A bit of information about pesticides/insecticides:
Neonicotinoids – so much focus is on these bad guys that people forget that they aren’t the only pesticides. There are many pesticides that are not neonicotinoids. If a plant doesn’t have the neonicotinoid tag, it can still be deadly. (Not all retail nurseries will require labels if their growers use neonicotinoids.)
Organic Pesticides – the difference between organic and non-organic plants is about the make-up of the pesticide. There are many organic pesticides that many organic growers use on their plants. The difference between a caterpillar dying from a inorganic pesticide vs an organic one is the different between me having a steel beam fall on my head or a monstrous tree fall on my head. Both are would kill me. One is non-organic and one is organic.
Chemicals – chemical doesn’t mean ‘bad’. All matter is made of chemicals. Our brains produce specific chemicals when we are afraid or stressed, chemicals that help us react properly. Many pesticides are not ‘chemicals’ as we usually think of chemicals. Many chemicals are totally natural. Some non-chemical pesticides are living organisms – virus, bacteria, fungi, etc. The use of the word ‘chemicals’ in a sentence like “they used chemicals on the plant” doesn’t tell us anything about whether the plant is safe for caterpillars. Salt, which is used to save caterpillars which have drowned, is a chemical.
Flea/tick ‘medication’ is actually a pesticide. It is called ‘medication’ because few people would feed their pets pesticides. When touching your dog or cat with flea/tick oral or topical medication, you transfer the pesticide to your hands. Touching caterpillars, chrysalises, or host plants can transfer that pesticide to them. This can be deadly for caterpillars.
Systemic – Systemic pesticides are absorbed into the plant and nothing can be done except wait for the plant to become free of the pesticide, sometimes months later. Non-systemic pesticides usually wash off after a few rains or irrigation washes the plants a few times.
Growth regulator – there are two kinds of growth regulators used on plants. PLANT growth regulator is totally safe for caterpillars. It affects how tall the plant grows. The other is INSECT growth regulator, preventing caterpillars from pupating properly. (The reason Easter lilies and poinsettias are shorter when you buy them as compared to when you grow them is simple: PLANT growth regulator.)
Green vomit – many pesticides cause caterpillars to vomit or spit bright green fluid. Not all pesticides do so. Caterpillars can die from pesticides without vomiting any green liquid.
Diarrhea – some pesticides cause diarrhea. Bt (an organic pesticide used specifically to kill caterpillars) often causes green diarrhea. Diarrhea from some diseases is brown.