The fig beetle, also known as the Green Fruit Beetle (Cotinis mutabilis or Cotinis nitida), is a large scarab beetle that becomes a common nuisance in gardens. These insects feed on ripening fruit, often leading to significant harvest losses for home gardeners. They are especially prevalent in the Southwestern United States, though a close relative, the Green June Beetle, inhabits the Eastern U.S. This guide provides strategies for controlling these pests, targeting both the adult stage and the larval stage.
Identifying Fig Beetles and the Damage They Cause
Identifying the fig beetle adult is easy due to its distinctive appearance and loud flight. The large beetle, typically 0.75 to 1.25 inches long, possesses a striking metallic green color on its back and a bright iridescent green underside. When flying, they make a noticeable, loud buzzing sound because they partially lift their hard outer wings (elytra), contributing to their clumsy flight.
Damage occurs when adult beetles feed on soft, thin-skinned fruit, such as figs, peaches, grapes, and tomatoes. They bore a hole into the flesh to consume the juices and pulp, rarely attacking healthy leaves or hard fruit. The larval form, often called a “crawlyback,” is a dirty white, C-shaped grub up to two inches long, commonly found in compost piles or lawns. Unlike some other beetle grubs, the fig beetle grub primarily feeds on decaying organic matter rather than plant roots.
Immediate Physical Removal and Trapping Methods
Immediate relief from adult fig beetles can be achieved through physical removal. Hand-picking the beetles is easiest in the early morning hours when the temperature is cooler and the insects are naturally sluggish. The collected beetles should be dropped into a container of soapy water, which quickly incapacitates and kills them.
A homemade fermentation trap can also exploit the beetle’s strong attraction to damaged and fermenting fruit. These traps, often made from plastic containers with an inverted funnel, are baited with overripe fruit, molasses, or a mixture of yeast and water. The fermenting odor lures the beetles into the container where they become trapped and drown. Commercial Japanese beetle traps are not effective against the fig beetle and may even draw more pests to the garden area.
Targeting the Larval Stage for Long-Term Control
Long-term control requires targeting the larval stage. The life cycle begins when adults lay eggs in areas rich with organic matter, such as compost, manure, or heavily mulched garden beds. The resulting grubs are the source of the following year’s adult population, making larval control a preventative measure.
Applying beneficial nematodes, specifically Heterorhabditis bacteriophora or Steinernema carpocapsae, is an effective method for grub control. These microscopic worms are natural predators that seek out and parasitize the grubs in the soil. Optimal application timing is late summer to early fall when the grubs are young, close to the soil surface, and actively feeding. The nematodes should be applied to moist soil, preferably during cooler evening hours, to protect them from ultraviolet light and ensure they can move effectively to reach their hosts.
Horticultural Practices to Discourage Infestation
Horticultural practices are an important layer of prevention, as the garden environment significantly influences fig beetle attraction. Garden sanitation is paramount because the beetles are highly attracted to the fermentation gases released by damaged or overly ripe fruit. All fallen, damaged, or overripe fruit must be removed from the ground daily to eliminate this powerful attractant.
Physical barriers, such as fine mesh netting or cheesecloth, can completely cover fruit clusters on trees or vines. The barrier must be fine enough to exclude the large adult beetles and should be applied just as the fruit begins to ripen. Modifying soil practices by reducing excessive application of manure or thick, late-season organic mulch can make the area less appealing for adult beetles to lay their eggs. Keeping the soil surface dry and hard in the early spring can also help trap pupating beetles before they emerge.