We have to be careful when using herbicides: too little won’t be effective enough, but too much can damage the grass you want to keep. That’s why it’s important to follow the directions closely and apply weed killer in the right amounts and with the right method.
When it comes to prodiamine, it’s safe to use on the most common turf grasses. However, since this pre-emergent herbicide prevents new growth from developing roots, it can damage the mature grass roots in your lawn if too much is applied at once or too frequently. As a trusted and effective herbicide, it will do its job well when put down right.
In This Article
How Does Prodiamine Work?
Prodiamine is a pre-emergent herbicide that’s applied in early spring or early fall, before annual weeds like crabgrass and poa annua show up. This herbicide comes as a dissolvable solid (as Prodiamine 65 WDG, water dispersible granules), as a liquid, sold as Prodiamine 4L, or as a granular solid, sold as Barricade.
The solution targets and prevents root development by interfering with cell division. When a seed starts to germinate, the first thing to appear is the root. When the seed’s new root comes in contact with the prodiamine barrier in the upper layer of the topsoil, the seed stops forming and dies off.
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By preventing new seeds from sprouting before your lawn revives from dormancy, the early herbicide application makes sure that there is no competition for your grass when it grows back in. When grass is able to create full coverage, it doesn’t leave space for other weeds to grow or establish during the rest of the season, reducing the chances of weeds showing up and you needing to do any more than a few spot treatments here and there.
What Happens If You Apply Too Much Prodiamine?
If too much prodiamine is applied, or if it’s applied too late, the herbicide can damage the mature grass roots that wouldn’t otherwise be affected by a light application. The same root-inhibiting effect that disrupts seed germination can also interfere with root health in mature grass. Known as “clubbing,” the roots absorb the excess herbicide and become stunted and misshapen. The damaged roots then aren’t able to take up water or nutrients, and the grass dies.
When Should I Apply Prodiamine?
A few simple rules will help you pinpoint when the best time will be to apply prodiamine:
- Apply before crabgrass sprouts – Prodiamine targets crabgrass and other annual weeds that show up when soil temperatures are between 55 and 70 degrees, so the best time to apply the herbicide is one or two weeks before that time when temperatures are about to enter the range for growth.
- Consider a split application – Many lawn caretakers like to do a split application of prodiamine, applying a half dose at the beginning of the season and the other half about 6 weeks later. Since seeds can germinate at any time over the season when the temperatures are right, a two-wave approach helps catch seeds that germinate later in the season.
- Don’t apply with grass seed – Prodiamine affects germination in seeds of all kinds, and while it’s made to be safe on certain types of mature grass, it will prevent grass seeds from sprouting as well as the weed seeds. Whether you’re overseeding or planting a new lawn, it should be scheduled for a season that you don’t apply pre-emergent.
When Is It Too Late To Put Down Prodiamine?
If you’ve missed the 55-degree mark, it may not be too late to put down an application of prodiamine. If you’re still within the first quarter of the season, you can put down a full or split application, and it won’t be too much for the yard to handle. If you’re halfway through, however, a half-application would be better to not stress out the grass as it begins to prepare for dormancy.
Once the soil temperatures are above 70 degrees in spring, a prodiamine application won’t have any effect since the crabgrass is no longer germinating. When temperatures drop below 55 in fall, prodiamine shouldn’t be applied because it won’t stay in the ground long enough to last until the next spring. While cold snaps and temperature fluctuations don’t degrade prodiamine, and it stays in the ground for several months, it will be rinsed away before the following growing season.
How Much Prodiamine Do I Apply?
The size of your yard will be the first factor in determining how much prodiamine to apply according to your yard’s measurement in square feet or acres. Since different types of the herbicide come in different forms and concentrations, following the directions on the product label closely is going to be your best guide for the application rate.
When you apply solid granules, a broadcast spreader will help distribute the application evenly. You can be sure of an even application of a liquid form by using a handheld or backpack sprayer with a spray nozzle. A dye can be added to liquid prodiamine to mark where you’ve applied it, so you don’t double over an area.
How Often Should I Apply Prodiamine?
Prodiamine can be applied once a year or twice with a split application. It shouldn’t be applied too frequently because too much of the herbicide can either begin to damage your lawn or create resistance among some weeds that may begin to sprout despite the herbicide. Yards should be given a rest every other season to either plant new grass or simply not stress it out.
Should I Reapply Prodiamine If It Rains?
If you apply a liquid form of prodiamine, or you’ve watered in solid granules (about a half-inch of water), and it rains more than you expected just afterward, you shouldn’t reapply the herbicide. It’s made to be used outdoors, and it has some staying power once it’s put down.
This is a situation where it’s better to be safe than sorry: if some of the herbicide did get rinsed away, what remains will still have a lot of prevention power. If not much got removed and you reapplied, the over-application will likely damage the grass while also suppressing new seed growth.
Last update on 2023-02-06 / Affiliate links / Somes Images and Data from Amazon Product Advertising API