Thrips (Order Thysanoptera)
First, the singular (just one insect) and plural (two or more insects) for this pest is 'thrips'; yea, it’s counterintuitive! Second, prior to myoporum thrips arriving in Hawai‘i, I had very few encounters or problems with thrips on my native Hawaiian plants. Therefore, the information and advice given below is largely a summary of the online writings of others.
Entomologists have described approximately 6,000 species of thrips. Most are very small (1 mm long or less), slender, with fringed wings (as adults), and distinctive asymmetrical mouthparts. The majority feed on plants by puncturing and sucking out the contents, although a few species are predators. Many species are pests of commercially important food and ornamental plants, and a few are vectors for plant disease viruses; some such as the myoporum (naio) thrips can cause extinction-level damage and death while others are a minor nuisance. Pest species generally attack the softer parts or new growth of plants resulting in scarring, dead tissue patches or trails, and galling of leaves. Thrips feeding is usually accompanied by visible black flecks of excrement. Because most thrips are tiny, they can be difficult to see and identify. One way to determine if thrips are infesting your plants is to put a blank sheet of white paper beneath the damaged leaves or flowers and shake the basal stem. If there are thrips, some will fall off, and you will be able to get a better look at them on the paper with a magnifying glass.
Thrips rapidly evolve resistance to insecticides. This evolution, along with their rapid reproduction, high mobility (by flight or wind), and ability to shield themselves from predators and insecticides within galls, deformed leaves and tiny crevices can make eradication or control difficult. Methods of eradication or control include: pruning infested leaves and stems, insecticidal soap, horticultural oil, neem oil, pyrethrin, spinosad, diatomaceous earth, kaolin clay, and sticky traps. Biocontrol agents for pest thrips include: predatory thrips, lacewings, minute pirate bugs, mites, and certain parasitic wasps. As previous mentioned, my experience with thrips is quite limited. Of the treatments above, I have only used pruning, insecticidal soap and horticultural oil with varied success. For more detailed information on thrips, I recommend the UCIPM webpage on thrips.
Image ID and credits from left to right: Assorted life stages of Tubuliferan thrips (courtesy of Scot Nelson & Dick Tsuda ©), Myoporum thrips (courtesy of Center for Invasive Species Research ©), Damage by Myoporum thrips (courtesy of Center for Invasive Species Research ©)