Golden Tortoise Beetle

Golden Tortoise Beetle (Metriona bicolor), also known as gold bugs, are common in Northern United states.

Adults are broadly oval to round and nearly convex in shape with some sculpturing of the surface and the edges broadly expanded. They are green-gold with purple mottling and about 1/4-inch long. A few related species have similar metallic appearance and may feed on different host plants. The golden tortoise beetle, Charidotella sexpunctata bicolor (Fabricius), is brilliant brassy or greenish-gold in life.

Golden Tortoise Beetle change color depending on the availability of the liquid layer. In the fall and winter, the beetles become less lustrous and are more orange and bronze with flashes of iridescent color. If you try and collect the beetle for an insect collection, the beetle soon turns dark brown as is dries, loosing the golden color. The beetles are most beautiful left alive.

These “peddlars” then carry with them a sort of moveable parasol that covers the body and helps deter potential enemies. When full grown them pupate on the plant, where they undergo transformation to the ultimate adult form. The pupal stage is also covered with the old larval skin and fecal matter. Adults emerge after a week or two and feed during late summer. They do not reproduce at this time and subsequently go into winter dormancy, hiding among plant debris or in other sheltered sites.

Management: Tortoise beetles are leaf feeders and do not usually affect sweet potato quality unless beetle numbers are excessive. Adequate fertilization, irrigation, and weed control are generally effective measures to compensate for leaf damage. Reduce or eliminate weeds of the morning glory family, such as morning glory and bindweed,from the garden and bordering areas.

Hand-picking and destruction of larvae and adults are labor-intensive but effective for reducing the population of tortoise beetles. Chemical control is generally not required for this pest. However, when the tortoise beetle population is high, 1–2 foliar applications of an insecticide may be needed to effectively manage these pests.