During the last several years, several products that combine a crabgrass herbicide with a broadleaf herbicide have been introduced. The introduction of these products has inspired some turfgrass managers to wonder if these products might be used in place of the more traditional method of weed control in turfgrass, which is to apply a preemergence weed control in early spring followed by a postemergence weed control targeting broadleaf weeds in late spring.
To attempt to control all of your weeds with one application, there are three general strategies that might be used:
Apply a preemergence herbicide combined with a postemergence herbicide during early spring.
Apply a preemergence grassy herbicide, postemergence grassy herbicide and broadleaf weed control while crabgrass is still in leaf stage.
Control both crabgrass and broadleaf weeds postemergence in late spring/early summer.
Preemergence herbicide/postemergence broadleaf control in early spring
The strategy here is to use an herbicide with long residual control. Defendor herbicide from Dow AgroSciences contains the active ingredient florasulam. It’s currently available in a co-pack with Dimension 2EW. Dimension and Defendor should be applied together in the spring with one application or with split applications about eight weeks apart. Because it’s meant to go out with Dimension, the application is made considerably earlier than other broadleaf herbicides. However, florasulam works well in cooler temperatures and control can be long lasting.
Research conducted at Ohio State University shows that a single application of Defendor herbicide will give greater than 90 percent control of dandelion and white clover for 84 days. On plots receiving sequential applications control was still nearly 100 percent at 98 days after the initial application. On the research plots, an application in late March resulted in a 100 percent decrease in dandelion bloom.
Weeds controlled include dandelion, white clover, common and mouse-ear chickweed, mustard and shepherd’s purse. This product may be an excellent choice in areas that are sensitive to the application of 2,4-D.
Pre and postemergence grassy weed control/postemergence broadleaf control in late spring
FMC Professional Solutions’ Echelon 4SC (prodiamine and sulfentrazone) and Calvalcade PQ (prodiamine and quinclorac) from Sipcam Advan offer both pre and postemergence control of crabgrass as well as some activity against broadleaf weeds. The advantage of this strategy is that both products contain a herbicide that will control leaf stage crabgrass as well as a preemergence herbicide. If these products are used on leaf stage crabgrass (mid- to late May in the Midwest), then the leaf stage crabgrass will be controlled and the preemergence barrier will be applied later, greatly decreasing the chances of late-season breakthrough of summer annual broadleaf and grassy weeds.
Sulfentrazone has some activity against broadleaf weeds but is excellent on sedges. Thus, if your turf is relatively free of broadleaf weeds but you have a problem with sedges and grassy weeds this may be a good choice. Quinclorac is effective on crabgrass and also postemergence against dandelion and clover.
Two recently introduced herbicides offer pre and postemergence control of annual and perennial grasses as well as annual and perennial broadleaf weeds. Mesotrione, marketed as Tenacity by Syngenta, has the advantage of being safe to seedling turfgrass, making it great for use at establishment or for overseeding. However, its preemergence activity tends to be shorter in turfgrass than on bare soil, and its postemergence activity is improved if more than one application is made.
Topramezone is a recent introduction from BASF marketed as Pylex. It has a similar mode of action to mesotrione. Topramezone inhibits carotenoid biosynthesis, which results in bleaching of affected leaf tissues. Pylex is only for use on centipedegrass or the cool-season turfgrasses Kentucky bluegrass, perennial ryegrass and tall or fine fescue. It’s important to note that Pylex is labeled only for spot treatment applications on sports turf and residential lawns.
Topramezone has pre and postemergence activity, and Pylex is labeled for the control of 15 grassy and 39 broadleaf weeds. It’s excellent for the control of goosegrass and sedges. In addition, research has found that it can be effective for the postemergence control of tillering crabgrass. In trials at Ohio State University, we found that control was similar or, in some cases, better than control of crabgrass with mesotrione or quinclorac. For broadleaf weed control, research at Ohio State found that topramezone has good activity against white clover but isn’t as active against broadleaf weeds such as dandelion or ground ivy. Both mesotrione and topramezone tend to offer better weed control if more than one application is made.
Postemergence grassy and broadleaf weed control in late spring/early summer
Many newer combination products have been formulated in an attempt to control broadleaf and grassy weeds postemergence with a single application (Table 1). Some of these products will also control yellow nutsedge. Quinclorac now appears in several combination products for crabgrass and broadleaf weed control, particularly dandelion and clover.
Products that control both crabgrass and broadleaf weeds include LESCO’s Momentum Q and Nufarm’s Quincept (2,4-D, dicamba and quinclorac), BASF’s Onetime (MCPP, dicamba and quinclorac), Q4 (2,4-D, dicamba, sulfentrazone and quinclorac) from PBI Gordon and FMC’s Solitare (quinclorac and sulfentrazone).
Quali-Pro’s 2DQ is similar to Quincept, but the rate of quinclorac is lower so it will not have activity on crabgrass. Its performance is comparable to some three-way herbicides on the market, such as PBI Gordon’s Trimec, or NuFarm’s Escalade 2 or Triplet. SquareOne herbicide (quinclorac and carfentrazone) from FMC is safe to seedling turfgrass and recommended when seeding ryegrass and fescues.
Last Call Herbicide is a new combination herbicide from NuFarm that contains the active ingredients dicamba, fluroxypyr and fenoxaprop. This is the first herbicide to combine fenoxaprop with broadleaf herbicides. Tank mixing with 2,4-D may reduce the effectiveness of Last Call, and it should not be applied within 21 days of a 2,4-D application or five days before a 2,4-D application. Consult the label for specifics. Our research suggests that Last Call can be effective against crabgrass that is in the 1-2 or even 2-4 tiller stage. However, for best results it should be used on leaf stage crabgrass. It’s labeled for sports fields, and is safe on Kentucky bluegrass, perennial ryegrass, tall fescue, fine fescue and zoysiagrass. Don’t use on desirable bermudagrass. In fact, Last Call is also labeled for selective removal of bermudagrass.
Putting it all together
There is no one best product to use if attempting all of your weed control with one application. The main issue is that of timing relative to the life cycles of the weeds being controlled and any overseeding practices on your fields.
Applying both pre and postemergence herbicides together in early spring may work. However, a single application in early spring runs the risk of weeds germinating in late summer after the preemergence herbicide has broken down. Having said this, it might be an excellent choice if you plan to do a lot of overseeding in the fall, because the preemergence herbicide should be broken down and not interfere with fall seeding operations. Of course, you could always spot apply one of the other broad-spectrum herbicides during summer if there are escapes.
If you’re doing any overseeding in the spring, then a late-spring application, after the seedling turf has matured sufficiently, might be your best strategy. You may be able to control all of your weeds with a single application by utilizing one of the herbicides with both pre and postemergence activity or tank mixing a pre/postemergent crabgrass herbicide with a broadleaf herbicide.
Depending on timing, there may be some tillering crabgrass that escapes the application. However, control should be good. If you’re not overseeding, then a pre/postemergence herbicide application to leaf stage crabgrass in late spring, with or without the addition of a broadleaf herbicide (depending on your weed pressure), will likely give you the best result.
There are a couple of issues if attempting to rely only on postemergence control. If you apply products too early, you may get good control but weeds are still germinating and new weeds will fill in. If you apply too late, then you may get incomplete control because tillering crabgrass and hardened broadleaf weeds are more difficult to control.
Depending on your location, sport, turfgrass species and predominate weed pressure, you may or may not be able to control all your weeds in one application. But, if you have ever wanted to, because of new product innovations, it has never been easier.