The question of whether flowers attract gnats is common, but “gnat” is a general term often applied to several small flying insects. The tiny flies hovering around indoor plants are usually fungus gnats, and their presence is not due to the plant’s blooms or nectar. These pests are primarily drawn to the moist, organic environment of the soil, indicating a specific condition within the plant’s container. Understanding the type of insect present is the first step toward effective management.
Identifying Common Flower Pests
The two most common small flying insects mistaken for flower gnats are Fungus Gnats and Fruit Flies; their differences dictate the correct removal method. Fungus Gnats are slender, dark gray or black insects with long, spindly legs, resembling a tiny mosquito. They are weak flyers and typically remain close to the soil surface or the base of the plant. If the insects emerge directly from the potting mix, they are almost certainly fungus gnats.
Fruit Flies appear tan or light brown with a more rounded, stout body shape and often possess distinctive bright red eyes. These flies are quicker and more agile fliers. They are attracted to fermenting sugars, hovering around ripening fruit, spilled beverages, or decaying organic material like old flowers or standing water in a vase, rather than the soil.
The Fungus Gnat Attraction Mechanism
Fungus gnats are drawn to the plant environment not by the flower, but by damp, decaying organic matter in the soil. Adult female gnats lay their eggs in the top inch of moist potting mix. The eggs hatch into translucent larvae with distinct black heads, which feed on fungi, algae, and decomposing plant material within the soil.
The primary factor creating this environment is overwatering, as excessive moisture promotes the growth of fungi that serve as the larvae’s main food source. The gnats are attracted by the scent of this fungal growth and decomposition. If the infestation is severe, the larvae may feed on delicate plant root hairs, which can stunt growth or cause leaf yellowing, especially in seedlings or young plants. The entire life cycle, from egg to adult, can complete in as little as 17 days, leading to rapidly escalating populations.
Immediate and Natural Control Methods
The most effective method for controlling fungus gnats is to break their reproductive cycle by altering the soil environment. Allow the top one to two inches of potting mix to dry out completely between waterings. This eliminates the moist conditions necessary for adults to lay eggs and for larvae to survive, significantly reducing the infestation over time.
To immediately reduce the adult population, yellow sticky traps are highly effective, as the gnats are strongly attracted to the color and become trapped upon landing.
For targeting the larvae in the soil, a solution of one part 3% hydrogen peroxide mixed with four parts water can be used as a soil drench when the plant needs watering. The peroxide kills the larvae on contact by oxidizing them and harmlessly breaks down into water and oxygen.
Applying a half-inch layer of fine sand or diatomaceous earth to the soil surface creates a physical barrier that prevents females from accessing the soil to lay eggs. If the problem is identified as fruit flies, a shallow dish of apple cider vinegar mixed with a few drops of dish soap will trap the adults. The vinegar acts as the attractant, and the soap reduces the surface tension, causing the flies to sink.