Gonipterus scutellatus (Mapondera et al. 2012; Schröder et al. 2020)
Larvae of the Eucalyptus snout beetle feed on the new flush of Eucalyptus trees. The first instar larvae feed on the epidermis of the leaves creating tracks on the leaf surface. The third and fourth instar larvae will consume the entire leaf. The adult Eucalyptus snout beetle feed on the older leaves of the Eucalyptus trees along the edges, creating a scalloped appearance (Tooke 1955).
The adult beetles measure about 8-9 mm in length, smaller individuals may occur when infestation levels are high. They vary in colour from rust brown to a dark brown appearance. There is a black X mark over the elytra with a white stripe on the scutellum. These markings may vary considerably from being prominent to very feint.
The larvae are slug-like in appearance, green and covered in a sticky slime . The fourth instar larvae measure 11 mm in length and 4 mm in width. The head is black and the body has a median dorsal line and a black lateral stripe. A black shield shaped dot is present on each segment of the larvae. The frass excrement of the larvae extends behind the body like a filament and often curls and sticks to the larvae (Tooke 1955).
The adult female will oviposit between 4 and 20 eggs on a leaf and cover them with a frass excrement. The frass excrement hardens and protects the eggs. The larvae will go through four larval stages before reaching the pre-pupa phase. During the pre-pupa stage the larvae will stop feeding, drop to the ground and burrow into the soil. They pupate in the soil and the adults emerge in search of a new host plant. The development time of the different stages of the life cycle is temperature dependant and it may take up to 90 days for the life cycle to complete. The female beetles will start to oviposit two to three weeks after mating. A single female can produce up to 270 eggs. The adult beetles can live up to 3 months. One and a half to two generations per year can occur in South Africa (Tooke 1955).
A biological control, Anaphes nitens, was released in 1926 and is established throughout the country. However, high infestations of Gonipterus sp.n.2 still occur and thus application of insecticides is sometimes required. Efforts to import and release other biological control agents are ongoing. Selection of more tolerant planting material is also possible.
Mapondera TS, Burgess T, Matsuki M, Oberprieler RG. 2012. Identification and molecular phylogenetics of the cryptic species of the Gonipterus scutellatus complex (Coleoptera: Curculionidae: Gonipterini). Australian Journal of Entomology 51:175-188.
Schröder ML, Slippers B, Wingfield MJ, Hurley BP. 2020. Invasion history and management of Eucalyptus snout beetles in the Gonipterus scutellatus species complex. Journal of Pest Science 93:11-25
Tooke FGC (1955) The Eucalyptus snout beetle, Gonipterus scutellatus Gyll.: a study of its ecology and control by biological means. vol 3. Pretoria
