Cedar-apple rust is sprayed twice a year: once during an active infection between spring and early summer, and again the following spring as prevention, timed to the tree's bloom rather than the calendar.

When Should I Spray During an Active Cedar-Apple Rust Infection?

Once cedar-apple rust is active, every apple, juniper, and cedar or red cedar tree in the area should be sprayed, including any that aren't yet showing symptoms, since spores travel by wind between the two host types. Fungi Max Multi-Purpose Fungicide, one of the fungicides labeled to control rust, is applied at the first sign of disease and repeated after 14 to 21 days.

How Should Spraying Be Timed the Following Spring, as Prevention?

Preventive spraying the next spring follows the tree's bloom rather than a fixed date: the first application goes on when the tree flowers, the second once about 75 percent of the flower petals have dropped, and the third 10 to 14 days after that. This timing matters because an active infection can't be controlled once it has already taken hold, so spraying ahead of and through bloom is what limits how severe the next outbreak gets.

Frequently Asked Questions

What does cedar-apple rust look like on an apple tree?

Small, pale yellow spots on the upper side of the leaves in mid-to-late spring, which develop black or brown spots at their center as the infection progresses. Advanced cases cause premature leaf and fruit drop.

Why does cedar-apple rust need both an apple tree and a cedar or juniper nearby?

Because the fungus can't complete its life cycle on just one host. It alternates between the two: spores from galls on cedar or juniper trees infect apple leaves in spring, then spores from the apple tree blow back onto the cedar or juniper later in the season to start the cycle again.

Can cedar-apple rust be treated once a tree already shows symptoms?

Not fully. An active infection can't be reversed once it's established, so spraying at that point is aimed at limiting spread to other trees rather than curing the ones already infected.

How much does Fungi Max Multi-Purpose Fungicide cost?

$24.95 for a 1-pint bottle.