Battling tomato blight should start early

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Battling tomato blight should start early Story Discussion Font Size: Default font size Larger font size
By LEE REICH
For The Associated Press | Monday, September 01, 2008 | No comments posted.
About this time of year, you might hear complaints about the sorrystate of tomato plants.

Yes, many do look unhappy, and it all began early this summer.Surprisingly, such tomato plants might still be loaded down with areasonably large crop of fruit -- surprising considering the leafloss on each plant. Then again, the crop might seem abundant onlybecause there are fewer leaves now hiding the tomatoes.

And the culprit is ...

Look more closely at tomato leaves to pinpoint the cause of theproblem. Find a leaf that still has some green on it and you maysee spots, each consisting of concentric light and dark rings.That's a symptom of early blight, a disease especially troublesomein wet summers.

Early blight also attacks tomato fruits, causing small ones to dropoff and leaving dark leathery spots near the stem ends of olderones. In a bad year, early blight kills entire plants.

There's not much you can do now. Earlier in the season, picking offinfected leaves may have helped, but this kind of treatment oftenresults in a race to see which kills a plant first, premature leafloss or diseased leaves infecting healthy ones. Fungicide sprays,such as Bordeaux mixture, are effective, but also would have to beapplied earlier in the season. And who wants to eat vegetables thathave pesticides on them? Especially when pesticides can be avoided.



Keep blight at bay

First let's deal with this year's fruit. Whole tomatoes, or soundparts of any ripe ones, are perfectly good to eat from a humanhealth standpoint. Taste them before plopping them into thesaucepan, though, because they might taste sharper than usual.

As for averting blight next year, the disease spends the winter ininfected plant debris, so thoroughly cleaning up and compostingevery bit of your old tomato plants at the end of this seasonlessens the sources of infection for next year. Clean up potatoplants, too, because they also harbor early blight.

To put distance between any overlooked debris and young plants,next spring set your tomato transplants as far as possible fromwhere this year

s tomatoes or potatoes grew. The ideal is to let three years elapsebefore returning them to where they grew previously.

Also, attack early blight by creating inhospitable conditions forthe fungus. It festers on moist leaves, so always grow your plantswhere sunlight and gentle breezes dry the foliage quickly. And whenyou water, avoid wetting the leaves.



Choose resistant varieties

How badly your tomatoes are battered by early blight also dependson what varieties you grow. So-called determinate tomatoes, whichhave a bushy growth habit, are more susceptible to early blightthan are indeterminate tomatoes.

Early blight is also most severe when tomato plants are heavilyladen with fruits, and this puts determinate tomatoes, which ripentheir whole crop over a short period of time, most at risk. Seedcatalogs, seed packets and plant labels usually specify whether atomato variety is determinate or indeterminate.

It turns out that most paste tomatoes are determinate -- good ifyou want to cook up a batch of tomatoes all at once, but bad whenearly blight threatens. One way to decrease early blight on yourpaste tomatoes is to grow one of the few indeterminate varieties.Try, for instance, San Marzano, an indeterminate paste variety thatis awful-tasting when fresh, but which cooks up into a mostdelectable and tangy sauce.