Tom's Blog

Wednesday, June 6, 2012

Summer herbicide techniques

We have now moved into summer brush and weed control mode.

During the period after our spring burns we controlled brush by foliar spraying with Garlon 3A aqueous the small resprouts that arose from fire-killed woody vegetation. This had great advantages, because the resprouts were small and hence required small amounts of herbicide. Also, they were easy to find because the native vegetation in the prairies and savannas was small so that the plants to be sprayed really stood out. Also, spacing between native species was wide so that spraying of resprouts could be accomplished without endangering "good" plants.

However, during the last two weeks of May, the native vegetation (as well as the target species) showed amazing growth spurts, and now it is no longer possible to use a foliar aqueous herbicide. We have switched to an oil-soluble herbicide (Garlon 4 Ultra in bark oil NT) used at a much higher concentration (20%). With this mixture, only small volumes of herbicide are required, which can be carefully applied to the target species. For woody plants such as sumac and buckthorn, a basal bark technique is used, with the herbicide applied with a paint sponge. For herbaceous plants such as sunflower, Canada goldenrod, and pale Indian plantain, the leaf spritz technique is used. A small amount of herbicide is deposited with a spray bottle on one or two upper leaves. No herbicide reaches the ground, or touches any of the "good" plants nearby. The herbaceous plant usually shows a response within an hour or so and by the next day has wilted. A few days later it is dead.
Small sumac being basal barked with Garlon 4 in oil using the paint stick technique.
The sponge technique is ideal for sumac. All that is required is a gentle swipe along the lower stem with a sponge saturated with herbicide. Within three or four days, the leaves start to turn red and within a week or so are brown.

Kathie and our two summer interns working on the south-facing slope, using the sponge stick technique.


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