What’s bugging my Myoporum tree?
If the damage looks like the photo, it’s probably myoporum thrips (Klambothrips myopori). These insects are recent invaders to California and are affecting Myoporum laetum trees and Myoporum ground covers up and down the coast.
Myoporum thrips are dark brown minute and slender insects, less than 1/10 inches long. They have puncturing and sucking mouth parts and cause damage to young Myoporum laetum leaves which is easily observed by the gall-like swellings and distorted stunted and leaf curling or folding on new shoots. In severely affected trees, die-back begins at the tips and moves towards the trunk.
Credit: Thrips image courtesy of G. Arakelian, LA Co. Dept. of Agriculture
How can I control?
Trees under stress due to drought, poor growing conditions, lack of soil fertility or other environmental problems are especially susceptible. It is evident that the extended drought and lack of water has encouraged thrips spead through out the state. So the first line of defense is to provide good growing conditions. For thrips affected trees, pesticide treatment may also be an option but for heavily infested trees control can be difficult. Article by Robert Muraoka, a licensed California Pest Control Adviser and a Registered Consulting Arborist.
Some pesticides may also kill beneficial insects, such as bees and other pollinators and predators like the minute pirate bug and green lacewings that eat thrips. Since application of effective pesticides that work well to treat thrips is difficult, we recommend seeking professional expertise and hire a licensed applicator with experience treating Myoporum trees if you decide to treat your trees. Consult the University of California IPM website for more information on thrips control. University of Davis Pest Notes Publication
What should I do if my tree is heavily damaged?
For valuable landscape trees, besides improving tree health by improving overall growing conditions, pesticide treatment may be an option. For heavily damaged or dying trees replacement of the tree may with a suitable tree may be the best option.
Hardy Replacement Trees
The following list includes selections that are known to tolerate wind, poor soil, and low water (once established) unless othewise noted. It is suggested that any new tree be watered regularly for the first year or two to establish a healthy root structure!
Acacia salicina - Willow Acacia
Arbutus 'Marina' - Strawberry tree
Ceanothus - 'Ray Hartman'
Corynocarpus laevigatus - New Zealand Laurel (please note: poisonous berry!)
Cupaniopsis anacardioides - Carrot Wood
Geijera parvifiora - Australian Willow
Heteromeles arbutifolia - Toyon (please note: more of a shrub that can be trained as a tree)
Laurus 'Saratoga' - Saratoga Bay Laurel
Leptospermum laevigatum - Australian Tea Tree
Lyonothamnus floribundus - Catalina Ironwood
Melaleuca ericifolia - Heath Melaleuca
Melaleuca linariifolia - Flaxleaf Paperbark
Melaleuca styphelioides - Black Tea Tree
Melaleuca quinquenervia (aka M. leucadendra) - Cajeput Tree
Pittosporum crassifolium - Karo Tree
Tristaniopsis laurina 'Elegant' - Small-Leaf Tristania
Quercus agrifolia - Coast Live Oak