Swarming leaf beetles

Rhyparida spp.

Swarming leaf beetles (Rhyparida spp.) are small (3-5 mm), shiny, brown or black insects that swarm after the first heavy rains of the season. A number of species are involved but they all have similar habits.
Eggs are laid in the soil and hatch into small larvae similar in shape to white grubs.
The wide host range includes commercial crops such as avocado, lychee, rambutan, durian, mangosteen and other rare fruits, maize, sugarcane, various ornamentals, native trees, especially cadaghi (Eucalyptus torelliana) and lemon-scented gum (Eucalyptus citriodora), and pasture species.

Major and sporadic. A serious pest in some localities, particularly where orchards are adjacent to pastures or sugarcane or in wet tropical coastal areas.

This insect causes damage to chempedak, cocoa, durian, grumichama, jaboticaba, jackfruit, longan, marang, mangosteen and rambutan. Swarms of this insect can cause severe damage to the new terminal growth on a range of crops. Damaged terminals have a burnt look. Development in young trees can be severely retarded. Occasionally developing fruits are attacked.