(Wolf’s milk, leafy euphorbia)
What does it look like?
Leafy spurge (Euphorbia esula L.) is a creeping perennial. Although it does produce viable seed, reproduction is mainly by its creeping roots. The clusters of cup-like flowers are greenish yellow in colour and are found at the end of the stems and branches. Leaves are alternate to spirally arranged, hairless and attach directly to the stem. Seedlings and mature plants both contain a milky juice that can cause skin irritation.
Its weedy nature…
Leafy spurge is a non-native plant of European origin. It is a serious weed of pastures, forage crops and hay fields, roadsides and reduced tillage situations. In cultivated fields it is very difficult to eradicate because of its rhizome and seed dispersal mechanism. Seeds are produced 30 days after the first flowers appear. Seeds, which are light and float well, are carried long distances along ditches, streams and floodplains. Leafy spurge is poisonous to most livestock, with the exception of sheep which can take approximately 2 – 3 weeks to get accustomed to grazing it.
Research has shown that leafy spurge root fragments can produce new shoots from as deep as 2.8m. Root lengths in this plant can be as much as 5 m. For these reasons, and the fact that seed capsules explode when mature and send seed several metres from the plant, this weed is very successful.
Herbicide treatments applied to infestations may need to be repeated in subsequent years in order to effectively treat the rhizomes. Application while the plants are young and actively growing will be most effective.
In a summer fallow situation, intensive tillage every 2 – 3 weeks, depending on weed growing conditions, is an effective mechanical control method for killing a high percentage of leafy spurge plants over the course of a season. Tilling should be done during hot, dry periods when winds are calm.
Tordon and Grazon are the most effective herbicides for controlling leafy spurge in non-legume pasture and forage. Other products such as Amitrol, Banvel, 2, 4-D or a combination of these can also be effective. Label directions must always be followed.
Selecting the proper herbicide is important as this weed is often found along water courses. In pastures with mature legumes or other desirable broad-leaved plants, spot applications of the above herbicides are recommended for patches of leafy spurge.
The black dot spurge beetle and the brown legged spurge beetle are available for the biological control of leafy spurge on drier sites.
In any chemical program be aware that the commonly used (and often cheaper) phenoxy herbicides (2,4-D, MCPA) are excellent at top growth kill, but only prevent regrowth for a month or more. This seldom translates into long term, significant reduction in thistle density the following season. It is most desirable, if possible, to use a herbicide that acts by moving down into the roots to maximize control.
Always follow any grazing or cropping restrictions and instructions on the label. Be aware that because of the mode of action of many herbicides they are most effective when the plant is actively growing. They will not work as well or sometimes not at all if the plant is stressed due to excessive heat, cold or extreme drought. Do not spray when a killing frost (-5oC or lower) is expected within the next two weeks.
Photographic credits to Alberta Agriculture, Food and Rural Development, the British Columbia, Ministry of Agriculture, Food and Fisheries, Field Guide to Noxious and Other Selected Weeds of British Columbia and Strathcona County, Transportation and Agriculture Services.