Why are Cape Cod Oaks in trouble again?
Oaks and White Pine were the predominate species established in our sandy soils, and are the backbone for carbon sequestration and recycling on this terminal moraine of the Laurentide glacier that carved this beautiful ocean peninsula called Cape Cod. As soils were depleted of organic matter, the White Pine’s ability to thrive gave way to the imported Pitch Pine, but the mighty oaks persevered. Is their decline imminent too? Can we possibly save the Cape’s only surviving deciduous primeval forest species? Or will only short lived trees like the poplar and the birch survive?
The choice could be ours.
First, a bit of history about the many pests attacking the oak trees. The exotic invasive Winter Moth defoliating caterpillar, introduced through global trade and climate change, ravaged the urban and natural forests for 15 years. With the introduction of natural predators, we are controlling this devastating pest, yet it still has a presence here on Cape Cod.
The Oak Gall Wasp, a native pest, which developed from environmental stresses, attacked our oaks five years ago. Fortunately the Oak Gall Wasp has subsided with its natural predators. Recently, the Gypsy Moth caterpillar re-emerged and devastated our trees for three years. It too has subsided.
Now the Lecanium scale has reared its ugly head and has infested oak trees everywhere on Cape Cod. Lecanium scale is a group of soft scale insects that feed on the sap of shade trees and woody ornamentals, such as the Cape Cod Oak trees. For a small period of time after the scale hatches, they are known as “crawlers,” the only time of their lifespan they are mobile. Once they find a sustainable spot to feed, however, they become immobile, spending the rest of their lives attached to the tree while feeding off its sap. They resemble reddish-brown turtle shells lining the branches and twigs of the trees. These shells are the scales, and they protect the body of the insect, and its eggs, from weather damage, predators and insecticides. Females will lay eggs beneath these protective shells, and when they hatch and come out, they are in the crawler stage, restarting their life cycle.
Is Mother Nature sending us a message about our native trees? Is the oak tree finished on our terminal moraine? Even if a predator can naturally quell the Lecanium scale in a few years, the oaks may not recover from this constant bombardment from insect pests. They will come back, but we may not see their return in our lifetime. Forest recovery can take generations.
What causes these back-to-back pest infestations? It’s important to know why so we can hopefully curtail this problem in the future. The Cape Cod forest is senescent and Mother Nature sends in her recycling forces, but this natural process is exacerbated by how we manage our landscapes. We rake the leaves, removing valuable organic matter and food for the trees. We apply harmful chemicals to our sandy soil, which to start is less than 3% organic matter with hardly any beneficial bacteria. These chemicals affect soil biology and overall soil health. They also affect our trees. Along with a 20% reduction in annual rainfall since 2012, you have your answer. Mother Nature bats last and we are seeing this in our Oak trees. As Arborists for over 40 years, we at Cape Tree Preservation find it frightening.
What can be done to save the distinctive oak?
Proactively we need to improve our Cape soils with organic amendments like compost, humates, kelp and fish emulsion, to name a few. We need to stop raking up our leaves and recycle this natural food source readily available in the form of compost.
There are also organic and environmentally safer solutions to Lecanium scale in the urban forest where we live and observe these beautiful shade trees.
A Horticultural oil application in the spring before leaf emergence will naturally smother the insects. A second application of soap in late summer will repress the next emergence of the pest. Organic approved products are best.
Systemically applied products can also be injected into the tree with an environmentally safer methodology than soil drenching.
Yes, we can save our oaks with affordable solutions, maybe not every one, but enough so that this majestic tree does not fall the way of the elm. We need our oaks for countless reasons, but especially to help mitigate the harmful affects of climate change.