What canopy-management practice can reduce cedar-apple rust on junipers?

What canopy-management practice can reduce cedar-apple rust on junipers?

• A. Galls pruned off before spore horns develop
• B. Fungicide spray on fruit trees only
• C. Watering to keep foliage moist
• D. Planting junipers closer together

Answer: (A)

Cedar-apple rust relies on spores produced by galls on junipers to infect apples. The key management move is to remove the source of those spores before they are released. Pruning galls off junipers early, before spore horns develop, interrupts the life cycle and greatly reduces the amount of rustable inoculum that can reach apples or crabapples. Think of the disease cycle: the juniper galls overwinter and then produce spore horns in spring. If you take out the galls before those horns form, there’s little to no spore release to infect nearby apple trees, which lowers rust pressure in the canopy of the orchard or landscape. Why the other options aren’t as effective: spraying fruit trees alone targets the symptom on apples but doesn’t reduce the primary inoculum coming from junipers; keeping foliage wet creates conditions that favor rust development; planting junipers closer together increases humidity and canopy moisture, which also promotes rust.

Cedar-apple rust relies on spores produced by galls on junipers to infect apples. The key management move is to remove the source of those spores before they are released. Pruning galls off junipers early, before spore horns develop, interrupts the life cycle and greatly reduces the amount of rustable inoculum that can reach apples or crabapples.

Think of the disease cycle: the juniper galls overwinter and then produce spore horns in spring. If you take out the galls before those horns form, there’s little to no spore release to infect nearby apple trees, which lowers rust pressure in the canopy of the orchard or landscape.

Why the other options aren’t as effective: spraying fruit trees alone targets the symptom on apples but doesn’t reduce the primary inoculum coming from junipers; keeping foliage wet creates conditions that favor rust development; planting junipers closer together increases humidity and canopy moisture, which also promotes rust.