About the author: Eric Maurer is the National Accounts Manager for Neudorff USA
A webinar presented by Eric about this topic can be viewed here.
What’s the deal with iron-based herbicides for weed control?
FeHEDTA (iron chelate) is an active ingredient in several herbicide products that are compatible with Montgomery County’s Pesticide Law. FeHEDTA is widely used as a selective broadleaf weed control in lawns for those seeking an alternative lawn care program.
Products that contain FeHEDTA as an active ingredient include, but are not limited to:
Fiesta® Turf Weed Killer
Bonide Weed Beater Fe
Captain Jack’s Lawnweed Brew by Bonide
Natria Lawn Weed & Disease Control
Natural Guard by ferti-lome Lawn Weed Killer
Pulverize Weed Killer for Lawns
Rachio Weed Watcher
Whitney Farms Lawn Weed Killer
NOTE: All products listed above are available in either previously diluted ready to use formulations, concentrate, or both. Concentrates, such as Fiesta®, must be diluted prior to application. Fiesta is used primarily by lawn care professionals. Please read and follow all label directions.
Products that contain FeHEDTA are selective herbicides for the control of broadleaf weeds, moss, algae, and some fungal diseases in turf and garden beds. Selective broadleaf control means it will kill weeds but does not harm the grass. They work quickly, delivering visible same-day results, even in cool weather. Since the active ingredient is made from iron, it has no unpleasant odor during or after application and people and pets can reenter the treated area once the spray is dry. The products can stain clothing or pets when wet.
Suitable for broadcast application or spot treatment, these products will help grass look its best, even in many pesticide-restricted areas such as lawns, parks, golf courses, cemeteries, sports fields, playgrounds, schools, and universities. Lawns and turf can be reseeded within one day of treatment and it is ideal for alternative lawn care programs or in areas that have enacted pesticide bans.
Mode of Action:
The iron is bound to a chelating agent that keeps it soluble and readily available for plant uptake. Broadleaf weeds absorb chelated iron easily and in larger quantities than grass which leads to cellular damage (cell necrosis) and ultimate plant death while the grass remains unharmed. Full coverage of the weed is important for the best results.
Weeds: Black medic, broadleaf plantain, bull thistle, Canada thistle, common chickweed, creeping buttercup, creeping charlie/ ground ivy, dandelion, dovefoot geranium, English daisy, false dandelion, heal-all, narrow leaved plantain, oxalis, Persian speedwell, prostrate knotweed, shepherd’s purse, silverweed cinquefoil, slender speedwell, white clover, wild chamomile.
Other plants: Algae, lichens, liverworts, moss.
Fungal Diseases: Rust, dollar spot, snow mold.
**Please read and follow all label directions specific to the state in which you are using the product.
The EPA has determined Iron HEDTA to be in Toxicity Category IV (the lowest toxicity category) so these products have a CAUTION Signal Word.
Use Precautions: Do not apply to drought stressed grass; ensure turf is well watered prior to application. Do not apply when the daytime temperature will exceed 85ºF. Do not apply to bentgrass. If unsure of grass sensitivity, test spray a small area of the turf. Do not apply to newly seeded areas prior to grass seed germination. Avoid spraying desirable plants. Any desirable plants or structures accidentally contacted should be rinsed with water. To avoid staining, wait until treated area dries before re-entry. Do not apply if rainfall is expected within 3 hours of application. Do not irrigate within 3 hours of application. Do not apply to the same area more than 4 times a year.
Directions for Use (Fiesta®)**:
Broadcast Treatment: Shake well before using. Mix one part Fiesta® with 24 parts water (5 oz. in 1 gallon of water). Apply the mixed solution at a rate of 2.5 – 10 gallons/1000 square feet.
Spot Treatment: Shake well before using. Mix one part Fiesta® with 24 parts water (5 oz. in 1 gallon of water). Thoroughly spray weeds to point of runoff using any standard hand-held or backpack sprayer. Use a coarse nozzle setting to reduce drift.
Repeat treatment in 3 to 4 weeks for best results.
Uniform coverage is important.
** Please read and follow all label directions specific to the state in which you are using the product.
This postcard provides a mixing table for Fiesta® : Fiesta Mixing Table postcard
What will I see?
Works quickly and results are visible the same day; dying weeds will be seen within hours of application. Treated weeds, algae and moss will turn brown or black. Occasionally a darkening of the grass leaf blades can occur after treatment; however, the grass will recover within a few days to weeks. May stain thatch (dead grass under turf); this does not affect the health of the grass.
YouTube time-lapse video:
Fiesta® Label Links:
For use in states other than CA –
For use in CA only –
Fiesta® Fact Sheets:
For use in states other than CA –
For use in CA only – http://www.neudorffpro.com/fileadmin/user_upload/Fiesta_CA_fact_sheet_1-_18.pdf
Iron Based Herbicides: Alternative Materials for Weed Control in Landscapes and Lawns (2014).
University of Maryland Extension. Deborah Smith-Fiola, Independent IPM Consultant, Landscape IPM Enterprises and Stanton Gill, Extension Specialist, IPM for Nurseries and Greenhouse
Report at: https://extension.umd.edu/sites/extension.umd.edu/files/_docs/programs/ipmnet/Iron%20Herbicide%20Info-UMD-IPMnet.pdf