Blossom end rot on Plants

Symptoms

Blossom end rot shows up as damage on the fruit itself. The first sign is a set of small, light brown spots at the blossom end of immature fruit. As the fruit ripens, that spot widens into a sunken, leathery lesion that turns brown or black. A fully formed lesion is often about 1/2 to 1 inch wide. Some fruit develops hard, brown areas inside with no mark on the skin at all. Other fruit shows both the internal browning and the outer lesion together. The spot stays dry and leathery as it ages. The color often shifts from light brown to a darker brown or black as time passes. You may notice the first spots on fruit that has not fully grown yet. On fruit left on the plant longer, the same spot becomes larger and more sunken. Checking both the outside and the inside of the fruit gives the clearest picture, since the rot can appear in either place.

Causes

A handful of conditions are named as causes of blossom end rot. The core cause is a low level of calcium in the fruit, together with a poor water balance inside the plant. That calcium shortage is often linked to low calcium levels in the soil itself. A high level of salt in the soil is also named as a cause. Soil that stays too dry, in other words low soil moisture, is another documented cause. Sandy soil is listed as a cause in its own right. Applying too much nitrogen fertilizer rounds out the list of documented causes. Tomatoes and peppers are the plants on which these causes have been documented. Fruit grown under these conditions often shows light brown marks at the blossom end before it matures. That damage can later turn into a sunken, leathery, brown or black lesion as the fruit ripens.

Diagnosis

Confirming blossom end rot starts with a close look at the fruit. Early on, immature fruit may show just a few light brown marks near the blossom end. As that fruit matures, the mark can deepen into a leathery lesion that turns black or brown. A confirmed spot is commonly about 1/2 to 1 inch wide. Cutting open the fruit can reveal hard, brown areas inside, even when the skin looks fine. Because that internal damage can appear with or without a visible outer spot, a clean-looking fruit is not automatically free of the problem. Checking for a shortage of calcium in the fruit, paired with poor water balance in the plant, is the main thing to confirm. Low soil moisture and sandy soil are two more conditions commonly found in confirmed cases. Excess nitrogen fertilizer application is the last cause worth checking for. Tomatoes and peppers are the two crops on which this diagnosis applies.

Treatments

A few steps can reduce blossom end rot once it appears. Follow recommended rates for fertilizers rather than applying more than the package directs. Going over the recommended rate is not part of that guidance. Monitor soil moisture so the root zone neither dries out nor remains saturated. In practice, that means avoiding both a dry root zone and a soggy one. Provide a consistent and ample supply of moisture to the plant. Keep that supply of moisture steady rather than occasional. Mulch around the base of the plant to help conserve soil moisture. A layer of mulch is one documented way to conserve that moisture. Maintain a steady rate of plant growth without stress. Avoid swings between fast growth and stalled growth. Remove affected fruit so that later-maturing fruit develops normally. Taking off the damaged fruit is the documented step for the fruit still forming. These treatments are documented for tomatoes and peppers, the crops blossom end rot is known to affect. Low soil moisture and sandy soil are both named among the causes of the disorder. Excess nitrogen fertilizer application is also named as a cause. These steps target the main driver: too little calcium reaching the fruit while the plant's water balance is uneven. High soil salt content and low calcium levels in the soil are two more documented causes of the disorder.

Prevention

Stick to recommended fertilizer rates instead of over-applying them. Keep soil moisture even, with the root zone never fully dry or fully soaked. Keep a steady, ample amount of moisture reaching the plant at all times. Spread mulch over the soil to help it hold moisture. Keep the plant's growth steady and avoid putting it under stress. Low soil moisture, sandy soil, and high soil salt content are among the documented causes of blossom end rot. Low calcium levels in the soil and excess nitrogen fertilizer application round out the list of causes. These causes and steps are documented for tomatoes and peppers. Clearing away fruit that already shows the damage lets fruit that forms later grow without it.

Plants most often affected

Blossom end rot affects tomatoes and peppers. The damage shows up directly on the fruit. A mild case starts as a few small, light-brown marks, and a more advanced case turns into a darker, leathery lesion. Some fruit even shows hard, brown areas on the inside with no outer sign at all.

• Garden Tomato