Monday, May 29, 2023
HomeCultivationDiseases of the Chili Pepper: Recognizing and Fighting Them

Diseases of the Chili Pepper: Recognizing and Fighting Them

Recognizing pepper diseases is the first step in defeating them: Here is the Guide!

What we will talk about:

Diseases of pepper caused by parasites

Root rot and withering.
There are mainly three fungi in the soil that cause severe rot and root rot diseases in chillies.
These fungi can cause similar symptoms, especially severe wilt and plant death, and can sometimes be confused with each other.

Often an accurate diagnosis of the disease requires the isolation of the infected plant and the analysis of the possible causes, however there are some differences in the symptoms that can help us to correctly identify the cause of the pathology, let's see in detail.

Phytophthora, collar and root rot

The rot is caused by a soil fungus, the Phytophthora capsici.
This mushroom is a serious pathogen for chillies all over the world, but the disease is particularly widespread in highly irrigated fields and has become a real emergency for many industrial crops, especially those in the United States and Mexico.

Ideal conditions for the disease: this fungus proliferates when soils are excessively wet, perhaps due to excessive irrigation or heavy rains or both.

Outbreaks of this pathogen usually occur in poorly drained soils or low-lying spots in the field where water tends to pool and stagnate. It is not uncommon to see fields where diseased plants are grouped together in particular areas of the crop, in specific rows or at one end of the field, while the rest of the plants may be healthy and show no indication of distress.

When the disease occurs in specific, isolated rows, this often indicates excessive watering and the spread of infectious spores by irrigation water. Furthermore, pepper plants grown near trees or very tall buildings can get sick due to shading which causes high humidity and slow evaporation, favoring the activity of this fungus.

Symptoms: Symptoms of Phytophthora rot usually occur in late summer – early autumn during periods when rains and warm nights coexist and when the foliage is dense and the plants touch each other shading each other.

The first symptom of infected plants is a severe wilting. Within a few days, infected plants collapse from root and stem infections and die, turning a pale yellow color. In many cases, plants start shedding leaves from below.

Diseased plants that are removed show severe symptoms of root rot, dead and blatantly discolored roots, and roots that tend to peel on contact.

marciume del colletto del peperoncino
The typical signs of collar rot

'Phytophthora capsici' also causes other diseases such as downy mildew and rot on fruit, leaves and stems.
Overrooting infections generally occur during the summer rainy season in very humid environments. Chilli fruits become infected when high humidity conditions persist for several days.

Control and prevention: excessive soil moisture triggers and intensifies the crown and root rot phase caused by this disease. If possible, avoid poorly drained soils that are not conducive to water absorption and evaporation.

Self the peppers are grown in pots, well drained soils or rich in perlite, the use of expanded clay both under the roots and on the ground and continuous removal of stagnations in the saucer are sufficient to avoid the disease.

For the plants grown in the field preventative practices include proper leveling of the land, using terraces, creating shorter rows, and controlled irrigation.

Attention, 'Phytophthora capsici' survives in the residues of dead plants and in the soil thanks to the production of 'oospores' which can live even for more than 2 years. In the event of an infestation, the total removal of the soil is absolutely recommended if the cultivation is in pots and crop rotation in the case of open field cultivation. Suggested rotational crops include lettuce, cabbage, onions, and small grains, such as wheat, barley, and oats. Unfortunately, chemicals have not proved very effective in controlling this disease.
The Metalaxylhowever, it is used on peppers for preventive rot control, however, once a plant is infected, metalaxyl it will have no effect healing. There is good news, however: many growers have started to select phytophthora resistant varieties with encouraging results. It is probable that within about ten years this pathogenic agent can be definitively defeated.

Verticillium rot

The Verticillium dahliae is a soil-borne fungus that occurs worldwide and causes disease in a diverse group of plants. Hosts of this fungus include several species of weeds and many crops, including Chillies, cotton, alfalfa, melons and ornamental plants. As with Phytophthora rot, Verticillium rot is primarily a problem in temperate climates. Ideal conditions for the disease: Verticillium dahliae survives in soil and crop debris through specialized structures called "microsclera". These structures allow the fungus to tolerate extreme environmental conditions and remain dormant in the soil for many years in the absence of a host. In the presence of humidity, the root exudates of sensitive plants stimulate the proliferation of microsclera. The fungus penetrates directly into the roots and then moves through the root bark to the conductive vessels of the plant that compose it xylem. The xylem spreads the fungus throughout the plant, showing symptoms on the top of the victim. Symptoms: The symptoms of Verticillium rot are highly variable, depending on the susceptibility of the host, the aggressiveness of the pathogen and the environmental conditions, in particular the temperature of the air and the soil and the available nutrients.

marciume da verticillium
Signs of Verticillium rot

Early symptoms include yellowing of the leaves lower and stunting of plant growth. As the disease progresses, excessive yellowing and leaf loss may occur. This fungus is limited to the internal vascular tissues of the stems and hence does not cause root rot or collar, however, varying degrees of xylem damage can occur, this is caused by the water-conducting tissues being clogged by the fungus, causing the pepper plant to wilt. Infected plants can recover overnight for a few days before stress leads to a rapid death. Control and prevention: unfortunately no suitable control measures are known after the appearance of Verticillium. In this case, the most effective system is undoubtedly prevention: Although Verticillium dahliae has a vast range of hosts, it is now established that a single plant's genetic predisposition is necessary for the disease to develop. So it is not uncommon for the disease to affect only some pepper plants and leave all the others unharmed, manifesting a typical "spot infestation". The experience of growers and studies associated with plant diseases have also shown that the disease tends to spread on monocultures of pepper and cotton. Those who cultivate in the open field, in the event of the spread of the infection, should begin a rotation of the crops for precautionary purposes. Fortunately, this pathology is much rarer for those who grow in pots! To date, unfortunately, there are no Verticillium dahliae tolerant pepper cultivars.  Rhizoctonia rot

the 'Rhizoctonia solani' is a common soil fungus that infects a large number of vegetables and crops. This pathogen causes root rot of mature plants and has similar effects to collar rot.

Ideal conditions for the disease: Infection with 'Rhizoctonia solani' is thought to occur in early spring during the seedling growth stage.

If environmental conditions are not optimal for the fungus, the plant may continue to grow despite the infection.
Plants infected with Rhizoctonia rot have reduced vigor compared to uninfected plants and suffer more from adverse conditions such as extreme heat, water stress, pests and disease.

This disease is widespread in monoculture fields and it is extremely easy to find it in seedlings grown in pots, it is one of the typical "neophyte" diseases and we often find ourselves giving the sad news to those who ask for information by attaching photos of plants now in the terminal phase .

Furthermore, this fungus has an extraordinary capacity for saprophytic growth (that is, it feeds on decomposing organisms) and can survive indefinitely in the soil in the absence of a host plant. In the event of heavy infestations it is necessary to sanitize the crop by totally eliminating the plants and the soil if the crop is in pots or by immediately working for a rotation in the case of open field cultivation.

Symptoms: 'Rhizoctonia solani' attacks plants on the stem near the ground. As the fungus moves slowly up the stem, the root of the plant rots and superficial reddish-brown lesions form.

pianta colpita da fungo rhizoctonia solani
The patches caused by Rhizoctonia

These reddish-brown lesions are a typical feature of this disease and diseased plants often produce an abundance of secondary roots above the decaying roots, but the most absolute evidence is given by the progressive and sudden death of the plants, in some cases this it can occur in a very short time, a distinctive sign is the literal detachment of the stem due to fungal lesions. It is possible to slow the progression of the disease however, once the infection has begun, vigor is greatly reduced and production is reduced to a minimum.

Control and prevention: There is no specific cure for this disease, the toughest plants could resist the infection but their vitality will remain marked forever and their resistance to bad weather will be totally compromised. There are currently no Rhizoctonia resistant pepper varieties. However, it is advisable to avoid water stagnation and reduce humidity at the first appearance of moss or fungi visible to the naked eye.

Seed and post-germination diseases

Seedling or seedling disease

The seedling disease, commonly called "seedbed disease", can be caused by a series of fungi transmitted by the soil such as the already mentioned (always them!) Rhizoctonia solani, Phytophthora capsici, but also Pythium and Fusarium. Seedling disease occurs when seeds or young seedlings are attacked by these pathogens. The seeds attacked by these fungi usually fail to germinate so in most cases it will be sufficient to remove them. The seedlings Instead can be damaged in two ways: the roots can rot causing the seedling to wilt causing it to die quickly, or the seedling can be stuck on the stem at ground level, causing the seedling to collapse.

piantine colpite da marciume del semenziaio
Seedlings affected by seedling disease

Although both seeds and seedlings can be attacked by these fungi, chillies grown directly from seed tend to be more sensitive than those purchased in seedling form, this is due to the controls that producers carry out on a daily basis to stem this disease. Seedling disease usually develops during colder, wetter periods, usually in spring soon after planting and as well as weakening seedlings, these conditions retard seedling growth, which keeps plants susceptible to attack by the fungus for a period of time longer. Excessive irrigation also increases the severity of the disease. This disease is typical of greenhouses with insufficient ventilation where high humidity and frequent environmental watering can favor the spread of the fungus. Even "balcony" seedbeds, in hobby cultivation, can suffer greatly from the attacks of these fearsome fungi. Further causes of early death of the pepper seedling can be poor quality seeds, improper sowing depth, high salt concentrations in the sowing soil; but also high winds, over-watering, severe nutrient deficiencies, pre- and post-plant herbicide applications, and insects. To be sure that your seedlings are suffering from "seedbed disease" it is essential that all these contributing causes are excluded.

In order to prevent seedling diseases, only high-quality seeds or seedlings should be planted and poor quality or poorly draining soils should be avoided.

Seed treatment with fungicides such as Previcur helps protect seeds from this disease before it occurs.

Diseases of pepper leaves

Parasitic foliar diseases can be caused by fungi, bacteria or viruses (which we will discuss in the next section).

Bacterial spot on pepper

This bacterial disease, caused by 'Xanthomonas campestris vesicatoria', is widespread throughout the world and is very common in pepper plantations.
Disease outbreaks can occur under particularly favorable environmental conditions (excessive irrigation or heavy rainfall) and can cause significant crop losses.

Ideal conditions for the disease: this bacterium survives in seeds, infected crop debris, soil and weeds. Bacterial spot epidemics they usually occur in July and August during the periods of great heat and high humidity.

The bacterium penetrates the leaves and stems through the stomata or any wounds present on the surface and is able to attack even the fruits if they have lacerations.

Yes spreads from one plant to another through the drops of water that splash during watering or rain, through the wind or with direct plant-to-plant contact, the severity of the disease depends on the level of resistance within the cultivar and on the environmental conditions.

Symptoms: the bacterial spotting of the leaf manifests itself with typically moist circular or irregular lesions which with the progress of time become purplish-grey with a central black area surrounded by an evident yellow halo.
Infections tend to appear most aggressive in the lower part of the plant, where infected leaves shrivel and eventually turn brown, dry and die, falling off the plant. Serious infections can cause massive defoliation of the plant.

maculatura batterica su pianta di peperoncino
The signs of bacterial spot on the leaves

The infection it can also affect flowers and causes its rapid detachment.
When the infection affects the fruit, small rounded lesions appear on the surface of the peppers, typically black and slightly raised compared to the surface of the fruit.

maculatura batterica sui frutti
The signs of bacterial spot on a fruit

Control and prevention: The ideal is to start a correct prophylaxis that foresees the cultivation of cultivars known for their resistance to maculation, the use of seeds of controlled origin, and the possible introduction of new plants through a period of quarantine.

Purchase only high-quality seeds that have been screened for the presence of the pathogen. If in doubt, you can proceed tosoaking the seeds in a solution of water and 20% bleach for 20 minutes, making sure to dry the seeds thoroughly afterward. Copper-based chemicals such as copper hydroxide, copper sulfate, and copper or ammonium carbonate can be effective in controlling these diseases.
These products are applied through foliar sprays before the rainy season to obtain better efficacy, it is important to note that these products can also be used after the epidemic has occurred, as long as care is taken to carry out the treatments in periods away from the rains.

There have also been cases of strains resistant to copper treatments, prevention is undoubtedly better than cure.

Bacterial leaf spot is capable of infecting many solanaceous plants, including belladonna and some minor herbs, therefore it is advisable to carefully check the soil and eliminate weeds.

"Frog eye" spots from Cercospora

The fungus responsible for this disease, Cercospora capsici, is active in the same environmental conditions that favor bacterial leaf spotting.

It is not uncommon to find these two diseases present on the leaves at the same time.

Ideal conditions for the disease: the Cercospora spot survives among the seeds and through the formation of spores on the leaves dead from the infection.

The infection occurs for direct penetration in the leaf. spores require water for germination and host penetration; however, even morning dew alone is known to be sufficient for the infection to develop.

The disease is most acute during periods of warm temperatures and excessively high humidity. As for the bacterial spot, also the cercospora has the particularity of being transmitted from plant to plant through drops of infected water, wind and direct contact.

Symptoms: the lesions caused by 'Cercospora capsici' are circular in shape and initially yellowish which quickly turn gray or white a few days after infection; later they turn dark brown with a reddish margin, a pale or yellowish halo may appear around the reddish margin.

foglia di peperoncino colpita da cercospora
leaf affected by cercospora capsici

The spots tend to dry out quickly and cause the material to detach from the leaf, giving life to the characteristic "perforated leaf", as if it had been obliterated several times. The most affected leaves tend to dry out completely and fall off the plant.

Control and prevention: the same prophylaxis practices for bacterial spot are useful in controlling Cercospora. Chilli cultivars vary in their susceptibility to Cercospora capsici, but some varieties, including for example the "Sandia" seem to be particularly susceptible.

White fever from Liveillula

White blight is a common disease on many types of crops, but when the environmental conditions are favourable, even chilli peppers are attacked by this pathogen. The fungus that causes the disease is 'Leveillula taurica'.

Ideal conditions for the disease: the disease is favored by high temperatures (from 28 to 35 degrees). Although high humidity promotes spore germination, infection can occur during periods of high or low humidity indiscriminately.

The fungus, under favorable conditions, reproduces very rapidly and the spores spread by the wind cause secondary infections which help spread the disease. White powdery mildew mainly infects the leaves but in rare cases it can also attack the fruit.

This disease is more acute on older leaves and usually the peak of the infection occurs in the period of greatest production, this can cause serious crop losses, so it is best to deal with the disease through prevention or at the very first signs.

White mallet has a wide range of hosts, including cotton, onion, tomatoes and weeds, making it particularly stubborn and difficult to control. In the event of a serious infestation, the total removal of the infected plants and also that of the soil, if possible, is absolutely recommended.

Symptoms: the main symptom of the disease is the presence of a white, powdery and fungal patina covering the underside of the leaves, the upper side of the infected leaves may instead present a yellow or brownish discoloration and, in some cases, the fungus can produce its whitish powder also in the upper part of the leaf.

foglia colpita da mal bianco
Leaves affected by white powdery mildew

The edges of infected leaves eventually curl upward, exposing the fungus to sunlight and causing it to droop in the short term.

Control and prevention: due to the wide variety of hosts of this fungus, sanitation practices such as the removal and destruction of infected plant debris are not always sufficient to stem the disease, furthermore, most chili cultivars does not possess high levels of tolerance to this mushroom.

The prevention and containment of this threat is usually entrusted to the use of fungicide sprays. The effectiveness of these sprays depends a lot on the early detection in fact, when the conditions are very favorable for this pathogenic agent, these products can prove to be underperforming or even useless.

Diseases of the pepper fruit

Fruit rot can be caused by infection with fungi, bacteria, or abiotic disorders (more on that later). Some viruses also cause damage to fruit, however, fruit rot is usually caused by secondary fungi or bacteria and viral causes are extremely rare. Parasitic organisms can attack fruit directly (primary causative agent) or attack weakened tissue due to of another organism or by environmental factors (secondary causal agent).

Fruits attacked by Phytophthora

The fungus that causes collar rot, Phytophthora capsici, can also attack fruit, causing a disease known as pedal gangrene. Ideal conditions for the disease: this disease attacks the fruit in the presence of high rainfall and extreme humidity, typical summer conditions in many regions and under these conditions the fruit becomes watery and susceptible to attack. Phytophthora capsici spreads from the soil to the fruit and the infection starts when the fungus penetrates directly into the skin of the fruitthrough pre-existing injuries. usually thewilting starts from lower edge of the fruit as an area usually more shaded and more humid, ideal for the propagation of the fungus and the germination of the spores. Symptoms: infected fruits shrivel and mold develops insidem, once inside the fruit, the seeds become infested with the pathogenControl and prevention: Fungicide sprays are not suitable for eradicating this very aggressive pathogen. It is therefore necessary to adopt a preventive prophylaxis and to avoid the existence of suitable environmental conditions for the propagation of the fungus.

Black mold from Alternaria

Several fungi cause black mold on pepper fruits, however, the organism most commonly associated with this problem is theAlternaria. Infections occur during periods of excessive moisture, usually late in the season when fruit is very ripe. Ideal conditions for the disease: Overfeeding, late watering, and early freezing increase disease severity, and mold can develop on harvested fruit that is not stored dry before processing. Furthermore, Alternaria takes root more easily on the fruits of plants that have already been attacked by other pathogens, whose defenses are therefore already put to the test. Control and prevention: To avoid the onset of black mold it is good to make sure to harvest the fruits when they are ripe, avoiding leaving them on the plant for too long, moreover, it would be good to avoid abundant watering at the end of the season or unnecessary fertilizing. The attacked plants should also be treated with fungicide to avoid proliferation.

Peppers affected by anthracnose

Anthracnose is caused by the Colletotrichum, has been known to attack chili pepper crops worldwide.Ideal conditions for the disease: The fungus persists in infected seeds, infected plant debris and weeds. Infection occurs during periods of excessive watering or rain on unripe fruit; however, symptoms often don't emerge until the fruit becomes ripe and completes its final color change. Symptoms: the symptoms appear initially as small watery lesions that expand rapidly. Fully expanded lesions are sunken and range in color from dark red to light brown to black.

frutti di peperoncino colpiti da antracnosi
pepper fruits affected by anthracnose

As the infection progresses, the spores appear as scattered dots or in concentric ring shapes within the lesions of the pepper fruit. Since this disease affects immature fruit, it is most commonly seen on fruit attached to the plant, but it is known that the infection can also arise on fruits already harvested whose conservation has not been adequate. Control and prevention: the use of clean seed and crop rotation are the two most important control practices. Also, fungicide sprays can be helpful in curbing the phenomenon.

Bacterial Soft Rot

Soft rot is primarily a post-harvest disease although occasional infections have been observed before this occurred. This disease is caused by the soil bacterium Erwinia carotovora, recently renamed Pectobacterium carotovora.  Ideal conditions for the disease: Infections occur during rain when soil containing the bacterium comes into contact with fruit. The bacterium enters the plant through any wound, especially those created by insects.The harvested fruits are instead infected through the end of the stem, where the cracks tend to retain moisture.  Symptoms: The tissue around the site of infection begins to soften and eventually turns into a watery mass, the infected fruit tends to collapse and hang over the plant like bags filled with water and as the contents spill out, the outer skin of the fruit peels dries and remains attached to the plant.

pomodoro colpito da marciume molle batterico
A tomato affected by bacterial soft rot

Infections that develop after the harvest are particularly harmful to the fresh pepper industry, as when infected fruit rots the disease spreads to all fruit in the storage site.  Control and prevention: Field or pot infections are more contained if the right countermeasures are adopted against the insects responsible for the lesions on the pepper fruits. If the fruit is washed after harvesting, the risk of infection can be reduced to a minimum, provided that chlorine or amuchina is used.

Chilli Viruses

Plant viruses are extremely small particles of nucleic acid that have the ability to cause disease in plants.

These particles they are not living organisms, as they do not carry out metabolic processes such as respiration or digestion.

However, viruses are considered parasitic agents because they reproduce within their host plant and can be spread from one plant to another by vectors such as man, agricultural machinery, gardening tools, insects, nematodes and fungi.

Controlling diseases caused by viruses is difficult because there are no chemicals available that are effective in controlling viruses; therefore the control strategies are mostly prophylaxis aimed at avoiding the outbreak of the infection.

IMPORTANT: Because every year they are discovered dozens of new viral strains affecting chillies (sigh!), in this article we will limit ourselves to mentioning the most widespread and universally known.

Chard curly tip virus

This virus (BCTV) was first identified in 1899 and remains to this day the most important viral disease of many crops including peppers, chillies, melons, beans, tomatoes, spinach and ornamental plants.

Conditions for the disease: the main responsible for the transmission of the virus are the leafhoppers, small grasshopper-like insects. These insects are extremely resistant and their tenacity, which is an evolutionary advantage for the species, is instead a danger for the plants they feed on. These small insects, which literally suck the sap of plants, are direct carriers of viruses and the micro-lesions they cause can be the gateway for other pathogens.

The infection is aggravated when rains are abundant in autumn and winter, as this favors the growth of annual and winter plants which are usually the favorite food of leafhoppers. The leafhoppers then migrate to cultivated fields and home gardens giving way to the infection.

Symptoms: chili peppers of all ages are susceptible to BCTV infection; however, the disease is more acute and aggressive in younger plants.

sintomi del btcv virus sulle piante
Plants affected by BCTV

Infected seedlings show yellowing, curl and twist of the foliage. If the infection occurs just after germination, for example in a seedbed, the death of the seedlings is almost certain.

The first symptom that manifests itself when the older plants are infected is instead thegrowth arrest.

As the disease progresses, symptoms include lightening of the leaf veins, curling, twisting and wrinkling of the leaves. Over time, the leaves become leathery and stiff, and the roots of infected plants gradually die.

Infected plants are severely affected and produce little or no fruit, and infection early in the season often causes premature plant death. Plants that survive to the end of the season are easily recognizable: They are typically weathered and yellowed.

Control and prevention: Since BCTV exists in several strains, each of which has different hosts and causes different diseases, it is difficult to achieve complete resistance in pepper plants. However, some cultivars are tolerant of some strains of the virus and could initiate disease limitation.

Weed control and proper insect limitation can be great precautionary methods to limit the chances of infection. Additionally, if possible, peppers should not share spaces with other BTCV-susceptible hosts such as tomatoes, beets, beans, potatoes, and spinach.

Recent research has shown that the severity of infection in peppers is reduced when the distance between plants is reduced, probably thanks to a phenomenon similar to the "herd immunity“.

Insecticide sprays have not been shown to be effective in preventing leafhopper transmission of BCTV.

Another solution to limit the infection is to place the pepper plants in cool and shaded places at the beginning of the season, in fact it is known that leafhoppers do not like to feed in places with little sun.

Spotted wilt of tomato – TSWV

Tomato spotted wilt virus (TSWV) has been called one of the most dangerous pests for the crops of many varieties, including our beloved pepper. The disease affects the fruits during ripening, significantly reducing the yield. ideal conditions for the disease: This virus is present throughout the temperate and subtropical regions and infects a diverse group of plant species, from tomatoes, peppers, chillies, lettuce, pineapples to many ornamentals and weeds. The virus is also transmitted from plant to plant and propagation is usually favored by the presence of thrips, especially 'Western flower thrips' or Frankiniella occidentalis, these thrips act as a "vector" and help the virus to spread.

Symptoms: TSWV symptoms are many and varied, but the disease is most commonly recognized by symptoms present on fruit.
Both green and immature fruits and red and ripe ones can be infected, the virus therefore makes no distinction based on the degree of maturity of the fruit.
Infected green fruits show small discolored spots. The red fruits show instead yellowish spots which unlike those of other diseases never turn red.
Others fruit symptoms include necrotic spots, spots with concentric ring patterns, and fruit distortion.
THE foliage symptoms include mosaic spots, ring spots, and foliar deformation.
In some cultivars, the leaf petioles die and the leaves fall off the plant causing defoliation.

effetti del virus TSWV sul peperoncino
effects of TSWV virus on chili peppers

When a new leaf is born from an infected plant, it usually grows severely deformed and plants that become infected at an early age struggle to grow.
All these symptoms are not necessarily present on all plants and the development of the symptoms seems to be closely related to the pepper cultivar.

Control and prevention: due to the wide range of hosts, including many ornamental plants and weeds, it is extremely difficult to eradicate this disease.
Efforts to control thrips have had little effect on controlling TSWV and although eradicating the disease may not be easy, the incidence and severity of the infestation can be reduced by removing all infected plants, avoiding contact with susceptible to the virus, by uprooting the weeds and using products to contain the amount of thrips.
Cultivars resistant to TSWV are known but not yet formalized, it is however the signal that within a few years it could be totally eradicated.

Alfalfa mosaic

Alfalfa mosaic virus is a virus transmitted by aphids with a wide range of possible hosts, including alfalfa, tomatoes, lettuce and potatoes. The primary source for transmission on chillies is, as the name suggests, is the medical herb. This virus causes slight excoriations and whitish spots on the leaves and, in some cases, the fruit can be deformed. Non-experts might confuse symptoms of the alfalfa mosaic with simple "foliar burns", but unlike the latter, the infestation tends to spread over the whole plant.

pianta colpita dal mosaico dell'erba medica
Plant affected by alfalfa mosaic

Alfalfa mosaic is only a problem when the chilli comes in contact with the alfalfa or other usual hosts of vector aphids, the best way to contain the virus is therefore to limit contact with these types of plants.

Cucumber mosaic virus

Like beetroot BCTV virus and alfalfa mosaic virus, cucumber mosaic virus has a wide range of guests, including chili peppers, and exists in numerous strains that vary in their ability to cause various diseases. Even this virus it is transmitted by some species of aphidsSymptoms: the symptoms of this disease are quite variable depending on the infecting viral strain; however, most plants exhibit some degree of leaf “shrinkage” as well as widespread stress, yellowing and whitish and yellowish spots on the leaves. If affected, the fruit can grow small and malformed.

foglie colpite dal virus mosaico del cetriolo
Leaves affected by cucumber mosaic virus

Control and prevention: It is advisable to avoid growing varieties such as tomatoes, lettuce and cucumbers near chillies, and many ornamental plants used for urban landscaping are potential hosts of the virus. As with all viruses, the affected plants should be completely destroyed and disposed of, as well as the soil and any residues, it is also advisable to sanitize the tools used on the plants.

Tobacco Mosaic Virus (TMV)

Tobacco mosaic virus (TMV) is one of the most common and widespread of all plant viruses. This virus infects numerous species, including vegetables and weeds. TMV persists and remains infectious for many years in dried crop debris and is easily transmitted by mechanical means, such as hands, cutting tools and other equipment, a contributing factor to its success. Due to the ease of transmission of this virus, it can become a serious problem for crops of all types, from pots to open fields, and the virus also remains latent in seeds. Symptoms: symptoms of this disease vary depending on the host and strain of the virus.

foglia colpita dal virus del mosaico del tabacco
Leaf affected by tobacco mosaic virus

The most common symptoms on chili peppers are light green mottled areas on leaves, moreover the fruit ripen unevenly e growth is blocked. We often witness the birth of squat and small fruits, which do not grow in length. Control and prevention: in most cases, crops, whether hobby or professional, have a lower risk of contagion if they are started directly from the seed, this is mainly due to the reduced handling of the seeds compared to that of the seedlings grown in industrial greenhouses; in any case it is good practice to use certified seeds. Fortunately we witness to a growing resistance of many chili varieties to this virus.

Multiple Virus Infections

Many of the above viruses can coexist on plantsMultiple infections make it difficult to diagnose the individual viruses involved, as the symptoms are many and varied. As you can imagine, multiple infections greatly increase the severity of the infection and the difficulty in eradicating threats.

Other Viruses

Geminiviruses. In recent years, researchers have identified several geminiviruses whose transmission occurs by the white flies. These viruses all have similar symptoms but are biologically and genetically distinct. The most common symptoms are lesions, curling or twisting of leaves, bright yellow mosaic, fruit distortion, fruit drop and extremely low yield. These viruses are transmitted, as mentioned, by white flies including Bemisia tabaci and fortunately they are not transmitted mechanically or through seeds. The fight against geminiviruses is difficult once the plants are infected, for this reason it is strongly recommended to provide a prophylaxis aimed at completely curbing whitefly infestations.

Nematode worm infestation on chillies

Root-knot nematodes

The nematode root-knot, Meloidogyne incognita, it causes damage to chili peppers all over the world and can be particularly active in warm, sandy soils.

The damage can also be serious in cultivation in pots, especially if they are used poor quality potting soil.

This microscopic, non-lamellated worm lives in the soil in its initial form it wanders in search of a host and when the nematode finds a host, the adult becomes sedentary, feeding directly on the roots of the plants.
The female nematode acquires a compact shape, similar to a pear, and reproduces inside the host tissue (the roots), laying its eggs in a sort of "gel" inside or on the root surface.
The eggs are laid in the ground and they can hatch immediately or winter until the temperature is more suitable for the adult life of this worm, usually this already happens in the first spring heats. The root-knot nematode has an extremely broad host range and attacks over 2,000 plant species, including peppers, cotton, alfalfa, tomatoes, and many ornamentals. Ideal conditions for the disease: Nematodes love very sandy and not very dense soils (this facilitates their travels during their first instar). In soils with a good humidity level and an optimal and not exaggerated drainage, nematode infections can resolve themselves in a short time and spontaneously and the damage can be temporary or very limited. The ideal temperature range for these worms is between 15 and 26 degrees Celsius. The damage varies greatly according to the age of the plant: the youngest and smallest plants can suffer greatly from the loss of root tissue and can die quickly. If the plants are adults and well developed they may experience difficulties in producing fruit or foliage, but once the environmental conditions have changed or the infestation has ended, they can return to their original stage of healthy plants. The nematodes move in the ground very slowly, it is clear that abundant irrigation, spades, movement of soil, can favor the propagation of these worms. Symptoms: the main symptom caused by the root-knot nematode is the formation of galls or knots on the root system. These nodes are caused by the reaction to the digestive fluid of the parasites. The size of the knots ranges from a few millimeters up to about 3cm, but since the roots of chillies are usually very small, the size of the knots is extremely small.

radici infestate da vermi nematodi
Roots infested with nematodes

The damage is mainly due to causes caused by the infectionespecially difficulty in water circulation in the roots And lack of macro and micro nutrients.
Infected plants then show signs of water stress (even after watering) or nutrient deficiencies. The plants attacked by these parasites are usually not very productive. Control and prevention: As you can imagine, the best way to prevent nemator infections is to use quality soil and, in any case, avoid ideal conditions for propagation. A good move is to favor the organic biosphere of the soil, changing it often and making sure that it is always adequately covered with nutrients: this will increase the "good" bacterial flora which represents a natural enemy of nematodes. Chemical solutions often turn out to be inefficient or unnecessarily laborious and often run the risk of obtaining the opposite result, precisely because of the death of the bacterial flora.

Diseases caused by Stress or external Environmental Factors

Apical rot

Blossom end rot is a fruit disease associated with incorrect watering And calcium deficiency.

Other factors contributing to the occurrence of the disease include root damage, excessive soil salinity, and heavy applications of high nitrogen (N) fertilizers.

Symptoms: The disease usually first appears as one small moist spot at the base of the fruit, which tends to spread and rot rapidly. Fruits affected by apical rot tend to ripen very quickly and lose elasticity. It is important to note that blossom end rot makes the affected area an ideal location for pests and it is therefore of paramount importance to remove affected fruit immediately. Control and prevention: Proper watering helps keep plants from disease. The use of fertilizers rich in calcium helps to solve the deficiencies, even if they are obviously useless if the fruits have already started to rot.


Sunburn occurs on pepper fruits and leaves that are directly exposed to excessive sunlight. It is true that many peppers love sunlight, but it is not correct to think that any condition is ideal for these plants, even chillies suffer when exposed to excessive temperatures. The effects are amplified if the environmental conditions change suddenly, for example when the plants are moved from a shaded area to one in full sun without providing for an adjustment period.

If a plant that has always been accustomed to direct sun begins to show signs of sunburn, can be the first indication of the presence of an infectious agent (fungi, viruses, parasites) and is recommended immediately investigate the phenomenon.

frutto colpito da scottatura solare
Fruit affected by sunburn

Sunburns usually present as very light spots without borders, most often the spots have an elongated shape on the leaves and circular on the fruits.

Foglia scottata dal sole
A sunburned leaf

One of the most frequent causes, and also the least serious, is the presence of drops of water on the leaves which give way to a "slow" effect. It is therefore recommended avoid foliar watering during periods of great heat.

Salt-abundant injuries

Soil or water with a high concentration of salts can be harmful to peppers. Even too abundant fertilization and close to crucial phases such as germination can overload the plants with unsolicited nutrients.

The damage is greater in very young plants and often results in stunting and death while adult plants are much better able to handle excessive amounts of salts.

Adult plants show symptoms such as leaf tip burns, leaf necrosis on the edges and sudden wilting.

Injuries from strong winds

Excessively strong winds can damage pepper plants.
The damage can cause rapid drying of the foliage and is accentuated in areas close to the sea as the wind laden with sea salt considerably accelerates the evaporation of the leaves.

Protecting plants from strong winds is certainly the only way to preserve them and it is also a way of preventing the onset of other diseases. The lesions caused by the wind can in fact be real gateways for other pathogens.

Nutritional deficiencies in chili peppers

This is one of the more difficult problems to diagnose, as the symptoms caused by nutrient deficiencies are similar to the symptoms caused by many other abiotic and biotic (parasitic) diseases.

Furthermore, the deficiencies are often multiple and if not treated immediately, they can cause the onset of other pathologies due to the stress of the plant and this combination could make diagnosis extremely difficult

Plants require a wide variety of nutrients, including major macronutrients (such as nitrogen, phosphorus and potassium) or micronutrients (such as iron, boron and zinc), so determining individual nutritional problems is not straightforward.

However, looking at the plant may be enough to diagnose some nutritional problems.
For example, nitrogen-deficient plants grow poorly and are pale green or yellow, while iron-deficient plants have new leaves that are severely chlorotic (pale and clearly nutrient-deficient), but with veins that remain green.

An excess of nutrients, on the contrary, usually presents itself with extremely dark colored leaves, thick edges, excessive leaf production (with consequent reduction of resources for fruit growth) and, in extreme cases, with burns, drying, falling foliar or root damage.

We will talk about nutritional deficiencies in a future article!



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