I've lived on my farm for about three years now. When we moved in, the existing raised bed garden was completely overrun with weeds. After clearing some of the weeds, it became clear that the smallest bed in the center was planted with strawberries. I left them in place, hoping for a better harvest the next year.
Since then, the bed has been productive, but troubled. Some plants are covered in spots, and I remove them, but it persists. I think this is most likely leaf blight.
I'm looking for ideas for treating the blight. Some pages recommend various sprays (chemical and natural), but I'd like to talk to someone with experience before I go around spraying all sorts of concoctions on my plants.
Another suggestion is to rotate the crops, which makes sense, but this bed is so well sizes and placed for strawberries that I'd like to keep them there if possible (how does one rotate perennials, anyway?)
One final suggestion was to burn everything in the bed and start over. I'm kind of leaning toward trying this. Any thoughts?
I garden organically, and I use sprays. Not copper or sulfur, but biological sprays containing bacteria to aid in combating disease. The whole disease complex can be complicated, but I'll try to give you a quick cliffs notes version. Most diseases are soil borne, and some are airborne (powdery mildew for example). If you have ideally balanced soil, diseases have a very difficult time thriving and affecting your plants. Achieving healthy soil requires soil tests, amendments, and time. This is the long term solution with side effects of healthier, better crops too. The book Building Soils Naturally by Phil Nauta is one book of many out there explaining this and is easy to read and understand.
Mulch. A lot of plants get infected when rain drops impact soil, splashing soil particles onto leaves. The undesirable and infectious microbes on the particles then either make a home on the surface of the leaf tissue or enter the plant thru the stomata on the underside of the leaves. That's a major mechanism for infection. Mulch on top of the soil arrests the falling raindrops, and improves the soil below in other ways that are better understood reading some soil books. Every gardener should be mulching.
For actively combating disease, I use a product called Serenade, which is a particular strain of bacillus subtillis good at controlling certain common diseases. I also use effective microorganisms (EM) which is a blend of many microbes, great for disease control and soil conditioning. I purchased my EM from Teraganix. There are other brands available too. EM is good for a foliar spray as well as a root drench. Those microbes will set up shop in the soil, aid in making elements available for the plant to use, break down organic matter, and help make it more difficult for bad diseases to get a foothold. Both the aforementioned products are OMRI listed, and I have success with them. Don't purchase these expecting it to be the magic cure and you'll never see disease again. You may still see disease, maybe a little here, a little there, but in my case it has helped prevent complete infection ruining the plants and entire fruiting crop. If you were to chose one, get EM, it has many more benefits all around, and can be applied foliar or on the soil.
Burning everything and starting over won't kill the bad microbes down in the soil. Burning is not the solution for diseases. It's great for clearing brush/grasses and has a nifty side effect of leaving a little biochar behind.
"Study books and observe nature; if they do not agree, throw away the books." ~ William A. Albrecht