Reviews – Spectracide Weed & Grass Killer

I spend hundreds of hours researching and testing so that I can provide you with the best money saving tips. I am supported by our readers and may earn a commission if you buy through our Affiliate Links at no cost to you. Thank you so much for your support. Read More

I have a real problem with weeds in the yard and honestly, they are out of control.  I’ve tried to hoe, pull, smother with weed cloth, and about everything else I can think of and nothing really works.  The weed that is most problematic is St. Augustine grass.

This particular grass will take over everything in the yard and is almost impossible to kill no matter if it is watered or not.  The roots go down really deep and it sends runners everywhere and eventually will pierce weed cloth or simply climb right on top of it.  Some people plant it on purpose but it’s a real problem for me due to it’s invasive nature.

I won’t use Glyphosate anywhere so I am trying an alternative that is Glyphosate free.  Spectracide looks promising due to it’s quick action and ability to kill down to the roots. 

Main Features

Active Ingredients: 

Diquat Dibromide2.30%
Dicamba*, dimethylamine salt0.77%
Other Ingredients:95.78%
*0.054 lb Dicamba acid equivalent per gallon or 0.63%

Application Rate: 7 oz per gallon

Application Temperature: Above 60

Rainproof: In 15 minutes

Visible Results: 3 hours


Before Photos

Here are the before photos showing the state of the weeds.  


I followed the manufacturer’s specifications and applied this at a rate of 7 oz per gallon.  That’s 14 tsp or about .8 cups.  I sprayed it on with a hand sprayer.  There was no wind and the temperature outside was about 65.  We expect a high today of 83. None of the weeds had been watered on purpose in weeks.  The manufacturer recommends to water grasses for a week prior to application but I didn’t want to wait a week to get started.  Watering ensures robust growth which helps in the absorption and kill rate.


Bright green foliage at the start

24 Hours

Dramatic change to brown and a lot of wilting

2 Days

3 Days

High kill rate with hardly any green at all


Typical tender broad leaf weed.

24 Hours

After 24 hours, this weed is history. Note that the St. Augustine is much harder to kill.

3 Days

100% dead. It was so dead I had a hard time finding it.


A tougher broad leaf weed with deep and thick roots.

30 Hours

Starting to show some brown patches and minor wilting. Be sure to check out my time lapse video for this weed.

3 Days

After 3 days this plant is still alive. For this particular weed, it will need a second treatment in order to get rid of it.

Dual Application Test With Watering

In this area, I decided to do a dual application test to see if I could get a better result.  In order to increase the absorption rate, I watered this area thoroughly and allowed it to dry.  Then, in full sun I sprayed on another application of Spectracide.  By the time I reached the 3 day mark, this area has significantly more brown spots and appeared to be over 90% dead which is a lot more than the area with a single application.


This is a typical patch of St. Augustine grass when it's completely out of control and about 2 feet tall.

24 Hours

After 24 hours, the change is barely perceptible but if you look closely, you can start to see a change of color starting at the base of the plant and working it's way upward.


Starting to see significant browning


Almost completely dead


In order to get the best results, I would recommend the following based on my in field tests.

  1. Water your weeds.  This seems counterintuitive, but it really works.  Watered weeds grow faster and are able to absorb the weed killer more easily.  I did a side by side comparison and this had a significant impact in the overall results.
  2. Apply at temperatures above 60 degrees.  The manufacturer recommends this and works the same way that watering does.  Over 60, plants grow better and therefore they are easier to kill.
  3. Apply evenly and thoroughly.  My large 2 gallon sprayer broke on me so I was forced to do this with a miniature hand sprayer.  This proved to be difficult to get an even coverage so I recommend you get a good one like the one shown below on Amazon.

Overall Impression


I would rate this at 4 out of 5 stars.  It was able to kill St. Augustine grass with 2 applications and completely wiped out other weeds with a single application.  I’m not surprised at all that it could not kill the toughest weeds with one spray since the grass is so resilient.  It contains no Glyphosphate, is very inexpensive, and worked well.  I paid around $17 and in concentrate form which makes 13 gallons.  

Leave a Reply

Your email address will not be published. Required fields are marked *