To Control Control of Biennial and Perennial Weeds

On September 26, 2019

To Control Control of Biennial and Perennial Weeds

Fall is an excellent time to manage biennial and perennial weeds. In particular, biennials such as common burdock, wild carrot, and bull, musk, and plumeless thistles are much easier to kill while they are in the rosette stage of growth and prior to surviving a winter. Extension Agronomist Dwight Ligenfelter points out once they start growth in the spring, they rapidly develop with the goal of reproducing and it becomes more difficult to control them. As you have heard many times before, late summer and fall is the best time to control most perennials with a systemic herbicide because herbicides are moved into the root systems allowing better control.

In general, the application window runs from early September through October, depending on where you are in the state and what weeds you are targeting. Applications to perennial species like horsenettle, smooth groundcherry, and woody species like multiflora rose should be on the early side of this window, while cool-season perennials like Canada thistle, quackgrass, and dandelion can be effectively controlled after several light frosts. With both biennial and perennials species, adequate leaf tissue must be present and it should be reasonably healthy to absorb the herbicide. For grass pastures, check the 2019 Mid-Atlantic Weed Management Guide: specific information on herbicide performance by weed species. Also be sure to consult a current product label for use recommendations and restrictions.

The most common herbicides used for broad-spectrum control of many weeds in the fall is glyphosate for grasses and broadleaves and 2,4-D or dicamba (Banvel, Clarity, etc.) for broadleaves. Other systemic products such as triclopyr (e.g., Crossbow, Candor, Crossroad, Remedy Ultra) or metsulfuron can be options as well. (However, be cautious of crop rotational restrictions with triclopyr and metsulfuron.) A combination of these products may be the best solution for a mixture of different perennial weeds. For most perennials including hemp dogbane, horsenettle, common milkweed, pokeweed, hedge bindweed, multiflora rose, poison ivy, and wild blackberry, make applications from September 1 through October 15 or before a hard frost. In general, applications by October 1 may be more effective. In northern areas of Pennsylvania, consider making the application before October 1. An additional two week application window can exist for Canada thistle and quackgrass, because of their cool-season habit of growth.
Favorable air temperatures should be a consideration immediately before, during, and after application. In general, the warmer the better, with daytime high temperatures in the mid-50s at a minimum. Cold nights and cool, cloudy days will reduce and slow the effectiveness of the applications. The more active the weeds are growing, the better the herbicide performance.

On another note, fall is the best time to kill declining sod stands (i.e., pure stand alfalfa or mixtures). Although glyphosate is better at controlling alfalfa in the fall than the spring, an additional herbicide application (e.g. 2,4-D/dicamba) or tillage will be required to completely control the alfalfa/mixture. Unless, you plan to get one last spring cutting, now is the time to control that old hay field; don’t wait until spring when it’s more difficult to get an effective burndown kill prior to planting.
Photo: Problem weeds in a pasture setting. Credit: Penn State Extension

To Become A Master Well Owner Volunteer

If you are interested in learning more about the proper management of private water wells, springs and cisterns and you are willing to share what you learn with others, you might be interested in applying for the Master Well Owner online course being offered by Penn State Extension!

The Penn State Master Well Owner Network (MWON) will provide free, online training for the first 20 volunteers who submit an application and meet the following criteria: 1) you must NOT be employed by any company that provides paid services to private water supply owners (i.e. water testing companies, water treatment companies, water well drillers, etc.) and 2) you must be willing to pass along basic private water system management knowledge to other private water system owners. The deadline to apply for this online course is September 27, 2019.

Each volunteer who applies and is accepted into the program will receive details on how to access the new, online MWON online course at no cost. Successful applicants will be able to start the course on September 30, 2019 and the course will end on November 22, 2019. The course includes six chapters covering private water system basics, well and spring construction, water testing, water supply protection, water treatment, water conservation, and outreach strategies. Each chapter includes a mixture of short videos and text along with links to additional resources and a short quiz. Volunteers must answer 70% of the online quiz questions correctly to be certified as a volunteer. A computer with a high-speed internet connection is recommended to view all the course materials and videos. To fill out an application for the MWON program, visit the following website:

Volunteers who successfully complete the training course and pass a short exam will receive a free copy of the 80-page publication – A Guide to Private Water Systems in Pennsylvania, discounted water testing through the Penn State water testing lab, and access to various MWON educational materials. In return, MWON volunteers are asked to pass along what they have learned to other private water supply owners and submit a simple, one-page annual report of their educational accomplishments.

Pennsylvania is home to over one million private water wells and springs but it is one of the few states that do not provide statewide regulations to protect these rural drinking water supplies. In 2004, Penn State Cooperative Extension and several partner agencies created the Master Well Owner Network (MWON); trained volunteers who are dedicated to promoting the proper construction, testing, and maintenance of private water wells, springs and cisterns throughout Pennsylvania. Since its inception, hundreds of MWON volunteers have provided education to over 50,000 private water supply owners throughout the state.

Quote Of The Week: “Fall has always been my favorite season. The time when everything bursts with its last beauty, as if nature had been saving up all year for the grand finale.” – Lauren Destefano