Pepper crops suffer from many diseases. Some of the common examples include the following:
Bacterial spot is a problem, especially during the rainy season. Small spots develop on leaves. Later, the leaves can turn yellow
and drop. Corky lesions develop on fruits. This disease is controlled by using pathogen-free seed, rotating crops, and spraying with organic fungicide mixes.
Bacterial spot on leaf
Bacterial soft rot is a serious disease on fruit. Infected fruits will collapse and hang like water-filled bags. Management strategies include rotating crops, using raised beds to enhance drainage, mulching to reduce soil water splash, and harvesting fruits carefully to avoid wounding.
Symptoms of Bacterial soft rot
Many viruses attack peppers. Some of the most common are Tobacco Mosaic, Cucumber Mosaic, Chili Venal Mottle, and Pepper Mild Mottle. Symptoms can be mosaic or mottling patterns on leaves, distortion of foliage and fruit, and stunting of plants. Many viruses can be prevented through the use of resistant varieties. Another strategy is to reduce their insect vectors. This is done by removing weed hosts, spraying with organic pesticides, and using mesh netting as natural barriers.
Symptoms of virus attack
Fig.1,2,3: Symptoms of Cucumber mosaic virus
Fig. 4: Potato virus
Fig. 5: Tomato etch virus
Fig. 6: Pepper mottle virus
Fig.7: Fruit mosaic
Fig. 8: Tomato Spotted virus.
Cercospora Leaf Spot causes "frog-eyes" to appear on foliage. This fungus is found during rainy weather and when plants are spaced close together. Organic Fungicides can be used to control this disease.
Cercospora leaf spot
Fusarium stem and fruit rot
Photo: wilted pepper plant
The causal agent of a stem and fruit rot disease of greenhouse sweet peppers was found to be Nectria haematococca (anamorph Fusarium solani). It infected wounds caused by salt damage at the stem base and scars left by careless leaf removal and fruit picking.
Symptoms
Soft, dark brown or black cankers are formed on the stem, usually at nodes or wound sites. These may girdle the stem in later stages of disease development. There is a dark brown discolouration of the internal portion of the stem that may extend a considerable distance. The lesions may eventually develop cinnamon or light orange-coloured, very small (<1 mm diameter), flask-shaped fruiting structures known as perithecia, which are the fruiting bodies of the fungus
Photo: Black cankers on the pepper stem Black lesion around the calyx of pepper fruit
due to Fusarium solani.
Control
Blossom end rot
Blossom-end rot can cause significant crop losses in peppers, especially early in the season. A serious disorder of tomato, pepper, cucumber and eggplant, blossom end rot is an environmental problem (not fungal) most often caused by uneven watering or by calcium deficiency. (These can be related; uneven watering can interfere with the uptake of calcium.) This common garden “disease” is often brought on by rapid growth from too much fertilizer, high salt levels or drought.
Symptoms: Blossom-end rot (BER) is a physiological disorder which causes a dark, sunken area on the lower (blossom) end of tomato, pepper, and eggplant fruits. On peppers, it may also occur on the sides of the fruit, near the blossom-end. The discoloration is usually tan, brown, or black and should not be confused with sunscald, which causes a whitish or translucent discoloration. Secondary pathogens may infect the BER-affected area, causing overall fruit rot.
Photo: pepper blossom end rot
Since this plant problem is physiological in nature, fungicides will not work as a control measure. We recommend the following:
Cause: The fungus, Botrytis cinerea (teleomorph: Botryotinia fuckeliana), is an opportunistic pathogen that easily invades weak, damaged, or senescing tissue. Usually, it is more of a problem on seedlings in greenhouses but can be a problem in the field. All aboveground portions of the pepper plant can be attacked but often disease starts on senescing flowers or fruit damaged by sun scald. Spores (conidia) are produced throughout the growing season under a wide range of temperatures and humidity. Cool temperatures (68°F is optimal but the fungus can grow between 50° and 80°F), high humidity, and free water on plant surfaces favor the disease, as do close plant spacing and irrigation practices that keep plants wet for a longer time.
Papper fruit with gray mold- powdery gray Fruit can abort due to gray mold infection, as seen above, Cynthia M. Ocamb, 2012. fungus on the fruit shoulders. Cynthia M. Ocamb, 2012.
Symptoms: the symptoms first appear on petals, injured fruit, or senescing leaves and is initially a dark, water-soaked, slimy lesion and then the affected areas turn brownish-gray and powdery-looking as sporulation develops.
Cultural control
Chemical control
Powdery mildew
Powdery mildew can cause significant yield reductions in peppers. The fungal pathogen has a wide host range and is spread by wind-blown spores. A variety of methods are available to manage powdery mildew on peppers.
Symptoms
The initial symptoms of powdery mildew on peppers are a powdery-white fungal growth on the undersides of leaves with light-green to yellow blotches on the upper leaf surfaces (Figure 1). These areas turn brown with time, and the affected areas coalesce, causing a general yellowing of the entire leaf. The outer edges of leaves may curl upward. The older leaves lower in the canopy are usually infected first and show symptoms before the younger leaves. Infected leaves drop from the plant prematurely. This loss of photosynthetic leaf area slows plant growth and fruit development. The defoliation also exposes fruit to direct sunlight, which can lead to sunscalding of the fruit.
Photo: powdery mildew on a green pepper leaf
Management
Low light and high humidity favor the development of powdery mildew on peppers, so cultural practices that minimize these conditions can help lower disease severity. Select sites with well-drained soils and good air circulation. Adjust planting densities and row orientations to promote good air circulation and light penetration into the canopy. Avoid excessive fertilization that would result in overly dense canopies. In greenhouse production, increasing the temperature in the greenhouse can lower humidity levels and slow disease development.
A second control method for powdery mildew on peppers is the application of fungicides. Several fungicides are available for controlling powdery mildew on peppers. However, products vary in their required pre-harvest interval (PHI), and some have crop rotation plant-back restrictions. Appropriate fungicide resistance management strategies should be used to prevent the development of fungicide-resistant strains of the pathogen.
The effectiveness of the applications will depend on early detection and thorough coverage of the leaves. Applications should begin before symptoms appear, as the disease is difficult to control once it develops. The initial application should be based on when the disease typically shows up in the region. Spray volumes and pressure, in accordance with the label, must be sufficient to reach the lower leaves, including the undersides of leaves where infection occurs.
Damping-off is primarily caused by Pythium spp. Seedlings affected by damping-off fail to emerge or fall over and die soon after emergence. Stems usually have a dark, shriveled portion at the soil line. Damping-off is generally limited to areas where drainage is poor or where soil is compacted, but whole fields can be affected, especially in early plantings exposed to rain.
Photo:Damping off of Photo: Damping off of pepper transplants
Pepper seedlings
Symptoms on affected pepper plants include rapid wilting and death of pepper plants. Close examination of the roots and stems is necessary to confirm the cause of disease. The disease can develop at any stage of pepper plant growth. Taproots and smaller lateral roots show water-soaked, very dark brown discoloration of surface, cortical, and vascular tissues.
Factors that influence the development of damping-off and root and crown rot diseases in peppers in a given season include varietal susceptibility, amount and frequency of irrigation, and soil compaction and drainage. Crop rotation, proper irrigation, and clean transplants are critical in managing this disease. Fields that have a history of root and crown rots may need fungicide treatments at planting.
The disease can be effectively prevented by:
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