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COLUMN: Troubleshooting tomato problems

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By Jeneen Wiche

This time last year, I had some healthy looking tomato plants, which was a delight because in 2009, I had some disease issues.

Turned out that 2010 was a bust though because of all the crazy heat we had. This year, the garden and the tomatoes look promising, but I am always on the lookout for emerging problems. So far, the 2011 daytime and nighttime summer weather and temperatures are absolutely perfect for tomatoes.

To maximize your tomato successes this summer, consider your tomatoes’ diet. We cannot control the weather but we can control what our plants eat, so to speak. At planting time, the soil was well prepared with composted horse manure and a little organic fertilizer and the plants were mulched with newspaper and grass clippings. Moderating soil moisture and preventing soil from splashing on the foliage goes a long way in preventing some potential tomato problems later.

This year, drainage in the garden is crucial because of significant rain events and pop-up storms. Tomatoes rather like being a bit on the dry side, so sitting in waterlogged soil can cause a problem. Rapid fluctuation in soil moisture is the primary cause of the most common tomato condition known as blossom end rot (as well as being a contributor to blossom drop, leaf curl and splitting fruit).

When plants fluctuate between too wet and too dry, a calcium deficiency develops in the plant, which then causes the blossom end of the fruit to rot. It’s quite a disappointing experience when you grasp that first ripe tomato and discover it’s half rotten.

You can avoid the onset of a calcium deficiency with good cultural practices, but if you do have a bout of it, there are products you can spray on your plants formulated to restore the calcium level.
High heat can cause some problems for our tomatoes, as well. Daytime temperatures in the 90s typically cause plants to stop blooming. When temperatures drop back into the 80s, they will rebound. Too much nitrogen can jeopardize bloom. Nitrogen encourages leafy growth at the expense of bloom. Use a fertilizer lower in nitrogen and higher in potassium and phosphorus during bloom time to encourage good blossom set.

Lack of magnesium, which aids in chlorophyll production and respiration of plants, can also delay fruit set and the best way to ensure that this doesn’t happen is to add composted manure to your garden every year. Healthy soil and a slow release source of nutrients do a great deal in sustaining healthy plants throughout the season.
I typically sucker my plants (the practice of removing the new growth that emerges between stems and branches) early in the season to encourage good branching structure. I will stop suckering once the tomatoes start to produce their second flush of fruit to ensure that there is plenty of foliage to sustain the plant and shade the ripening fruit from the hot summer sun. Sunscald can destroy tomato tissue and cause hard blisters, which ruin the fruit.

Foliar diseases like early and late blight, septoria leaf spot and anthracnose are being diagnosed by the University of Kentucky Extension already, so monitor the lower leaves of plants. Many bacterial and fungal diseases linger in the soil from year to year so rotating your crop is a good defense. Keep the garden clean and weed-free, and mulch your plants to avoid soil-borne diseases from splashing up onto the plant.

Remove leaves as they appear infected and don’t inadvertently spread it by handling healthy plants afterward.

In terms of insects, the best advice is a daily inspection. Early detection of aphids can be realistically controlled by using insecticidal soap. Handpicking tomato hornworms is easy (but leave the ones with the little white sacks covering the caterpillar, these are eggs of beneficial wasps that you want in the garden). Pyrethrin and pyrethroid based bio-insecticides work on many pests if they become more than a pick and squish maneuver.

Pick tomatoes when they are uniform in color and still firm. Don’t store them in the refrigerator or place them in a sunny window, this does not further ripening; it just makes them mealy. Instead, store tomatoes in a basket in a cool corner of the kitchen.