Euphyllura olivine, the olive psyllid, was discovered in July in the California counties of San Diego and Orange and positively identified in September The life stages of Euphyllura olivina include an egg, five nymphal instars, and adults both sexes. Olive psyllids are very small insects ranging from 0. The life cycle is about 3 months depending on temperature. Females may lay more than 1, eggs. Females start egg laying when new shoots appear on olive trees.
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Additionally, we present results of foreign collections of its parasitoids and initial non-target studies of a possible biological control agent, the Mediterranean parasitoid Psyllaephagus euphyllurae. The current distribution of the psyllid appears to be limited to the California coast between Monterey and San Diego; there have been no reports of infestations on olives in the major production areas of central and northern California. Psyllaephagus euphyllurae was the major primary parasitoid found in our foreign collections.
The potential non-target impact of P. Behavioral observations in choice tests confirmed no attack on the non-target hosts, although the parasitoid did remain longer on N. The olive psyllid, Euphyllura olivina Costa Hemiptera: Liviidae , native to southern Europe, was first reported on olives Olea europaea L. Euphyllura olivina is an economic olive pest in its native region, feeding almost exclusively on the flower blossoms and soft growing tissue of olive.
Classical biological control i. Thus, the introduction and permanent establishment of a parasitoid specializing on the olive psyllid in California would provide an efficient means of controlling and slowing the spread of this pest.
Psyllaephagus euphyllurae Masi Hymenoptera: Encyrtidae is the most common primary parasitoid associated with this psyllid in its native range [ 4 , 5 , 6 ]. The genus Psyllaephagus Ashmead consists of more than species, most being primary endoparasitoids specific to species of Psyllidae [ 7 ]. Representatives from this genus have been successfully used in classical biological control projects targeting various pest species of Psylloidea.
Recent examples include P. Psyllaephagus euphyllurae is a thelytokous female only population that reproduces by parthenogenesis solitary endoparasitoid with a preference for late psyllid instars [ 11 ].
No data on adult longevity nor fecundity are available in the literature. In the western region of the Mediterranean basin, the parasitoid appears to be bivoltine, entering a resting state as a pre-adult in a mummified host melanized exoskeleton in early summer [ 12 ]. This resting state is synchronized with the lack of hosts during the summer months when the olive psyllid enters a reproductive diapause [ 2 , 13 ].
Both the psyllid and P. This host—parasitoid synchronicity suggests that P. Surveys were conducted during spring months of , , , , , and when olive psyllid nymph populations would have been highest. Initial surveys in and were conducted in San Diego and Orange counties of southern California. Afterwards, surveys were extended north to San Francisco. All surveys were conducted on ornamental trees free of pesticides, some of which were at Spanish missions established in the late s to early s along the California coast.
The presence of psyllids was assessed by spending 5—10 min searching the canopy and suckers for the waxy excretions produced by the insects. The number of trees sampled at any one site varied from 1 to 50, proportionally to the number of trees present. The numbers of collection sites each year varied from 27 to Local parasitoids that could be attacking this psyllid were also surveyed.
Sampling of psyllid parasitoids was conducted in , , , and consisted of collecting cuttings from the surveyed sites. The first collection in was conducted in San Diego County, the first area in the state known to have olive psyllid populations.
Ten trees were sampled for wax infested stems harboring psyllid nymphs on 10 June five from the Presidio public park in San Diego, and five found along public roads in Carlsbad. Cuttings were placed in cages constructed of plastic Ziploc bags, modified with a screen opening to allow for ventilation.
Bouquets of two or three 0. Two months later, cages were examined for the presence of parasitoid adults and mummies.
For surveys in and , stems with nymphs were placed into large bags and exposed to ambient conditions for 2 to 4 weeks to allow for development of potential parasitoids.
Collections of parasitized mummified olive psyllids were conducted in , , , and in Spain, in the coastal regions of Catalonia, Valencia, and southeast and west of Murcia Table 1 on psyllid-infested olive trees in abandoned and active commercial organic orchards throughout each area.
Field-collected mummies were placed in 0. Voucher specimens for parasitoids collected in Spain for the years , are deposited at the Entomology Research Museum, University of California, Riverside.
Those collected in have voucher specimens deposited at the same university museum, in addition to the United States National Museum in Washington D.
Neophyllura arctostaphyli Schwarz Hemiptera: Liviidae is native to California and is a close relative to the target species both in the subfamily Euphyllurinae. It is usually found on Arctostaphylos spp. The two other psyllids selected are associated with native plants common to the regions of central and northern California: Euglyptoneura nr. Non-target species for the host specificity tests came directly from field collections in California.
Infested manzanita cuttings were collected in El Dorado and Napa counties. Infested deerbrush Ceanothus integerrimus Hook. The target species, E.
Culturing of the parasitoid P. Thus, P. The resulting adult P. Two sets of experiments were conducted to assess P. In sequential no-choice tests, P. In choice tests, P. To prevent desiccation of the cuttings, the stems were wrapped with cotton and tightly fitted through the lid of a small container filled with water. After 24 h, females were transferred to new cages containing the other host type if exposed to the non-target species first, they were transferred to a cage containing the target host, and reciprocally.
To account for the limited availability of olive psyllid-infested cuttings at the time of parasitoid emergence, females were released in groups of three or five in target cages while always released singly in non-target cages.
After the end of the second h exposure, wasps were removed, and the psyllids were left to incubate for 2—3 weeks after which cages and plant materials were examined to determine the number of parasitized nymphs mummies and the presence of psyllids and adult wasps.
Leaves or other plant parts were sometimes cut into smaller pieces to ensure they were of similar sizes between the two choices and across replicates. Host plant materials were placed parallelly 2 cm apart and the wasp was released at an equal distance from them.
Preliminary observations were conducted to define the following distinctive behaviors: 1 resting, i. An additional behavior was included but was never observed: 7 host feeding, i. These observations were scored by two individuals properly trained for objectivity.
After release, females that did not display an obvious searching behavior i. Parasitoid behavior was continually observed until either a psyllid was attacked, or the parasitoid left and rested outside of the host patch i.
The presence of psyllids was confirmed at the end of each observation by lifting the wax covers. Observations were repeated until there were 10—15 replicates for each non-target species. As advanced maternal age, host deprivation, and egg depletion are known factors prompting host feeding behavior in several parasitoid species [ 14 ], the occurrence of host feeding behavior was further investigated by conducting a small number of observations with older wasps.
Mean host patch time on target olive vs. The change in distribution of the olive psyllid is graphically portrayed by the increase in survey sites found with this pest between and Figure 1. The open and closed circles show that the sampling effort was limited to the coastal regions for central and northern CA, and coastal and inland regions for southern CA, where a greater number of olive trees were found infested by this pest.
During the initial year of surveys in southern California Orange and San Diego counties 25 of 50 locations had olive psyllid infested trees, and in , 26 of 57 were infested. Caged olive cuttings from San Diego County sampled for the presence of parasitoids averaged 3.
No parasitoid developed or emerged from any of the nymphs collected during the and surveys in the California coastal region. Frequency of PDR reports for this pest has increased from one record per year in — to 4—5 records per year in — The dominant primary parasitoid recovered in the foreign collections was P.
Hymenoptera: Pteromalidae , were the next most abundant species Table 2. In and , we also recovered a low proportion of Psyllaephagus pulchellus Mercet , another primary parasitoid. Numbers relative abundance of primary and secondary parasitoids emerging from mummified olive psyllids collected in Spain in — Although efforts were made to have nymphs of mixed ages on material of each host plant, it was not always possible to determine the exact numbers and stages of the wax-covered psyllids before the tests because lifting or removing the wax could lead to the permanent displacement of the hosts.
Unfortunately, it was later discovered that wax is not a good indicator of psyllid presence. This percentage was the highest for E. In contrast, psyllids or psyllid exoskeletons were found in all E. Despite this drawback, seven P. Non-target species tested in the sequential no-choice tests with numbers of replicates n for each sequence of exposure, and numbers of adult Psyllaephagus euphyllurae reared from each target T and NT hosts.
It was later discovered that wax is not a good indicator of psyllid presence and that we had set up a number of cages with no psyllid hosts. A total of 62 observations replicates were conducted but only 37 wasps were responsive and demonstrated a clear searching behavior. Then, the females would or would not climb on the plant parts to continue this searching behavior.
Host patch time was significantly longer on the target host plants than the non-target host plants, at least for two of the three non-target species tested: E. There was no significant difference in patch residence time when searching on manzanita vs. Encounters with the target host plant always led the wasps to start searching the plant parts, and encounters with wax always triggered probing behavior Table 5.
However, attacks did not always end in oviposition because oviposition attempts sometimes caused the psyllid host to flee and successfully escape the attack. Total number of observations n on target and non-target host plants with numbers of observations where female parasitoids were seen probing the substrate Pr , host finding Hf.
Probing on non-target plant species was observed in one test only with manzanita Table 5. However, it did not lead to host finding, and, eventually, the wasp left the non-target plant species to investigate the target host plant where it searched and probed the surface.
However, that wasp was unsuccessful at locating a host because of the unusually thick layer of wax protecting them in this specific replicate most wax varies in thickness from 2—10 mm. In the remaining observations on non-target plant species, probing was never observed Table 5.
Oviposition was different from probing in terms of duration and wasp movement. While probing was characterized by quick insertions less than second of the ovipositor into the substrate wax or host , oviposition lasted longer 2. Additionally, the wasp remained completely motionless during oviposition, a clear contrast with the restless activity during searching and probing. Oviposition attempts often resulted in the host fleeing the attack.
However, once the ovipositor was inserted into the host, they seemed temporarily paralyzed for the duration of oviposition but were usually able to walk away soon after the attack.
EPPO Global Database
Euphyllura olivina (Costa, 1839)