I found this applicable quote:
"Ethylene is not a universal attractant for all insects that are parasitic on trees.
Ethylene is a plant hormone that plays important roles in plant development, ripening of fruits, and stress responses. While some insects can detect and respond to ethylene released by plants, this response is not universal across all tree-parasitic insect species.
Here are some key points about ethylene and its effects on tree-parasitic insects:
- Bark beetles: Some bark beetle species, like the mountain pine beetle, are attracted to ethylene released by stressed or damaged trees. The ethylene signals a suitable host tree.
- Wood-boring insects: Ethylene can attract certain wood-boring insect pests like ambrosia beetles and some weevil species to trees releasing the hormone due to injury or disease.
- Fruit flies: Ethylene produced during fruit ripening attracts fruit flies and other frugivorous insects, but this is less relevant for tree parasites.
- Plant response: Ethylene can induce defense responses in plants, potentially making them less attractive to certain herbivorous insects.
- Species-specific: The attraction or repellence to ethylene is highly species-specific and depends on the insect's biology and host preferences.
Many other chemical cues like pheromones, host volatiles, and primary attractants play more significant roles in host location for most tree-parasitic insects than ethylene alone.
So while ethylene can be an important signal for some bark beetles and wood borers, it is not a universally attractive or repellent compound across all insects that feed on or infest trees. The responses vary greatly by insect species and life stage."
Also:
"Here are a few examples of trees that do not significantly produce the ethylene hormone:
- Conifers: Most coniferous trees like pines, firs, spruces, and cedars produce extremely low levels of ethylene compared to angiosperms (flowering plants). Ethylene production is negligible in healthy, unstressed conifers.
- Ginkgo (Ginkgo biloba):The ancient ginkgo tree species does not produce any detectable amounts of ethylene, even during seed development.
- Redwoods (Sequoia sempervirens):The tall redwood trees native to coastal California produce virtually undetectable ethylene levels.
- Douglas Fir (Pseudotsuga menziesii):This important coniferous tree species is another very low to non-ethylene producer.
- Bald Cypress (Taxodium distichum):No significant ethylene production has been reported in this deciduous conifer tree.
The key reason many gymnosperms (non-flowering seed plants) like conifers do not produce ethylene is that they do not rely on the hormone for fruit ripening, abscission, or other ethylene-related developmental processes like angiosperms do.
However, ethylene can still be produced in response to severe stresses like wounding, bacterial infections or environmental conditions in some of these trees. But under normal circumstances, ethylene biosynthesis is negligible or completely absent in certain tree species.
