Garden Pests Decoded: What's Eating Your Plants and What to Do

What the damage looks like: Curled, puckered, or yellowing leaves; sticky residue (called honeydew) on leaf surfaces; ants clustering on stems (they farm aphids for that honeydew). Look closely at the undersides of leaves and near new growth — aphids congregate in dense colonies.

What to do: A strong blast of water dislodges most aphid colonies. Insecticidal soap sprays are effective for heavier infestations and have a low impact on beneficial insects when applied carefully. Encouraging or purchasing ladybugs and lacewings — both natural aphid predators — supports biological control over time. Avoid over-fertilizing with nitrogen, which produces the soft new growth aphids prefer.

What the damage looks like: Large, irregular holes in leaves or whole leaves stripped to the midrib. You may also notice dark pellet-shaped frass (droppings) on leaves or the soil below. Some species, like tomato hornworms, are large and visible; others are small and hide in rolled leaves.

What to do: Hand-picking is effective for large caterpillars. For smaller species or widespread infestations, Bacillus thuringiensis (Bt) — a naturally occurring soil bacterium — is widely used and targets caterpillars without harming most beneficial insects. Row covers over young transplants prevent moth egg-laying before damage begins.

What the damage looks like: Irregular holes in leaves, often with smooth edges, and a telltale silvery slime trail left behind. Damage is heaviest on seedlings and low-growing plants, and typically occurs overnight since slugs avoid daylight.

What to do: Reduce habitat by removing boards, dense groundcovers, and debris near affected plants. Allow soil surface to dry out between waterings — slugs need moisture to move. Iron phosphate-based slug baits are widely considered low-risk to wildlife and pets compared to older metaldehyde formulations, but read all product labels carefully and follow instructions. Copper tape around containers creates a mild deterrent.

What the damage looks like: Fine stippling or bronzing across leaf surfaces, starting on the upper side. In severe cases, fine webbing appears between leaves and stems. Spider mites are nearly invisible to the naked eye — hold a white piece of paper under a suspect leaf and tap; moving specks indicate mites.

What to do: Spider mites thrive in hot, dry conditions. Increasing humidity and ensuring consistent watering can slow population growth. Water sprays help dislodge them. Insecticidal soap or neem oil (a pressed seed extract) are commonly used options. Avoid broad-spectrum insecticides, which kill the predatory mites that naturally keep spider mite populations in check.

What the damage looks like: Yellowing leaves, sticky honeydew on leaf surfaces, and a cloud of small white insects that scatter when you brush the plant. Like aphids, whiteflies are sap-suckers and tend to cluster on leaf undersides.

What to do: Yellow sticky traps placed near affected plants monitor and reduce adult populations. Insecticidal soap is effective against nymphs (immature stages), but adults are harder to contact-kill. Remove heavily infested leaves and dispose of them away from the garden. Reflective mulch around the base of susceptible plants can confuse and deter whitefly adults.

What the damage looks like: Wilting or yellowing plants that don't respond to watering, often with roots visibly chewed when you dig up the plant. Grubs (the larval stage of various beetles) feed underground, making them harder to detect than surface pests. Patches of dead lawn-grass can also signal grub activity below.

What to do: Dig around affected plants to confirm grub presence before treating. Beneficial nematodes — microscopic organisms applied in water — are a biological option that targets soil-dwelling larvae. They require moist soil and specific temperature conditions to be effective, so follow application guidance carefully. Encouraging birds to forage in garden beds also helps reduce grub populations naturally.

What the damage looks like: Brown, tan, or white bumps clinging to stems and branches — these waxy shells protect the insects feeding underneath. Affected plants show yellowing, stunted growth, and leaf drop. Scale is common on woody shrubs, fruit trees, and houseplants moved outdoors.

What to do: Small infestations can be scraped off with a soft toothbrush or cloth. Horticultural oil sprays — applied to thoroughly coat stems — smother scale by blocking their air holes and are generally considered safer for beneficial insects than systemic pesticides. Timing matters: treat when the fragile crawler stage (newly hatched, mobile juveniles) is active, typically in late spring to early summer depending on your region.