Healthy Myoporum Foliage

All across the Southern California coast, from San Diego to Santa Barbara, our landscapes are being attacked by a foreign invader. This enemy comes from Australia (or possibly New Zealand), is so tiny that you would probably miss it if you didn’t know it was there, and can cause some serious damage.  This new pest is known as the Myoporum Thrip (Klambothrips myopori) and as you might have guessed attacks Myoporum.

There are two species of Myoporum which are popular in California and are especially susceptible including:

• Myoporum laetum – a large shrub/small tree
• Myoporum ‘Pacificum’ – a large, fast-growing groundcover

Myoporum Thrip Damage

These plants are popular because of their aesthetics, low maintenance requirements, and hardiness. Relatively few pests or diseases attacked these plants until recently. Now the Myoporum Thrip is causing hundreds of thousands of dollars worth of damage to our Southern California landscapes. Often used along freeways and roads you can see miles worth of these plants severely infested and in many instances completely defoliated.

Thrips feed on the foliage causing it to twist and distort. Leaf galls will also appear where the adults lay their eggs and the larvae develop. If the infestation is heavy enough it can completely defoliate the plant and cause death.

Identifying this pest is not difficult if you look closely. While very small, the adults are only 2 -2.5 mm in length, they are visible to the naked eye. They are distinguishable by their long skinny bodies. The adults are a dark brown or black color, while the larvae are a translucent to slightly orange color. You’ll know they are there by the tell-tale damage on the plant.

Myoporum Thrip Adults

So how do we combat this new invader? Since it’s not a native species, the Myoporum Thrip has no natural enemies here in Southern California. That’s why it has run rampant. At the moment there is no effective solution except to provide proper cultural care, which might or might not help. Imidacloprid (Merit), a systemic insecticide, may help somewhat, but it’s not entirely effective and may harm other beneficial insects. Researchers are working on biological controls to help stop the devastation. In the past they have been able to introduce natural enemies of a pest, such as parasitic wasps, that have helped control similar epidemics. For now we’ll just have to wait and see.