Liquid Copper Fungicide & Citrus Canker

Citrus canker, caused by the bacterium Xanthomonas citri, is a disorder affecting the leaves, fruit, and stems of most citrus trees. Citrus canker doesn’t typically kill wholesome citrus plants, but it can damage fruit and also cause your plant to look unappealing. Liquid copper fungicide sprays can be effective in managing citrus canker, and therefore are considered an organic solution to infection problems in citrus trees.

Citrus Canker Symptoms

Indicators of canker diseases begin as elevated lesions on both leaf surfaces, mainly on the undersides, and might later reveal on the fruit, stems and twigs. These lesions subsequently become corky, with raised, water-soaked stone and margins centers surrounded by a yellow halo. Older lesions may darken if they are colonized by saprophytic fungi. While almost all citrus varieties might be infected by citrus canker, grapefruit, early orange varieties and Mexican lime are particularly vulnerable. Mid-season oranges, tangerine hybrids, and Valencia oragnes are less susceptible, while tangerines are considered tolerant of canker infection.

Disease Cycle

Citrus canker infection generally occurs as new shoots are emerging, or when the fruit is in early phases of development. Warm, moist weather encourages the disease, so regular summer or spring rainfall provides ideal infection conditions. While citrus canker is largely a cosmetic disease which isn’t likely to eliminate your citrus tree, when conditions are highly favorable for infection, it can lead to leaf drop, shoot dieback and fruit fall, which can stress your tree and leave it vulnerable to other diseases and insect pests.

Liquid Copper Fungicides

Liquid copper fungicide is a protectant which you apply before the maturation of citrus canker to prevent infection. Copper fungicide is not systemic, so it can’t be transported through your citrus plant to eliminate the pathogen. Once implemented, it remains only where it contacts your citrus, and will not spread upon the leaf or fruit surface. This means that liquid copper fungicides might not be as helpful in decreasing existing infections since they are in preventing citrus canker from developing. The rapid growth of young leaves tends to create the effectiveness of liquid copper fungicide short-lived, and you’ll have to reapply it for the best results.


To guard early orange varieties and grapefruit, spray five applications of copper fungicide at 21-day intervals. Three applications at the same interval are usually enough to guard less susceptible Valencias and mid-season citrus varieties from illness. Remember that program rates are quotes because growth speed and rain can cause copper residues to decay at different prices. To make certain you get the very best coverage and optimum safety, browse the product label and follow all directions for rates and timing. The application of liquid fungicide is most successful in preventing citrus canker when it is implemented to coincide with leaf flushes, which usually require spraying about every three to four weeks from spring through autumn. It’s best to cut copper fungicide usage whenever possible, as copper can accumulate in the ground and might harm your plants. More frequent uses of liquid copper fungicides at lower speeds can decrease the risk accumulation or damage.

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