KState Extension: Unsightly Tomatoes – Blossom-end Rot and Stinkbugs to Blame

Submitted by Krista Harding, Southwind Extension

A common plant problem for tomatoes is blossom-end rot. Blossom-end rot causes tomatoes to have a sunken, brown leathery patch on the bottom of the fruit. This problem is most common on tomatoes, however, it can also affect squash, peppers and watermelons.

Blossom-end rot is not a disease. It is caused by a lack of calcium in the developing fruit. Many people often assume that this means there is a corresponding lack of calcium in the soil, but that is not necessarily the case. So what causes blossom-end rot then? There are several possible causes.

Tomato tops often outgrow the root system during cooler spring weather. As long as it is cool, the root system can keep up. Once the weather turns hot and dry, the plant has a problem. Water, with the calcium it carries, goes to the leaves and bypasses the fruit. This causes a spot on the bottom of the tomato to form. The plant will respond with new growth, and the condition corrects itself after a couple of weeks.

Heavy fertilization, especially with ammonium forms of nitrogen, can encourage blossom-end rot. Heavy fertilization encourages more top than root growth and the ammonium form of nitrogen competes with calcium for uptake.

Disturbing the root system, such as hoeing too deep, can also encourage blossom-end rot. Inconsistent watering could also be a factor. Try to keep the soil moist but not waterlogged. Mulching will help because it keeps the soil surface cooler and provides a better environment for root growth.

But, some years you can do everything right and the condition still shows up because of the weather. Remember that blossom-end rot is a temporary condition and plants should come out of it in a couple of weeks. You might want to pick off affected fruit to encourage new fruit formation.

Another tomato plant culprit is stinkbugs. Stinkbug damage appears as golden-yellow, pink or white spots on fruit. Stinkbugs are shield-shaped insects that emit a foul odor when disturbed.

Stinkbugs injure the fruit by using its mouthparts to probe. Color development is affected where probing occurs, which results in the off color or cloudy spots. Heavy feeding causes spots to spread and because of that, tomatoes may develop a golden color. If you look closely, you can see pinprick-sized puncture wounds in the middle of the spots. Hard, whitish tissue develops beneath the skin of the area of wounding.

By the time you notice the spots, stinkbugs are often gone. That makes control impossible. The good news is that affected tomatoes are still safe to eat.

Spider mites are also starting to cause significant damage. They love hot, dry weather and the conditions have been favorable for them. Look for leaf stippling (tiny white spots that causes the leaf to appear silver in color) and for webbing on the underneath side of the leaf.

A good strong jet of water will knock them off the leaves. If that doesn’t work, horticulture oils or insecticidal soaps can be used. However, these need to be applied early in the morning when temperatures are cooler and the plant can rehydrate.

As a reminder, the Extension services are free of charge! Take advantage of our expert knowledge to help get your plant questions answered.

Krista Harding is a K-State Research and Extension Agricultural agent assigned to Southwind District. She may be reached at 620-244- 3826 or [email protected]

Leave a Reply

Your email address will not be published. Required fields are marked *