Figure 1: The compound leaf of poison ivy with its distinct three leaflets, hence the “leaves of three, let them be” saying. However, there are many plants that have compound leaves with three leaflets, but the middle leaflet of poison ivy is attached to a long petiole, a distinct characteristic.
Photo: Supplied
Table 1.
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Figure 2: Excellent poison ivy control was achieved with all treatments. Note the brown (necrotic) poison ivy carcasses amongst the native vegetation that was along the woodlot of the trial site.
Photo: Supplied
Table 2.
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Figure 3: An unsprayed plot area that demonstrates the density of poison ivy at this site.
Photo: Supplied
Table 3.
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Q: I have poison ivy along the edge of my field, and I’d like to control it without using glyphosate, because when I use glyphosate, it also kills any desired vegetation. What herbicides can be used that will kill the poison ivy and leave grass species alone?
There are several selective herbicides that are labelled to control poison ivy. Since poison ivy is a noxious weed under Ontario’s Weed Control Act, such herbicides can be used, provided the noxious weed is within proximity to agricultural land. Common labelled herbicides are shown in Table 1. During the 2021 season, their control of poison ivy was evaluated in Bruce County, Ont.
Poison ivy control
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At six weeks after application, all treatments provided exceptional poison ivy control (Table 2, Figure 2) when compared to the unsprayed control (Figure 3). At this research site, the poison ivy population was so dense that there wasn’t any desired grass underneath its canopy. However, none of the herbicides applied would kill desired grass species.
Do you need to add 2,4-D to dicamba?
Yes. Higher rates of dicamba are required to get adequate control of poison ivy. This makes a dicamba + 2,4-D tank mix more cost-effective (Table 3).
Have a question you want answered? Hashtag #PestPatrol on Twitter to @cowbrough or email Mike at [email protected].
