![]() ![]() If a spore happens to land on the leaf of a tomato plant that stays wet long enough, the spores will germinate. ![]() Many area farmers and gardeners may not have done well at preventing the initial infection, and now spores are blowing in the wind. However, these recommendations only delay the onset of the diseases, because while the initial infection of plants originates from bits of last season’s overwintered dead plants, by midsummer the air is full of spores coming from new infections around the neighborhood. Fall cleanup helps, as does covering the soil with mulch when you plant in spring. The first recommendation to avoid these diseases is to do anything you can to prevent spores from splashing. This explains at least partially why these diseases start on the lower leaves and work their way up the plant. If the leaves are wet, the spores germinate and infection begins. Usually early rains splash up spores from these bits of tissue in a garden, and the spores land on tomato leaves. In contrast, the pathogens that cause early blight and Septoria leaf spot can survive from one season to the next on even microscopic bits of dead tissue, which will be the source of infection the next season. If tubers are destroyed (actually, simply allowed to freeze on the surface of the ground), the pathogen does not survive to infect the next season’s crop. The late blight pathogen generally can overwinter here only in the potato tuber, a living bit of the plant. ![]() Since tomatoes do not overwinter in the Northeast, even if you had late blight one year you are unlikely to get it the next. The pathogen that causes late blight can survive from season to season only on living tissue. Many callers tell me their plants are dying from late blight, but that is actually rare. The diseases that most commonly cause the demise of tomatoes are Septoria leaf spot and early blight. Hence this column about common tomato diseases and the basics of building a simple, inexpensive tunnel to protect tomatoes. Then and there we both realized that it is not a far-fetched idea for even small-scale gardeners to cover their tomatoes. This year at the Common Ground Country Fair, when Mark Hutton (vegetable specialist with UMaine Cooperative Extension) and I were doing our normal Q&A session, tomato problems dominated the discussion. ![]() The difference between my tunnel tomatoes and garden tomatoes is that the leaves of plants in the garden or field get wet, and moisture favors fungal growth, while leaves in the tunnel are relatively dry. I have lots of advice, but I warn folks that although they may be able to stave off the problem for a while, their plants likely will succumb. This decline is by far the most common problem about which people contact me. We grow only paste tomatoes outdoors in a garden, because most garden tomatoes (including mine) succumb to disease by late summer. This is OK with me, as most of my tomato plants are still doing fine – because most are in a high tunnel. Sadly, most tomato plants in gardens across Maine and the rest of the Northeast died before summer ended, as they do almost every year. As you read this in December, you are probably already looking forward to next year’s tomatoes, but as I write this in mid-October, I am looking out my window at very dead tomato plants in my garden. ![]()
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