In the San Joaquin Valley, the warm weather has stimulated quite a bit of fall flush. Citrus leafminer loves these new leaves and is attacking all varieities of citrus vigorously. While the damage is unsightly, most varieties of mature trees can take this damage and continue to grow at a normal rate. Nursery trees, new plantings, limes, and lemons with multiple crops in coastal California need insecticides to reduce the damage.
The nights are finally cooling down and this in combination with shortening daylength, signals pests to slow down their development and in some cases go into diapause. Citrus leafminer will stop development soon and just sit in leaves in various stages through the winter. The youngest larval instars will die due to the cold. The older larval instars and pupae will become prey to predators and parasites. The leafminer population will survive primarily as a few pupae and adults, which is why it will start out in very low numbers in the spring.
Recently single adult psyllids were found on two traps about 1 mile apart from each other in Upland California (San Bernadino County). The host plants in and around these traps are being treated and these finds will expand the quarantine zone (20 miles around a psyllid find). The populations in Imperial, San Diego, and Los Angeles counties countinue to have the occasional new psyllid finds, but the area that is being treated has not expanded very much. This is evidence that the insecticide treatments are very effective - if we can find this tiny insect! We continue to get the good news that no huanglongbing disease has been found in California.