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Sunday, May 6, 2012

How to Get Fewer Disease Problems on Tomatoes

Q. At the nursery I purchased some heirloom tomatoes. They got silvery/shiny areas on back of leaves which turned into dry dead spots.  The plant is also dropping blossoms what is this? I applied fungicide but do not know if this is appropriate. My homegrown tomato plants do not have this. Please let me know.  I do not want my other tomato plants infected.

A. You have noticed something that I have been talking about. This is concerning the quality of homegrown vegetable transplants being superior to the transplants grown by commercial growers for the mass markets.
            To get transplants ready for markets growers usually have to grow transplants in some sort of protected culture such as greenhouses, cold frames, hot frames or hoophouses. When grown for mass markets the grower has to produce transplants at the lowest cost possible to improve profit margins.
            This may mean that in many cases these transplants may not be grown under the cleanest conditions and the growing conditions also may not be the best. This means that mass market transplants can be very subject to earlier development of diseases and insect problems.

            When you grow transplants at home you can afford to start with cleaner materials and as a consequence have fewer insects and diseases to contend with. You can also get the exact variety you want by ordering the seed ahead of time.

            Sometimes the commercial grower will apply pesticides just before shipping transplants to the nursery to remove any pest problems that might be developing, pests that may already be there and make sure they are pest free when delivered to the nursery.

            Several problems can cause silvery discoloration to the leaves including the natural silvery-green color of some tomato plants. These dead spots may or may not be related to the grey green color of the leaves. The brown spots could be due to feeding damage by insects or a disease problem. It is hard to say exactly without seeing a fresh plant sample with the disease present or several high-quality pictures.
            As far as blossom drop on tomatoes remember that they are finicky. Temperatures to high during the day, too low at night, and irrigation which is missed, an unusually hot day when temperatures abnormally been cool, all can play a role. Tomatoes grown excluding bees for pollination may cause the flowers to abort.

            If you are worried about a lack of bees then use your electric toothbrush to vibrate the plant for better fruit set. Touching the electric vibrating toothbrush to portions of the plants close to the flowers for a few seconds may improve fruit set if bees are limited.

            I would suggest you consider applying some preventive sprays to transplants brought into the garden from a nursery or garden center. This is seldom needed for homegrown transplants or from commercial growers who maintain clean facilities and planting material. Sprays would include insecticidal soap applications every few days, spraying Neem oil and some other organic sprays specifically for vegetables.
            In the future I would recommend growing your own transplants if you can and you will see fewer problems like you are mentioning. Local producers of vegetable transplants can be found and are usually higher priced but cleaner with fewer pest problems.

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