Animal: Squirrels. The one who discovered my tomatoes last summer was not much harm really. I’m planning to put water out for her when the tomatoes get going, later this summer, and protect the fruit with wire if she gets greedy.
Insect: Aphids, aka "plant lice." [shudder] I pick off entire leaves rather than wash them off (too kind).
Whatever: Powdery mildew. I’ve found chamomile is a good preventative but not so great at eradication. Baking soda solution works but tends to dry up the affected leaf (or the affected spots on the leaf) too. So far so good on my melon vines, which lost a few leaves but bounced back. Poisonous store-bought spray did nothing to help save my pattypan squash from it, one year. Never again!
Environmental: Sunburn (indoors). My lemon tree loves the sun beating through a south-facing window, but everything else scorches and dies, including thyme. I’m going to try Margaret’s sedum angelina, in a last ditch effort to avoid hens and chicks. Something has to keep the cat out of the pot. He’s another garden pest, btw, but he’s alright.