
Alternaria
Alternaria sp.
Pathogen:
Type:
Fungus
Risk:
HIGH

Frutos
Alternariosis

WHO CAUSES IT?
Alternaria sp. is a very large genus of phytopathogenic fungi, comprising numerous species capable of affecting a wide variety of plants, especially weakened, senescent, or damaged plant tissues. Many Alternaria species exhibit primarily necrotrophic behavior, colonizing tissues that have suffered wounds, physiological stress, mechanical damage, or unfavorable environmental conditions. The fungus produces a mycelium made up of branched hyphae that develop on or within the affected tissues and subsequently form conidiophores that produce numerous conidia. These conidia are one of the most important structures for the dispersal of the pathogen and can remain viable for extended periods in plant debris, affected fruit, seeds, soil, crop structures, and other contaminated surfaces. Conidia production increases particularly when infected tissues and favorable environmental conditions are present, and these conidia can be released and transported by wind, water splash, rain, irrigation systems, and agricultural operations. After reaching a susceptible surface, conidia can germinate when sufficient moisture is present, producing germ tubes that penetrate directly into tissues or take advantage of wounds, microlesions, and weakened areas. Once the infection is established, the fungus progressively colonizes cells and tissues, causing their death and forming new lesions in which it can again produce reproductive structures. In this way, successive infection cycles occur during the favorable period. The presence of infected plant debris constitutes an important source of inoculum, since the pathogen can survive between growing seasons in diseased plant material and resume its activity when suitable temperatures and humidity levels are present again. In fruit, infection can occur both during development in the field and during ripening, harvesting, handling, and storage, especially when wounds or damage facilitate fungal penetration.
SYMPTOMS
Alternaria leaf spot causes necrotic lesions on fruit that can begin as small, discolored, or sunken areas and progress to dark spots and areas of rot. The disease tends to advance more rapidly when the fruit has wounds, insect damage, abrasions, cracks, or any other alteration of the epidermis. The lesions can increase in size and acquire brown, black, or grayish tones, and may appear dry and sunken or progress to a softer rot depending on the Alternaria species, the affected fruit, and environmental conditions. In humid environments, a dark-colored sporulation mass may develop on the surface of the lesions, which is an important source of new conidia. The infection can considerably reduce the commercial quality of the fruit and, if it progresses during storage, can cause significant losses due to spoilage and rejection of the production. The disease may manifest as:
• Circular or irregular spots that are dark brown, grayish, or black.
• Sunken lesions that progressively increase in size.
• Necrosis and death of affected tissues.
• Appearance of rot areas on the fruit.
• Development of dark, dry, or leathery areas.
• Presence of dark sporulation on the lesions under high humidity conditions.
• Cracks or deterioration of the epidermis around the infected areas.
• Progressive spread of lesions from small initially affected areas.
• Internal rot in advanced infections.
• Loss of firmness and deterioration of fruit quality.
• Appearance of secondary infections favored by tissue deterioration.
• Loss of commercial value and an increase in fruit discarded during sorting and marketing.



TEMPERATURE AND HUMIDITY
20–27 °C
85–100 %
TRANSMISSION PATHS
Conidia transported by wind, rain splash, irrigation water, contact between fruits, infected plant debris, contaminated tools and equipment, hands and clothing of workers, insects and other agents that produce wounds or carry inoculum, contaminated plant material, contaminated seeds.
Do you want to remove this disease? Choose how you want to treat it.
TREATMENTS
Chemical treatment
• AZOXISTROBIN 25% [SC] P/V
• CIPRODINIL 37.5% + FLUDIOXONIL 25% [WG] P/P
• DIFENOCONAZOLE 1.67% [EC] P/V
• FOLPET 50% [SC] P/V
• FOLPET 80% [WG] P/P
• CUPRIC HYDROXIDE 50% (EXPR. IN CU) [WP] P/P
• METIRAM 70% [WG] P/P
• COPPER OXYCHLORIDE 30% (EXPR. IN CU) [WP] P/P
• COPPER OXYCHLORIDE 35% (exp. in Cu) [WG] P/P
• COPPER OXYCHLORIDE 35% (EXPR. IN CU) [WG] P/P
• COPPER OXYCHLORIDE 38% (EXPR. IN CU) [SC] P/S
• COPPER OXYCHLORIDE 50% (EXPR. IN CU) [WP] P/P
• COPPER OXYCHLORIDE 52% (EXPR. IN CU) [SC] P/V
• PIRACLOSTROBIN 6.7% + BOSCALIDE 26.7% ( ) [WG] P/P
• PIRACLOSTROBIN 6.7% + BOSCALIDE 26.7% (I) [WG] P/P
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WG] P/P
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WP] P/P
• TRIBASIC COPPER SULFATE 19% (EXPR. IN CU) [SC] P/V
Authorized treatments in organic farming
• CUPRIC HYDROXIDE 50% (EXPR. IN CU) [WP] P/P
• COPPER OXYCHLORIDE 30% (EXPR. IN CU) [WP] P/P
• COPPER OXYCHLORIDE 35% (exp. in Cu) [WG] P/P
• COPPER OXYCHLORIDE 35% (EXPR. IN CU) [WG] P/P
• COPPER OXYCHLORIDE 38% (EXPR. IN CU) [SC] P/V
• COPPER OXYCHLORIDE 50% (EXPR. IN CU) [WP] P/P
• COPPER OXYCHLORIDE 52% (EXPR. IN CU) [SC] P/V
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WG] P/P
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WP] P/P
• TRIBASIC COPPER SULFATE 19% (EXPR. IN CU) [SC] P/V
Biological control
• BACILLUS SUBTILIS (STRAIN QST 713) 1.34% [SC] P/V
Recommendations
• Remove and destroy affected fruit and infected plant debris, avoiding leaving them accumulated within the plot or near the plants.
• Maintain proper plot hygiene and regularly remove plant debris that could act as a source of inoculum.
• Avoid excessive moisture on the fruit and promote good ventilation within the vegetation through proper crop management.
• Use irrigation systems that reduce wetting of the aboveground parts, especially when environmental conditions are already favorable for the disease.
• Avoid irrigation that maintains high humidity on the fruit for prolonged periods.
• Properly control the density and structure of the vegetation to facilitate air circulation and reduce the duration of the wet period.
• Avoid wounds and mechanical damage during cultivation practices, as injuries can facilitate the entry of Alternaria sp.
• Handle the fruit carefully during harvesting, transport, and sorting to minimize bruising, cuts, abrasions, and other injuries. • Control pests that can wound the fruit and facilitate secondary fungal infection.
• Remove damaged, overripe, or injured fruit before storage to prevent them from becoming sources of contamination.
• Maintain facilities, crates, tools, and handling equipment in good hygienic condition and avoid the accumulation of contaminated plant debris.
• Avoid placing diseased fruit in storage chambers or areas with healthy fruit.
• Maintain storage conditions that limit condensation and surface moisture on the fruit.
• Conduct regular crop inspections to detect the first lesions and act before a high production of conidia occurs.
• Apply authorized phytosanitary treatments for the crop and for Alternaria, strictly following the dosage, timing, and maximum number of applications specified on the label.
• Initiate phytosanitary interventions according to the risk of infection and favorable environmental conditions, avoiding waiting until the disease is widespread. • Alternate active ingredients from different modes of action to reduce selection pressure on pathogen populations.
• Avoid repeated applications of active ingredients with the same mode of action when authorized alternatives are available.
• Combine phytosanitary measures with cultural, hygienic, and moisture management practices to reduce exclusive reliance on fungicides.
• Follow the recommendations of integrated pest management programs and the specific restrictions for each authorized product.
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*The recommended treatments are still recommendations according to the databases of the authorities and at no time do they replace the guidelines established according to the legislation of each country
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TREATMENTS
Homemade treatments
There are no home treatments
Natural allies
Chemical treatments
There are no treatments for this disease. Treatments are directed at the insect vectors that transmit it. See insect treatments.
RECOMMENDATIONS
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