conifer collection with new species and varieties of cedars , firs , spruce and other conifers . For a selection of the healthiest hemlock trees in some of the most prominent locations , we have used a combination of soil drenches and spraying horticultural oil to control HWA . As of the spring of 2021 , we have 125 hemlock trees remaining . In place of the 175 hemlocks we have lost , we have added 65 new taxa of conifers to our collection .
For the vast majority of pests , we do not apply any pesticides and instead utilize best cultural practices and / or let nature take its course . Following is a brief explanation of the few insecticides , fungicides and herbicides that we have made the decision to use :
Several years ago , a new insect pest called Winter Moth was discovered in eastern Massachusetts and it quickly became a serious problem as the caterpillars completely defoliated a wide range of tree species just after they leafed out in May each year . Many of our newly planted trees were being lost after two consecutive years of being defoliated , so we made the decision to spray a small selection of young trees with a product called Conserve until they became successfully established . Strict environmental guidelines for applications were followed , and our arborists stayed after closing hours in the evening to perform the spraying when no visitors were present . Fortunately , a biological control for the winter moth has now been established in eastern Massachusetts which keeps the winter moth in check , so we have not had to spray for the caterpillar since 2017 .
Bronze birch borer continues to pose a serious threat to our white birch trees , so for the past ten years we have treated some of our most important specimens of birch trees each year with a total of 120 capsules ( each containing 2 ml ) of Bidrin insecticide injected directly into the trunks of the birches .
Dutch elm disease continues to be a concern , so over the past five years we have treated a handful of selected mature American elms with the systemic fungicide Tebuject each year , injecting a total of 96 capsules ( each containing 6 ml ) directly into the trunks of the elm trees . In some previous years different fungicide capsules were injected directly into the elm tree trunks , depending on what was recommended and available at the time .
Our magnificent old European beech trees , having reached the end of their normal life span and showing increasing signs of decline , have been inflicted with phytophthora canker in recent
Mount Auburn Cemetery | Climate Action & Sustainability Plan 53