Early Blight and Sunscald on Tomatoes


“What are the best varieties for the low country of South Carolina?  I have problem with what appears to be early blight and due to the heat, sun scalding.  I want hybrids and fungicides I can use.

thanks for your help,

ron”

_____________________________________________________

Hi Ron,

Thank you for the email regarding your tomato problems.

Sunscald on Tomato

First of all, no matter what tomato variety you select, you are going to want to make sure that it is a variety with a good range of disease resistance.  One of the easiest methods to combating Early Blight and Sunscald is making sure your plants are as healthy as possible.

Seed companies don’t sell any tomato varieties that are particularly noted for having wonderful Early Blight resistance, and there are a couple of reasons for that.  First of all, research really hasn’t been done at the level of seed development for the home gardener in that respect.  Plant breeders have been gear more towards late blight because it is a more devasting disease and there are few cultural options for controlling it.

However, don’t be discouraged.  The solution to lowering your risk of having Early Blight starts right in your garden.  Early blight tends to get off to an early start in the spring when wet weather is experienced soon after transplants are set. These type of conditions are ideal for infection of young tomato plants by the early blight fungus.

Growing a crop in the same area for several years often leads to increased disease problems.  Early Blight control is based on crop rotation, removal and destruction of crop debris from previous crops, staking, mulching, and timely application of fungicides.  What I do at the end of the gardening season is pick up every stem, leaf, and fruit (no matter how small) and burn
them or put them in a garbage bag for the dump.

Staking and mulching are important in an Early Blight control program, since staking keeps foliage and fruit from contacting the soil surface, and mulching cuts down on “soil splash” onto lower parts of the plant. Since soil particles often contain the early blight fungus, this is a good way of keeping the fungus from invading plants. Plastic, or organic mulches (pine straw or even newspapers) are equally effective.

Application of fungicides is also generally needed for Early Blight control, if you are into that kind of thing.  Field tests have shown that chlorothalonil, maneb, and mancozeb fungicides –
all available at gardening supply stores under a variety of trade names –  provide effective early blight control when used according to label directions and applications are started early in the season. As an added plus, any of these fungicides may be “tank mixed” with an insecticide such as malathion or Sevin (or newer formulation, Eight), thus allowing a single application for control of disease and insects.

Begin fungicide applications as soon as possible after transplants are set out and continue at 7 to 10-day intervals throughout the season. Also, applications should be made after a rain. Other leaf diseases such as leaf mold, gray leaf spot, and Septoria leaf spot are controlled by these fungicides.  Make sure to read and follow label directions concerning rates, application intervals, and the number of days required from the last application until fruit can be harvested.

As for the sunscald, this comes from not having enough leaf cover over the tomato as it is developing.  UV rays damage the pigments inside the tomato — just like it does to human skin.  In turn, the ‘pigment initials’ for lycopene and other carotenoids that are present in a ripe tomato to give it color are damaged enough that they will not have color.  Natural enzymes and plant hormones ripen the tomato so it is soft and deteriorate the chlorophyll so it is the ripe color.  However, with no lycopene or other carotenoids there, it’s just whitish and lacking pigment.  Controlling the
Early Blight so you are not losing foliage and staking your plants will aid in controlling the sunscald.

As for some varieties that are good for South Carolina, I recommend:

–Large:  Better Boy, Better Bush, Big Beef, Celebrity, Early Girl II, Park’s Whopper
–Cherry:  Juliet (these are the best I’ve had against Early Blight in my garden and they are really good with Late Blight too), Small Fry, Super Sweet 100, Sweet Million, Tomatoberry Garden
–Plum:  Viva Italia

I hope this information helps you out.  If you have any other questions, please feel free to ask.

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