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Phosphite vs Phosphate [Treating Pythium Blight]

Posted by Nate Bahler on Jul 29, 2021 9:58:45 AM
Nate Bahler

We have had a ton of rain in the Northeast this July and we are seeing a LOT of disease issues this year because of it.  

Pythium Blight is one in particular that we are seeing a lot of this summer. There are many different strategies for treating Pythium.  The one that we’d like to dive into a bit more today is using Phosphites. 

A lot of people when they hear Phosphite, think Phosphate.  These are not to be confused.  Phosphate fertilizers have become banned in lawn care use in CT.  Phosphorus is a naturally occurring and essential nutrient for plants but increased levels of these nutrients can jeopardize water quality in its run-off.


How are Phosphites used in lawn care?  

Phosphite is actually a derivative of Phosphate.  An oxygen molecule is removed and it becomes PO3 vs PO4. 

Phosphite materials have been around since about the 1970s. They were originally mainly used in the golf world. 

Phosphites actually have very unique fungicidal properties. They were proven to be very helpful at slowing the onset of a couple different diseases - most namely being Pythium. PO3-PO4


How do Phosphites work as a fungicide?

They are the only fungicide that can enter the plant and move upward in the plant as well as downward in the plant, giving you full plant protection. Every other fungicide on the market enters the plant and can only move upwards. 

Phophites do not kill fungal spores but they do inhibit them from expanding.  A phosphite actually initiates an ISR response inside the plant. It triggers the grass plant to think it’s under attack from a fungal pathogen - think about how vaccines and viruses work.  Like vaccines, however, they don’t have a curative effect - they need to be introduced as a preventative measure. 

With that being said, there's no wrong time to start a phosphite application protocol. In the summertime, we can have diseases coming in many waves. 

A phosphite program is also not necessarily “one and done”.  Oftentimes they need to be reapplied every month or so when we are in the weather conditions that favor lawn disease (hot, wet, humid, dark). 


How do we use Phosphites in our Programs here at Green Meadow?

We use phosphites in conjunction with a product that kills fungal spores on impact.  Why? Because the products that kill fungal spores and give us the immediate set back we need only hang around for about 7 days.  Adding Phosphites to this program gives us the longevity and preventive control that we need. 

If you have any other questions regarding this, please feel free to reach out!

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Since 2007, Green Meadow Lawn Care has provided homeowners throughout the greater Tolland, Connecticut area with premium fertilization programs, tick control, mosquito management, seeding & aeration and tree & shrub care. 

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