Help please! I live on the Bis Island of Hawaii, in Paauilo. We are at about 2700 feet with mildly cool temps. It can be wet up here but it has been dry this year. My problem is with my tomatoes AND many other plants I try to grow (squash, beans, eggplant,peas, cukes). With the tomatoes,squash and cukes the bottom leaves begin to yellow, brown patches may appear around the edges/tips of the leaves(but NOT circles or spots as in blights)and very light coating of white mildew will appear, esp. under the leaves. The branches die off one by one, moving up the plant until the whole plant is affected. It does produce fruit slowly the whole time and the fruit is mostly unaffected. But the plant dies off soon after fruiting.It affects ALL my plants, whether grown in the ground OR in good quality potting soil, away from the ground plot. If I put seedlings in the ground they almost never make it to fruiting, even with treating them for fungus from the start. The potted ones will grow to maturity, coming down with the disease right before fruiting starts. The squash/cukes sucumb the same way. Have tried treating with Neem oil, Garden Dust (copper/rotone), milk, baking soda-NOTHING has helped-even when I start treating BEFORE any signs of the disease shows up. Most of the people I have talked to here for advise have said they have all given up trying to grow tomatoes on the Big Isl(inc. a few nursery employees!). Pretty bleak outlook. Any ideas what this could be (it doesn't seem to fit a wilt or blight disease and if it is a powdery mildew it is non-responsive to treatment)? Is there anything I can try that I haven't already? Maybe disease resistant varieties (where would I get them???)??? I am so frustrated and ready to give up on growing vegetables all together. Mahalo Nui Loa for any and all help.
Also-my basil and lavender plants will get a milder varity of some mildew if I over water them-have to let them completely dry out before watering.