COMMON NAME

Monolepta beetle

Order

Suborder

Family

Genus

Species

Alias

Coleoptera

Chrysomelidae

Monolepta australis

Red-shouldered beetle

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Description

They are yellow with a reddish-purple band across the shoulders and a dot on each wing cover. Similar in appearance to lady beetles, but more elongate. The larvae look like flattened grubs; white with a hard brown formation at both ends of its body.

Adult size: 6 mm

Out and about

They can be seen all year round but are most numerous in late summer. We found that we would see a few stray beetles around the garden and believe them to be scouts. Found in northern Australia; particularly in northern NSW, the Northern Territory and throughout Queensland. They are present in fruit growing areas and where sugar cane is grown. It doesn’t seem to be such a pest in cooler areas. They are in all but the most southern states. Although these areas are tropical and sub-tropical this beetle likes a warm, dry climate. A hot dry spell seems to be when the eggs are laid and following heavy rainfall (typical of tropical climates), the adults emerge, although we have seen swarms when the dry weather is prolonged.

Reproduction and Life cycle

The female lays her eggs in the soil, favouring pasture grasses and sugarcane where the larvae will feed on the roots. The larvae pupate in the soil and emerge as adults in the spring. Their reproduction cycle takes 2 months and there can be three to four generations throughout the year.

To deter

- Mulching will also help to keep the soil moist, which may deter the female from laying eggs. - Keep water up to plants during dry spells

To control

They are very difficult to control in plague numbers - Spray with pyrethrum - target the “scouts’ as you see them - Spray with neem oil- a drench around susceptible trees could break the cycle by acting on the larvae - Cover seedlings until they are established (though last season’s beetles may have already laid their eggs in the soil) - Manage weeds - They are attracted to yellow and white. Using sticky traps may help to control them and white containers filled with water to lure and drown them.

Plants to repel

Plants to attract

Predators

Spiders / Soldier beetle / Tachinid flies / Braconid wasp will parasitise the beetle and the eggs Some ground beetles will eat eggs and larvae Monoleptophaga caldwelli is a parasitic tachinid fly that specifically targets the Monolepta beetle but it won’t have much effect if they are in plague numbers.

Why they are a Pest

Adults eat the leaves and flowers of a large variety of plants. Flowers that have been attacked will produce poor quality fruit or the fruit may not set at all. Larvae feed on roots, particularly grasses. Host plants include legumes, avocado, corn, eucalyptus trees, grasses, cotton, citrus, carambola (star fruit), lychee, macadamia, mango and strawberry, as well as many ornamental plants. Eucalyptus torelliana is a particular favourite. If favourable conditions have allowed them to breed up in huge numbers, they form swarms on emerging from the soil in spring. They can cause serious damage within a few hours and will decimate a crop virtually overnight.

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