Submitted to: Proceedings, IOBC
Publication Type: Proceedings
Publication Acceptance Date: 4/25/2006
Publication Date: 10/9/2007
Citation: Yokoyama, V.Y. 2007. Olive fruit fly biology and cultural control practices in california. IOBC/WPRS BULL. 30:277-285.
Interpretive Summary: Olive fruit fly is an exotic insect pest that was accidentally introduced into California, where the only domestic source of canned table olives produced for US consumption are grown. Laboratory and field studies were conducted to show weather conditions that may adversely affect the development of the pest in olives. Cold (41ºF) and humid, and hot (95ºF) and dry conditions caused complete mortality of the immature, developing stages of the pest in fruit. However, the immature stages infesting the fruit showed low to moderate mortality when exposed to either 59ºF or 77ºF. These observations suggest that olive fruit fly will not become a major pest in the hot and arid interior valleys of California where canning olives are produced, but may develop into large pest populations in the temperate coastal areas where olives are grown for oil. Small fruit was found to be susceptible to egg laying by olive fruit fly adults and the females laid eggs from 13 to 64 days after emergence. The findings suggest that growers may need to monitor pest populations soon after the spring bloom. A higher number of adults was trapped in trees with fruit and water at the base than in trees without fruit and water. Based on these data, non-harvested fruit and standing water should be eliminated from orchards to prevent attraction of the pest. When late stage larvae, young pupae, and old pupae were subjected to immersion in sand and water, a high level of mortality occurred in the young stages, which suggests that flood irrigation and high spring rains may be beneficial for population control. This research provides growers with cultural control practices to mitigate olive fruit fly populations in olive orchards, and supports the $68-100 million annual production of olives in California.
Technical Abstract: Olive fruit fly, Bactrocera oleae (Gmelin), first found in California, USA in 1998 was investigated in laboratory and field studies. Mortality of 1-5, 6-8, 9-11, and 12-14 d-old immature insects in olives was 19-75, 13-58, 5-27, and 0-7% when exposed to 15C and 60% relative humidity (RH), and was 14-31, 8-32, 16-38, 4-22% when exposed to 25C and 35% RH, respectively. Mortality decreased with in increase in age at all temperatures except for 9-11 d-old larvae exposed to 25C and 35% RH. Mortality was 100% in all immature stages in fruit exposed to 5C and 85% RH., and 35C and 25% RH. The pre-ovipositional period for adult females was 13.0 ± 4.0 d; peak oviposition occurred at 19.7 ± 1.8 d; and, egg laying ended after 63.7 ± 3.8 d (mean ± SEM) at 23C. Olive fruit fly was found to attack fruit <1.0 cm3. The mean number of adults trapped in baited yellow panel traps with male attractant was higher in olive trees with irrigation water at the base (39.9 ± 8.7 adults per trap per week) than in olive trees without irrigation water (27.7 ± 6.4 adults per trap per week) in the absence of fruit in the canopy. The highest numbers of adults were collected between 2 and 9 October. The daily mean temperature (15C) and relative humidity (74%) was similar in trees with and without water at the base. Percentage mortality of olive fruit fly 3rd instars was greater than young (0-4 d-old) and old (9-12 d-old) pupae after immersion in water and sand for 1-5 d, and young pupae were in general more susceptible than old pupae.