There's a lot of effort that goes into preventing food safety problems, and a lot of literature about it. And then there's botulinum toxin, which is literally the most potent toxin that we know of.
Botulinum toxin
It's one of the most potent toxins we know of, with an LD50 of ~2 ng/kg when injected, or 1000 ng/kg when consumed orally.
"The conditions that favor the germination of C. botulinum spores include low acidity, moisture, the absence of oxygen, and storage at room temperature".
"C. botulinum spores can only germinate in a very low-oxygen environment. They will not germinate in the presence of oxygen."
"A jar that contains botulism toxin does not appear spoiled. It does not have masses of growth, mold, or yeast; it does not have an odor; it is not slimy; and it does not taste funny. These signs of spoilage are likely pointing to other microorganisms, such as molds or yeast."
"Clostridium botulinum, a bacterium, and its spores are readily found in the soil and can be present on the foods we regularly prepare and eat. The bacteria are destroyed at boiling water temperatures. The danger comes when the spores (a means of survival under adverse conditions) of these bacteria, which are not destroyed at boiling water temperatures, germinate to produce new bacteria. ... C. botulinum spores can survive the boiling point of water (212°F) but are destroyed at 240°F."
Urushiol
The active ingredient in poison ivy and poison oak. It's virtually invisible, and symptoms don't appear until 48 to 72 hours after contact, meaning that it might take a little while to trace it back to a specific booby trapped house. It grows naturally, and in some cases can be found in concentrated amounts oozing from a vine.