The common lawn pre-emergents (prodiamine, pendimethalin, and dithiopyr) work to help reduce the germination of certain seeds… Mostly grasses and only a handful of broadleaf weeds. The labels will list which weeds are targeted. To prevent more broadleaf weeds, a specialty broadleaf pre emergent like isoxaben is required.
Pre-emergents work by preventing the germination of seeds of the target species. So in order to be effective, a pre emergent needs to be applied BEFORE those seeds germinate. For winter annual weeds (annual weeds that are present in the fall, winter, and spring, like poa annua), a pre emergent needs to be applied in the fall before soil temps fall below 70F. In order to prevent summer annual weeds (like crabgrass), a pre emergent needs to be applied in the spring before soil temps reach 55F. (In very southern areas, timing can be more closely tied with periods of higher moisture AND climbing soil temps. Consult your state extension service for more specific guidance)
Pre emergents will not kill existing weeds. Pre-emergents alone will rarely control a weed problem. Pre-emergents are tools to **reduce** the need for post-emergents. They rarely eliminate the need for post emergents.
The labels of pre emergents have many important instructions and use restrictions. ALWAYS READ THE ENTIRE LABEL. For example, you are limited to 2 applications of each active ingredient per year.
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crozbot87
Still a bit early in my opinion. GDD tracker although more accurate in the Great Lakes region, shows Virginia somewhat in the yellow, not green. Maybe another week if the weather stays the same.
MyNameIsNemo_
Definitely – air temps in the 70s for six days next week for your zip. Soil temps will rise quickly with that much warm air for so long.
No-League-1368
The best advice I’ve ever received around preemergent: Better a month early than a day late.
Go ahead and get the first app on the ground.
Do another in May to cover the remainder of the growing season.
shadowdog21
Are you doing split applications? Or are you only planning on putting it down once? Barricade early and dithiopyr later is a good option if you have crabgrass issues last season.
5 Comments
The common lawn pre-emergents (prodiamine, pendimethalin, and dithiopyr) work to help reduce the germination of certain seeds… Mostly grasses and only a handful of broadleaf weeds. The labels will list which weeds are targeted. To prevent more broadleaf weeds, a specialty broadleaf pre emergent like isoxaben is required.
Pre-emergents work by preventing the germination of seeds of the target species. So in order to be effective, a pre emergent needs to be applied BEFORE those seeds germinate. For winter annual weeds (annual weeds that are present in the fall, winter, and spring, like poa annua), a pre emergent needs to be applied in the fall before soil temps fall below 70F. In order to prevent summer annual weeds (like crabgrass), a pre emergent needs to be applied in the spring before soil temps reach 55F. (In very southern areas, timing can be more closely tied with periods of higher moisture AND climbing soil temps. Consult your state extension service for more specific guidance)
Pre emergents will not kill existing weeds. Pre-emergents alone will rarely control a weed problem. Pre-emergents are tools to **reduce** the need for post-emergents. They rarely eliminate the need for post emergents.
The labels of pre emergents have many important instructions and use restrictions. ALWAYS READ THE ENTIRE LABEL. For example, you are limited to 2 applications of each active ingredient per year.
*I am a bot, and this action was performed automatically. Please [contact the moderators of this subreddit](/message/compose/?to=/r/lawncare) if you have any questions or concerns.*
Still a bit early in my opinion. GDD tracker although more accurate in the Great Lakes region, shows Virginia somewhat in the yellow, not green. Maybe another week if the weather stays the same.
Definitely – air temps in the 70s for six days next week for your zip. Soil temps will rise quickly with that much warm air for so long.
The best advice I’ve ever received around preemergent: Better a month early than a day late.
Go ahead and get the first app on the ground.
Do another in May to cover the remainder of the growing season.
Are you doing split applications? Or are you only planning on putting it down once? Barricade early and dithiopyr later is a good option if you have crabgrass issues last season.