under 40 Code of Federal Regulations (CFR) Part 158. FIFRA requires the EPA to 

regulate the use of a pesticide to the extent necessary to prevent unreasonable adverse effects on 

the environment, including human health, where 'unreasonable' is defined as taking into account 

the economic, social, and environmental costs and benefits of the use of the pesticide. 
Isoxaben is registered for use on a variety of non-agricultural sites including turf grass, 

ornamentals (landscape, container and field), groundcovers/perennials, conifer 

plantations/hardwood nurseries, non-bearing fruit and nut trees, non-bearing vineyards, and other 

non-cropland. It is also registered for agricultural use on bearing fruit and nut trees, vineyards, 

and eucalyptus. The primary risk concern for isoxaben is to non-target terrestrial plants, 

primarily from spray drift resulting from broadcast applications. 

Non-Agricultural Usage 

In the professional turf and ornamental market (e.g., golf courses, horticultural nurseries, 

landscape contractors), isoxaben makes up a small fraction of the herbicides used in each sector 

(Table 1; Kline and Co., Inc., 2006, 2009, and 2011). In 2011, isoxaben usage was 

approximately 2% of all herbicides applied (an estimated total of 50,000 lbs a.i.) in the turf and 

ornamental market with the largest uses reported for horticultural nurseries ( < 1 % of total; 

28,000 lbs a.i.), golf courses (<0.3% of total; 9,000 lbs a.i.) and institutional turf(< 0.6% of total; 

7,000 lbs a.i.). Less usage of isoxaben was reported in the landscape contractor and lawn care 

operator sectors in 2011 (3,000 lbs a.i. applied in each sector, respectively). From 2006 to 2011, 

isoxaben usage by golf courses and horticultural nurseries increased, while usage by landscape 

contractors decreased. In the consumer market (e.g., lawns and gardens), isoxaben usage made 

up less than 4% of total herbicide usage on lawns. Less than 223,000 lbs a.i. were applied in 

2011 and less than 139,000 lbs a.i. were applied in 2009. 

Table 1. Non-Agricultural Usage of Isoxaben in Professional Turf & Ornamental and 

Consumer Markets by Sector (2006, 2009, and 2011) 

Year Site/Sector Lbs A.I. % of Total (data) (Thousand) 

2011 Golf Courses 9 0.3 

2006 Golf Courses 2 0.3 

2011 Horticultural Nurseries 28 0.9 

2006 Horticultural Nurseries 21 1 

2011 Institutional Turf 7 0.6 

2006 Institutional Turf No usage reported No usage reported 

2011 Landscape Contractors 3 0.3 

2006 Landscape Contractors 7 2.3 

2011 Lawn Care Operators 3 0.04 

2011 Consumer lawn <223 <4.2 

2009 Consumer lawn < 139 <3.6 

Source: Kline and Co., Inc., 2006, 2009, and 2011 
Maximum Single Application Rates on Isoxaben Labels for Non-Agricultural Uses 

The maximum single application rate on nonagricultural sites, including turf, landscape 

ornamentals, field grown ornamentals, groundcovers/perennials, and home lawns ranges from 

0.5 - 1 lb a.i./acre. These data are based on registered labeled uses of isoxaben. 

References 

Kline and Co., Inc., 2006, 2009, and 2011.