Location: Application Technology Research
Project Number: 5082-21000-018-20-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 15, 2018
End Date: Sep 14, 2023
(1) Determine the relationship between abiotic stress and diseases of trees in orchards, ethanol production, and the attraction and colonization of ambrosia beetles; (2) Determine the implications of symbiotic and opportunistic auxiliary fungi associated with ambrosia beetles on the rapid dieback of trees in orchards; and (3) Establish the efficacy of selected insecticides and repellents for protecting trees against ambrosia beetle attacks and/or reducing the effects of stress in trees.
To address Objective 1. A study will be conducted to evaluate ambrosia beetle colonization and ethanol emissions from drought-stressed vs. healthy apple trees. Experiments will also examine the effects of fire blight and Phytophthora on ambrosia beetle host colonization and ethanol emissions. Ambrosia beetles will be confined with no choice using small chambers to the stems of trees subjected to varying degrees of water stress or pathogen infection (fire blight and Phytophthora). Ambrosia beetle colonization will be evaluated every 2-4 days after initiating drought stress. Ethanol emissions and leaf gas exchange will also be measured from trees subjected to abiotic stress and pathogen infection. To address Objective 2, the potential of opportunistic, weak pathogens of apple and ambrosia beetle symbionts to colonize apple cambial tissue and produce decline symptoms will be evaluated. The pathogenicity of seven fungal species: Phomopsis mali, Botryosphaeria dothidea, Paraconiothyrium brasliinese, Fusarium acuminatum, Fusarium solani, and Ambrosiella grosmanniae will be evaluated for drought-stressed and non-water stressed dwarf apple trees. Isolates will be propagated accordingly and pipetted into holes drilled into xylem of selected trees. Ambrosia beetle colonization, ethanol emissions, and tree health parameters will be evaluated. To address objective 3, insecticides, repellents, and fungicides will be evaluated as protectants against ambrosia beetle attacks and/or colony establishment in potted apple trees. Trees will be flood-stressed or irrigated with dilute solutions of ethanol to induce ambrosia beetle attacks. Topical and drench treatments will be compared. The potential of systemic acquired resistance (SAR) inducers and plant growth regulators for managing drought stress and opportunistic pathogen-related Rapid Apple Decline in apple trees will also be evaluated. Trees will be monitored from ambrosia beetle attacks and also dissected to assess ambrosia beetle colonization success. RNA will be extracted and genes encoding pathogenesis related (PR) proteins will be evaluated. The induction of PR-genes associated with the presence of biotic and/or abiotic stress will be examined.