Fig-tree Borer Longhorn Beetle

Phryneta spinator

Fig-tree Borer Longhorn Beetle, Fig Tree Borer, Willow Borer

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Phryneta spinator is a large, black longhorn beetle with pale brown and grey mottling. They're a frequent pest of Ficus and Salix plants. Female beetles create a T-shaped slit at the base of branches, in which they lay eggs. The hatched larvae begin to chew and bore their way through the branches, ejecting pellets of sawdust. Many gardeners and smallholders have lost trees due to these beetles; mainly because the symptoms can go unnoticed until it's too late. Trees are most at risk when another pest or disease has already attacked them, or are old and beginning to show signs of poor health. Tree branches should be monitored closely for abnormal holes or markings so infestations can be detected before the damage becomes too severe.

Traits

Bores into the trunks of Ficus.

Appearance

Adults: Mature beetles are strong and robust with broad long, antennae; measuring roughly 3.5 cm. The antennae are almost equal to body length. They are dark, grey-brown with light brown mottling with a prominent spine on both sides of the thorax. Males are smaller than females. They'll make a clicking or squeaking sound when held. Larvae: The larvae are flat, cream-coloured and legless grubs. They can reach a length of up to 4 cm when full size. They possess small heads with large cream bodies. Powerful, large, mouthparts allow them to chew through the tree trunk. Pupae: Pupae develop beneath the bark. Eggs: No description is available for eggs. Eggs are laid in slits in the bark of trunks, so are too difficult to see.

Symptoms

Damage on the bark from beetles grazing. Signs of grazing on the surface of fruits. T-shaped slits at the bottom of tree trunks, branches and stems. Sawdust and insect droppings may be found around tiny holes left in trunks and branches. Bad infestations can result in death of trees.

Activity

Diurnal

Personality

Order

Coleoptera

Family

Cerambycidae

Metamorphosis

Complete

Distribution

Africa

Biological treatment

No information exists on natural enemies for the beetles in southern Africa. Regularly monitor trees for any suspicious-looking markings, holes and slits. Create a physical barrier by covering trunks with steel mesh. The mesh should cover the trunks from the surface of the ground to approximately one meter. Clear weeds from the trunks as the females can use it as a shelter when eggs are laid. Plant garlic or other herbs which could act as a repellent for these unwanted beetles. When a fresh hole is found, you can use a piece of wire and stick it into the hole. You can hook the grub out and kill it. Use a sealer, in a paste form, and apply to the hole. This will seal off the hole and prevent further infections. If you can see areas of expelled sawdust, it's a good indication of where the grub is located. Taking care, use a sharp knife (or gardening tool) to cut vertically through the bark. Once you find the larva, you can insert a long, sharp wire into the hole to ensure the grub is dead. Cover up the burrow and damage with pruning sealant.

Chemical treatment

A synthetic pyrethroid can be sprayed on the trunks and branches to kill adults as they emerge, but this treatment will need to be repeated a couple of times throughout the season. Likewise, it's challenging to know when the beetle will appear and from where.

Attracts

Repels

Only one type of parasitic fungus is known to attack these beetles, but more research is needed.

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