Tea Shot Hole Borer

Importation of invasive species continues to plague global trade. Many of the world trade goods are packed on wooden pallets and trash wood is often used as “dunnage” material placed between shipping containers and the ship’s hold to prevent cargo from shifting. All wood used in packing (solid wood packing material) is required to have the bark removed and be treated for insects. Once the cargo reaches its destination, the wood is often unloaded and piled as rubbish. The rubbish can sit for years until it is chipped, burned or otherwise disposed. This wood can contain species of insects that are not present in the destination area for the cargo. If the wood is not treated (compliance is less than 100 percent (go figure)) then insects living in the wood can be transported to new locations. The insects complete their development in the piles of discarded wood and breed in their new home.

Many species of wood boring insects are contained by natural enemies and plant resistance in their native area. Some of these insects find themselves well adapted to their new environment. They find plenty of susceptible trees to infest and have few natural enemies. The trees often have little resistance to the new pest and natural enemies are left behind in their old home. These insects can become invasive causing economic and environmental damage. Part of the solution to this problem is to either treat the wood at 100 percent, or use substitutes for solid wood packing in international shipping.

A recent wood boring pest insect invader is the Tea Shot Hole Borer, Euwallacea fornicatus. In its native South Asia, the beetle is a pest of Tea. In its new home in California, the beetle is a pest of avocado trees. The beetle bores holes in trees and spreads a fungus in the galleries it creates. The beetle feeds on the fungus. In avocado trees, the fungus causes branches to shrivel and die. In the worst case, the fungus will kill the tree. The presence of this pest in California threatens many of the state’s avocado trees.

Tea shot hole borer
Photo: Gevork Arakelian

California is responding by $100,000 in emergency spending to control the beetle and protect a $460 million avocado industry. Tea shot hole borers are difficult to control because they live inside the wood. The cryptic lifestyle makes the beetle larvae difficult to detect until the damage is done. Pesticide are not very effective because sprays do not readily reach the inside of the tree where the beetle is feeding. Preventing these invasive species from entering the country is expensive, but it is the best and least expensive option available.