Pear Scab (Venturia pyrina) is a fungus that infects the leaves and fruit of European and Asian pears. It can lead to premature defoliation which leads to less flowering the following spring and greater susceptibility to other diseases in the winter.

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Cause:

  • A fungus that infects the leaves and fruit of European and Asian pear trees

  • Fungus is harbored in leaves infected the prior year and overwinter on the orchard floor

  • Unlike apple scab, pear scab can also overwinter as conidia (or spores) on twig lesions, as well as on leaves and shoots

  • Wet leaves, rain volume, and temperature all affect the degree of infection and infection period

Symptoms:

  • Small, raised, fuzzy, olive-colored spots first appear on fruit leaves at cluster

  • Grayish-brown spots on leaves and hard rough lesions on fruit

  • Fungus leads to the fruit splitting

Timing:

  • Early growing season through peak (March-April) infecting leaves around bloom time

  • Secondary infections with fruit formation

  • Ideal temperatures for infection are 60-75°F (16-24°C)

How to Avoid:

  • Purchase trees that have a higher degree of resistance to pear scab (see suggested varieties here)

  • Keep the orchard floor clear of fallen leaves at the end of the season or finely chop and spray fallen leaves with sulfur to prevent the spread of the disease

  • Pruning out infected twigs during dormancy can offer some benefit

  • Sanitize pruning equipment between trees

How to Treat:

  • Sulfur can be sprayed just before bloom and then every 7-10 days during infection times

  • Application of liquid fish, compost, or other nitrogen sources can break down leaves and prevent the spread of the disease the next year. The recommended ratio is 25:1 to 40:1, carbon to nitrogen.

Why it Matters:

Pear Scab can lead to premature defoliation which leads to less flowering the following spring and greater susceptibility to other diseases in the winter.

Sources: MyIPM, Pennsylvania State University Extension, Kansas State Research and Extension, University of California IPM, and Michael Phillips, “The Holistic Orchard”.