From root rot and powdery mildew to scale and spider mites, Alexa Smarr has seen it all. But the horticulture agent associate for the Baltimore County office of the University of Maryland Extension says pest eradication shouldn’t start with a chemical spray, but with an understanding of “the disease triangle.”

“We tend to want to attack the pest without taking into consideration other factors,” says Smarr.

Here’s the triangle: For a plant to be unhealthy, there must be a susceptible host, a pathogen, and an environment conducive to disease. If azaleas need some TLC because of overcrowding and mildew caused by too much shade, for example, spraying for the mildew is just a Band-Aid.

“If you have foliar fungus, you can treat it,” she says, “but if it’s caused by environmental conditions like poor air circulation, or the plant is susceptible to our summer humidity, you need to alter the conditions or consider planting a resistant plant.”

Her solution? Improve garden health through prevention: Remove high-maintenance plants that often require spraying in favor of those suited to our climate and the site; leave spent flower heads such as black-eyed Susans that will be enjoyed by insect-consuming birds and dead leaves that can be a habitat for natural pest predators.

If you need pest management, Smarr suggests horticultural soaps and oils that work on contact with insects. “Neem oil is common and effective, and it comes from the neem trees, so I would consider it natural,” says Smarr. “But it’s important to remember that there is no standard for the term ‘natural,’ so just because something is ‘all natural’ doesn’t mean there are no synthetic carriers or inert ingredients.” (If you’re a zealot, opt for products labeled “organic.”)

Don’t feel like an ogre, however, if you do use chemicals: Just use them as a last resort, as part of an integrated approach to care, and follow the label instructions.

Fixated on being totally “green?” Then learning to live with imperfection while nature runs its course will be a tough but important lesson. For example, when you soap-off larvae, you could just as easily be getting rid of something beneficial, such as ladybug larvae, as something harmful.

“We need to learn to tolerate some damage,” Smarr advises. “Remember that you can’t have butterflies without caterpillars that chew your leaves.”

If garden bugs had lobbyists in Congress, they’d tell you many of their kind get a bad rap from gardening novices. They’d be partially right: Certain types oaf bugs play a critical role in the eco-system. So it really comes down to the question: Are they “good bugs” or “bad bugs”? Here’s a sort of police lineup on an assortment of critters you’ll find in the Mid-Atlantic region.

---

Ladybugs
If this common and very welcome beetle is plentiful in the summer, it’s because there are lots of aphids, mites, and other small insects to snack on. The adults of this tough, hard-shelled little species overwinter in large groups, then re-emerge around May until September.
Verdict: good bug.

---

Greenhouse Whitefly
There’s a “Wanted” poster out for this one: Considered to be one of the biggest pests associated with indoor plants, it also can be found in gardens in the South, the tropics, and homes throughout the U.S. The whitefly looks like a tiny moth with milky white wings and feeds on the juice from a variety of plants. It infests each host by depositing a layer of white, waxy material, which, if touched, feels more like a frothy coating that eventually suffocates the plant.
Verdict: bad bug.

---

Honeybees and Bumblebees
Both of these are crucial for cross-pollination in our gardens. Without bees, our gardens’ health would suffer and many species of flora would eventually perish. If you’re allergic to bee stings, admire them from a safe distance: They only sting when provoked.
Verdict: good bugs.

---

Japanese Beetle
The adult beetle, metallic green in color, damages leaves and ripening fruit, including vines, flowers, shrubs, and trees, as well as numerous budding roses. But cool it on the chemicals: As the beetle does its damage from late May to mid-July, it’s easiest to pick them up by hand.
Verdict: bad bug.

---

Daddy LongLegs
A harmless fellow with long, thin legs, daddy longlegs live on tree trunks and open ground and primarily feed on small insects and decaying organic matter. They mature in summer and are valuable to humans by keeping a variety of insects under control.
Verdict: good bug.

---

Aphids
These bad actors often lay their eggs on the stems of the host plant, such as roses, peas, potatoes, and apple trees, then go camouflage on you, blending in with the color of the plant. Infestation often occurs when there’s limited plant variety. In a balanced garden setting—say, a good mix of herbs and annual and perennial flowers, etc.—they do less damage. Mix up a harmless brew of one part dish soap and two parts water and spray directly onto aphids.
Verdict: bad bug.

---

Praying Mantis
Put away your weapon, I mean you no harm! The alien-looking, often motionless praying mantis is a wonderful bug and most beneficial to our gardens. It dines on caterpillars, flies, butterflies, bees, and some moths. It attaches its egg cases to tree limbs or shrubs in the fall, and new hatchlings, green in color, suddenly break out of their egg case on a warm, late spring day, all at once and perfectly formed, by the hundreds.
Verdict: good bug.

---

Giant Cicada Killer
This common, black, giant wasp drinks plant nectar, while larvae feed on cicadas. Adult females work together to dig elaborate connected tunnels in their hunt for cicadas. Then, one at a time, they sting the victim and carry it back to the nest.
Verdict: hung jury.

---