Thursday, May 31, 2012

It’s summertime, what should I be doing with my invasive plants?

Invasive species and invasive species management change with the seasons.  Some invasive species are more recognizable at certain times of the year and the success of control techniques often depend upon the right timing.  The River to River CWMA is creating a series of article about invasive species in the different seasons.  Be sure to also read THIS article on invasive species in fall.

You’ve spent all spring pulling garlic mustard and are gearing up for your fall and winter treatments of woody invasive plants. But what should you be doing with invasive plants during the summer?

It is tempting to stay indoors and avoid the heat, ticks, and chiggers that come with summer, but this time of year is ideal for controlling several invasive species. Herbaceous plants, such as Japanese stiltgrass and teasel are good targets for those warm summer months. Both of these species flower and set seed in the summer and then die (stiltgrass is an annual and teasel is a biennial). To effectively control infestations, you need to eliminate seed production; which means controlling them in the summer. Control teasel by spraying the rosettes or young bolting plants in early summer or hand-pulling the flowering plants in midsummer. For Japanese stiltgrass, wait until mid-summer to spray infestations. You can mow, hand-pull, or weed-whip infestations of stiltgrass anytime in the summer before flowering. Be sure to revisit control areas to follow up and retreat any new growth.

These invasive species are best controlled
during the summer months.  Clockwise from
top-left is johnsongrass, Japanese stiltgrass,
teasel, and Chinese yam.

Johnsongrass and Chinese yam are both best targeted in summer. While these two are both perennial plants, they are most vulnerable in the summer months. Look to treat Johnsongrass in early summer, just before it flowers. Chinese yam is best controlled in June, before the aerial tubers (bulbils) are formed.

Good information, including control recommendations for these and other species, can be found on the River to River CWMA Species of Concern page:

Working the summer comes with its own set of safety risks. Overheating and dehydration are real possibilities. Be sure to take plenty of breaks and drink lots of water when working on hot days. Also, it is a good idea to avoid working alone during the summer. Having someone else with you can ensure speedy treatment if necessary.

Another factor to consider when working in the summer is the impacts heat can have on herbicides. Excessive heat can increase the ability of herbicides to volatize, where the herbicide turns to vapor and can drift away. This can be a serious problem. The loss of the active ingredients from the herbicide mixture due to volatilization can drastically reduce its effectiveness. Additionally, those vapor pockets that form can drift over and damage non-target plants. You can reduce the risk of excessive volatilization by not using ester-based herbicides when the temperatures are over 90°F.

Summer is a great time of year to get out and control certain invasive species. Using the proper precautions will keep your treatments effective and you safe. Lastly, don’t forget to find time between all of your summer invasive plant treatments to set aside at least a few days to go fishing and camping!