Randy:
It could have been due to the drought adversely affecting the scale
insect's natural predators, but just guessing.<<
Or, it could be that the stressed trees are more profitable hosts to the insects. My Ph.D. thesis focused on a rangeland grasshopper - damage by the main species of Wheat Grass feeding grasshoppers was always highest on stressed and damaged plants.
This can also be seen by repeating sweep net sampling along transects. Sweep one day, get diversity and density numbers for herbivorous insects. Come back next day and sweep same transect. Not uncommon to see insect numbers increase.
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