October 09, 2003
There has been good and bad news about the olive fly. High temperatures in inland valleys and the Central Valley has spared many olive groves. Over 100 degree temperatures decreases the activity of adult flies and kills eggs and developing pupae. Olives being delivered to canneries have minimal fly damage.
Coastal areas have been hard hit. A Fremont test site for Spinosa for several years has suffered intense infestation despite repeated applications. Last year ornamental trees in the Southern San Francisco Bay Area had attack rates of 200-300% (2-3 eggs laid per olive). This year similar insect activity has been seen in the North Bay to Marin county. Growers in Sonoma and Napa report major activity for the first time.