If you haven’t met tuliptree scale, Toumeyella liriodendri, its high time you did. I found dense patches of it at a local playground the other day. I was tipped off by honeydew, which can mean tulip poplar aphids, but also scales. Tuliptree scales feed primarily on tulip poplar, Liriodendron tulipifera, though it is occasionally found on other trees including Magnolia spp. It occurs throughout the eastern US from New England to Florida.
Unlike many other soft scales in our area, tuliptree scale produces crawlers at the end of summer and into fall. The scales overwinter as 2nd instars on twigs. In spring they develop to adults and produce lots of honeydew throughout the summer. In late summer honeydew production declines as female scale begin producing eggs and crawlers. A single female can produce over 3000 crawlers over three months. This could make control difficult since you cannot target a whole cohort of crawlers with a single application of oil or insecticide.
Honeydew from tuliptree scale supports dozens of other species. Researchers have recorded 93 hymenopteran species that collect honeydew of tuliptree scale and a dozen or so ant species. This is an amazing diversity of creatures that would not be in a tree if these scales were absent. This disproportionate effect of one species on the animal community suggests a potential foundational or keystone role. Since these scale produce so much honeydew they can be heavily tended by ants. Ant tending can reduce scale mortality by predators and increase scale abundance.
Tuliptree scale cause considerable damage to trees. They can kill central leaders resulting in bushy plants with codominant leaders. They can kill trees or reduce tree growth rate. High densities of scales can remove more carbon than a tree produces. In this case trees are surviving on reserved energy that is gradually depleted.
Reference: Burns, DP, Donely, DE. 1970. Biology of the Tuliptree Scale, Tourneyella liriodendri (Homoptera: Coccidae). Annals of the Entomological Society of America, 63, 228-235.