Olive Pest Research Articles

The Genetic Polymorphisms and Colonization Process of Olive Fly Populations in Turkey

The olive fruit fly, Bactrocera oleae, is the most important pest of olives in olive growing regions worldwide, especially in the Mediterranean basin and North America. Despite the economic importance of the olive fly, the colonization route of this species is unclear. We used nuclear microsatellite markers and mitochondrial DNA to provide information about the population structure and invasion route of olive fly populations in Turkey, as representative of the Eastern Mediterranean region. Adult fly samples were collected from 38 sublocations covering all olive growing regions in Turkey. The simple sequence variability data revealed a significant genetic variability in olive fly populations and a certain degree of differentiation between Mediterranean and Aegean populations. Mediterranean populations harbor higher levels of microsatellite variation than Aegean populations, which points to the eastern part of the Mediterranean as the putative source of invasion. mtDNA results suggest olive flies from the western part of Turkey are closely related to Italo-Aegean flies of the Mediterranean basin and the olive fly populations have invaded the northern part of the Mediterranean basin through western Turkey. In addition, finding specific American haplotypes in high frequencies might indicate that Turkey is the possible source of American olive fly populations. In order to more precisely characterize the population structure and invasion routes of this organism, more DNA-based sequence analysis should be carried out worldwide.

Insecticidal Activity of <i>Bacillus thuringiensis</i> on Larvae and Adults of <i>Bactrocera oleae Gmelin</i> (Diptera:Tephritidae)

The olive fruit fly Bactrocera oleae is a major olive pest in Algeriaand other Mediterranean countries. Its attacks, in some cases, seriously compromised production. Bacillus thuringiensis is a spore-forming soil bacterium which produces a protein crystal toxic to some insects. The objective of this study was to search for isolates toxic to larvae and adults of B. oleae. Four doses test were performed on neonate larvae, second instar larvae and third instar larvae. Seven Bt strains examined, showed highest toxicity levels against adults. 86% mortality was observed against neonate larvae after 7 days of application by Bt toxin isolate. The mortality of the second instar larvae was 65% mortality at dose of 108 UFC/mL. The third instar larvae was very susceptible to Bt strain with 70% of mortality. This study demonstrated that some local Algerian B. thuringiensis isolates exhibit toxic potential that could be used to control B. oleae.

Influence of fruit traits on oviposition preference of the olive fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), on three Portuguese olive varieties (Cobrançosa, Madural and Verdeal Transmontana)

The olive fly, Bactrocera oleae (Rossi), is the major pest of olives in Mediterranean countries. Previous studies have stated that different olive tree varieties are not infested at the same time. Thus, in this work, the objective was to investigate several fruit physical and chemical parameters that could influence the B. oleae infestation progress in three olive varieties with different susceptibility degrees (Cobrançosa, Madural and Verdeal Transmontana). Concerning physical parameters, the influence of maturity index, weight, volume and puncture resistance was studied, while in chemical parameters moisture, oil content and fatty acids composition were determined.Physical factors do not seem to be a determinant factor for selection of varieties. However, such factors could be important within the variety since the oviposition was correlated with some of them, being positively correlated with maturity index and negatively correlated with hardness in all varieties, with the stronger correlations observed in Cobrançosa. For Madural and Cobrançosa, a positive correlation was also established between oviposition and weight and volume. Concerning the chemical parameters, based on the principal component analysis, it was possible to separate the three varieties, which allows for concluding that they are chemically distinct.There are reasons to believe that some of these chemical parameters, namely the fatty acids composition, may influence the olive fly in the selection of the olive variety for oviposition.

Prevalence of <I>Candidatus</I> Erwinia dacicola in Wild and Laboratory Olive Fruit Fly Populations and Across Developmental Stages

The microbiome of the olive fruit fly, Bactrocera oleae (Gmelin), a worldwide pest of olives (Olea europaea L.), has been examined for >100 yr as part of efforts to identify bacteria that are plant pathogens vectored by the fly or are beneficial endosymbionts essential for the fly's survival and thus targets for possible biological control. Because tephritid fruit flies feed on free-living bacteria in their environment, distinguishing between the transient, acquired bacteria of their diet and persistent, resident bacteria that are vertically transmitted endosymbionts is difficult. Several culture-dependent and -independent studies have identified a diversity of species in the olive fruit fly microbiome, but they have not distinguished the roles of the microbes. Candidatus Erwinia dacicola, has been proposed to be a coevolved endosymbiont of the olive fruit fly; however, this was based on limited samples from two Italian populations. Our study shows that C. Erwinia dacicola was present in all New and Old World populations and in the majority of individuals of all life stages sampled in 2 yr. Olive fruit flies reared on olives in the laboratory had frequencies of C. Erwinia dacicola similar to that of wild populations; however, flies reared on artificial diets containing antibiotics in the laboratory rarely had the endosymbiont. The relative abundance of C. Erwinia dacicola varied across development stages, being most abundant in ovipositing females and larvae. This uniform presence of C. Erwini dacicola suggests that it is a persistent, resident endosymbiont of the olive fruit fly.

Dispersal and field progeny production of Trichogramma species released in an olive orchard in Egypt

Dispersal ability and field progeny production of augmentative released biological control agents depend on ecological adaptations of the particular species or strains used. Four species of the egg parasitoid genus Trichogramma were compared aiming to select suitable candidates for control of lepidopteran olive pests. Three of them (T. bourarachae Pintureau and Babault, T. cordubensis Vargas and Cabello, T. euproctidis Girault) had been previously collected from olive groves, whereas the commercially available strain used (T. evanescens Westwood) was originally isolated from sugarcane fields. During five consecutive field releases in an olive orchard near Cairo, dispersal and/or progeny production of these species was monitored using sentinel eggs placed at different heights in the release tree canopies as well as in neighboring trees (“distance effect”). The cardinal direction of dispersal was random for T. euproctidis and T. evanescens. Significant higher parasitism occurred on sentinel eggs placed on the middle part of tree canopy and highest parasitism was observed in trees where wasps had been released. Field progeny production was highest for T. bourarachae, followed by T. euproctidis and T. cordubensis. T. evanescens propagated less under field conditions. Inter-tree dispersal of all species except T. bourarachae was limited and, for biological control, releasing material should therefore be distributed on each olive tree, preferably also at different levels of the canopy.

Efficacy of spinosad bait sprays to control Bactrocera oleae and impact on non-target arthropods

A field study was conducted during 2005 and 2006 in Terra Quente, northeastern Portugal, to evaluate the efficacy of the spinosad-based insecticide Spintor Cebo® (Dow Agrosciences Iberica, S.A.) against the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), as well as the impact of the treatments on non-target arthropods. Results suggest that this insecticide could be as effective as dimethoate and since it was reported as having more benign toxicological and ecological profiles, it seems to be a good alternative to control the pest in Continental Mediterranean climates such as Terra Quente. However, its use should be evaluated carefully, mainly in conditions that increase the arthropod biological control agents’ propensity for feeding on it (e.g. absence of pollen, nectar and honeydews) to identify unintended impacts on conservation biological control of olive pests as a result of its application.

Prospects for improving biological control of olive fruit fly, Bactrocera oleae (Diptera: Tephritidae), with introduced parasitoids (Hymenoptera)

Olive fruit fly is a key pest of olive and consequently a serious threat to olive fruit and oil production throughout the Mediterranean region. With the establishment of Bactrocera oleae in California a decade ago, interest was renewed in classical (introduction) biological control of the pest. Here we discuss the prospects of identifying natural enemies of B. oleae in Africa and Asia that may help reduce B. oleae populations in California and elsewhere. Based on the current understanding of Bactrocera phylogenetics, early opinions that B. oleae originated in Africa or western Asia rather than the Mediterranean region or the Near East are taxonomically and ecologically supportable. Closely related to cultivated olive, the wild olive Olea europaea cuspidata is widely distributed in southern and eastern Africa, the Arabian Peninsula, and eastwards into Asia as far as southwestern China. Little is known regarding the biology and ecology of B. oleae in Africa and eastern Asia, especially in wild olives. While the diversity of parasitoids of B. oleae in the Mediterranean region is low and unspecialized, a diverse assemblage of parasitoids is known from B. oleae in Africa. Conversely, regions in Asia have remained largely unexplored for B. oleae and its natural enemies.

Seasonal incidence of scale insects, whiteflies and psyllids (Hemiptera) of olive and their natural enemies in Egypt

Scale insects, whiteflies and psyllids (Hemiptera) are the main olive pests in Egypt. The aim of this work is to study the incidence of scale insects, whiteflies and psyllids and their natural enemies on olive trees in different locations in Egypt during 2009-2010. The results of the present work indicated that the seasonal abundance of Lucaspis riccae Targioni-Tozzetti (Hemiptera: Diaspididae) on olive trees reached maximum during November and February in first and second years, respectively. Percent parasitism by Aphytis libanicus Traboulsi (Hymenoptera: Aphelinidae) reached maximum during December with percent parasitism 11.1 and 12.2 %, during the two years under considerations, respectively. The insect population of Parlatoria oleae Leonardi (Hemiptera: Diaspididae) reached maximum during October, 20092010. Percent parasitism by Aphytis lingnanensis Compere (Hymenoptera: Aphelinidae) and Habrolepis aspidioti Compere and Annecke (Hymenoptera: Encyrtidae) reached maximum during December and November with percent parasitism 6.5 and 12.5 in the first year, respectively and in November in the second year with percent parasitism 6.9 and 14.2 %, respectively. The predator Chilocorus bipustulatus L. (Coleoptera: Coccinellidae) reached maximum during February and March in the first and second years, respectively. In this work the abundance of Saissetia coffeae (Walker) (Hemiptera: Coccidae) reached maximum during October in the first and second years. Percent parasitism by Metaphycus flavus (Howard) (Hymenoptera: Encyrtidae) reached maximum during October and September with parasitism rates 11.5 and 13.5 % during the first and second years, respectively. The predator Scymnus syriacus (Marseul) (Coleoptera: Coccinellidae) reached maximum during October in the first and second years. The populations of Saissetia oleae (Bernard) (Hemiptera: Coccidae) reached maximum during October in the first and second years. Percent parasitism of Metaphycus lounsburyi (Howard) (Hymenoptera: Encyrtidae) reached maximum during October during the first and second years, with percent parasitism 34.2.1and 40.1 % respectively. The predator Exochomus flavipes (Thunberg) (Coleoptera: Coccinellidae) reached maximum during October in the first and second years. The seasonal abundance of Aleurolobus olivinus Silvestri (Hemiptera: Aleyrodidae) reached maximum during April in first and second years. Percent parasitism by Encarsia olivina (Masi) (Hymenoptera: Aphelinidae) reached maximum during April during the first and second years with percent parasitism 0.6 and 0.5, respectively. The abundance of Siphoninus phillyreae (Haliday) (Hemiptera: Aleyrodidae) reached maximum during October in first and second years, respectively. Percent parasitism by Encarsia inaron (Walker), (Hymenoptera: Aphelinidae) reached maximum during October in first and second years with percent parasitism 1.8 and 2.9%, respectively. The results of the present study indicated that the seasonal abundance of Euphyllura straminae Loginova (Hemiptera: Psyllidae) reached maximum during March in the first and second years. The predator Orius sp. reached maximum during March in the first and second years.

Life history and demography of Psyllaephagus zdeneki (Hymenoptera: Encyrtidae), a potential candidate for biological control of olive psylla, Euphyllura pakistanica (Hemiptera: Psyllidae)

Life history and demographic parameters of Psyllaephagus zdeneki Noyes and Fallahzadeh (Hymenoptera: Encyrtidae) were studied on its host the olive psyllid, Euphyllura pakistanica Loginova (Hemiptera: Psyllidae). Experiments were conducted in a growth chamber at 20±1 °C, relative humidity of 60±5%, and a photoperiod of 16:8 (L: D) hours. Four different olive cultivars (Fishomi, Shenge, Oil and Yellow) were used to test possible host plant influence on parasitoid performance. The pre-imaginal developmental period of female P. zdeneki varied from 24.96 (on Fishomi) to 26.34 (on Shenge) days, and for males from 21.63 (on Fishomi) to 24.44 (on Yellow) days. Adult female longevity differed significantly among the four cultivars, ranging from 12.46 (on Fishomi) to 14.97 (on Shenge) days. For each cultivar, adult female longevity was significantly greater than male longevity. Life table parameters showed survival rates (l x ) in newly emerged females were 84.61, 82.25, 85.71 and 78.12% on Fishomi, Yellow, Shenge and Oil, respectively. Female egg deposition was highest on Yellow (138.4 eggs per female) and lowest on Fishomi (116.3 eggs per female). The highest and lowest intrinsic rate of increase were 0.28 (on Shenge) and 0.24 (on Oil), respectively. The mean generation time ranged from 14.6 (on Shenge) to 16.7 (on Oil) days. These results are discussed with respect to the potential impact P. zdeneki as a natural enemy of E. pakistanica, the most important pest of olive in the Fars province of Iran, as well as the influence of olive cultivar on parasitoid life table parameters.

Seasonality in the occurrence of two lepidopterous olive pests in Egypt

Abstract Prays oleae Bern, (OM) and Palpita unionalis Hüb., (JM) are two of the most important pests in olive groves in Egypt. A 3‐year monitoring study using sex pheromone traps in semi‐arid and arid olive groves was performed. In the semi‐arid grove, flight pattern of the OM was the same as in other Mediterranean countries, but in dates concordating plant phenology. The moth completes three generations annually: the first flight is in March to April, the second is in May to June and the third occurs in August to October. In the arid olive grove, an interesting flight pattern was observed. First flight was always very close or overlapped with the second one with no male catches during August to October. However, eggs were present most of the season, indicating unusually high female presence and oviposition activity of the OM during the absence of males in the traps. Generally, moth densities were significantly lower in low fruiting years than in higher ones and were also lower in the arid olive grove than in the semi‐arid one. In contrast, JM males were present all season, exhibiting six to seven and three to four overlapping flight peaks in arid and semi‐arid olive groves, respectively. Moth densities were significantly higher in the arid olive grove than those in the semi‐arid one. This study shows that trapping location and fruit bearing year are characteristics that strongly affect the grove‐specific information needed to estimate correctly adult emergence and thus the timing of control measures.

Altered GPI modification of insect AChE improves tolerance to organophosphate insecticides

The olive fruit fly Bactrocera oleae is the most destructive and intractable pest of olives. The management of B. oleae has been based on the use of organophosphate (OP) insecticides, a practice that induced resistance. OP-resistance in the olive fly was previously shown to be associated with two mutations in the acetylcholinesterase (AChE) enzyme that, apparently, hinder the entrance of the OP into the active site. The search for additional mutations in the ace gene that encodes AChE revealed a short deletion of three glutamines (Δ3Q) from a stretch of five glutamines, in the C-terminal peptide that is normally cleaved and substituted by a GPI anchor. We verified that AChEs from B. oleae and other Dipterans are actually GPI-anchored, although this is not predicted by the “big-PI” algorithm. The Δ3Q mutation shortens the unusually long hydrophilic spacer that follows the predicted GPI attachment site and may thus improve the efficiency of GPI anchor addition. We expressed the wild type B. oleae AChE, the natural mutant Δ3Q and a constructed mutant lacking all 5 consecutive glutamines (Δ5Q) in COS cells and compared their kinetic properties. All constructs presented identical K m and k cat values, in agreement with the fact that the mutations did not affect the catalytic domain of the enzyme. In contrast, the mutants produced higher AChE activity, suggesting that a higher proportion of the precursor protein becomes GPI-anchored. An increase in the number of GPI-anchored molecules in the synaptic cleft may reduce the sensitivity to insecticides.

Effect of heat stress on survival and reproduction of the olive fruit fly Bactocera (Dacus) oleae

The olive fruit fly Bactrocera (Dacus) oleae Gmelin is a major olive pest in Greece and other Mediterranean countries. Its population density and respective olive infestation is usually low in many areas of northern Greece during summer months. To some extent, this may be due to the prevailing high temperature and low relative humidity conditions. In the present work the effects of short term exposure to high temperatures on the survival and egg production of B. oleae pre-imaginal stages and adults were studied under laboratory conditions. Different larval instars within infested green olive fruits, adults and pupae and were exposed for 2 h to a series of different high constant temperatures ranging from 34 to 42°C. Subsequently, survival percentages of pre-imaginal stages and adults as well as the number of eggs laid by females previously exposed to high temperatures were determined. At temperatures up to 38°C high survival percentages of larvae and adults were observed, whereas pupae displayed a relatively increased heat tolerance up to 40°C. Female longevity and egg production were substantially reduced after heat stress. Prior acclimation at 33°C for 1 and 3 days resulted in increased adult survival following heat stress. We discuss the results with respect to the ability of the fly to survive and reproduce under high summer temperatures.

Dynamics of oil quality parameters changes related to olive fruit fly attack

AbstractIn order to evaluate the role of intrinsic characteristics of olive cultivars on dynamics of oil quality parameters changes related to the olive fruit fly (Bactrocera oleae (Gmelin)) attack, two specific olive cultivars were compared, Istarska bjelica and Buža. I. bjelica is characterised by late ripening, a lower flesh/stone mass ratio and higher oleic/linoleic ratio, the total phenols content and oil mass fraction compared to Buža. Oil samples were obtained at two harvesting dates, from fruit lots with 0, 25, 50, 75 and 100% of infestation degree, expressed by mass. Oil and water content in olive paste, as well as total phenols, fatty acids composition and standard chemical and sensorial oil quality parameters were determined. At equal maturity level, the cultivar with a higher oil (24 ± 1% vs. 16 ± 1%) and lower water content (54 ± 2% vs. 61 ± 4%) was more susceptible to hydrolytic degradation, while the one with the lower total phenols content (231 ± 32 vs. 575 ± 124 mg/kg) and oleic/linoleic fatty acid ratio (5.7 vs. 9.1) was more liable to oxidative deterioration of oil. Lower susceptibility to negative flavours formation could be related to the absence of ripening induced by fly attack and less favourable environment for larvae growth (higher total phenols content, lower water content and flesh/stone mass ratio).Practical applications: Understanding the impact of olive fly attack is the basis of scientific and practical interest in the production of olives and olive oil. Different intrinsic characteristics of olive cultivars could lead to different susceptibility to oil quality deterioration caused by olive fly attack, which opens a possibility to adjust and minimise pesticide treatments. Knowledge about this topic could contribute to the reduction of costs of olive pests control, as well as to the improvement of quality and food safety concept in olive oil production.

Response of coccinellid community to the dimethoate application in olive groves in Northeastern Portugal

In this work we assessed the effects of the application of dimethoate on the coccinellid community. The field work was carried out on a weekly basis, in two different olive groves, from April to November of 2002 and 2003 and captured coccinellids were identified to species level. Principal response curves (PRC) method was used to analyse the effect of the dimethoate application on the abundance of coccinellid species. A total of 23 species were identified from the two olive groves. Nine species occurred in both olive groves and in the two years of the study. Scymnus interruptus was the dominant species in the control grove with 46.4% of the total Coccinellidae recovered while in the grove treated with dimethoate, Rhyzobius chrysomeloides represented 35.7% of the total number captured. PCR showed that the main effect of the treatment was a significant reduction of the abundance of the most common species of the coccinellid community (S. interruptus and Chilocorus bipustulatus) in the treated grove. This can also have implications on the preservation of ecological functions associated with coccinellids, namely their role as control agents of olive pests.

The Ladybeetle Community (Coleoptera: Coccinellidae) in Southern Olive Agroecosystems of Spain

The aim of this survey is to faunistically describe ladybeetle assemblages from the canopies of olive orchards in southern Spain (Córdoba and Granada) and determine the indicator ladybeetle species that are representative of each region, taking into account (1) the ecological importance of predatory ladybeetle species in olive orchards and (2) the variability of ladybeetle community composition in relation to landscape configuration and different farming systems (organic, integrated, and conventional), using ordination and classification methods. The total number of coccinellids collected was 481; they belonged to 9 genera and 13 species. Canonical correspondence analysis (CCA) showed a clear separation between orchards from Granada and orchards from Córdoba, taking into account ladybeetle species, environmental variables, and sampled orchards. The land use types and geographical locations showed that Scymnus mediterraneus Iablokoff-Khnzorian 1972 and Platynaspis luteorubra (Goeze, 1777) captured at higher latitudes benefited more from a larger organic olive area and from the presence of holm oak forests in the surrounding area. Coccinella septempunctata L., 1758 and Hippodamia variegata (Goeze, 1777) were found at lower latitudes and at higher longitudes. Ladybeetle assemblages can vary in response to the type of farming system, especially with regard to pesticide use and landscape configuration. Nevertheless, evaluation of species composition might help identify the state of conservation of these agroecosystems. This knowledge could be used to improve the sustainability of agricultural landscapes to increase the presence of coccinellids and their ecological function in olive pest control.

Biology and parasitism rates of Pteromalus nr. myopitae (Hymenoptera: Pteromalidae), a newly discovered parasitoid of olive fruit fly Bactroceraoleae (Diptera: Tephritidae) in coastal California

An undescribed wasp, Pteromalus nr. myopitae (Hymenoptera: Pteromalidae) opportunistically parasitizes the olive fruit fly Bactrocera oleae (Rossi) (Diptera: Tephritidae), an introduced pest of olives in California. The native or typical host of P. nr. myopitae is unknown. We demonstrate that P. nr. myopitae is a solitary, ectoparasitic, idiobiont parasitoid of the third instar host inside fruit, and pupation occurs in the host tunnel. Reproduction of P. nr. myopitae on B. oleae in olives in the laboratory and in field cages generally failed. Host-feeding was not observed, and adults fed honey and water lived longer than those provided with water alone. Parasitism in non-commercial olives in the moderate coastal climate of San Luis Obispo occurred primarily from August to October, and was absent from a nearby location with more extreme climate and a low population of B. oleae. Greater parasitoid numbers were associated with greater host densities, and proportion of hosts parasitized was generally higher at lower host densities during 2 years of the study. The geographic range of the parasitoid extends along the coast from San Francisco Bay to Ensenada, Baja California, Mexico, and also inland in the Sacramento Valley, with one record in the San Joaquin Valley. The potential of the parasitoid as a biological control agent of B. oleae is probably low, however, the extent of its interference with other parasitoids being considered for release in California is unknown and warrants further study.

Attraction of DifferentTrichogrammaSpecies toPrays oleaeSex Pheromone

AbstractChemical cues play a major role in the process of host selection by parasitoids, a process that has been discriminated into several steps such as habitat location, host location, and host acceptance. Egg parasitoids are known to rely on infochemicals of the adult host stage, e.g., pheromones, rather than cues emitted by the inconspicuous host eggs themselves. Here, we show that three different Trichogramma (Hymenoptera: Trichogrammatidae) species were attracted to the synthetic sex pheromone of the olive, Olea europea L., pest Prays oleae (Bern) (Lepidoptera: Yponomeutidae). In Y-tube olfactometer experiments, we revealed differences in the behavior of four tested Trichogramma strains to different concentrations of the host pheromone. Although wasps of Trichogramma oleae (Voegele & Poitale) (IO47) were significantly attracted to two concentrations of the host pheromone, another strain of the same species (IO24) did not show a response to any offered concentrations. Trichogramma cacoeciae Marchai females showed greatest attraction toward the pheromone to three of five offered concentrations. Bioassays with Trichogramma bourarachae Pintureau & Babault wasps showed a positive response of the parasitoids to three concentrations of the host pheromone. Detection of the moth sex pheromone may result in an enhanced searching effort by Trichogramma wasps in an area with host eggs and eventually lead to an increased parasitism rate of these eggs. The results of this research should help enhancing the efficacy of the use of Trichogramma wasps as biocontrol agents against the olive pest.

Olive Fruit Fly, Bactrocera oleae (Rossi) (Insecta: Diptera: Tephritidae)

Revised! EENY-113, a 4-page illustrated fact sheet by H. V. Weems and J. L. Nation, is part of the Featured Creatures collection. It describes this serious pest of olives in the Mediterranean — distribution, identification, life history and habits, hosts, and management procedures. Includes references. Published by the UF Department of Entomology and Nematology, July 2009. EENY645/IN270: Olive Fruit Fly Bactrocera oleae (Rossi) (Insecta: Diptera: Tephritidae) (ufl.edu)

Damage evaluation of Rhynchites cribripennis (Col., Attelabidae) in olive fruits

Abstract Rhynchites cribripennis is a pest of olives widely distributed in the Mediterranean region. The adults drill holes in the flesh of olives, resulting in fruit drop. Although earlier studies reported high damage levels, its damage potential has not been specifically investigated. In the current study, the damage potential of this weevil was evaluated with regard to its density. Olive shoots were enclosed in muslin cages, along with two or four adult weevils, during the initial phase of the olive fruit development. In each cage, the shoots bore 357 fruits, on average. The percentage of fruits dropped and the damage level on the fruits were recorded at about 1‐month intervals. At harvest, the fruits that remained on the shoots were individually weighed to evaluate the damage as regards fruit weight. The results showed that R. cribripennis can cause a significant damage because of fruit drop (54 ± 6%, 38 ± 4% and 16 ± 2% in the cages with 4, 2 and 0 adults, respectively). The damage was more severe in fruits within the first month after their formation. A single feeding hole was shown to cause the drop of small fruits. The high percentage of dropped fruits caused a significant decrease in the weight of the olives at harvest among treatments. These results show that R. cribripennis can cause serious damage to olive production and offer useful information for quantifying its damage potential and developing a more rationale control strategy for this pest.

Combined Effects of Heat Stress and Food Supply on Flight Performance of Olive Fruit Fly (Diptera: Tephritidae)

Abstract The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is a newly invasive pest of olives, Olea europaea L., in California. The table olive industry is located in California's Central Valley, where daily high summer temperatures can be >35.0°C. This study investigated the effects of high temperatures (heat stress) and food conditions on the flight performance of B. oleae in laboratory flight mill tests. Flies were provided food (honey and hydrolyzed yeast) and water for a 1-wk preconditioning period and then subjected to 24-h preflight exposure to diurnal temperature regimes (low-high temperatures of 18.3–35.0°C and 18–37.8°C) and deprivation of food. Flies with the preflight stress conditions had significantly lower flight performance (1,305 m and 0.989 h at 18.3–35.0°C and 1,152 m and 0.966 h at 18.3–37.8°C) than control files that were held under no-stress preflight conditions (constant 23.9°C, food, and water) and flew 1,982 m for 1.54 h. Flight distance and duration were further reduced when no water was provided during the 24-h preflight exposure to high temperature stress. Flight distance and duration also were decreased when the preflight exposure period was increased to 2 and 3 d. When flies were deprived of food and water during the preconditioning period, there was significant adult mortality and flight performance was poor (<50 m and <2 min) after 24-h preflight exposure to either the 18.3–35.0°C or the 18.3–37.8°C temperature regime and deprivation of food. Heat stress and food deprivation also reduced postflight fecundity and adult longevity. The results are discussed with respect to the ability of B. oleae to survive summer heat and food deprivation by dispersing to refuges with food, water, and shelter.