Hairy galinsoga (Galinsoga quadriradiata = G. ciliata) is a troublesome weed of vegetable crops in the Northeastern United States that can be difficult to control once established on a farm. Hairy galinsoga spreads throughout a farm by seeds that germinate quickly after exposure to light. Rapid production and germination of these seeds result in several generations in a year. Once hairy galinsoga is present on a farm, the seeds can easily spread by wind and equipment. Left uncontrolled, hairy galinsoga will take over production areas until a hard frost. Awareness of the life cycle and biology of hairy galinsoga are key to figuring out the best options for controlling it in your fields.

Growth Habit

Hairy galinsoga is a broadleaf annual weed with hairy leaves and stems, and opposite-toothed leaves. Mature plants of hairy galinsoga typically produce multiple branched stems and can reach two feet in height. Plants produce small white flowers with a distinctive yellow disk center in clusters at branch ends.

• Germination of seed begins when soil temperatures are in the mid-50s °F.
• Viable seeds will survive in the soil for four years at most, with a large number not surviving the first year.
• Hairy galinsoga will begin to emerge in the spring and will germinate throughout the growing season.
• Flowering will start mid-summer and continue through the first frost.
• Hairy galinsoga seeds have no to little dormancy and will quickly germinate when exposed to light and warm temperature.
• Spreads by seed dispersal.
• Growth is responsive to nitrogen and phosphorus.

Management Strategies

Control of hairy galinsoga is a multi-year process that involves several strategies for control of seed production. Organic and no-spray farming operations will need to rely on well-timed cultivation and strategic planning to compete with galinsoga populations.

• If hairy galinsoga is not currently present on your farm, take precautions to not unwittingly import it through soil amendments or borrowed equipment.
• Start scouting fields around mid-May for emerging populations and pull them by hand (or hoe) when populations are small or through mechanical cultivation for dense populations. Make sure that weather conditions will be dry for at least 48 hours after cultivation to prevent re-rooting of the dislodged plant.
• Preventing seed production is crucial for successful galinsoga control. Therefore, hand weeding, weed-whacking, and mowing should be conducted before galinsoga starts flowering.
• Clean farm and cultivation equipment when moving between infested fields and areas where galinsoga is not present.
• Utilize crops grown in black plastic or thick mulches, which impede hairy galinsoga growth.
• In areas heavily infested with galinsoga, moldboard plow the seeds as deep as possible followed by several years of shallow cultivation, allowing for seeds buried deeply to die off.
• Use stale seed bedding after the fields have been prepared for planting during the spring and summer. Allow time for weed seeds to germinate and then follow with light cultivation or a flame weeder to kill emerged seedlings prior to planting.
• Use tarps to encourage germination over a two-to-three-week period before planting. Depending on the temperature and timing, cultivation or flaming may be needed once the tarp is removed prior to planting.
• When possible, in heavily infested fields, use two to three years of dense cover crops, such as buckwheat or sorghum-Sudangrass, preventing seed production through cover crop management practices such as timed mowing.
• Where multiple years of cover crops are not possible, use frequent shallow cultivation in fields where crops are not planted once every three to four weeks.
• Consider organic matter loss when using cultivation as a regular means to manage weeds.

Farm Decision Tool

Hairy galinsoga management is a multi-year process for farms not relying on herbicides. Identification of existing hairy galinsoga populations on the farm along with reflection on previous activities and how they impact these populations, is the first step to developing a management plan. Use the charts below to identify your hairy galinsoga populations, current management methods, and develop a plan of action to eradicate hairy galinsoga from your production areas.

References

• Grubinger, V. (2014). Galinsoga Management. The University of Vermont.
• Grubinger, V. (2004). Flaming Stale Seedbeds for Weed Control.
• Lounsbury, N., Birthisel, S., Lilley, J., Maher, R. (2022). Tarping in the Northeast: A Guide for Small Farms (PDF). University of Maine.
• Mohler, C., Teasdale, J., DeTommaso, A. (2021). Manage Weeds on Your Farm: A Guide to Ecological Strategies. USDA Sustainable Agriculture.
• Mohler, C., Johnson, S. (2009). Crop Rotation on Organic Farms. USDA Sustainable Agriculture Research and Education.
• Uva, R., Neal, J., DiTomasso, J. (1997). Weeds of the Northeast. Cornell University Press.

September 2022