Dry stone wallers have only a few natural predators. Apart from power wielding town planners and permit officers, who make sure that only concrete contractors get any approval for municipal projects (in their continuous regime to eradicate dry stone walling and wallers in their natural habitat) the only other thing that poses any dangerous threat to the existence, and well being, of wallers is the looming presence and insidious incursion of the ominous plant species known as 'toxicodendron' in Latin, and commonly referred to as 'poison ivy'.
This dreaded 'weed of prey', if allowed to prowl unchecked and attack indiscriminately, can render an unsuspecting waller helpless, turning them into a writhing mass of itchiness within two days of exposure to its venom. In many parts of Canada wallers put themselves at risk anytime they are working in any area where there are rocky fields or overgrown farmland. Essentially the plant thrives in the same environment as most wallers do.
If it is hot day and a waller walks through a patch of the mature plant wearing shorts, or rubs against the plant with their bare arms, unless he or she has an immunity to the toxin, the poison ivy will affect them in an adverse and potentially disabilitating way. Contact with poison ivy can make skin bubble and fester and cause itchiness of unparalleled magnitude. Gasoline applied to patches of inflammation, if discovered early enough, can sometimes reduce the extent of the irritation. Prednisone and various special creams will often help the irritation to eventually subside in more severe cases.
Here we see a picture of the dreaded flora lurking about masquarading as a harmless broad-leafed plant amongst the grasses. Patches of the tender ivy are unobtrusively snuggled up to this small boulder, leaving any unsuspecting waller at risk who may be attracted to pick up such a rock and use it in their wall. Moving the stone, even while avoiding any skin contact with the actual poison ivy plant may still yield nasty skin irritation, just from handling the stone itself, which may have been 'primed' with toxic residue from the plants growing adjacent to it.
Thinking hands need to maintain a 'hands-off' strategy when working near this exploitive and sinister species of vegetation.