Agricultural and Forest Entomology (2019) 21, 227-234

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Chad M. Rigsby, Emma E. Shoemaker, Mary M. Mallinger, Colin M. Orians and Evan L. Preisser (2019)
Conifer responses to a stylet-feeding invasive herbivore and induction with methyl jasmonate: impact on the expression of induced defences and a native folivore
Agricultural and Forest Entomology 21 (2), 227-234
Abstract: 1. Trees attacked by multiple herbivores need to defend themselves against dynamic biotic challenges; appropriate responses to one stressor can elicit hormonal responses that are antagonistic to another. Hemlock (Tsuga canadensis) infestation by hemlock woolly adelgid (HWA; Adelges tsugae) results in the accumulation of the defensive hormone salicylic acid.
2. We explored the potential for HWA infestation to interfere with anti-folivore-induced defence signalling and its implications for a native folivore (hemlock looper; Lambdina fiscellaria). Hemlocks were infested with HWA and/or sprayed with methyl jasmonate; foliar defences were analyzed and foliage quality for looper larvae was assessed.
3. Both treatments activated foliar defensive traits, including a HWA-mediated increase in peroxidase activity and an accumulation of cell wall-bound phenolics and lignin, as well as a methyl jasmonate-mediated increase in lipoxygenase activity. The two treatments had an additive effect on other defensive traits and both treatments negatively affected looper performance.
4. These results suggest that salicylic acid and jasmonic acid are not strictly antagonistic in conifers and that both have a role in anti-folivore defence signalling. The present study illustrates the need for a better understanding of hormone signalling, cross-talk and induced responses in conifers.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Chad M. Rigsby

Research topic(s) for pests/diseases/weeds:
resistance/tolerance/defence of host

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.

Lambdina fiscellaria Hemlock (Tsuga)
Adelges tsugae Hemlock (Tsuga)