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What is Bitter Pit?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

Bitter pit is a physiological disease of apples which causes the fruit to become deeply pitted with necrotic tissue. While still technically edible, apples with bitter pit are unsightly and not very tasty, so they can be difficult or impossible to sell at market, potentially representing a catastrophic loss for the grower. This condition has been studied since the 1800s, and it has proved difficult to fully understand or eradicate, much to the frustration of many orchard owners.

This condition is classified as a post-harvest disease, meaning that it usually shows up after the fruit is collected and put into storage, although sometimes fruit will display early signs when it is picked. Bitter pit starts from the inside out, typically with the core of the apple first, as the tissue slowly turns brown, dessicated, and rotten, and the outside of the fruit develops distinctive sunken spots with dead tissue underneath.

A healthy apple. Bitter pit causes apples to become deeply pitted.
A healthy apple. Bitter pit causes apples to become deeply pitted.

The cause of bitter pit is not fully understood. It is believed to be linked with calcium deficiency, and many apple growers use calcium sprays to reduce the incidence of bitter pit. However, apples from trees with plentiful supplies of calcium have also been known to develop bitter pit, so clearly it is influenced by a number of factors. Varietals like Baldwins, Delicious, and Gravensteins are among the most susceptible to bitter pit.

Water supplies available to the tree may also have something to do with bitter pit. If a tree experiences extremely hot, dry weather in the summer months, the fruit appears more likely to be diseased. As a result, agricultural associations strongly recommend watering routinely and heavily in hot weather, and keeping an eye on the moisture level in the soil even when the weather isn't hot. Thinning the crop to promote the development of healthier fruit is also recommended; better to have a moderate crop of really good apples than a bumper crop of poor fruit.

Bitter pit is also believed to be linked to the treatment an apple tree receives while it is dormant. Traditionally, trees are pruned and fertilized during the dormant season to promote healthy, even growth in the spring. Over pruning and excessive applications of nitrogen can cause bitter bit, as can excessive thinning of trees when the fruit starts to set in the fall. Furthermore, tree damage can also contribute to the development to bitter pit, presumably because such damage interferes with the tree's ability to distribute nutrients to the fruit.

Frequently Asked Questions

What is bitter pit in fruits, and which fruits are most commonly affected?

Bitter pit is a physiological disorder that affects the quality of certain fruits, particularly apples. It is characterized by small, dark, sunken spots on the fruit's skin and brown, corky areas within the flesh. The disorder is most prevalent in apple varieties such as Honeycrisp, Granny Smith, and Jonathan, but can also affect other fruits like pears. Bitter pit is caused by a calcium deficiency in the fruit tissues, often exacerbated by irregular watering and nutrient imbalances.

How does bitter pit affect the taste and texture of apples?

Bitter pit creates a noticeably unpleasant taste and texture in affected apples. The dark spots on the skin lead to underlying areas of the flesh that are dry and corky, giving the fruit a bitter flavor and a gritty, unappealing texture. This can significantly reduce the fruit's market value and consumer appeal, as the eating quality is compromised.

Can bitter pit be treated or reversed once it appears on the fruit?

Once bitter pit symptoms appear on the fruit, they cannot be reversed. However, preventive measures can be taken to minimize the occurrence of bitter pit in future crops. These include ensuring balanced fertilization, particularly with calcium, regulating irrigation to maintain consistent soil moisture, and thinning the fruit to reduce competition for nutrients. Post-harvest calcium treatments can also help reduce the incidence of bitter pit during storage.

Is it safe to eat apples with bitter pit?

Apples with bitter pit are safe to eat, as the disorder is not caused by pathogens or toxins. However, the affected areas may have an off-putting taste and texture. Consumers often cut out the bitter, corky spots before consumption. While not harmful, the overall eating experience of apples with bitter pit is generally considered inferior to unaffected fruit.

What role does calcium play in preventing bitter pit in apples?

Calcium is crucial in maintaining cell wall structure and stability in apples, which helps prevent bitter pit. Adequate calcium in the fruit helps to ensure firmness and cell integrity, reducing the likelihood of the disorder. Calcium sprays during the growing season and post-harvest calcium chloride treatments are common practices to enhance calcium content in apple tissues, thereby mitigating the risk of bitter pit.

How can apple growers monitor and manage the risk of bitter pit?

Apple growers can manage the risk of bitter pit through vigilant monitoring and adopting best horticultural practices. Soil and leaf tissue tests can help determine calcium levels and guide fertilization. Regular irrigation schedules, proper tree pruning, and fruit thinning are also essential to ensure adequate calcium uptake and reduce stress on the trees. Additionally, selecting rootstocks and varieties less susceptible to bitter pit can be a strategic long-term approach.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

Discussion Comments

strawCake

@KaBoom - That's terrible for your local farmer! And for you, because you couldn't eat the delicious apples!

This disease sounds like a real bummer though. Especially because it doesn't show up until after the apples are harvested. Imagine thinking you had an awesome crop of apples and then later discovering they were all unsaleable? Horrible!

KaBoom

A small local farm near my apartment lost their entire crop of apples to this disease one year. It was really sad! I used to always visit their stall at the Farmer's Market, and they had the best apples.

One year, I went, looking forward to the delicious apples. They were there, as usual, but no apples in sight! When I asked them about it, they told me most of their apples had been infected with bitter pit.

Luckily they had grown other stuff to sell. It would have been awful if they hadn't! I know it put a pretty big financial hardship on them that year though.

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    • A healthy apple. Bitter pit causes apples to become deeply pitted.
      By: Thibault Renard
      A healthy apple. Bitter pit causes apples to become deeply pitted.