Aug 5, 2015
New certifications combat nursery tree viruses, costs

Fruit tree viruses cost growers and producers thousands of dollars each year, and increased expenses often get passed down to the consumer. New standards to test for viruses in fruit trees and small fruit in nurseries will help combat these rising costs.

The Pennsylvania IPM Program at Penn State and the Pennsylvania Department of Agriculture (PDA) collaborated recently to develop the standards for new virus-tested certification programs in nurseries. According to Ruth Welliver, project coordinator and plant pathology program manager at PDA, the new standards will ensure sampling methods for viruses in nursery and production situations remain consistent and accurate.

“Viruses can be unintentionally and rapidly spread during the production of nursery stock. Once a tree has been infected by a virus it cannot be cured, and the only way to remove a virus from an orchard or a block of nursery trees is to destroy the infected trees,” said Welliver.

While some viruses have a minor impact on infected trees, others such as Plum Pox virus can cause very serious diseases. Economic impacts of fruit tree viruses include delayed maturity, reduced growth and yields and poor fruit quality.

The research team reviewed several sampling methods currently used in nurseries to develop a standard method. Experimental sampling was done in orchard and nursery settings using two viruses with different methods of transmission.

“We also looked at virus lists for Prunus, apple, and blueberry – three crops with nursery and fruit production establishments in Pennsylvania – and selected not-commonly-tested viruses to verify our assumptions about their presence in certified and uncertified material,” Welliver explained. “For example, blueberry shock virus is common in Oregon, but is not known to occur on the East Coast. Consequently, few East Coast states test nursery material for this virus.”

After one season of surveying and testing data for targeted viruses, the research team compared their finding to survey methods currently used in the state certification program and reported their recommended changes to the National Clean Plant Network (NCPN). These recommendations are being considered for incorporation into model nursery certification standards and can be viewed at NCPN’s website.

Tactics such as developing best management practices for growing nursery crops as a means to prevent the spread of viruses and diseases is part of a grower’s integrated pest management, or IPM, program. IPM aims to manage pests — such as insects, diseases, weeds and animals — by combining physical, biological and chemical tactics that are safe, profitable and environmentally compatible.

— Penn State Extension

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