Tomato Pox and Tomato Fleck

We've encountered tomato fleck more often, but we've seen both disorders in our tomato experiment this year. It's not uncommon to see symptoms of both on the same fruit. In fact, early on, scientists thought they were manifestations of a single problem, but now they are considered two disorders.

Tomato pox and tomato fleck are abiotic disorders, meaning they aren't directly caused by pathogens, insects, or other living organisms. There is also a genetic factor, with some cultivars being more prone to tomato pox and tomato fleck than others.

In both cases, the symptoms are only on the fruit surface, and the internal quality of the fruit is not affected. However, fruit with tomato pox and tomato fleck might not be as marketable and could be graded lower by U.S. Department of Agriculture standards or sold as canners. Also, shelf life is shortened when fruit have tomato fleck.

Tomato Pox/Fruit Pox

With tomato pox, you'll see small and rough tan, whitish, or brown raised or sunken spots that are slightly elongated to oval on the fruit surface. The spots are areas where the skin has ruptured.

Tomato pox is more prevalent when temperatures are high during the growing season, which causes rapid plant and fruit growth. In Central Pennsylvania, during June and July 2024, there were 14 days when daytime temperatures reached 88˚F or higher, which is about the threshold when plants suffer from heat stress (you can read more about Heat Stress and Tomatoes.) Additionally, there were 12 nights with temperatures above 70˚F. The heat made those 61 days one of the hottest periods on record, with June and July ranking as the 9^th warmest in the last 131 years.

Once you see tomato pox on the fruit, you can do nothing to cure it. There are some things you can do to avoid or minimize its prevalence. Promoting good airflow in your planting by using good plant spacings helps by reducing temperatures and humidity levels around the plants. Recommended spacings are 18 to 24 inches between plants in a row and a minimum of 5-6 feet between rows for staked tomatoes; 24 inches between plants in a row and a minimum of 4-5 feet between rows for determinate tomatoes without stakes; and 24 to 36 inches between plants in a row and a minimum of 5-6 feet between rows for indeterminate tomatoes without stakes. Installing a shade cloth over the plants is another option to reduce temperatures around the plants. Keep an eye on your fertility program, especially avoid oversupplying nitrogen and potassium. Lastly, take notes and talk to others to determine which cultivars resist Tomato Pox and which ones to avoid.

Tomato Fleck/Goldspot/Goldspeck

With tomato fleck, you'll see gold or yellow irregularly shaped spots on the fruit surface. The symptoms can mimic damage caused by Brown Marmorated stink bugs (BMSB) (you can read more about Brown Marmorated Stink Bug Damage on Tomato.) thrips, or mites. Look for the presence of these pests to rule them out as the culprits. Also, with tomato fleck, spots are found initially on the fruit's stem end and can appear uniformly on the fruit, whereas you'll typically see insect and mite damage in patches. With brown marmorated stink bugs, you'll find white, spongy tissue below the feeding damage.

Scientists are unsure of what causes tomato fleck. However, it is generally thought to be related to excess calcium in the fruit. Plant nutrients interact, and calcium, phosphorus, and potassium nutrition have been implicated in tomato fleck. When insufficient potassium levels are in the soil, excess calcium can accumulate and be taken up by plants. Calcium uptake can be increased by applying soluble phosphate fertilizer to the soil. This can lead to excess calcium accumulation in the fruit, and tomato fleck can appear. Scientists have found a link between cultivars with blossom end rot resistance and the incidence of tomato fleck because blossom end rot-resistant tomatoes accumulate calcium in the fruit. As with tomato pox, tomato fleck is more prevalent when temperatures and humidity are high during the growing season. Potassium uptake by plants is decreased when humidity levels are high, which can lead to tomato fleck.

You can do a few things to avoid or minimize the prevalence of tomato fleck. However, once the fruit has tomato fleck, it can't be cured. Apply potassium through the drip line. This will help keep the calcium-to-potassium ratio below 1.5. Fertilize with magnesium based on soil test results. Calcium and magnesium compete for cation exchange sites in the soil, so having sufficient magnesium can help avoid excess calcium uptake. Since high temperatures and humidity are linked to tomato fleck, promoting good airflow in your planting by using good spacing can help, as can installing a shade cloth over the plants to reduce fruit temperature. Like with tomato pox, take notes and talk to others to determine which cultivars resist tomato fleck and which ones to avoid.

Want to read more about these disorders?

Physiological Disorders in Tomato Fruit Development

Gold Fleck of Tomato

Common Physiological Disorders of Tomato

Tomato Fruit Disorders

Gold Flecking More Pieces to the Puzzle

Gold Fleck of Tomato

Fruit Pox

Changes Associated with Gold Flecks and Fruit Pox Symptoms on Tomato Fruit

Physiological Tomato Fruit Disorders

Physiological Disorders in Tomato