Pepper disorders and diseases
Peppers must be free of diseases and disorders. Customers are willing to purchase healthy fruits. Furthermore, fruit that looks good on the outside but presenting internal brown flesh or soft texture will not lead to happy customers. Starting point is a healthy fruit at harvest. But also postharvest there are dozens of different diseases and disorders, which are not always easy to recognize. A good diagnosis is important. By recognizing the symptoms of a disease or disorder, it can be linked to the cause. After which, measures can be taken to prevent the disease or disorder from happening again in the future.
Identification of disorders and diseases usually takes place by carefully looking at the symptoms. Some symptoms are visible from the outside, while others can only be found internally after cutting the fruit. It is important to detect the quality issues as early as possible in the supply chain to reduce further incidence. These quality issues should be reported back in the chain to correct the source of the cause. Retailers can also benefit from knowledge about disorders they may encounter. For them, it is important to know whether the cause lies in a previous stage in the supply chain or is due to their own operations. Common causes of deterioration of peppers are dehydration, bruises, moulds and rots.
Frequently occurring disorders and diseases
Example of bruises caused by over-filled crates. Photo by WUR
Bruising and injuriesRough handling can lead to damage of the skin, at any stage of the supply chain. For example, the effect of harvesting in bags can manifest itself in bruises and injuries at a later stage. Bruising can also occur due to too tight packaging, broken field crates or over-filled crates that causes pressure on the peppers. Bruises are usually soft with discoloration of the underlying flesh. These mechanical damages not only make the fruit unattractive but often also lead to secondary rot development. Sun damage symptoms are a lighter, sometimes white, colour of the pepper skin.
Too cold temperatures for too long causes chilling injury with peppers. Photo by triart / Shutterstock.com
Chilling injuryPeppers should not be stored below 7 °C as they are sensitive to too low temperatures. Symptoms of chilling injury include pitting or sunken spots on the skin, skin discolourations, pulp water infiltration, off-flavor, shrivelling and increased susceptibility to decay. This disorder is caused by several days of storage below the minimum temperature. Damage depends further on the duration and of the temperature. The longer the period at low temperature and the lower the temperature, the greater the damage. Symptoms appear especially after transfer to higher temperatures.
Red jalapeno pepper with corking. Photo by Kelsey Armstrong Creative/Shutterstock.com
CorkingPeppers can show signs of corking on the skin. This is a pre-harvest issue that happens when there is a disbalance of the internal and external growth of the pepper, where the internal part of the peppers grows faster, producing vertical skin marks to recover the difference in growth. Peppers showing these traits might be declassified but are still edible.
Desiccated sweet bell pepper. Photo by WUR
DesiccationPeppers have high water content. Some of this water is lost by transpiration. However, water loss through punctures or otherwise damaged skin can be significant. Some shrivelling of the skin can then occur. Desiccation can also lead to loss of glossiness. The risk of shrivelling symptoms increases with a combination of low relative humidity and higher temperature increasing the vapour pressure difference.
Botrytis on bell pepper. Photo by MakroBretz/Shutterstock.com
MouldsOne of the most common mould is the grey mould or Botrytis. Unfortunately, Botrytis can continue to develop at the storage temperature of the peppers. Therefore, the prevention of Botrytis remains very important by avoiding mechanical injuries. Long periods of high humidity or condensation can stimulate the growth of stem-scar moulds. Especially when the stem is not nicely cut at its natural breaking knot.These moulds can be of a light type, and disappear, for example, after opening the (foil) packaging and exposure to the drier outside air. It does not necessary lead to breakdown of fruit tissue. But if the mould causes tissue to decay, this of course has serious consequences for the marketability of the pepper.
Rotten bell peppers. Photo by Igor Kovalchuk/Shutterstock.com
RotsSeveral types of pathological diseases can occur, such as Alternaria, Erwinia, Pseudomonas, Bacillus, Xanthomonas, and Cytophaga. For example, Alternaria manifests in wounds and bruises. Bacterial rot can be caused by, for example, species of Erwinia, which gain access through insect punctures or other skin injuries. In addition to damage, rot is often also linked to senescence. The development of rot after harvest can often be controlled by quickly cooling and preventing bruising and injuries.
Peppers in decay. Photo by Lea Rae/Shutterstock
SenescenceOverripe fruit can easily deteriorate, it is a consequence of aging. Surface breakdown, softening and off-flavours are part of the deterioration. This last stage of the fruit is called senescence. Senescence is enhanced by higher temperatures. The peppers with senescence symptoms may have been stored under suboptimal conditions such as too high temperature or were simply stored or in transport for too long.
Bell pepper with thrips injury. Photo by WUR
Insect damagePeppers can show silver-like skin made by previous thrips infection. Although perfectly edible, thrips leaves traces on the skin will declassify the peppers.
Did you know?
Pepper stems have a natural breaking point.Loose peppers are sold with their stem attached. It has a natural breaking point, looks nice and the stem weight is included in marketable product. But it also can cause damage in adjacent fruits. For flowpacks with 2 or more bell peppers, the stem is usually shortened in the packhouse.
Peppers in Europe are one of the top vegetables grown under Integrated Pest Management (IPG)This is due to the fact that they are grown in greenhouses and that abundant use is being made of natural enemies to control insects. They are still checked for Maximum pesticide residue levels (MRLs) but this is not an issue in IPG grown crops