When To Apply Prodiamine 65 WDG? (Hint: Not In the Summer)

Troublesome weeds such as crabgrass produce up to 150,000 seeds, many of which stay behind, ready to germinate the following spring and repeat the cycle.  

Effective control of weeds can only be done with a good pre-emergent such as Prodiamine 65 WDG.

If you’re wondering when to apply Prodiamine 65 WDG, I’ve seen the best results when applied during the spring before soil temperatures reach the optimal range for weed seed germination. Find out below when to apply it correctly for your type of lawn.

What is a Pre-Emergent Herbicide?

A pre-emergent herbicide is a chemical lawn care formulation that’s used before the weeds take flight in your lawn or garden.

Pre-emergents contain several herbicides that work collectively to create a barrier of vapor that destroys weeds before their emergence.

Pre-emergents for residential use often come in granular form, and are mixed with fertilizer.

With pre-emergents, timing is of utmost importance for effective control of weeds before they germinate.

What is Prodiamine 65 WDG?

Brought to you by Quali-Pro—a leading name in the development of innovative, and post-patent formulations, Prodiamine 65 WDG (Wettable Dispersible Granule) is an effective pre-emergent herbicide that’s formulated to kill pre-emergent grass, and broadleaf weeds.

Prodiamine 65 WDG is a non-staining formula that’s effective against crabgrass, bluegrass, witchgrass, spurge, knotweed, henbit, chickweed, foxtail, and goosegrass.

This pre-emergent herbicide can be used in established turf grasses (excluding golf course putting greens), sod nurseries, landscape and container ornamentals, Christmas tree farms, and established perennials and wildflower plantings.

Prodiamine WDG is not to be confused with Prodiamine 4L, because the former contains 65 percent of the active ingredients Prodiamine, whereas the latter contains 40.8 percent.

Prodiamine WDG works similarly to birth control for the targeted weed, where it blocks plant cell division steps required for chromosome separation and cell wall formulation.

While Prodiamine WDG is highly effective at controlling several different types of weeds, I should mention that the results may not be 100 percent, which is the case with any other pre-emergent herbicide.

Depending on the stubbornness and resilience of some hard-to-control weeds, you may notice some weeds crop up during the growing season after applying Prodiamine 65 WDG.

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How to Mix and Apply Prodiamine 65 WDG?

Prodiamine 65 WDG can be mixed in several different concentrations according to your grass type, application process, and how long you want the pre-emergent to last.

Each application rate listed below will give you two months of control, aka split applications.

Measuring Soil Temperature

Whether you’re planting seeds or trying to get rid of weeds, you need to check the soil temperature before initiating the process.

Even the best planned Prodiamine 65 WDG applications can fail if the temperatures aren’t appropriate for the occasion.

You don’t need any expensive fancy gadget to measure soil temperature but can do so with a simple soil thermometer.

Warm Season Grasses – Bermuda, Tall Fescue, Centipede, St Augustine, Zoysia and Bahia Grasses

Apply Prodiamine WDG in the early spring when soil temperatures are approaching 55-degree F at the recommended rate of 183oz/5.2g per 1,000 square feet.

Next application is in the mid spring when soil temperature is over 65-degree F and reaching 70-degree F. At this interval, you should apply Prodiamine WDG at the rate of .183oz/5.2g per 1,000 square feet.

The 70-degree soil temperature window is when crabgrass germination is at its peak, so you want to double down on the application amount at this temperature. Go hard this time, and apply .46oz/13g per 1,000 square feet.

Your Prodiamine WDG grand total per year for Tall Fescue, Bermuda, St Augustine, Centipede, Zoysia and Bahia Grasses works out to .83oz/23.5g per 1,000 square feet.

You can mix the aforementioned dosages of Prodiamine WDG with either one gallon water or liquid fertilizer, each of which serves as a carrier for the pre-emergent. Water in with ½” of water within 24 hours. Here is a Prodiamine factsheet for your reference.

Cool Season Grasses – Kentucky Bluegrass, and Ryegrass

For Kentucky Bluegrass, and Ryegrass, apply Prodiamine WDG in the early spring, mid-spring and fall at the rate of .183oz/5.2g per 1,000 square feet.

The reason Kentucky Bluegrass and Ryegrass have a less total annual dosage of .55oz/15.6g per 1,000 square feet is because these grass types have shorter growing seasons than warm-season grasses.

Why Can’t I Apply Prodiamine in the Summer?

As the name suggests, pre-emergent herbicides work applied earlier on in the growing season by creating a barrier or weed prevention zone in the top one or two inches of the soil, hence preventing weeds from emerging through the surface.

The big reason why you have to lay Prodiamine down early, even in split applications, is so that the weed seeds die as soon as they come into contact with the barrier.

Prodiamine WDG is only effective if applied before the weeds emerge, and applying in the summer will totally be ineffective, and here’s why!

Target weeds grow slower in very hot and humid conditions because this is a time when the turfgrass is under stress.

And when weeds aren’t growing vigorously, they won’t absorb as much Prodiamine WDG, making it hard to control them at this stage. Adding to this, a lawn under stress could cause injury problems.

Timing your Prodiamine application is all about timing—you want to apply this pre-emergent when it’s not too hot or dry, but well enough into the growing season when the weeds are actively growing.

Apply Prodiamine WDG when the weeds are young and blooming, but not in the summer because their cuticle layer is thicker and mature by this time.

Furthermore, smaller weeds are easier to control than larger weeds. Take for example crabgrass—a weed that has a deeper root system, and robust photosynthetic ability owing to its rich foliage.

Therefore, the earlier you apply the Prodiamine WDG, the more your chances of success at controlling the weed.

All in all, when the weather in late July and August in most areas of the country is hot and dry, the window for effectively treating weeds with Prodiamine 65 WDG has passed until fall.

Common Mistakes when Using Prodiamine WDG

1. The first, biggest mistake homeowners make with Prodiamine 65 WDG applications is penetrating the barrier by aerating the soil after application. Refer to these tips on aerating soil.

If you aerate the soil after applying Prodiamine, you’re basically puncturing the soil, and making way for the weeds to grow through the aerated holes.

2. Another common mistake is saturating the entire yard with Prodiamine WDG for it to be effective.

You don’t necessarily have to spray Prodiamine WDG across your entire yard, but the first thing to do is scout out the problem areas, and only treat those weed-prone areas.

3. You must also water the area after applying Prodiamine WDG to create a zone that prevents weed germination. Watering should be done at least a week before the first germination date for effective results.

4. Remember, more is not always better, so apply Prodiamine 65 WDG only in the doses mentioned above. Applying too much Prodiamine will not harm your turf, but will drastically reduce the efficacy of the pre-emergent.

5. Prodiamine WDG can be mixed with liquid fertilizer and applied to your lawn. However, if you’re using dry fertilizer, do not apply Prodiamine 65 WDG just yet, but wait a couple of weeks to fertilize the lawn.

6. You can apply Prodiamine to slightly wet grass, but if the soil is too saturated, the pre-emergent will not sink through it properly and, hence will not be effective.

Instead, apply Prodiamine 65 WDG before rainfall or 24 hours to 48 hours following rainfall.

Final Thoughts

Prodiamine WDG is a solid pre-emergent that only delivers unsurpassed results when applied at the right time to your lawn.

It should never be applied in the summer, as the weeds have already reached their highest growth rate, and will not absorb Prodiamine 65 WDG and die.

When you apply Prodiamine, be sure to water the area to activate the weed prevention barrier. In areas with rainfall, wait for a day before rainfall and one to two days after rainfall to apply Prodiamine WDG.