Wild Parsnip

Wild Parsnip Burns and Blisters

Wild parsnip is among the rapidly increasing invasive weeds in many areas of Wisconsin. We see wild parsnip growing up in the roadsides and in other uncultivated areas above other grass and roadside plants. Wild parsnip is a yellow-green, tall plant that grows up to around five feet tall. Wild parsnip is of concern because humans develop a severe skin irritation from contact with its leaves Wild Parsnip Pics.   Plants have chemicals called furocoumarins that cause an interaction between plants and light that induce skin inflammation. Once the furocoumarins are absorbed by the skin, they are energized by UV light on both sunny and cloudy days. They then bind to DNA and cell membranes, destroying cells and skin. Parsnip burns usually occur in streaks and elongated spots, reflecting where a damaged leaf or stem moved across the skin before exposure to sunlight. You can brush against wild parsnip plants and not be affected. Parsnip is only dangerous when the plant sap from broken leaves or stems gets on your skin. One of the worst things to do is to use a weed eater to remove wild parsnip. This type of mechanical removal will splatter the plant sap all over the person and cause widespread burns and blisters. In cases of mild exposure to wild parsnip, affected areas turn red and feel sunburned. In severe cases, the skin first turns red and then blisters form. The arms, legs, torso, face, and neck are most vulnerable and affected areas may feel like they have been scalded. Blisters form a day or two after sun exposure and soon after the blisters rupture and the skin starts healing. But for many people, the ordeal is not over as dark red or brownish “scars” remain in the burned areas for several months to years. Wild parsnip germinates in the fall and forms a rosette or a small clump of leaves at the soil surface. In the spring the plant will then produce a plant which may reach up to five feet tall. The plants are yellow-green and produce umbel-shaped flower heads that are 4 to 8 inches in diameter. The individual flowers are yellow with five petals. Plants can be controlled mechanically by cutting them just below the soil surface. Mowing will not kill wild parsnip plants but will reduce seed production. If herbicides are needed and practical, a timely application of 2,4-D and/or dicamba to plants in the rosette growth stage (early fall or late April to mid-May) should control all treated plants. Careful applications of glyphosate will also kill wild parsnip plants. By the time plants are bolting or flowering, mowing is the best alternative. Why are we seeing more of this weed now? The delay in mowing roadsides until mid summer opens the door for this plant to complete its life cycle and produce ripe seeds well before any mowing is done. When roadsides and pastures are mowed in late July and August, parsnip seeds move as hitchhikers on the mowers. Mowing also creates a much more favorable environment for parsnip seeds to germinate than if the sites were left undisturbed. Relatively mild winters may enhance survival of wild parsnip plants that germinate and become established in the fall. Being able to readily identify wild parsnip and early detection of infested areas will minimize inadvertent and excessive exposure to this plant and the often painful results that follow.

For further information on Wild Parsnip please see the included links below:

Ken Williams

UW-Extension Agriculture Agent

Waushara County

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