We do love beech trees: American, European, copper, weeping. They are all magnificent. Their impressive size and gnarly solidity stand out for permanence and imperturbability. But, they are not invulnerable. Along with the many challenges all plants are facing, beeches have more than their share of problems, including phytophthora fungus, beech bark disease, and now the mysterious and deadly beech leaf disease.
While phytophthora fungus and beech bark disease are fairly well understood and treatable with non-toxic natural processes, beech leaf disease has all of us PRFCT land care types thinking hard about what to do when beloved trees become afflicted. The cause, now identified as a nematode (microscopic worm), is not well understood. As a result, no one knows the best way to control it. The main option being offered to treat it, though, is a chemical fungicide called Broadform, which is highly toxic to people and pets and lethal to beneficial organisms. It is so toxic that New York State Department of Environmental Conservation (DEC) had to make a special dispensation to allow its use for residential ornamental plants. And, yet no one knows if it will even be effective. Is it worth it to bend our resolve and put our children and pets in harm’s way to possibly keep a treasured tree holding on until we know more about the disease and have better solutions? I don’t know. I can only suggest that people make their own decisions based on as much unbiased (no income potential) input as possible until we learn more. I will update you as I find out more about this disease.
But there is another part of this story I am thinking about: the woolly beech aphid. Also known as the boogie woogie aphid, it is a fuzzy, sucking insect that lives on the underside of beech leaves and “dances” by raising its hind legs when threatened. (Watch them boogie down here.) It is harmless to all beeches, but a nuisance to humans because of the large amounts of clear, sticky “honeydew” produced. This gooey sap (aphid poop) drips on objects below (cars, benches, you) and then attracts an unsightly, but also harmless, dark “sooty” mold. Since these aphids don’t hurt the tree, I let them be, waiting for predators to show up and feast on them and reduce the goo. But this year I’ve been asking, where are the predators?
Right now, woolly aphids are far more numerous than normal, which is not surprising. When host plants become weak from causes such as disease, pests, like aphids, thrive because it is easier for them to get their sucking parts through struggling cell walls. Beneficial insect predators (lacewings, ladybugs, hoverflies, and parasitic wasps) typically show up when aphid populations are large enough to attract their attention. They feast, multiply, knock back the aphids, and then move on when there isn’t enough left to eat. It can take a season or two for this natural, balanced prey/predator food cycle to complete.
The problem with this year’s woolly beech aphid infestation is not just that the beeches have been weakened by problems like beech leaf disease, but that predator population numbers are also alarmingly low. The ladybugs, lacewings, and other hungry friends just aren’t showing up. Can their dwindling populations be a consequence of widespread spraying for ticks and mosquitoes? All insecticidal sprays, even the “organic/natural oil” ones, kill. They don’t just kill ticks or mosquitoes. They also kill the bugs—butterflies, lacewings, bumblebees—we love and need. When people resort to chemicals to control pests, they destroy the food sources for beneficial insects, which eventually destroys the beneficials themselves. The cycle of natural pest control is broken.
My request to you is: Put down those insecticidal sprays. Nature, if given time, can take care of pests—if we can be patient and let them. There’s always something that will eat the pests we wish to control. Waiting and thinking before acting always brings new observations, insights, and a peaceful interaction with our natural world. While I’m waiting and observing, I will take my hose and simply wash off just the aphids on the branches that hang over my picnic table and leave the rest for the food web.
Quote: “When you surrender, the problem ceases to exist. Try to solve it, or conquer it, and you only set up more resistance.” —Henry Miller, A Literate Passion: Letters of Anais Nin and Henry Miller 1932-1953
Book: Changes in the Land: Indians, Colonists and the Ecology of New England by William Cronon
Rebecca McMackin recently recommended this book. It is a seminal work, which opened the environmentalist conversation about indigenous land management practices and sustainability. A seriously thought-provoking history of land use and resource management, it raises so many questions about preconceptions of what was and what we are doing now.
Woolly Beech Aphid photo by Haruta Ovidiu, University of Oradea, bugwood.org