Corn meal, yes the stuff you cook with, is an excellent treatment for several garden diseases. Texas A&M started to study, or at least notice, the phenomenon in the 1990s on peanut crops. Prior to the use of corn meal, peanut fields had to be rotated into another crop to let the diseases die out. After they started using corn meal they could repeat the peanuts in the same fields season after season. Not sure why, but the research was never competed. Nowadays the TAMU profs are on a campaign to disavow all knowledge of the project, but it lived for over 10 years on their website. During that time the organic community in Texas took off and ran with the idea. I am living proof that it has worked in my garden every year since 2002 when I first tried it. In fact it worked so well that I converted to all organic that year. For a lawn we apply at 20 pounds per 1,000 square feet. Not sure how that would convert to a potted plant. I'd say a "light dusting" with corn meal and repeat in 3 weeks. I have used a heaping handful under my roses as a fertilizer confident that it is protecting the roses from the typical powdery mildew and black spot. Corn meal works by attracting the predatory Trichoderma (try koh DER mah) fungus. If there are any mushroom growers on this forum they will testify as to the devastation caused by a trichoderma "infection" in their mushroom crop. The fungus that directly decomposes corn meal initially attracts the trichoderma. The population of trichoderma builds on those other fungi. When the first fungus species are gone, the trichoderma latches onto all the other fungi at the surface to munch on. Those would include the disease. Corn meal is the most reliable and effective organic solution to fungal disease. I would go farther to say it is more reliable than chemical fungicides and certainly much more organic. Being a biological process, it takes 3 weeks to see the results from corn meal. The disease is stopped fairly quickly, but sustained new growth is really where you see the result.

My grandfather used to control gnats in the house in a similar fashion. Put a banana peel in your stainless sink and let the gnats gather there. Bring in a small propane torch and make a quick pass over the peels. You might be able to use a bananal peel to lure the gnats away from your plant before you hit them with the heat gun. Somehow, I'm in love with the heat gun trick. It just seems very manly!

Fertilizer choice won't have any effect on fungus gnats, just the plants. I disagree about using wilt as an indicator of when to water or as an attempt to get rid of FG's. About to wilt = healthy, actually wilted = extreme distress. As plants grow, they will use more moisture so the pot will dry more quickly, so a set schedule is rarely ideal. Drying at the top really won't help since the gnats will just use the moist soil at the bottom of, and within the center of the pot, especially if they are able to access the drain holes as mentioned. (Assuming your pots have drain holes. Do they?) The only bone of contention I have, a very minor one, with the excellent advice here would be that I wouldn't call a potting mix crappy if the only reason for that label is that it is able to support fungus gnat larvae. They need organic matter, so although it's certainly possible to have/make/(buy?) a potting mix without such, many people are perfectly happy with potting mixes containing such, either store-bought or home-made. Since fungus gnats are so easy to defeat/control/avoid, I don't find this one feature, seeing a few fungus gnats in small enough amounts that they do not bother plants or people, a significant enough detriment to call a potting mix crappy. (Please don't interpret this as arguing that FG's can damage plants, not saying that, just that a few seem harmless.) Some don't tolerate any fungus gnats, and I respect that, and support their efforts to get rid of them. Some may create a mix that does have organics but not of a type/texture that harbors FG's. As you learn, you can do the best possible job with what you can get and afford. Instead of overwatering, think under-drying and excessive moisture within the "soil" as the issue. I water many plants daily, if I feel like it, although they can go for a few days, some longer...

Bugs happen - it's a fact of life :-) If one needed to sterilize the soil or remove and replace soil every time there was an outbreak of aphids or other crop damaging insects, there would be very few productive gardens in this country! Aphids are easily controlled by hosing down with water, insecticidal soap, applications of Neem or other horticultural oils and with homemade sprays using plant extracts like garlic or citrus oil. Their eggs can overwinter in the soil but generally just disturbing the soil adequately before planting - a pretty common process with any spring garden prep - and then mulching well after planting will discourage their development. But even removing every single egg present in your garden now will not necessarily ban any aphids from returning when food sources appear. As I said to begin with........bugs happen. Leaf footed bugs are harder to control but they overwinter as adults in weedy, brushy areas so cleaning up/mowing/cutting back any areas like this in proximity to your raised beds will help to control their populations as well. Again, removing any soil from the beds will have NO impact on these critters. Powdery mildew does not over winter on soil. It needs plant tissue or debris to survive so if you clean up the beds properly before spring planting, you have removed the potential for any existing spores to develop. PM is much more of a climate/cultural related pathogen - it develops when air circulation is limited, in shade and when soils, air temperatures and moisture create a "perfect storm", often late season when soils are dry, temps high and with a high dew point or humidity, especially overnight. Providing sufficient sunlight, improving air circulation and making sure soils remain evenly moist during the critical periods will help enormously. Again, Neem or hort oils, baking soda mixtures and even spraying with diluted milk will help to control but these remedies need to be applied before you see signs of PM to be most effective. Blights are indeed soil borne pathogens and soil sterilization would help to control these problems but is often so impractical that most just deal with the issues via crop rotation. And just to clarify what was mentioned above, tomatoes are members of the Solanaceae or the nightshade family, as are peppers. eggplants, and potatoes. All of these can be subject to similar blights so you want to avoid planting these in the same location season after season. In fact, it is recommended to use at least three year cycle of rotating locations for best control. You can also seek out resistant varieties as well. Sunlight is never an enemy of a productive vegetable garden :-) It may just mean you have to water more often. Skip the A-frame pallets - they are not helping. And wind is usually not a concern either unless you get gale force ones - I live at the beach and get very strong winds off the water and they have never damaged my veggies. In fact, some veg are wind pollinated so allowing/encouraging breezes are beneficial. Winds/breezes also help to allow proper air circulation so beneficial for your PM issues. Other than adding some fresh OM to your beds - compost, composted manure, shredded leaves, etc. - there is really nothing else you need to do before spring planting. Don't remove any soil - just work what you have together with fresh OM and you are ready to go. But expect to devote some time and attention to your garden on pretty much a daily basis during the growing season. The more time you spend working and inspecting your garden, the more proactive you can be in thwarting off problems.