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In the Garden: Knowing culprit keeps tomato problems in check

These tomatoes have blossom-end rot caused by a calcium deficiency.
These tomatoes have blossom-end rot caused by a calcium deficiency.

How are your tomato plants growing? If you’re having troubles with them, or have in the past, you’re not alone.

As a Spokane County Master Gardener, I answer a lot of questions about how to grow this popular crop. As a matter of fact, tomatoes are the most commonly asked about vegetable crop in the Master Gardener plant clinic.

Let’s look at problems often seen in this region and how to deal with them.

Blossom-end rot: The fruit has a blackened end to it, caused by a calcium deficiency in the soil. It usually occurs during hot summers where plants become stressed by a lack of moisture. The plant stops developing the fruit, causing the deformity, and focuses instead on staying alive. The solution? Provide regular water to your plants. Consider adding calcium to the soil at planting time as a preventive measure.

Blossom drop/failure to produce fruit: This can occur early in the season when there aren’t many pollinators out and about. It’s also caused when daytime temperatures are very high or when nighttime temperatures are too low.

Cat-facing: This odd-named physiological problem causes tomatoes to be misshapen. It can result from abnormal development of the flower, extended exposure of young plants to cool temperatures, high levels of nitrogen in the soil or overly aggressive pruning.

Physiological leaf roll: Early in the season, if the temperatures are chilly, you’ll often see leaves that are cupped or rolled. This is caused by cool weather and should resolve once the temperatures become warmer and more stable. However, if the problem doesn’t resolve, it could be a tomato virus and should be diagnosed by a plant expert. Generally speaking, viruses are bad news for tomato plants.

Hornworm: This large, damaging green caterpillar with a spike on its hind end is the larva of the sphinx, or hawk, moth. If you spot them, hand-pick and dispose of them. If you have a particularly heavy infestation of them, spray the plants with Bacillus thuringiensis, or Bt. This is a strain of bacteria that is safe for humans but deadly to caterpillars. You can find Bt at local garden centers; be sure to follow the label directions.

Stink bugs: If you spot puncture marks or areas on the tomato where the skin is white or golden, often accompanied by brown mottling, that’s the work of stink bugs. These green or brown shield-shaped insects are becoming more prevalent in this area and do a lot of damage to fruit and vegetable crops. The adults overwinter in weedy areas, so tidy up around your garden to eliminate habitat. Hand-pick the bugs if you see them causing damage.

Slugs: Active at night, slugs can chew large holes in tomatoes. Check places where they might hide during the day. Make sure you’re not overwatering the plants, causing standing water, and don’t let tomatoes hang down onto the ground. There are organic slug baits available at garden centers as well.

Susan Mulvihill can be reached via email at