Scab Fungus at a Page Orange Tree

The Page orange (Citrus × tangelo) is a hybrid citrus that is a cross between a Clementine mandarin tangerine and a Minneola tangelo, a grapefruit-tangerine hybrid. Released in 1963, the tree is famous because of its small, sweet fruits, which ripen early in the season. Unfortunately, the Page orange is susceptible to citrus scab, a fungal disease that wreak havoc on young fruits and leaves. Preventative fungicide sprays can keep the disease at bay.


Citrus scab is first recognizable as elevated, orange dots on tender young leaves leaves. The dots finally become wartlike growths that are covered using a scabby tissue that is often grayish. The leaves become twisted, twisted and stunted, and might flip yellowish-green or yellowish. Scabs on fruit appear a few days after initial symptoms on leaves. New scabs are mild cream or pale yellow, darkening with time into a rotting green or dark grey color.

Scab Disease Cycle

Citrus scab is spread by spores, which spread to foliage and fruits through irrigation or rain water. The fruits and leaves have to be moist for three to four hours for the infection to take hold. Only young fruits and leaves are susceptible. Leaves are at risk until they’re a few days old, while vegetables are at risk for their initial two months of growth. According to the University of Florida IFAS Extension, the spores are most inclined to take grip of wet weather when temperatures are between 75 and 82 degrees Fahrenheit.

Scab Management

Routine applications of fungicide will help control the disease, especially if the disease continues from season to date. Choose a fungicide such as neem oil and then spray on the tree thoroughly, following the instructions on the label, prior to the tree flowers in the spring and when the flowers drop. Spray a third time since fruits are developing. Don’t spray when you’re expecting rain, since it will simply be washed away.

Scab Prevention

You can help avoid citrus scab by occasionally pruning the tree to allow better air circulation, which will dry the leaves faster and allow a preventive fungicide to cover more area, and by taking extra care not to get the leaves or fruit of the tree moist as you water. Pull away all tall weeds in the tree, as they can donate to the humid conditions that fungal diseases adore. If you can, move the tree to an area with more sunlight.

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