That is powdery mildew on your squash plants. If the soil is bone dry while the pepper plant is wilting yes it is under-watering. But the same wilting affect can be the result of other problems including over-watering.

I think you may have 2 separate problems, judging by the photos. The white spots are probably powdery mildew, which is a type of fungus. If you're not growing organically, you may wish to treat with daconil; there is one specifically for fruits and vegetables, so use that. It's very effective. If you are growing organically you may, as suggested, try neem oil. However, don't apply it in sunlight and don't apply it if you expect temps over 90 degrees Fahrenheit, or it will burn the leaves. You may want to try a sulphur-based insecticide. "Safer" puts out one of those, but read and follow the directions, and make sure it's safe for vegetables. It is treatable if you start working on it before it invades lots of leaves and weakens the plant. =================================================== Now, about that pepper plant. It could also be powdery mildew or it could be another, more serious disease. If you're not seeing white and/or diffuse yellow on the leaves, then it may not be powdery mildew. You folks in the south get some plant diseases that those of us in the cold zones rarely or never experience. I'd feel a lot better if someone who is familiar with your part of the country would chime in. I hate to speculate, but... First, if the pepper is planted in soggy ground that does not drain well, that could be your problem. If the other plants around it are not having problems, I'd suspect a virus, root nematodes (we don't get those up here), or soil-borne bacteria (we rarely have to deal with that either). I don't like the way it is wilting. If sitting in water is not the problem, I'd suspect a systemic plant disease. I'm sorry to say that you may have to destroy the plant if it doesn't improve in a few days (and I doubt it will). By "destroy" I mean you must dig it out, root and all, and put it in the trash. Don't compost it and don't leave it around; if it's diseased you don't want to contaminate other plants. Since peppers are related to tomatoes, eggplant, and potatoes, it may infect those plants if you have them. Try googling "peppers wilting" and see if can diagnose the problem. Again, I don't have any experience with some of the diseases that are common in your part of the world. Link below to University of Florida info on diseases of peppers in FL. Best of luck. Here is a link that might be useful: UFL Pepper Diseases

First off, I'd suggest a pair of gloves with some duct tape wrapped around them to save your hands. No need to pick up a ton of glochids :) I can't much say what's causing the red spots and leaf drop, but if I had to guess, maybe rot? How well draining is the soil? If the spots are soft and the soil stays we for long periods of time, that could be what it is. If the spots are soft, you should probably cut out the soft parts, and if the soil stays wet for long periods of time, a soil transplant is probably in order. This is simply pure speculation, but another possible reason as to why it's loosing branches might be because in their natural environment, this type of cactus gets large and tree-like, and maybe it's simply naturally shedding its lower limbs. But since it looks like you've got a Brasiliopuntia, I wouldn't get overly upset about anything falling off it. If all else fails, you can root pretty much any part of it. The leaves are actually pads that can be rooted to start new plants, and you can root the branches that are falling off too. I really don't know if you could re-root the main trunk. With such a big specimen (an a nice one at that!), I think you'd have to be awfully unlucky to loose it permanently. To root a piece, just let the cut part dry for a day or two, put it in some well draining soil, and wait until you see new growth. Then give it a bit of moisture every so often. Opuntia family cacti are fairly easy too root, and it looks like you're not in short supply of starts if you mess one up. As for soil, cacti are pretty good about growing in low nutrient soil. As long as the soil dries out fairly quickly, you should be fine, although I don't think a nice dose of fertilizer during the growing season will hurt it. Personally, I mix a good bit of perlite (pumice works better, but I've never gotten any) in with my cactus soil to improve drainage. I can't quite tell what you're using from the picture, but it might not like ordinary potting mix. As for light, it probably likes a lot. You might want to consider moving it outdoors during the summer. In the winter, I guess there's not much you can do, but it shouldn't grow too much then anyway. The grow light might help, though. As for the draft, Brasiliopuntia are a more tropical type of cactus, and I'm not too familiar with tropical cacti, but I don't think the chill would be that much of a problem. If its survived it in the past, I wouldn't worry about it now. If this is its first year in the cold, I'm not sure what its minimum temperature requirement is, but as long as its indoors its probably nothing to worry about. For water, I would personally water it more during the summer, but that would probably make it grow faster, so as long as its doesn't mind once every three weeks in the summer, it should be fine. I think once a month in the winter should do, although, again, since its more tropical, it might like more water, but as I said, I've never had one of these. I know that lack of water can cause Christmas cacti to loose pads, its possible that this works the same way. (Yeah, I know, maybe too much maybe not enough isn't very helpful) Good luck, and you're probably better off getting a second opinion.

Hi paracelsus, thanks for your post. No it is neither caterpillar nor snail. As a matter of fact I moved it indoors for a while because I at first also thought it was insect bites.