Spectracide vs Roundup: Which herbicide works best?

Weeds are always a pain for any gardener. But, once they invade your land, lawn, or garden, you must look for the most effective way of controlling or killing them.

While weeding by hand, burning, and using farm tools to remove them can work, the traditional methods can be cumbersome.

Herbicides become a convenient option because all you have to do is spray on the unwanted plants and wait a few hours.

Two of the best herbicides that are popular nowadays are Spectracide and Roundup. While they take up a significant market share, you might be confused when it comes to choosing between the two.

Both herbicides work efficiently when it comes to killing weeds in gardens. However, their chemical composition is different, meaning that they work differently.

Roundup uses a chemical called glyphosate, while Spectracide uses diquat dibromide. Choosing which of the two chemicals to buy has always been challenging for most farmers.

So, which one works best?

Spectracide vs. Roundup: What is the difference?

Spectracide is a non-selective herbicide that kills any vegetation on contact. It contains diquat dibromide, fluazifop-p-butyl, and dicamba dimethylamine salt as its active ingredients.

The percentage of diquat dibromide in Spectracide is 2.30%. The rest are fluazifop-p-butyl at 1.15% and dicamba dimethylamine salt at 0.77%.

On the other hand, Roundup is a systemic, broad-spectrum herbicide that kills weeds on contact. It contains glyphosate and diquat as its active ingredients. The percentage of glyphosate in Roundup is 18%, while the diquat is 0.73%.

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How does Spectracide work?

Spectracide kills weeds upon contact. In other words, you have to spray it directly on the leaves of the plants you want to eliminate from your lawn or garden.

Then, the chemical will enter the plant through the leaves and move down to the roots. In the process, the active ingredients in the herbicide will destroy the plant’s cell membrane and interfere with photosynthesis.

Spectracide works quickly. After about 3 hours, the plant will appear frozen and eventually die. Some plants may take up to 3 weeks to die off.

NOTE: You must be precise when applying Spectracide must because it will only kill the parts of the plants that it contacts.

How does Roundup work?

Roundup is a non-selective herbicide that will kill almost any plant. It uses its active ingredient glyphosate to prevent plants from making specific proteins needed for growth.

When you apply it to a weed, the plants absorb it through the leaves, and tiny amounts of it will go to the roots.

As a result, it will stop the shikimic acid pathways of the weed and inhibit the action of the plant enzyme crucial to the synthesis of three amino acids, namely phenylalanine, tyrosine, and tryptophan.

However, Roundup only works well on growing weeds and grass. Therefore, it will not stop any seeds from germinating.

Spectracide vs. Roundup: When to apply?

Spectracide and Roundup are non-selective herbicides that destroy most plants, including grass. Therefore, the best time to apply them is before planting a lawn or eliminating weeds in places like sidewalks.

Also, the herbicides will only work on actively growing weeds above the soil. So the only issue with the two products is that they do not kill seeds.

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Which works better, Spectracide or Roundup?

Roundup works better than Spectracide in killing weeds. Generally, Spectracide is an excellent herbicide choice if you want to kill weeds growing around your crops.

However, in that case, it will only kill the plants that come into contact with the chemical. Therefore, even if you have a large field, the weeds that do not come into contact with Spectracide will not die.

On the other hand, Roundup is non-selective and will kill all weeds. Furthermore, once you spray it on any weeds, the chemical can easily spread from one plant to another.

Spectracide can only work by applying it to the weeds you want to kill. You will have to repeat the spraying several times to eliminate all unwanted plants.

But if you are going to kill all weeds without repeating the procedure, use Roundup by applying the chemical around the areas you want to clear.

Does Spectracide kill the roots?


When applied to a plant, Spectracide enters the weed through the leaves and goes directly to the roots.

It will then begin killing grassy weeds down to the roots almost immediately. If you are worried about plants that spread through a complex root system, Spectracide is definitely one of the best herbicides you can use.

Is Spectracide an excellent alternative to Roundup?

Spectracide is an excellent alternative to Roundup. You can use it to kill all broadleaf weeds, including dandelion, chickweed, white clover, and yellow nutsedge.

However, you must ensure you apply the herbicide to all plants to kill them.

Is Spectracide safer than Roundup?

Spectracide and Roundup are herbicides with chemical compounds that are toxic. However, the diquat dibromide in Spectracide is somewhat more moderately harmful to humans than glyphosate.

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Furthermore, unlike glyphosate, which has been linked to some cancers, no studies indicate that diquat dibromide causes cancer.

But the chemical can be hazardous to humans and animals and toxic to aquatic invertebrates. Therefore, take precautionary steps like wearing gloves when applying them and not allowing the pesticide to enter or run off into storm drains.

Is Spectracide as toxic as Roundup?

Spectracide and Roundup are both toxic herbicides.

Although they will kill unwanted plants, they can also disrupt the soil microbiome and cause toxic effects to earthworms, leading to compromised plant health, crop performance, and nutritional value.

Environmentally, Spectracide and Roundup can be toxic to aquatic life. Furthermore, humans should avoid contact with the chemicals because they can cause several side effects like skin and eye irritation.

To sum it up, both Spectracide and Roundup are toxic to humans, animals, aquatic life, and the environment.


Spectracide and Roundup are two of the most commonly used herbicides. You can use them to kill almost any weed on your garden, lawn, patio, or farm.

Roundup works by stopping the shikimic acid pathways of the weed, while Spectracide destroys the plant’s cell membrane and interferes with photosynthesis.

However, since the two products have chemical compounds, you should handle them carefully because they can cause skin and eye irritation. They can also damage the environment, destroy the soil microbiome, and harm aquatic life.

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