Prickly solanum 'pico' beetle

How would I recognise it and what is its lifecycle?

Pico beetle adults are easy to recognise. They are oval shaped, around 1 cm long and have a whitish abdomen with distinctive longitudinal black stripes and a yellow and black head. They have a black belly, unlike the similar Colorado potato beetle (Leptinotarsa decemlineata), which has an orange belly.

Adult pico beetles

Lifecycle

After about a 50-day pre-oviposition period, females lay batches of yellow eggs in clumps on the underside of leaves, which are also easy to see and take around 14 days to hatch. A single female can lay over 300 eggs, so populations can build up rapidly. The larvae are yellowish with a black head and black legs, and mature larvae have a row of black spots on each side of the body. The larvae feed for about 2 weeks before pupating in the soil, with new adults emerging after about 16 days. A whole life cycle can be completed in 6 weeks. Short day length, cold temperatures and poor food quality may stimulate adults to burrow into the soil for periods ranging up to a few months. 

Pico beetle larvae

How does it damage pico?

The adult beetles and larvae feed on the leaves. They eat away the leaf blades, skeletonising the plant. If they are hungry enough, they will destroy all green parts of the plant, including the stems

Pico beetles strip the leaves, leaving only the vein intact.

Will it attack other plants?

Some non-target attack has been observed on eggplant (Solanum melongena) at sites where the pico has been devastated by the beetle, so that there are many starving beetles with no pico left to eat. Testing in the laboratory conducted prior to the beetles’ release has shown that the beetle can complete development on eggplant leaves, but that eggplant is a poor-quality host. Populations of beetles reared exclusively on eggplant declined to extinction.

In choice tests with eggplant, pico beetles almost exclusively attacked pico. So, while testing shows a potential risk of non-target attack on eggplant if their preferred host plant pico isn’t available, any damage can only be short-lived spillover attack. In Jamaica, where the beetles were collected, they do not attack eggplant and pico is the only host plant. 

How effective is it?

In the laboratory the beetles are voracious feeders and are expected to be able to have a major impact on pico. Early post-release surveys in Vanuatu showed that pico declined by at least 95% in areas where the beetle successfully established.

How can I get the most out of it?

The adults are capable of flight, but we do not yet know how fast they will disperse. If redistribution proves to be necessary, the adults or larvae can be shifted to new sites by collecting the leaves they are feeding on and transferring them onto pico plants at new sites.