Discovering petunia blooms suddenly riddled with holes can be a frustrating mystery for any gardener. Petunias are susceptible to damage because their tender foliage and sweet scent attract various herbivores. Since the destruction appears overnight, the culprits are usually nocturnal creatures that seek shelter during daylight hours. Identifying the specific feeder is the first step toward protecting your flowers and ensuring continuous blooming.
Common Nocturnal Pests That Target Petunias
The primary suspects responsible for consuming petunias after sunset are slugs, snails, earwigs, and various caterpillars. Slugs and snails are mollusks that require moist, cool conditions to avoid desiccation, making the night their preferred feeding time. They hide during the day beneath leaf litter, mulch, or dense ground cover, emerging when the sun sets.
Earwigs feed on petunias after dark, often seeking refuge in dark, tight spaces during the day, such as beneath pots or inside flower heads. Cutworms, the larval stage of certain moths, live just below the soil surface and emerge at night to feed on the base of young plants. The tobacco budworm caterpillar also feeds voraciously on petunia buds and petals.
Larger mammals, such as deer and rabbits, are frequent nighttime feeders. These animals often browse during the cooler hours of dusk and dawn to avoid human interaction. Their feeding habits are determined by local population density and the availability of other forage.
Deciphering the Clues: Matching Damage to the Culprit
The evidence left behind on the petunia plants helps identify the specific pest responsible for the damage. Slugs and snails leave telltale signs, including irregular, ragged holes chewed into the leaves and flower petals. The most distinctive clue is the shiny, dried slime trail left on nearby surfaces, soil, or the plants themselves.
Cutworms cause a specific type of damage. These caterpillars sever the stem cleanly at or just below the soil line. If the damage involves large holes chewed into buds or petals, and small, dark droppings (frass) are visible, the culprit is likely the tobacco budworm caterpillar.
Earwigs typically chew small, scattered holes in the petals and leaves, often creating a shot-hole appearance. They may also hide directly inside the tubular flower heads during the day. This damage is usually less extensive than that caused by slugs.
When the damage involves large sections of the plant being removed, the culprit is likely a larger mammal. Deer tear and pull at the foliage and flowers, leaving ragged, uneven edges because they lack upper incisors. In contrast, rabbits use sharp incisors to make cleaner, angled cuts, often consuming low-hanging flowers and leaves close to the ground.
Targeted Strategies for Stopping Nighttime Feeding
Implementing effective control measures requires matching the strategy directly to the identified pest. To deter slugs and snails, gardeners can create barriers using abrasive materials like diatomaceous earth scattered around the base of the plants. Placing shallow beer traps, which attract and drown the mollusks, or applying iron phosphate baits are effective methods.
Controlling cutworms involves creating a physical shield around the stem. Cardboard or foil collars pressed an inch into the soil and extending an inch above the surface will prevent the larvae from climbing up and severing the stem. Tilling the soil in the fall and spring can also expose overwintering larvae and pupae to predators or desiccation.
To manage earwigs, focus on removing their daytime hiding places, such as dense mulch, leaf piles, and ground cover near the petunias. Trap them using rolled-up newspaper or short sections of bamboo placed overnight near the damaged plants. The earwigs will crawl inside for shelter.
Protecting petunias from deer and rabbits requires exclusion methods or repellents. Physical barriers, such as mesh fencing at least eight feet tall, exclude deer from the area. For rabbits, a shorter, fine wire mesh fence buried a few inches into the ground is usually sufficient. Applying scent or taste-based repellents containing putrescent egg solids can also make the petunias unappealing to browsing mammals.