A Healthy Habitat Approach to Pest Management
By Amy Yarger
Butterfly Pavilion showcases over 500 different species of plants in its tropical conservatory and public gardens, but around here, it’s the bugs that come first. The horticulture team has learned that pest management at an invertebrate zoo is a challenging and exciting journey, but well worth the results for everyone involved. We have also found that many gardeners, even those who don’t house exotic butterflies and giant stick insects, have an equal stake in creating healthy habitats.
Our approach is commonly called “ecosystem gardening” in that we must consider the interactions of many different kinds of plants and animals with each other, and with abiotic factors like climate and soil. In a gardener’s eyes, her garden is an entire world. Here, as “head honchos” of our own little world, the first thing we do is keep a close and interested eye on everything that happens. Staff and volunteers spend some time every day scouting for potential problems and recording data about plant health, bloom season, and what insects and other animals are present. Some of this data is only used internally to help us anticipate management issues that occur on a seasonal basis. My favorite records, however, contribute to larger citizen science efforts, such as Project BudBurst and The Great Sunflower Project, which track phenology and pollinator diversity across the country.
Our approach also takes a look at the underlying health of the plant. Many pests and diseases capitalize on plants that are already struggling due to improper placement or stress. One example of this is the spike in scale insects Butterfly Pavilion horticulturists see during the winter in our Wings of the Tropics exhibit; these sap-sucking insects appear like bad magic wherever the heater fans are blowing. The plants, normally found in the dim, still understory of the rainforest, are not accustomed to the drying influence of hot air, and they thus become more vulnerable to pests. We have learned to keep the area around the heater fans relatively clear, especially in winter when the exhibit needs more heat. A gardener with a “problem child” plant might consider what the root cause of the plant’s vulnerability is. Sometimes, it’s just wiser to move on to a new plant, choosing one that will thrive instead of struggle in that situation.
Our horticulture team does not expect perfect eradication in most cases, either. If our plants’ leaves have some chewing from caterpillars, we are willing to accept that if it means we’ll see more butterflies in a couple weeks. Other pests, like red aphids on our goldenrod, get decimated by convergent lady beetles (Hippodamia convergens) every spring in the garden. We know the ladybugs don’t eat every last one, but they keep the pest population at a level where the goldenrod can still thrive. Studies have shown that most people don’t even notice pest damage unless over ten percent of the plant material is damaged.
However, not every pest has such an easy solution. This is when our horticulture team has big decisions to make. Even though we do not use pesticides in our gardens or butterfly exhibit, we choose from a variety of options to reach a feasible level of control. Each horticulturist must take into account all the factors that are affected by the pest control method in question: cost, effectiveness, appearance, and risk to the environment. One type of control we rely on is physical, such as barriers, traps and mechanical removal. Our horticulture volunteers act as our Pest Squad, using soft toothbrushes to remove scale from our tropical plants or gently removing caterpillars to be raised by our lepidopterist. We also sometimes use a small fan and homemade sticky traps made from index cards and petroleum jelly when we spot whitefly in the greenhouse.
Another type of control for pests is biological. In our gardens and exhibits, pests have their own enemies, and any gardener can make use of them to keep the garden community healthy. Butterfly Pavilion horticulturists not only want to discourage pests but want to encourage beneficial organisms such as predators, parasitoids, and pollinators. Ladybird beetles are the most famous examples, of course, but parasitic wasps and predaceous mites are available for gardeners to buy and apply in their own gardens. When spider mites infest our angel’s trumpet, we release predatory mites and keep the environment extra moist to give the predators and the plant a chance to collaborate. In our outdoor gardens, plants such as lovage, yarrow, and rabbitbrush attract the wasps and beetles that eat soft-bodied pests. Even the biggest pests have their predators. It’s thrilling to see the “circle of life” happen in the garden, even if sometimes that means we have to clean up rabbit bits after the fox has visited.
By aiming for diversity of form and function, our tropical exhibit and gardens allow for natural interactions that keep infestations from getting out of control. This diversity also connects our guests with the wild world; we often see kids who have never seen a monarch butterfly or a bald eagle or even a rabbit. Getting the chance to experience that world is a small joy that may lead to a life of stewardship.
Amy Yarger is Horticulture Director at Butterfly Pavilion in Westminster.