Phytophthora
White Tip Of Onion
Phytophthora Porri
Pathogen:
Oomycete
Type:
Risk to the plant:
CRITICAL
DESCRIPTION
WHO CAUSES IT?
Phytophthora porri is an oomycete that causes the disease known as onion white tip. This pathogen is characterized by producing sporangia that become mobile zoospores, which can swim in soil water in search of roots of susceptible plants to infect. It can also produce oospores, which are resistance structures that survive in unfavorable conditions in the soil or in plant remains. Phytophthora porri can proliferate in cool, moist conditions, causing rapid and widespread infection of onions.
SYMPTOMS
This fungus causes the formation of small light-colored dots on the leaf. The Taches increase rapidly in size when there is humidity and cold (< 15º C). The lesions are basically located on the upper half of the leaf, often surrounded by what is sometimes a moist area of considerable size and green color. After some time, the affected areas and the tips of the leaves wither. White color on the tips of the leaves is a typical characteristic of a Phytophthora infection. This fungus can cause rot when the crop is stored.
• Chlorotic or whitish Taches on the leaves, especially at the tip.
• Necrotic lesions that may extend to the base of the leaves.
• Plant rot and general weakness.
• Reduction in the quality and quantity of the harvest.
TEMPERATURE AND HUMIDITY
15 ºC - 25ºC
80% - 100%
HOW IS IT SPREAD?
Water, soil, remains of infected plants.
HOW TO REMOVE IT?
Home remedies
There are no home treatments
Chemical treatments
• AZOXISTROBIN 25% [SC] P/V
• CUPRIC HYDROXIDE 20% (EXPR. IN CU) [WG] P/P
• CUPRIC HYDROXIDE 25% (EXPR. IN CU) [WG] P/P
• COPPER OXYCHLORIDE 38% (EXPR. IN CU) [SC] P/V
• COPPER OXYCHLORIDE 50% (EXPR. IN CU) [WP] P/P
• PIRACLOSTROBIN 6.7% + BOSCALIDE 26.7% ( ) [WG] P/P
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WP] P/P
• CUPROCALCIC SULFATE 20% [WP] P/P
Authorized treatments in organic farming
• CUPRIC HYDROXIDE 20% (EXPR. IN CU) [WG] P/P
• CUPRIC HYDROXIDE 25% (EXPR. IN CU) [WG] P/P
• COPPER OXYCHLORIDE 38% (EXPR. IN CU) [SC] P/V
• COPPER OXYCHLORIDE 50% (EXPR. IN CU) [WP] P/P
• CUPROCALCIC SULFATE 20% (EXPR. IN CU) [WP] P/P
• CUPROCALCIC SULFATE 20% [WP] P/P
Insect allies
PREDATORY MITES
LADYBUGS
LACEWINGS
PARASITIC WASPS
HOVERFLIES OR PARASITIC FLIES
PREDATORY BUGS
There are no natural allies
Mycodiplosis oidii (predatory mosquito)
EFFECTIVE PRODUCTS TO ELIMINATE THIS DISEASE
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• Maintain good irrigation management to avoid excess water in the field.
• Practice crop rotation to reduce pathogen pressure in the soil.
• Use onion varieties resistant or tolerant to Phytophthora porri.
• Improve soil drainage to avoid water accumulation.
• Eliminate and destroy infected plants and plant residues.
• Apply specific fungicides according to local recommendations.
• Carry out regular monitoring to detect the disease in time.
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