by DAVID AUSTIN, UF/IFAS
Those Pesky Bugs
If you are like many people, you might cringe at seeing some unknown creature crawling across your prized plant. Your Spidey senses might kick in, and you may want to act. Before you reach for a spray bottle, please take a breather and identify your new invader. It might just be a garden guest you want around.
Garden Guests
“Bug” has become a general term often used for small alien creatures invading your garden space. If you are an entomologist, you have a different definition of a bug. Entomologists study arthropods, which includes most creepy crawlers you may or may not think of as bugs. More commonly, entomologists are associated with studying insects, and even ticks, spiders, and mites. All of these fall under the group called Arthropoda. The classification or phylum Arthropoda includes sea animals such as lobsters, crabs, shrimp, and even barnacles, as well as land crawlers such as millipedes and centipedes, to name a few. Entomologists don’t generally study them. Translated from Latin, Arthropoda means “jointed foot” or legs. It’s a huge category, with insects leading the way in diversity. In your garden, insects might be the ones that concern you the most, although you may be surprised that most insects aren’t there to disrupt your life.
True Bugs
Insects belong to the subphylum Hexapoda, meaning “six feet” (legs). Within Hexapoda is the Class Insecta, which contains approximately 30 Orders of insects. A number that may vary slightly depending on the taxonomist being referenced. Entomologists call a group of insects in the order Hemiptera true bugs. This group includes familiar garden residents like stink bugs (Pentatomidae), leaf-footed bugs (Coreidae), and beneficial predators like assassin bugs (Reduviidae). Each of their families is listed in parentheses and linked to articles on specific members of their families. Hemiptera also includes some of the worst garden pests, including aphids, whiteflies, scale, and mealybugs.
Figure 1.
Caption: Figure 1. The two stink bugs in the photo above are considered true bugs. One of them feeds on plants, and the other is a predator that eats other insects. Can you tell which is which? (Photo: Steve Schoof / North Carolina State University)
Friend or Foe?
Distinguishing between the good and the bad may be challenging, partly because an insect can be helpful or harmful, depending on the current reason for being in your garden. It is estimated that more than 99% of insects are beneficial or do not cause harm to humans and other animals. The other 1% or less give the others a bad name. Sometimes, someone on social media will post a photo of an insect with the caption “Friend or Foe.” This can be confusing since we might ask: a friend or foe of what or who? Suppose you are growing pollinator plants and hoping to attract butterflies. In that case, a Gulf fritillary butterfly caterpillar eating your passionflower vine might be a welcome guest, but it might be the opposite if you are growing passionfruit to eat. A stink bug that feeds on caterpillars might be welcome in your vegetable garden but not your butterfly garden. Identifying the insects and knowing why they are there is the key to decision-making.
Figure 2.
Caption: Figure 2. An eastern tiger swallowtail butterfly (Papilio glaucus) pauses to take some nectar from Egyptian star flowers commonly called Pentas, which attract an abundance of pollinating insects. Photo by David Austin
The Eye of the Beholder
Planting host plants to rear butterflies is a good and common practice by gardeners to help support butterfly populations. Butterflies often get a pass, and gardeners are even gleeful when they catch their caterpillars munching away. On the other hand, their Lepidopteran cousins, the moths, often get no respect. For example, a favorite nectar plant, Pentas lanceolata, also known as the Egyptian star flower, is a go-to nectar source for butterfly and pollinator gardeners (Figure 2.). Many butterfly gardeners will grow this plant to supply nectar for butterflies and hummingbirds, but when a large fat worm with a horn on its tail comes along and starts munching on the plant, it is often considered enemy number one. While gardeners plant host plants for butterflies, how dare this intruder make a host of your plant without permission? This hornworm, as they are called, will grow into a tersa sphinx moth and doesn’t harm the plant. It will grow back just fine. Tersa sphinx moths are beneficial pollinators and are not known to damage crops. Well, except for Egyptian Star flowers!
Caption: Figure 3. A Tersa Sphinx moth caterpillar (Xylophanes tersa) sits perched on leaves of its host plant, the Egyptian star flower (Penta lanceolata) shown above. Photo by Teá Montagna, https://www.sphingidae.us/xylophanes-tersa.html. This large hornworm turns into the moth below (Figure 4.). Photo by Teá Montagna, https://www.sphingidae.us/xylophanes-tersa.html
Figure 4.
Welcome Guest or Unwanted Pest? Is the Praying Mantis Good or Bad?
Your garden is full of good bugs that eat pests. Some, like ladybugs (actually a beetle), feed on aphids, scales, and other soft-bodied insects. If they happen upon them, they also eat caterpillar eggs, including butterfly eggs. That also goes for lacewings. Another voracious predator that is coveted in the garden for the damage they do to pest populations. Just like the ladybug, they can also eat other “good bugs” that you’d instead they didn’t. Both are sold online and elsewhere for release in the garden as natural pest eliminators. Another one that is sometimes sold for this is the praying mantis (Figure 5). This scary-looking creature eats lots of harmful insects. But truthfully, it would just as soon eat one of your butterflies as an insect pest!
Caption: (Figure 5.) A Carolina mantis (Stagmomantis carolina) kept in captivity peers out of its confinement, waiting for its next meal. Photo by David Austin
What to Do?
The answer can be as simple as stop worrying and let nature take its course! Planting a diverse plant palette will attract various insects and other arthropods. All those good bugs will be happy to come and enjoy the buffet. The natural ecosystem doesn’t require much care. Maybe we should emulate Mother Nature and sit back and enjoy the scenery.
For more information on beneficial garden insects, read the University of Florida article at https://edis.ifas.ufl.edu/publication/IN120
David Austin is a Residential Horticulture Agent with UF/IFAS in Highlands County. You can reach him at davidaustin@ufl.edu. You can also follow his Hometown Gardener Facebook page for horticulture happenings in the Heartland.