Garden Notes

Defoliated oak trees have become an increasingly common sight around the Island. Photos by Susan Safford

Fuzzy fear

By Abigail Higgins - June 8, 2006

Caterpillar stress is mounting for those of us who live in the areas afflicted on the Island this season. Their presence makes it unpleasant to be outdoors: continually wiping them off the back of the neck, listening to the sound of their excrement raining down, smelling the odor of the destruction they wreak. It causes one to be seized by the idea that one must do something!

Unfortunately, even if one had the arborist come and correctly treat every tree on the property for each of the various caterpillars, it would not change the fact that next year could see a repeat of the same scenario. This caterpillar outbreak situation is somewhat baffling because no one has come up with a workable model that explains the situation, which is that six different species of caterpillar have gone into population overdrive. One thing is likely though: the European winter moth, one of the six and a recently arrived exotic, is going to be with us from here on out and, until natural control forces evolve, will cause widespread damage.

Speaking of natural control forces evolving, today at work, one of the bright young people I work with brought up a question of ecology. Is spraying (spraying anything at all, contact poisons as well as "eco-intelligent" control measures such as Spinosad) actually useful and a good idea? Doesn't spraying represent interference that prolongs the state of dis-equilibrium? Since I am not an entomologist I have no good answer and even if I were, I suspect there is no clear-cut agreement on this subject.

But yes, in the overall scheme of things, attempts at controlling nature often have unintended consequences. I remember walking through the DDT-fogged woods as the spray planes flew overhead, to catch the school bus in the early 1950s when gypsy moth caterpillars defoliated large swathes of New England. I was just a little girl. (I think this may have occurred on more than one occasion.) How many of the Island's then children have had health problems that are ascribed to "faulty genes," the covert cause of which was that aerial DDT spraying? The gypsy moth is still here, needless to say.

Several species are involved in the current caterpillar infestation, but they are difficult to identify positively because under outbreak conditions, caterpillars can change their coloration. Here, the green creature is most likely a winter moth, Operophtera brumata.

Nonetheless, for emergency protection of a treasured tree or plant, I recommend spraying it thoroughly with a Bacillus thuringiensis (Bt) solution, with an added spreader/sticker. Mix according to label directions. For it to work, the caterpillars must ingest the Bt. Shortly thereafter they will stop feeding and are soon dead.

Know your caterpillars

This might be a good place to put in a plug for a recently published caterpillar guide, "Caterpillars of Eastern North America" by David L. Wagner (Princeton University Press, Princeton, 2005, 512 ppg.) It is such a well-done, complete compendium! Certainly this might seem to be a specialized book, but it seems to me that there is a great interest currently in planting butterfly gardens, and there are no butterflies without caterpillars. Every insect is illustrated in color as both caterpillar and butterfly or moth on its own page. The description system is organized with paragraphs as follows: recognition; occurrence; common food plants; and remarks. The remarks sections often contain directions for rearing the caterpillar in question. It would be impossible to encounter a caterpillar on Martha's Vineyard, or anywhere in eastern North America for that matter, that could not be identified with this guide in hand.

As an antidote to the grimness of the caterpillar-festooned oaks and beeches in my yard, and to keep out of the way of the webbing, for solace I turned to reading and re-reading my two volumes of the late Christopher Lloyd's garden writing on a recent rainy day. My books are "The Well-Tempered Garden" and "The Adventurous Gardener." They have been reprinted and reissued in various editions and in paperback over the years. If you enjoy garden writing, if you have questions about procedures, plants, or garden aesthetics, do yourself a favor and check out Mr. Lloyd's writings. His opinionated-ness is earned by years of hands-on gardening, working in the nursery business, teaching horticulture, and ownership of one of Britain's better-known garden destinations, Great Dixter. But it is at the same time valid and engaging. Mr. Lloyd's writing steers close at times to cutesy but always manages to veer away at the last minute, sometimes to a very profound observation. I take the liberty here of quoting a couple of paragraphs, from "The Well-Tempered Garden," on scent.

These specimens are fall cankerworm, Alsophila pometeria.

"There are some flowers that we expect to be scented; if they are not they are out. Others, of which we do not demand this quality, may surprise us by producing it. 'Where does the scent come from? It cannot be that gladiolus,' we say, while the gladiolus indulges in a quiet smirk at our expense.

"Show a red rose to anyone with the slightest vestige of a sense of smell, and he will automatically put his nose into it. Lacking scent, it may still make a name for itself as an exhibitor's flower, but it will touch nobody's heart. A red rose is not just a nice arrangement of sumptuously colored petals. It embodies all that we have ever known and felt about roses right back to our first childhood garden. White roses arouse no expectation of scent, but neither do they involve their beholders. Before the cold chastity of an 'Iceberg', it is easy for the head to rule the heart." Nicely put.

Another book, on loan to me from a client, "Summer-Blooming Bulbs," from the Brooklyn Botanic Garden paperback series, merits a brief mention. As the title implies, it is a slim (111 pages) compendium of bulbs for summer gardens. Becky and Brent Heath, of Becky's Bulbs, have contributed a center informational section consisting of tables for the different hardiness zones across the country, which lists bulbs for perennializing and for naturalizing. It is printed on yellow paper, as is the index/bibliography section. The book is informative and is well illustrated on every page with color photographs. Definitely a resource to encourage the greater use of summer blooming bulbs.