Virgilio Caleca

Relation of fruit color, elongation, hardness, and volume to the infestation of olive cultivars by the olive fruit fly, Bactrocera oleae

The susceptibility of olive cultivars to the olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), has seldom been studied. This article examines factors associated with olive fruit fly infestation of 16 commonly planted Sicilian olive cultivars. Total infestation data were simultaneously correlated with categorical and quantitative factors using ordinal logistic regression. When all factors were included in the analysis, year, sampling date, cultivar, and fruit color were highly significant, but the quantitative factors fruit volume, fruit elongation, and fruit hardness were not. When the analysis was repeated excluding cultivar, all quantitative factors were significant, and elongation and volume were highly significant. Spherical, large, and hard fruit seemed to be preferred by B. oleae over fruit that are elongate, small, and soft. Therefore, fruit color, elongation, volume, and hardness provide useful information regarding the susceptibility of cultivars. In both organic and conventional olive cultivation, information about olive cultivar susceptibility to olive fruit fly will help orchard managers to produce quality oil and table olives while reducing treatments for olive fruit fly control.

Pathogenicity bioassays of isolates of Beauveria bassiana on Rhynchophorus ferrugineus

BACKGROUND The control of Rhynchophorus ferrugineus (Olivier), the main palm pest in the Mediterranean Basin, is problematic because of its biology and the current restrictions in many European countries on the use of chemical insecticides in urban areas. Entomopathogenic fungi have been studied as potential biological control agents, but information on their natural incidence is limited. Strains of Beauveria bassiana (Balsamo) Vuillemin were isolated from symptomatic insects collected on dead palms, and their pathogenicity against different instars of R. ferrugineus was evaluated in the laboratory. RESULTS The overall percentage of infected insects found in Canary palms was 7%. In laboratory bioassays, hatching of eggs treated with three different isolates of B. bassiana was 41.2, 26.8 and 29.9%, significantly lower than the control (62.4%). Larvae and adults were treated with a single isolate in two ways: spraying each insect with a conidial suspension or feeding them with fruit portions previously immersed in the same conidial suspension. At the end of the two trials, the mortality of treated larvae was 88 and 92%, and the mean survival time was 10.4 and 11.8 days, significantly different from the control, where no insect died during the trials. Mortality and survival time recorded in either trial on adults did not significantly differ between treatment and control. CONCLUSION This study shows that the pathogenicity of wild isolates of B. bassiana differs among the tested R. ferrugineus instars. The low mortality of treated adults supports their use as vectors of B. bassiana as a potential tool for reducing R. ferrugineus populations.

Risk assessment of non-target effects of Closterocerus chamaeleon (Girault) parasitoid of the eucalypt gall maker Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae)

The pre-release risk assessment, a recommended practice in biological control programmes, was carried out before introducing Closterocerus chamaeleon (Girault), a eulophid parasitoid of the eucalypt gall maker Ophelimus maskelli (Ashmead) (Hymenoptera, Eulophidae), in Sicily, Italy. We evaluated its host specificity in laboratory small arena no-choice tests on six non-target hosts, using O. maskelli as a control species. The non-target species fit with at least one of the following criteria: a) common geographical origin; b) ecological or behavioural affinities with the target host; c) concealed habit of the preimaginal stages; d) taxonomic affinity; e) taxonomic affinity with hosts of congeneric parasitoids of the candidate agent; and f) presence in Italy/Sicily. Closterocerus chamaeleon performed an oviposition sequence of 10 recognisable behaviours, always leading to parasitization when exposed to O. maskelli. The same behaviour sequence was carried out on the gall maker Leptocybe invasa Fisher et La Salle, the only non-target species living on Eucalyptus, but just until Step 6, i.e. until ovipositor extraction and insertion, and never until egg-laying. All of the other non-target hosts were ignored. Furthermore, the adult parasitoid longevity was assessed in three rearing conditions: 1) no food/no parasitisation permitted; 2) food/no parasitisation permitted; and 3) food provided after parasitisation. Adult wasp longevity was significantly higher in treatment 2 (21.1 days ± 4.1 SE) than in treatment 1 (3.6 days ± 0.5 SE) or 3 (3.8 days ± 0.6 SE). Laboratory tests carried out in this study on C. chamaeleon indicated high host selection ability, later confirmed by our post-release field data.

Primi reperti in Sicilia su diffusione e biologia di Leptoglossus occidentalis Heidemann (Heteroptera: Coreidae), cimice americana dei semi delle conifere

In questo lavoro si riportano i primi dati raccolti in Sicilia sulla diffusione e la biologia di L. occidentalis Heidemann, un insetto originario dell’America settentrionale dove è considerato dannoso alle conifere per la produzione di semi. I dati in nostro possesso datano i primi ritrovamenti di L. occidentalis al settembre 2002 in una località vicino Gangi (PA), mentre la prima segnalazione pubblicata per la Sicilia è relativa ad alcune catture effettuate a Niscemi (CL) nel 2003. Il coreide è distribuito in tutte le province dell’isola (30 siti), da località vicino al livello del mare fino a località di montagna, ed è stato raccolto su strobili e piante di Pinus halepensis Miller, P. laricio Poiret e P. pinea L., P. nigra J.F.Arnold e Pseudotsuga menziesii (Mirb.) Franco, ma anche nei pressi e dentro i fabbricati. Femmine del coreide poste in laboratorio su germogli di P. menziesii a temperatura di 22 °C ± 1 e con U.R. del 80% hanno deposto fino a 148 uova a distanza di 3 giorni se raccolte alla fine di maggio e dopo 73-92 giorni se raccolte in novembre. Per le femmine che hanno deposto in laboratorio, l’ovideposizione si è protratta in media per 35 giorni. In laboratorio si sono ottenuti adulti del coreide non prima di 61 giorni dalla deposizione. Sulla base dei dati raccolti non si può desumere il numero di generazioni che L. occidentalis compie nelle diverse aree della Sicilia, ma al momento non pare siano più di due all’anno.

Rearing of Prays citri on callus derived from lemon stigma and style culture.

A new method for rearing the citrus flower moth (Prays citri Mill.) (Lepidoptera, Yponomeutidae) on lemon [Citrus limon (L.) Burm.] callus is reported. In the present research callus (an undifferentiated mass of plant cells that can be grown under sterile conditions on an artificial medium in vitro) was induced from lemon stigma and style explants cultured on Murashige and Skoog (MS) medium supplemented with 500 mg l−1 malt extract, 13.3 μM 6‐benzylaminopurine, and 146 mM sucrose. Also somatic embryogenesis and plant regeneration were obtained from the cultures of styles and stigmas of lemon. Adults were obtained from larvae on infested flowers collected in the field. Different oviposition substrates were used: white oval pearls (WOP), black oval pearls (BOP), rooted shoots (RS) of lemon obtained in vitro, and artificial flowers containing lemon callus (AF). Larvae were reared on lemon callus. Adults oviposited on RS, on WOP, and on AF. BOP were rejected as oviposition substrates. The flower moth reared on callus oviposited fertile eggs. In our tests P. citri completed three generations on callus or on callus plus shoots. In the latter case the larvae preferred callus and fed on shoots only after callus was completely eaten. The life cycle on callus at 23 ± 1 °C lasted about 21 days. There were significant differences between oviposition substrates for what concerns the number of eggs laid. It was observed that females generally preferred WOP (about 25 eggs/female) to AF (about 20 eggs/female) or RS (about 12 eggs/female) as oviposition substrate. Nevertheless the percentage of eggs that developed into adults was higher when AF sealed with stretched Parafilm were used (about 70% of eggs developed into adults). The method of rearing P. citri with AF was labour‐saving and the feeding substrate (callus) had less tendency to become mouldy or decompose than when WOP and RS were used. Since such a diet is available for the insect all year round and callus can be produced in unlimited quantity, it could be possible to obtain a mass production of this moth.

Description of dryocosmus destefanii new species (Hymenoptera: Cynipidae: Cynipini) from Quercus suber L. in Italy

A new species, Dryocosmus destefanii Cerasa Melika n. sp. associated with a Cerris section oak, Quercus suber L., is described from Italy. Description, diagnosis, host associations and biology for the new species and an illustrated identification key to the Western Palaearctic Dryocosmus species are given. The description is supported by morphological and molecular data.

Behavior-modifying and insecticidal effects of plant extracts on adults of Ceratitis capitata (Wiedemann) (Diptera Tephritidae)

The Mediterranean fruit fly Ceratitis capitata is a major pest of fruit orchards worldwide. In order to develop control methods based on natural products, particularly required in organic farming, a laboratory study was carried out to evaluate the response of adults to leaf extracts from four plant species: Ruta graveolens, Eriobotrya japonica, Rubus ulmifolius, and Ficus carica. Air-dried leaf powders were subjected to an ethanolic cold extraction. Chemical composition was assessed by GC/MS analysis. Extracts were tested in laboratory bioassays to assess the electroantennographic (EAG) response, attraction/repellence toward ovipositing females, and induced mortality toward adults. Among the extracts tested, only R. graveolens elicited significant differences compared to the control in all the bioassays. This extract, whose main volatile compounds were 2-nonanone and 2-undecanone (45% of the total), recorded the greatest EAG response, and stimulated a positive oviposition response compared to the control. Ruta graveolens extract elicited a significant insecticidal activity, confirmed to be dose-dependent. LD50 and LD90 concentrations were 3.64 and 6.01% (v/v), respectively. To our knowledge, this is the first study reporting a single plant extract, from R. graveolens, acting as attractant and oviposition stimulant, and at the same time having insecticidal properties toward C. capitata adults. The incorporation of such extract or its components into food bait could be useful in medfly “attract and kill” control strategies.

Barcoding of parasitoid wasps (Braconidae and Chalcidoidea) associated with wild and cultivated olives in the Western Cape of South Africa

Wild and cultivated olives harbor and share a diversity of insects, some of which are considered agricultural pests, such as the olive fruit fly. The assemblage of olive-associated parasitoids and seed wasps is rich and specialized in sub-Saharan Africa, with native species possibly coevolving with their hosts. Although historical entomological surveys reported on the diversity of olive wasp species in the Western Cape Province of South Africa, no comprehensive study has been performed in the region in the molecular era. In this study, a dual approach combining morphological and DNA-based methods was used for the identification of adult specimens reared from olive fruits. Four species of Braconidae and six species of Chalcidoidea were identified, and DNA barcoding methodologies were used to investigate conspecificity among individuals, based on randomly selected representative specimens. Morphological identifications were congruent with DNA data, as NJ and ML trees correctly placed the sequences for each species either at the genus or species level, depending on the available taxa coverage, and genetic distances strongly supported conspecificity. No clear evidence of cryptic diversity was found. Overall seed infestation and parasitism rates were higher in wild olives compared to cultivated olives, and highest for Eupelmus spermophilus and Utetes africanus. These results can be used for early DNA-based detection of wasp larvae in olives and to further investigate the biology and ecology of these species.

Modeling Environmental Influences in the Psyllaephagus bliteus (Hymenoptera: Encyrtidae)–Glycaspis brimblecombei (Hemiptera: Aphalaridae) Parasitoid–Host System

Abstract Glycaspis brimblecombei Moore (Hemiptera: Aphalaridae) is an invasive psyllid introduced into the Mediterranean area, where it affects several species of Eucalyptus. Psyllaephagus bliteus Riek (Hymenoptera: Encyrtidae) is a specialized parasitoid of this psyllid that was accidentally introduced into Italy in 2011. We developed a model of this host–parasitoid system that accounts for the influence of environmental conditions on the G. brimblecombei population dynamics and P. bliteus parasitism rates in the natural ecosystem. The Lotka–Volterra-based model predicts non-constant host growth and parasitoid mortality rates in association with variation in environmental conditions. The model was tested by analyzing sampling data collected in Naples in 2011 (before the parasitoid was present) and defining several environmental patterns, termed Temperature-Rain or T-R patterns, which correspond to the host growth rate. A mean value of the host growth rate was assigned to each T-R pattern, as well as a variation of the parasitoid mortality rate based on temperature thresholds. The proposed model was applied in simulation tests related to T-R patterns carried out with a data series sampled between June 2014 and July 2015 in five Italian sites located in Campania, Lazio, Sicily, and Sardinia regions. The simulation results showed that the proposed model provides an accurate approximation of population trends, although oscillation details may not be apparent. Results predict a 64% reduction in G. brimblecombei population density owing to P. bliteus parasitoid activity. Our results are discussed with respect to features of the host–parasitoid interaction that could be exploited in future biological control programs.

New records of Cynipidae (Hymenoptera) from Italy

Summary New records of Cynipid gall wasps and inquilines for the Italian peninsula and Sicily and their new host plants for the Palaearctic Region are listed and commented on. Among them we find: Cerroneuroterus cerrifloralis (Müllner 1901) as new for Italy and new for the Palaearctic region as host on Quercus suber; Andricus multiplicatus Giraud 1859 on Q. suber, as new host for the Palaearctic region; Aylax papaveris (Perris 1839), reported in Italy over a century ago, but later overlooked; Cerroneuroterus minutulus (Giraud 1859), also reported more than a century ago from Sicily, but later overlooked. Among the inquilines are here listed: Synergus variabilis Mayr 1872, emerged from Janetia cerris (Kollar 1850) galls (Diptera Cecidomyiidae), and found for the first time in the Palaearctic Region as host on Q. suber; Saphonecrus haimi (Mayr 1872) and Saphonecrus barbotini Pujade-Villar & Nieves-Aldrey 1986, are new records for Italy.