Sunday, June 08, 2025

Springtime Chow Down on Local Flora

Springtime, and the woods is full of fresh green foliage. With such tenderness and delectability in abundance, it's not surprising that very hungry caterpillars and other insects respond by chowing down. 

Earlier this spring, the tent caterpillars got busy in the Barden at Herrontown Woods defoliating the  black cherry trees. In the photo are one of many new "tents," and the brown, droopy remains of the previous year's.


Last year's black cherry chow down was particularly extravagant, resulting in near total defoliation that ultimately extended to the neighboring pin oak. In the process, the caterpillars built lavish highways of silk, the better to navigate over the cherry's rough "black potato chip" bark. Once the communal caterpillars had had their way with the trees, they individually wandered off to pupate, and the trees grew a second set of leaves. This relationship seems to keep the black cherry trees perpetually stunted, but still healthy enough to grace the Barden grounds. 

Another woody plant burdened by the overwrought appetites of native caterpillars is the Hearts a Bustin (Euonymus americanus). Because deer browse was preventing this native shrub from growing to maturity in the wild, we transplanted some into cages in the Barden at Herrontown Woods. For years, they thrived, but this year the webworm larvae of the American ermine moth (Yponomeuta multipunctella) showed up to chow down. As with the black cherry trees, the Hearts a'Bustin' shrubs are having to be way more generous than seems fair. 

Interestingly, the Hearts 'a Bustin' we have growing in sunnier locations are thus far sustaining less damage from the insects. Perhaps the extra sunlight strengthens their defenses.


More modest in their appetites are caterpillars found on ferns. Deer tend to avoid eating ferns, and insects may find them less edible as well.



Early in the process of creating what became the Barden, we discovered a pussy willow growing there. This spring, some of its leaves were getting "windowpaned" by larvae of the imported willow leaf beetle (Plagiodera versicolora). Like kids that won't eat the crust of bread, the larvae leave the leaf veins uneaten.







Oaks sustain a tremendous variety of insects, among them the wasp Callirhytis seminator. The wasp lays its egg on the oak, simultaneously injecting a chemical that causes the oak to create a growth called a Strawberry Oak Gall, or Wooly Sower Gall. The gall conveniently provides food for the wasp larva.

These are but a few examples of the varied ways plants support the local insect population, which in turn provides sustenance for birds.





3 comments:

  1. Thanks so much for the caterpillar lesson! Some time ago I read a book from the 1910's called "Useful birds of Massachusetts and their Protection". One of the things this book impressed on me was how many caterpillars song birds eat in the spring when they are raising their young. This inspired me to build a wren house for my garden. It's such a treat to watch the wrens show up with one juicy caterpillar after another! I've never had a need for pesticides.

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    1. I had thought that birds would be gobbling up the tent caterpillars that defoliate the black cherry trees, but it's going to take more focused watching than I've been able to muster thus far. I suppose it's possible that our resident house wrens are patrolling for larvae on the Hearts a bustin shrubs in the sunny locations and avoiding the ones in the deeper shade.

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    2. According to the Useful Birds book, Baltimore orioles will eat tent caterpillars and blue jays will eat their eggs.

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