Citrus Blight Found in Yucatan, Mexico.

Area of Science:

• Plant Pathology
• Horticultural Science
• Agronomy

Background:

• Citrus blight is a significant tree decline disease affecting citrus production in humid regions globally.
• The disease, of unknown etiology, lacks reliable visual diagnostic symptoms, necessitating laboratory testing.
• Historically, citrus blight has not been reported in Mexico, despite its presence in other major citrus-growing areas.

Purpose of the Study:

• To confirm the presence of citrus blight in Mexico using established diagnostic methods.
• To investigate the potential factors contributing to the emergence of citrus blight in Mexican citrus orchards.
• To correlate diagnostic test results with observed tree symptoms and horticultural practices.

Main Methods:

• Water injection tests to assess trunk water uptake capacity.
• Analysis of zinc and potassium concentrations in outer trunk wood.
• Immunological testing for specific citrus blight-associated proteins in leaves.
• Correlation of diagnostic findings with visual symptoms and rootstock information.

Main Results:

• Declining trees in Yucatan, Mexico, exhibited significantly lower water uptake compared to healthy trees.
• Wood analysis revealed elevated potassium levels and, in one location, increased zinc in declining trees.
• Leaf samples from declining trees tested positive for specific blight proteins, confirming disease presence.
• Visual symptoms observed in Mexican trees mirrored those of citrus blight in Florida and Cuba.

Conclusions:

• Citrus blight is confirmed to be present in Mexico, specifically in the Yucatan region.
• Climatic conditions (dryness) and the use of susceptible rootstocks (Cleopatra mandarin and Volkamer lemon) are likely factors in the disease's emergence.
• Changes in rootstock to mitigate tristeza virus disease inadvertently increased susceptibility to citrus blight.