Understanding Erythrina Stem Borer (ESB)
Coral trees (Erythrina spp.) are striking and beloved additions to many Southern California landscapes—but they’ve come under threat from a little-known yet highly destructive pest: the Erythrina stem borer (ESB), also called the Erythrina twig borer (Terastia meticulosalis). In the latter half of 2015, this pest was spotted multiple times from San Diego to Ventura, raising serious concerns among plant enthusiasts and professionals alike. What makes the ESB especially troubling is once it invades, it can wreak havoc—infesting seeds, damaging branch tips, and in severe cases, killing entire coral trees.
What damage does it cause?
The ESB larvae burrow directly into the flower, stem, or occasionally the leaf petiole, then follow the stem’s path. As they move downward, the larvae feed on the stem tissues, hollowing out the stem and causing the tips to die off, often turning black and sometimes collapsing. This damage can extend to the entire upper and lateral portions of the plant canopy, effectively killing them.
The damage mimics the effects of pruning, prompting new lateral shoots to grow below the affected area. However, these new shoots can also become infested and eventually die. Over time, the cycle of infestation and regrowth can severely weaken the tree’s structure and health. In severe cases, the entire tree can be killed, although this process may take several years.
Management and Treatment
In addition to the recommended treatment options, it’s important to include regular maintenance practices to help manage or prevent infestations. One key step is pruning—removing any dead or infested branches can reduce the likelihood of the pest spreading further throughout the tree. In addition, raking and disposal of fallen leaves might reduce regeneration.
When it comes to applying treatments, timing is crucial. For the best results, treatments should be applied during the spring and summer months, before pests become active and begin infesting the tree. Additionally, a follow-up application in the fall—just before the tree enters full dormancy—can help provide continued protection through the cooler months.
