How do I get bittersweet nightshade out of my pasture and how harmful is it to animals?
Question:
How do I get bittersweet nightshade out of my pasture and how harmful is it to animals?
Answer:
Bittersweet/climbing nightshade (Solanum dulcamara) is toxic to wildlife, as you obviously know. The lengthy species page from the USDA and the US Forestry Service says:
“Climbing nightshade contains solanine (glycoalkaloid and alkamines collectively), a mildly toxic substance known to be poisonous ([42,81,88,159,178], review by [55]) to humans, livestock, mice, dogs and rabbits ([48,81], reviews by [53,55,104]). Unripe berries have the highest concentration of toxins, followed by vegetative tissue, and then ripe berries [55]. While some describe the amount of toxin in climbing nightshade as not “dangerously poisonous” (review by [59]), others report that children may be especially sensitive to it (review by [164]). A handbook on poisonous plants indicated that climbing nightshade is only likely to cause symptoms in humans who have eaten 10 or more unripe berries; a fatal dose would require about 200 unripe berries [55]. In large doses, solanine will slow the heart, reduce body temperature, cause vertigo, delirium, convulsions and possibly death (review by [104]). If ingested by horses, climbing nightshade can cause labored breathing, nausea, weakness, trembling, constipation, diarrhea, and possibly death [48]. Laboratory mice that ingested climbing nightshade fruit of various degrees of ripeness experienced gastrointestinal problems or behavioral changes [81].”
While I am not a toxicologist, my understanding is that the amount of solanine is lower than some other Solanum species, but that data has definitely shown that it can be poisonous to varying degrees across multiple species depending on the amount ingested. I would err on the side of just accepting it is bad for home and livestock animals to consume it and take reasonable steps to minimize their chances of doing so. Hand pulling is the typical method for home gardeners to remove it, but that wouldn’t really work for a pasture. You can see options for chemical intervention on the species page from Penn State Univ Extension, and because it’s a larger scale treatment I will recommend you contact a ME-licensed pesticide applicator in your area to conduct a site evaluation and discuss the options, especially if you will have animals regularly feeding on the other plants there.
Happy gardening.