Beneficial insects are the rage, but they can cross good versus bad category lines. For example, one caterpillar, Helicoverpa zea, is considered to be among the worst insect pests of plants in the entire world. But let’s start with the positive aspects of native caterpillars. You will want to attract those that will benefit your personal space and the larger ecosystem even though you may barely notice them. Doug Tallamy, author of Bringing Nature Home and Nature’s Best Hope, promotes and rates plants that serve as larval food hosts for native caterpillars, as those immature insects are essential for almost all backyard birds’ diets when feeding their young. With alarming news from Cornell University about the disappearance of backyard birds, we all should be planting larval food sources whenever possible.
Although oak trees lead the list in numbers of butterflies and moths, Lepidopterans, laying eggs on their foliage (more than 443), the most commonly available species is willow oak, Quercus phellos. Charlotte, North Carolina, has a significant problem with the larva of fall cankerworms eating their foliage, a native species, to the extent that the city and homeowners wrap the trunks of these trees with plastic coated with Tanglefoot. This prevents the wingless females emerging from their soil-based pupation from climbing up the trees to lay their eggs. In most parts of the country with a normal ebb and flow, these caterpillars are not a pest. Charlotte’s arborists speculate that the problem has occurred because they overplanted one species.
If you have space, plant other types of oaks. Live oaks, white oaks, chestnut oaks, and post oaks are my favorites. Source your tree from a Southern supplier so it will have the genetics adapted to this part of the country. Don’t worry about size — even if you chose a one-gallon tree from a mail order company. Small trees properly planted and cared for can outgrow a massive tree-spade transplant in less than a decade and live for well over 100 years.
For a smaller yard or one already supporting large shade trees, choices abound for shrubbier plants with flowers that attract pollinators. Aronia arbutifolia, red chokeberry, grows in every South Carolina county. It reaches about 10 feet tall with half that spread, has a deep purplish-red fall color, and is happy in sun or part shade. For the flower arrangers, Malus angustifolia, Southern crabapple, has delicate pink flowers spaced on interestingly branched limbs, and it flowers early to provide pollen for pollinators. It definitely will fruit more prolifically if it receives a good bit of sun, and the leaves support 200 species of plump, juicy caterpillars that parenting birds can use to feed their young.
But on to the downside of caterpillars, even native ones. On larger woody plants, they are seldom a problem or even noticed, but on herbaceous perennial native host plants they can ruin their appearance. A balance seems to exist, however, as those heavily consumed plants continue to come back strong each year. But on some fruit and vegetable crops, imported and occasionally native Lepidopteran pests can be devastating.
Do you know why the end of sweet corn is often cut off when sold in the grocery store? If you have been lucky enough to pick sweet corn right out of a field and shuck it as the water boils, then savoring it while the sugars are at their peak, you’ve surely seen the corn earworm, Helicoverpa zea, one of the most destructive insect pests in the world. Caterpillars have voracious appetites; immature moth larvae can destroy a crop, especially beloved greens. However, Bacillus thuringiensis, commonly referred to as BT, is a naturally occurring soil organism that, if applied when the caterpillars are quite young, stops them from eating, with death occurring soon afterward. It is remarkably safe as it only effects the very young larva of Lepidopterans; it has no effect on any other organisms. Other strains of BT target mosquito larva among other insects. The one for caterpillars is effective only for a limited number of days, and sometimes these pests are unnoticeable until they have gotten larger and are no longer susceptible. Picking them off by hand can be effective in some situations, but some caterpillars have stinging hairs.
Many registered pesticides are available to control caterpillars and other leaf-feeding insects. Check with Clemson Extension specialists or shop with a knowledgeable supplier, and ask questions about which products are the least toxic. Some will be dangerous to beneficial insects. It is safer for humans and beneficial insects to spray a liquid rather than applying a dust. Once the spray dries, the risk to beneficial insects is lower than if they were to land on a toxic dust. Making those applications early or late in the day, when beneficial flying insects are not active, also helps to protect them.
Wasps are stinging insects that evolved before bees, and almost all consume insects for protein. They sting and capture caterpillars, spiders, beetles, and other invertebrates to eat and to feed their young. Adults of some species also consume nectar. The social wasps, including yellow jackets and paper wasps, aggressively defend their nests, have painful venom, and are equipped with barbless ovipositors that enable them to sting repeatedly. They can be dangerous, especially in a small yard. But others are solitary, non-threatening, and actually beneficial in gardens. Certain wasps are major deterrents to caterpillars as they lay their eggs on those immature insects.
Have you ever seen a tomato hornworm caterpillar that looks like grains of rice are stuck upright on its back? Actually, those are the pupa of tiny parasitoid wasps that started life as an egg inserted into a caterpillar. The larvae tunneled through the insect gathering nourishment until emerging as pupae. Soon after the eggs are laid, the host animal stops eating and is no longer a threat to vegetation, dying after the adults emerge. To attract these small, non-stinging Braconid wasps, plant flowers with very small blossoms as the adults feed on nectar. Buckwheat fills this need perfectly, but don’t let it go to seed or you’ll have more next year than you want.
As plants evolved into different shapes and sizes, so did bees. It was safer to gather pollen and nectar than to tangle with other insects. The European honeybee, an important pollinator, has had a short history in our country, arriving with the European colonists. Our nearly 4,000 native bees are mostly solitary — bumblebees being an important exception — and really do a lion’s share of general pollination. Many are ground nesters, so be aware that landscape fabric seals off potential areas for them to use, and it doesn’t prevent weeds for very long anyway. Try to have some relatively open spaces in your yard. You may see a large number of small bees hovering together and worry they will sting you or your children, but don’t fret because they are not defending a common hive. It means that particular space is perfect for their needs. The hovering bees most often are the earlier hatched males that are waiting for their potential mates to emerge. Some bees need mud, while mason bees require a small tubular space once found in the pith of certain plant stems. Considerate bee-friendly gardeners can build or buy mason bee houses.
Research shows that pollinators find the plants they need more easily when a variety are grouped together based on different blooming times. Plus, all bees need water. A large container with a landing platform will suffice. Bubblers and certain fountains are fine as well. Some pedestal birdbaths that tip easily can be dangerous to children, and water should be changed frequently.
Carpenter bees lay eggs in tunnels they construct in wood, and some houses are plagued by their burrowing. They do act as pollinators and their good almost always outweighs the bad. They look like bumblebees but have smooth, hairless abdomens. The males, which cannot sting, have a white face and act aggressively trying to defend the tunnel created by the females. Painted wood is far less attractive to them than unpainted or stained surfaces. Approved insecticides plug holes. Plus, traps and other methods can be used to solve problems with these bees.
Bumblebees are social. Nearly 50 species are native to our continent. They nest in the ground with a queen, and her worker bees will defend the colony but not nearly so aggressively as wasp family members. Only mated queens overwinter, so a new colony is started each spring. Bumblebees, which are large and powerful, can work when low temperatures and cloudy days keep European honeybees inside their hives. Another important difference for farmers and gardeners growing crops that need pollination is that bumblebees are like Dolly Parton in the chest department, with very powerful flight muscles. When searching for pollen, bumblebees latch onto a flower and vibrate chest muscles without involving their wings, a process called buzz pollination. It results in a rain of pollen being released and then landing on the bees and the awaiting female flower parts. If you’re a tomato grower, you will definitely want bumblebees in your garden.
Aphids are ubiquitous, feeding on annuals, perennials, and certain woody plants. They are a particular nuisance as they excrete a sugary liquid called honeydew, which supports an unattractive sooty mold. At times, wingless females give birth without mating and a population can explode on individual plants. Fortunately, they have very soft bodies and a strong stream of water from a garden hose nozzle will knock most of them off plants and injure them to the extent that they cannot climb back on.
Ladybug beetle larvae, which look like small alligators, are voracious aphid eaters. Learn how to identify them and be excited when you see them. They’re far more effective than the more spectacular praying mantids. Don’t order insects for your yard. When you have the right pests for them to eat, they will find you.
Rose growers are especially plagued by Japanese beetles. But Pat Henry, co-owner of South Carolina’s beloved Roses Unlimited, says during the two or three weeks when they are active in her garden, she simply ignores them and then lives with the damage. Traps for these imported pests attract males, and gardeners will bring more into their yards than they capture.
The best way to garden for beneficials is to always understand and identify the insect or pest problem and decide if it warrants a chemical response; if a pesticide is necessary, speak with a Clemson Extension expert or knowledgeable garden center to find the least toxic product labeled for that purpose. One that works only on a small group of insects, instead a broad-spectrum product, is best. For example, some homeowners still apply 50-pound bags of broad-spectrum insecticide to their yards to control fire ants when baits are available that only require a few pounds per acre and almost exclusively target the red imported fire ant.
It is important always to read the label and follow directions exactly for safety and protection of the environment. The label directions are the law. The Clemson Home and Garden Information Center’s horticulture experts answer phone calls all day during the week. They are helpful to talk to and have numerous phone lines associated with this number: 1-888-656-9988.
We can all join with the Xerces Society for Invertebrate Conservation in making the world more supportive of pollinators. Providing a variety of micro-environments in our yard, learning to accept a certain amount of imperfection in plants, and limiting pesticide use will turn our property into a more environmentally sustainable landscape. We can also use our resources to advocate for and support financially organizations that promote greener communities.