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Wild parsnip: Another weed to put on your watch list

As if poison ivy, spotted knapweed, Japanese knotweed, autumn olive, palmer amaranth and others were not enough to be watching and keeping off your property, another new weed is starting to spread in the Lower Peninsula of Michigan. Wild parsnip has now been identified by Michigan State University Extension Educators in the Mecosta, Osceola and Wexford Counties in multiple locations.

Wild parsnip is a member of the Umbelliferae family relating it to parsley and carrots. It has genetic lineage to domestic parsnip that is grown by gardeners for its edible root. It lives from two to three years and enters its reproductive stage in the second year of life, growing to a height of 3 – 5 feet. It has a distinctive yellow ap-pearance, being most noticeable in July when it blossoms looking similar to Queen Anne’s lace (sometimes called wild carrot) in size and shape, but because of its coloration, reminds people of domestic dill that gar-deners raise for pickling.

Wild parsnip populations have been expanding for some time in Minnesota, Wisconsin, Ontario and the Up-per Peninsula of Michigan. It is found commonly in those locations along roadways, recreational trails, fence rows, and in abandoned fields. What makes wild parsnip an un-wanted guest are the juices in the plant. When the plant is cut or broken plant juice or sap that comes in contact with human skin can cause severe skin irritation that can persist for some time. This burn can cause scarring that may last for a year or more. The plant chemical in the sap, furocoumarin, causes phyto-photodermatis of the skin. It does this by absorbing into the skin, and then when exposed to sunlight within 8 hours, becomes energized by the ultra violet rays of the sun, destroying skin cells at the location of absorption.

The burning sensation of wild parsnip is no more severe than poison ivy, but the scarring side effect does last much longer. And unlike poison ivy that does not affect all people, wild parsnip burns almost all that are ex-posed to it regardless of their level of skin sensitivity. But the burning is only caused by the sap. If someone just touches the plant and gets no internal juice on their skin, they suffer no irritation. Often it will be the person that is cutting or mowing wild pars-nip and in the process is spraying droplets of the plant’s juices into the air, that will become affected.

Animals can also get parsnip burn on their skin if they have juice contact in areas with little hair or if they are eating cut portions of the plant. Fortu-nately most livestock do not like the taste of parsnip plants so they do not readily graze it. And wild parsnip is not a rapid growing plant so agricultural fields for hay or silage that have parsnip creeping in from the field edge seem to keep controlled by mowing and chopping of the crop. The literature does report that wild parsnip can cause decreased feed consumption which can lead to fertility issues in cattle and other grazing animals if the animal is forced to eat it (in chopped feeds or in drought situ-ations on pasture). But as with most toxic plants in forage crops, the solution to pollution (toxicity) is dilu-tion, meaning if animals eat enough safe forage and other grains it will dilute out any toxic impact from un-safe plants. Thus if you do find wild parsnip on or near crop property, irradiate its population while it is still at a low level so that it cannot spread and become a more serious problem.

Mowing does not kill the plant but if done frequently enough to keep the plant from blossoming; it will pre-vent it from producing seed and spreading. The plant reproduces and spreads only by seed. We suspect that is one reason why it is showing up along recently paved roads and trails – it is being spread into new areas by construction ditch bank re-seeding projects that are using weedy hay or straw and possibly seed contaminated soil.

Many herbicides will provide effective control of wild parsnip. The common 2,4-D herbicide that is used to control lawn weeds will provide control of parsnip while not harming surrounding grasses in abandoned field settings. Best timing for control is to spray the plant any time in the spring or early summer before it blos-soms, or in the fall after new fallen seeds have germinated. Parsnip found in crop fields, most commonly hay, pasture or others with permanent sod cover must be carefully controlled with herbicides or with cultural practices that will be safe for the crop and for the food supply. Consult with an MSU weed specialist or an MSU Extension Educator for control recommendations. Always read and follow all herbicide label direc-tions before applying.

Wild parsnip is a new weed that we must add to our list of weeds to keep a watch out for and handle carefully when controlling. As with many of these invasion weeds early control when populations are low is much easier than letting the plant get a strong foothold. For more information contact an MSU Extension Agricultural Educator in your area.