How to Manage Pests

Pests in Gardens and Landscapes

Pear decline

Pear decline is caused by a microorganism called a mycoplasma, which is spread by pear psylla. Trees with pear decline have poor shoot and spur growth, dieback of shoots, upper rolling of leaves, reduced leaf and fruit size, and premature leaf drop. Sudden tree collapse can result from tissue damage at the graft union on highly susceptible rootstocks, but slow decline is more common.

Life cycle


Some tolerant rootstocks may be available. To keep the disease in remission on susceptible rootstocks, control pear psylla and maintain trees in good vigor; reduce stress caused by inadequate irrigation, nutrient deficiency, weed competition, and lack of pruning. Consider replacing trees on susceptible rootstocks with resistant ones.

Rolling and discoloration of leaves
Rolling and discoloration of leaves

Statewide IPM Program, Agriculture and Natural Resources, University of California
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