The question of whether roses attract flies often arises from observing various insects congregating around the blooms. While the general assumption is that roses primarily appeal to bees, the interaction with the insect order Diptera (flies) is complex. This relationship is driven by visual cues, chemical signals, and the broader garden ecosystem. Understanding this attraction requires looking beyond the flower itself to the surrounding environment and the different types of flies present.
The Nuanced Answer: Roses and Insect Attraction
Roses do attract flies, but this attraction differs significantly from what draws traditional pollinators like bees. The appeal depends heavily on the specific rose cultivar and its physical structure. Modern hybrid tea roses, with their dense layers of petals, often conceal or reduce access to pollen and nectar, making them less attractive to many insects.
Flies are generalist visitors attracted to a wide variety of floral resources. Single-petal or “old-fashioned” rose varieties expose their reproductive structures, making them more accessible to flies seeking pollen or nectar. This attraction is frequently incidental; flies visit for general floral resources rather than participating in a specific, co-evolved pollination mechanism.
The Chemistry of Attraction: Olfactory Signals
Roses lure insects, including flies, by emitting Volatile Organic Compounds (VOCs). These airborne chemicals are released from the petals and pollen, creating the floral scent profile that guides insects to the flower. Roses emit a diverse bouquet of VOCs, including terpenes, fatty acid derivatives, and aromatic compounds.
A major component in many rose scents is the aromatic compound 2-phenylethanol, a known insect attractant. Other common compounds like geraniol and citronellol also act as general attractants for a wide range of insects, including those in the Diptera order. These chemical signals work in concert with visual signals, such as the color of the petals and the ultraviolet (UV) light spectrum visible to many insects.
The overall composition of the rose’s scent often appeals to generalist feeders like flies. The composition of VOCs varies significantly between wild species and modern cultivated roses, as domestication can lead to the loss or gain of specific scent chemicals. The rose’s scent is its primary long-distance communication tool, signaling the availability of food resources.
Identifying the Visitors: Pollinators Versus Pests
Flies observed near a rose bush fall into two main groups: beneficial visitors and nuisance species. Many beneficial flies are excellent pollinators, sometimes second only to bees in overall pollen transfer for certain crops. The most important beneficial flies in a rose garden are Syrphid flies, commonly known as hoverflies or flower flies.
Adult hoverflies feed on nectar and pollen, aiding reproduction, while their larvae are highly beneficial predators. A single larva can consume hundreds of aphids during its development, making them valuable biological control agents against common rose pests. These beneficial flies often mimic wasps or bees with striped yellow and black patterns, but they are harmless and possess only a single pair of wings.
Nuisance flies, such as the common house fly (Musca domestica), are frequently drawn to honeydew—the sticky, sugary excrement produced by sap-sucking pests like aphids. Their presence acts as a warning sign for an underlying pest infestation on the rose bush. Other nuisance flies are attracted to decaying spent blooms or organic matter near the base of the plant.
Strategies for Managing Unwanted Flies
Managing unwanted flies around roses should focus on sanitation and controlling secondary attractants. Since house flies are primarily attracted to honeydew, controlling the aphid population will significantly reduce their numbers. A strong jet of water from a hose can physically dislodge many aphids from the new growth and buds of the rose bush.
Removing spent rose blooms (deadheading) eliminates potential sources of decaying plant material that attract flies seeking moisture or a place to lay eggs. Keeping the area around the rose bush clean of fallen leaves and other organic debris also reduces the habitat for fly larvae and other pests. Avoid using broad-spectrum insecticides, as these chemicals indiscriminately kill the beneficial hoverflies whose larvae control the aphid population.