Q. I used to see oleander growing everywhere, especially on all the freeway medians. Now it’s almost all gone. What happened?
Oleander leaf scorch is a bacterial disease spread by several species of insects, particularly sharpshooters. It first appeared in Riverside and Orange counties in the 1990s and quickly spread to most of Southern California. The bacteria (X. fastidiosa) affects the plant’s vascular system, resulting in symptoms that mimic water stress or salt toxicity. Leaves begin to wilt and turn yellow, then brown before falling. This wilting starts at the end of individual branches before spreading to the whole plant. (Drought will cause wilting and yellowing in the entire plant all at once.) Although drought stress can be reversed with prompt irrigation, leaf scorch has no remedy. Once a plant has been infected, it will succumb within 5 years.
Leaf scorch spreads quickly, so if one plant shows signs of infection it should be removed anddestroyed.
Q. I heard that there is a new invasive pest that affects figs and will ruin the fruit. What is it, and is there any way to protect my fig crop?
The black fig fly has been seen in Los Angeles, Orange, Riverside, San Bernardino, Ventura, and San Diego counties. The female will lay her eggs in the osteole of unfertilized immature fruit. (The osteole is located at the bottom of the fig.) Once the eggs hatch, the larvae tunnel their way through the fruit, ruining it. Affected fruit will appear wrinkled and become spongy, often dropping to the ground. Sometimes a tiny exit hole is visible.
Protect your fruit by placing little mesh bags over them when they are still small (about ½ inch). Pick up fallen fruit immediately and dispose in the regular trash. The flies pupate in the soil and emerge in spring, so removing infested fruit can interrupt their life cycle. As of today, there are no known biological or chemical treatments for black fig fly. Sprays are unlikely to be effective since the larvae are protected inside the fruit.
Frequent inspection and elimination of infested fruit will hopefully slow the spread of this pestuntil an effective treatment is available.
Q. How can I find out about the latest agricultural pests in California?
The University of California Department of Agriculture and Natural Resources (UCANR) has an extensive integrated pest management database that is continually updated. Just go to https://ipm.ucanr.edu.