Yellow Spots and Streaks in St Augustine Turf Grass Lawn are Caused By Lack of Iron


By Rick Orr 04/14/2020
St Augustine lawn with iron chlorosis caused yellowing
The yellow streaks and spots in this lawn are caused by the lack of iron. THe condition is called Iron Chlorosis

Lack of Iron Causes Yellowing

The yellow streaks and spots are caused by a lack of iron in the leaf. It is called iron chlorosis. Iron chlorosis turns a St Augustine lawn into a patchwork of unsightly yellow spots and streaks. Iron chlorosis is common during the summer months when rapid growth exceeds the plant's ability to extract Iron from the soil. There is no permanent fix for iron chlorosis. The only solution is to apply supplemental iron in a form that the St Augustine grass can absorb.

Foliar Applied Liquid Iron

The best fix for the iron chlorosis is foliar applied liquid iron. The best and most expensive supplement is chelated iron. A good alternative is iron sulfate - which not only is absorbed by the St Augustine grass plant but also promotes iron to be released from the soil (acid-forming)

I also use acid-forming fertilizers to create micro releases of iron. Most of the soils in Pinellas are alkaline (high pH). Iron is readily available in neutral to slightly acid soils (low pH). Acid forming fertilizers will lower the soil pH – if only for a brief time – and releasing iron to be used by the plant.

Iron Absorption is Slow

Iron absorption is slow and playing “catch-up” takes time – there is no “spray today – lawn looks great tomorrow” scenario. For best effect, small amounts of preventative foliar applied liquid iron should be applied year-round to iron-deficient lawns - not just when yellow spots and streaks appear. Applying small amounts throughout the year helps build up iron in the plant and enables the St Augustine grass plant to "coast" through the rapid growth of summer without going "yellow".

DIY Solutions

For the homeowner, this is a difficult problem to solve. The best solution is to apply acid-forming fertilizers with high iron content every 2 – 3 months. The iron content can be found in the analysis on the container. Millorganite is a good (but expensive) source and a very good product to keep the yellow out. With Millorganite be prepared to use 50 - 100 lbs. per thousand square feet or about 5 – 10 bags for an average lawn. Millorganite has a noticeable musty smell when applied to lawns during the rainy season.

Professional Solutions – Custom Formulations for Pinellas County

Throughout the year, I use a water-soluble blend of acid-forming fertilizers plus a chelated iron. This foliar applied liquid application used throughout the year will prevent yellow spots and streaks in even the most difficult lawns. During the nitrogen blackout periods, I rely on the more expensive chelates to keep the grass green and to mask the effects of low nitrogen.

Rick Orr Owner-Operator APL Pest Control/Creator of ILOVETURF.COM
APL Pest Control

Rick Orr is the creator of, Owner/Operator of APL Pest Control and a graduate from VA Tech in Agronomy (Turf Ecology).  

Since 1980, Rick worked in the green industry, mostly with golf courses, resorts and large communities. Rick worked as a Golf Course Superintendent of Fripp Island Resort, agronomist for Seaside, FL and the spray tech for Vinoy Golf Course. Rick has been certified as an arborist, landscape and irrigation contractor and adjunct professor for Environmental Horticulture (SPC) in Pinellas County.  

Home Pest Control came naturally. Entomology (bug science) was part of agronomy studies. Nearly every indoor pest problem starts outdoors. Crossing over to home pest control from lawn spraying was a natural process – the technology, methods and materials used for home pest control are modifications of the ones used for lawn spraying. 

The results of that work is a one of the top rated pest control companies in Pinellas County – APL Pest Control. APL Pest Control is a family owned business serving residential and commercial properties in Pinellas County, FL. 

Free Price Quote for Home Pest Control and/or Lawn Spraying CLICK HERE

To learn more about APL Pest Control CLICK HERE

Speaking Engagements - Does it seem like you are only hearing one side of water restrictions, fertilizer bans, plant restrictions, and many other urban landscape hot topics? Rick Orr is available for speaking engagements for your HOA, Community or Professional Association or Garden Club about a variety of subjects. To contact Rick you can find him on FacebookTwitterLinkedIn and Instagram for booking information.