Myoporum is a genus of approximately 30 species of plants in the Myoporaceae family. Most are from Australia and New Zealand, while Myoporum sandwicense, or naio, is native to most of the islands of Hawaii. The species range from trees to low-growing plants cultivated as drought-tolerant, perennial ground cover. Some of these ground-covering varieties have been grown extensively along freeways in California to prevent the erosion of hillsides. Formerly known as being virtually pest-free, this genus is being ravaged in California by a newly discovered insect pest that has spread to Hawaii.
In desert areas such as southern Arizona, Myoporum parvifolium has been used as an evergreen ground cover where there is good drainage. It is ideal for slight slopes or large open areas that do not receive foot traffic. This species grows quickly and prefers full sun. Plants should be placed 2 to 3 feet (0.2-0.3 m) apart, and grow to between 3 and 6 inches (7.5-15 cm) tall. The plants generally require some irrigation during the summer.
One particular species has been widely planted throughout California as a low-maintenance evergreen ground cover that produces white flowers in the summer. Myoporum pacificum has been used in both residential and commercial gardens, and to stabilize embankments and slopes along highways. It grows rapidly and can grow to 30 feet wide.
With the discovery of the pest Myoporum Thrips, it is no longer recommended to use this species as a ground cover. It is difficult to control the thrips with insecticides. Pruning infested sections and destroying them is an effective means of control. This method may be feasible for ground covers in yards, but not for extensive plantings along roadways. Alternate types of plants such as Ceanothus are being suggested as an alternative to Myoporum in these uses.
The thrips insect pest was first discovered in 2005, in San Diego County. The adult and its larvae severely damage new growth, causing swelling and the distortion of leaves. The thrips were identified as a new species in 2007 and named Klambothrips myopori. It is thought that they were originally from Australia or New Zealand. They have been working their way north in California and have been found in Hawaii.
It is thought that the thrips would attack all species of Myoporum. There is particular concern in Hawaii about naio, which is a keystone species and has been found to be infested with the thrips in some areas. It grows in a variety of environments, ranging from shorelines to sub-alpine forests. At higher elevations, this species can grow to 45 feet (150 m) high, but normally only grows to 15 ft (50 m) in cultivation. These trees bloom all year with fragrant 1/4-inch (62.5 mm) bell-shaped flowers.
There are problems with some species of Myoporum being invasive weeds in parts of California. It is thought that birds disperse the seeds to new areas after eating fruit produced by the plants. Ironically, the newly identified thrips might serve as a biological control agent in these cases.