Fresh-market bell pepper growers are challenged to produce visually perfect fruit to match consumer preferences. Various physiological disorders can affect the appearance and desirability of bell peppers; these often arise from environmental stresses and nutritional imbalances. Understanding these physiological issues is essential for growers to manage and mitigate them effectively.
This publication covers common physiological disorders in bell peppers—including their likely causes, visual characteristics, and potential management practices—to help growers improve fruit quality, reduce losses, and enhance the market appeal of their bell pepper crops.
Pancaking
Pancaking is the term used to describe an atypically flat fruit shape (Figure 1). This is thought to be caused by improper pollination and is more prevalent when temperatures are extremely hot (as during early fall and late spring) or cold (late fall, winter, and early spring). Incomplete pollination will produce fewer seeds, resulting in improper fruit development. Certain varieties are more or less susceptible to pancaking. In general, peppers with an elongated blocky shape will resist pancaking better than peppers with a shorter blocky shape.
Pointy or Tapered Fruit
Pointy or tapered fruits taper from the shoulder to the blossom end of the fruit (Figure 2). These fruits usually have three lobes, although a three-lobed pepper may still have a blocky (square) shape. Certain varieties are more susceptible to tapering. In general, a four-lobed blocky pepper is the most preferred fruit shape. However, there will be a normal distribution of three-, four-, and five-lobed fruit within all bell pepper varieties. Typically, varieties that have a distribution of more four- and five-lobed fruits will tend to have fewer pointy fruits. In addition, a five-lobed pepper fruit is usually less desirable than a four-lobed fruit since it may have more of a pumpkin shape instead of a blockier appearance.
Blossom-End Rot
Blossom-end rot (BER) is a disorder resulting in necrosis (dead tissue) at the blossom end of pepper fruits (Figure 3). Blossom-end rot is thought to be a symptom of a localized calcium deficiency that occurs early in fruit development (Bangerth, 1979; Marcelis & Ho, 1999). This calcium deficiency can cause cell death, resulting in the characteristic “rot” appearance.
Interestingly, this disorder is usually not caused by a lack of calcium in the soil—though that can certainly occur. Rather, blossom-end rot is usually caused by poor calcium uptake in the fruit. Calcium uptake in the plant occurs primarily by mass flow via the xylem tissue. Anything that inhibits water movement and/or transpiration into the fruit can cause blossom-end rot. Because calcium is relatively immobile in the plant, even temporary disruptions in calcium uptake can cause localized deficiencies in rapidly dividing plant cells.
Genetics, growth rate, irrigation, relative humidity, and calcium fertilization may affect the incidence of blossom-end rot in peppers and tomatoes (Diaz-Perez & Hook, 2017; Taylor & Locascio, 2004; Taylor et al., 2004). The plant’s leaves tend to accumulate more calcium compared to fruit, so the incidence of blossom-end rot may increase in plants with excessive foliar canopy growth (Taylor & Locascio, 2004).
Fertilizers that contain high levels of ammonium also have been shown to cause blossom-end rot—the ammonium can compete with calcium for uptake. Because of calcium’s lack of mobility within plants, foliar sprays of calcium rarely correct blossom-end rot because the calcium doesn’t travel from leaves to fruit.
Sunburn or Sunscald
The scalded tissue is more prone to infection.
Sunburn or sunscald is when a pepper’s skin burns from exposure to direct sunlight (Figure 4). Growing a bigger shade canopy to protect peppers from the sun will reduce sunburn. Staking and stringing pepper plants to prevent them from lodging and exposing the fruit to sun also will reduce sunburn. Sometimes, if peppers are planted on an east-west orientation, the south-facing rows of peppers may experience sunscald as they are exposed to a higher incidence of sunlight.
Secondary pathogens can invade sunburned tissues. Foliar applications of kaolin clay or calcium-based products can act as a sunscreen and reduce sunburn. The cultivar can also influence the incidence of sunburn. Plants with larger canopies, thicker fruit cell walls, and darker skin color appear to be less susceptible to sunburn damage.
Suntan
Suntan is similar to sunburn—but suntan is discoloration (tan), rather than burning, of the pepper skin because of sun exposure (Figure 5). Suntan is less severe than sunburn. The same management practices apply.
Silvering or Epidermal Separation
Silvering looks like silver stripes on the fruit, hence the name. It is the visual symptom of epidermal or skin separation. This occurs when rapid expansion causes an air layer to form in the outer skin of the fruit (Figure 6). Silvering typically becomes a problem when it is hot and wet, especially during the early fall and, to a lesser degree, in the late spring. Some varieties are particularly prone to silvering.
In past studies, epidermal separation has been associated with Phytophthora-resistant cultivars and genotypes rather than a specific production system (Wyenandt et al., 2017).
Blue Nose or Purpling
Blue nose or purpling is the prevalence of purple color on pepper fruits (Figure 7). Typically, the tip of the pepper (nose) shows purpling, but in severe cases, the sides of the pepper also will be purple. This purple color is caused by anthocyanin, a purple-pigmented secondary metabolite in plants that they express during times of stress, such as in cold or hot temperatures.
Varieties that lack anthocyanins will not purple. Anthocyanin-less varieties do not express anthocyanin and will have green stems, green fruit, and yellow anthers (Figure 8a; Kovács et al., 2017).
Varieties that express anthocyanin will have purple anthers (Figure 8b), purple seedling stems, purple joints, and—if conditions are favorable—purple pigment expressed on the fruit. There are completely purple bell pepper varieties that heavily express anthocyanin.
Bicolor or Light-Colored Fruit
Consumers prefer uniform medium- to dark-green fruit. Light-green or yellow-colored fruit can be caused by genetics and excessive canopy. Bicolor fruit is yellow on one side and green on the other (Figure 9). When this occurs, the light-green side is on the inside of the canopy, and the dark side is facing the outside of the canopy. The side deprived of sunlight remains yellow.
Surface Cracking or Corking
Surface cracking and concentric radial cracking are small imperfections (cracks) that appear on the surface of the fruit (Figure 10). A probable cause is the fluctuation of day and nighttime temperatures and water (from dew or irrigation) sitting on the shoulders of fruits. Cracking usually occurs on the shoulders of the fruit but can appear anywhere. Different varieties exhibit differences in susceptibility to cracking. Many older jalapeño varieties were susceptible to surface cracking.
Blossom-End Cracking
Blossom-end cracking appears as cracking or fissures between the lobes on the blossom end of the fruit (Figure 11). The cracks in these fruits may go unnoticed by harvesters and become a problem in the packing house—especially because of water intrusion during washing. Different varieties have differences in susceptibility to blossom-end cracking.
Crowded or Misshapen Fruit
Misshapen fruit are simply poorly formed fruit (Figure 12). One of the most common causes of misshapen fruit is crowding. Crowding is when the crown fruit develops in the crotch of the first branching node and develops indentations where it grows into the stems.
Flat sides may occur when fruits grow against each other. On some occasions, when plants are very tightly trellised, crowding of branches can also result in misshapen fruit. Poor pollination is yet another cause. Growing a bigger plant or varieties with longer internodes/longer fruit stems can reduce crowded or misshapen fruit.
Stip
Stip is the presence of black spots under the surface of the fruit (Figure 13). It is not a symptom of a disease or from insect feeding. It is thought to be related to calcium deficiencies, but the cause is often unknown. Some varieties and types of peppers are more susceptible. Stip is more common in current mini sweet peppers.
Breakers
Breakers are fruits that are starting to mature and turn color (Figure 14). They’re sometimes referred to as chocolate since the fruits appear brownish before they start to turn red. This is different from suntanned fruit (Figure 5). In open-field production of mature green bell peppers, breakers are considered undesirable.
Growers can get more money for fully mature red, orange, or yellow peppers, but they need to be left longer in the field and are susceptible to more diseases, rots, and sun damage. Faster maturing yellow and orange varieties tend to turn color quicker than red varieties. Generally, green bell peppers that mature to red take longer to turn color—this is why green-to-red maturing varieties are almost exclusively grown for green bell pepper production. Harvesting on time will reduce the number of breakers.
References
Bangerth, F. (1979). Calcium-related physiological disorders of plants. Annual Review of Phytopathology, 17, 97–122. https://doi.org/10.1146/annurev.py.17.090179.000525
Diaz-Perez, J. C., & Hook, J. E. (2017). Plastic-mulched bell pepper (Capsicum annuum L.) plant growth and fruit yield and quality as influenced by irrigation rate and calcium fertilization. HortScience, 52(5), 774–781. https://doi.org/10.21273/HORTSCI11830-17
Kovács, Z., Csilléry, G., Szőke, A., Kiss, E., & Veres, A. (2017). Characteristics and regulation of anthocyanin biosynthesis in pepper-review. Columella Journal of Agricultural and Environmental Sciences, 4(1), 47–58. https://doi.org/10.18380/SZIE.COLUM.2017.4.1.47
Marcelis, L. F. M., & Ho, L. C. (1999). Blossom-end rot in relation to growth rate and calcium content in fruits of sweet pepper (Capsicum annuum L.). Journal of Experimental Botany, 50(332), 357–363. https://doi.org/10.1093/jxb/50.332.357
Taylor, M. D., & Locascio, S. J. (2004). Blossom-end rot: A calcium deficiency. Journal of Plant Nutrition, 27(1), 123–139. https://doi.org/10.1081/PLN-120027551
Taylor, M. D., Locascio, S. J., & Alligood, M. R. (2004). Blossom-end rot incidence of tomato as affected by irrigation quantity, calcium source, and reduced potassium. HortScience, 39(5), 1110–1115. https://doi.org/10.21273/HORTSCI.39.5.1110
Wyenandt, C. A., Kline, W. L., Ward, D. L., & Brill, N. L. (2017). Production system and cultivar effects on the development of skin separation or “silvering” in bell pepper fruit. HortTechnology, 27(1), 37–44. https://doi.org/10.21273/HORTTECH03144-16
