Pear decline
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What is Pear decline (Candidatus Phytoplasma pyri)?
Pear decline is a disease caused by Candidatus Phytoplasma pyri, transmitted by pear psylla insects or through grafting infected stock. It affects pear trees and is more prevalent in trees with certain rootstocks. The disease is distributed in pear-growing regions worldwide. Infected plants show symptoms such as early or premature foliar discoloration, wilting, scorching, and reduced vigor. Leaves may turn red, curl downward, and drop prematurely. The disease is associated with reduced fruit set and size. Environmental conditions, such as the presence of pear psylla and susceptible rootstocks, contribute to its spread.
How does Pear decline (Candidatus Phytoplasma pyri) occur?
Candidatus Phytoplasma pyri reproduces and spreads through specific mechanisms. The phytoplasma is transmitted to healthy trees through grafting infected stock or by pear psylla insects after a few hours of feeding. The insect remains infective for its entire lifespan. The pathogen survives in the roots of infected trees from season to season and fluctuates in the aboveground portions of the tree. It does not survive in aboveground phloem elements during late fall and winter but rebounds when new phloem tissue is produced in the spring.
Symptoms
1 - Plant Health
• Pear Decline leads to poor shoot and spur growth, dieback of shoots, reduced leaf and fruit size, premature leaf drop, and in severe cases, sudden tree collapse. • These effects can significantly impact the overall health and productivity of pear trees.
2 - Economic Impact and Soil Health
• Reduced tree health can affect nutrient cycling, soil microbial activity, and overall soil fertility. • Pear Decline can have economic implications for commercial pear growers. Reduced fruit quality and yield due to the disease can result in financial losses for farmers.
Solutions
1 - Cultural Control
• Maintain tree health through proper care, by addressing stress factors like inadequate irrigation, nutrient deficiency, weed competition, lack of pruning, and pest damage. • Use resistant or tolerant rootstocks: Choose rootstocks known to have a high level of tolerance or resistance to pear decline. • Careful grafting techniques: When grafting, graft below the union of the Asian pear with its rootstock to avoid creating highly decline-susceptible trees. • Implement integrated pest management (IPM) strategies to manage psylla populations.
