Alberto Lanzoni

Biological traits and life table of the exotic Harmonia axyridis compared with Hippodamia variegata, and Adalia bipunctata (Col., Coccinellidae)

Abstract:  As part of an environmental risk assessment study of exotic natural enemies used in inundative biological control, life‐history characteristics of Harmonia axyridis (Pallas), Hippodamia variegata (Goeze) and Adalia bipunctata (L.) (Col., Coccinellidae) were quantified under laboratory conditions at 25°C on Myzus persicae (Sulzer) as prey. Comparative studies showed significant differences among pre‐adult development times: H. axyridis developed slower ( = 19.8 days) than H. variegata ( = 18.1 days) and A. bipunctata ( = 18.4 days). Differences were also evident in the duration of egg, larval and pupal stages. No measurable differences among the three species were found for fecundity, oviposition rate and adult longevity. Harmonia axyridis exhibited the longest pre‐oviposition ( = 7.4 days) and interoviposition ( = 3.6 days) periods and the shortest oviposition period ( = 13.7 days). The Bieri model was used to describe age‐specific fecundity for the three species of coccinellids. The intrinsic rate of increase (rm), net reproductive rate (R0) and mean generation time (T) were higher for H. variegata (rm = 0.114, R0 = 52.75, T = 41.88 days) than for H. axyridis (rm = 0.089, R0 = 26.27, T = 38.81 days) or A. bipunctata (rm = 0.081, R0 = 18.49, T = 40.06 days). Our findings show that the biological traits of H. axyridis do not seem to be factors that may contribute to the invasiveness of this coccinellid.

Overwintering, phenology and fecundity of Harmonia axyridis in comparison with native coccinellid species in Italy

Classical biological control is generallyunderstood as an environmentally safe practiceof insect pest management. However, questionshave been raised about possible negativeeffects for native species. As part of a riskassessment study a semi-field trial was carriedout in northern Italy in order to compare theoverwintering of the native species Propylea quatuordecimpunctata (L.) and Adalia bipunctata (L.) (Coleoptera:Coccinellidae) with the exotic Harmoniaaxyridis (Pallas) (Coleoptera: Coccinellidae).All the experiments were carried out from April1998 to April 2001. Harmonia axyridis wasable to overwinter successfully in northernItaly. Fecundity, oviposition rate, longevityand rate of increase of overwintering femaleswere calculated and the phenology of the threespecies was studied. Harmonia axyridisoverwintering mortality (31.9%) was lower incomparison with mortality of native species(68.9% for P. quatuordecimpunctata and61.3% for A. bipunctata). As aconsequence, post-overwintering rate ofincrease of the exotic species was higher.Longevity of overwintered females was similaramong the species. Mean fecundity of H. axyridis (783.8 eggs per female) was slightlyhigher than A. bipunctata (720.2 eggs perfemale), and much higher than P. quatuordecimpunctata (193.7 eggs per female). H. axyridis and A. bipunctatacompleted four generations and P. quatuordecimpunctata three generations in a year. The results show that H. axyridisappears to posses a high potential for establishment in Italy.

Comparative Life History of Liriomyza trifolii and Liriomyza huidobrensis (Diptera: Agromyzidae) on Beans: Effect of Temperature on Development

Abstract The influence of four constant temperatures (15, 20, 25, and 30°C) on development time and survivorship of Liriomyza trifolii (Burgess) and Liriomyza huidobrensis (Blanchard) was studied in laboratory experiments. L. huidobrensis required more time for embryonic development at 25 and 30°C, and less time at 15°C, compared with L. trifolii; at 20°C there were no differences between the two species. Larval development time for L. huidobrensis was longer than for L. trifolii at 20, 25, and 30°C. At 15°C no differences were detected. Pupal development of L. huidobrensis was always faster at 15, 20, and 25°C than that of L. trifolii. Total preimaginal development time was quicker at 15 and 20°C in L. huidobrensis than in L. trifolii; at 25°C no significant differences were found. Highest survival of L. trifolii (68%) occurred at 20°C, while that of L. huidobrensis (61%) occurred at 15°C. At 30°C no adults of L. huidobrensis emerged. The estimated lower threshold temperatures for egg, larva, pupa and total development of L. huidobrensis ranged between 7.3 and 8.1°C, and they were always lower than L. trifolii thresholds, which ranged between 9.9 and 10.7°C. The Logan model was used to describe the relationship between development rate and temperature. The quantification of development times presented in this study, combined with fecundity under different temperatures, could be incorporated into a phenological model that will aid in predicting population charges of leafminers.

Evaluation of Bt-toxin uptake by the non-target herbivore, Myzus persicae (Hemiptera: Aphididae), feeding on transgenic oilseed rape.

As consequence of the concern about the biosafety of genetically modified plants, biological and ecological studies are considered crucial for environmental risk assessment. Laboratory experiments were carried out in order to evaluate the transfer of the Cry1Ac Bt-toxin from a transgenic Bt-oilseed rape to a non-target pest, Myzus persicae Sulzer. Cry1Ac protein levels in plants and aphids were determined using a double sandwich enzyme-linked immunosorbent assay. Phloem sap from (Bt+) and (Bt-) oilseed rape plants was collected from leaves using a standard method of extraction in an EDTA buffer. Bt-toxin was present in phloem sap, with a mean concentration of 2.7 +/- 1.46 ppb, corresponding to a 24-fold lower level than in oilseed rape leaves. Toxin was also detected in aphid samples, with a mean concentration in the positive samples of 2.0 +/- 0.8 ppb. The evidence that Bt-toxin remains in herbivores, in this case an aphid, could be useful to clarify functional aspects linked to possible consequences of Bt-crops on food chains involving herbivore-natural enemy trophic systems. Further studies are needed in order to improve the knowledge on the functional aspects linked to the transfer of the Cry1Ac Bt-toxin from GM-oilseed rape to aphids and their possible consequence.

Parasitic hymenoptera fauna on agromyzidae (diptera) colonizing weeds in ecological compensation areas in northern Italian agroecosystems.

Abstract Parasitoids (Hymenoptera) associated with agromyzid leafminers (Diptera: Agromyzidae) were studied in three rural farms located in northern Italy. The parasitoids were reared from mined foliage of weeds growing in field margins. We reared 998 Hymenoptera specimens, representing five families, 23 genera, and 53 species, from leafminers infesting weeds. Eulophidae was the most abundant family (67.64%), followed by Braconidae (28.86%), Eucoilinae (1.40%), Tetracampidae (1.40%), and Pteromalidae (0.7%). Braconids was the most species rich family, accounting for 28 species; eulophids were represented by 19 species, pteromalids by four species, and eucoilins and tetracampids by one species each. The dominant parasitoid was the eulophid Pediobius metallicus (Nees), representing 18.17% of the total, followed by Diglyphus isaea (Walker) (12.73%), and Neochrysocharis formosa (Westwood) (10.82%). The most abundant braconid parasitoid was Dacnusa maculipes Thomson (9.62%). More than 80% of parasitoids were recovered from 10 plant species: Cirsium arvense (L.) Scopoli, Plantago lanceolata L., Sonchus asper (L.) Hill, Papaver rhoeas L., Picris echioides L., Lactuca serriola L., Myagrum perfoliatum L., Ranunculus velutinus Tenore, Arctium lappa L., and Medicago sativa L. The retention and the management of wild plants within field margins can be crucial tools to enhance the populations of biological control agents of agromyzids and to conserve rare parasitic wasp species.

Spatial Patterns and Sampling Plan for Liriomyza huidobrensis (Diptera: Agromyzidae) and Related Parasitoids on Lettuce

Abstract Field experiments were carried out in 2000 and 2001 in northern Italy, with the aim of developing a composite sampling strategy for estimating populations of Liriomyza huidobrensis (Blanchard) larvae and mines on lettuce. Larval parasitoid populations also were sampled to estimate the contribution of these beneficials to pest control. Covariance analysis and parallelism test indicated that there were not significant differences in the coefficient of Taylor’s power law between treatments (untreated versus treated) and between seasons (2000 versus 2001) for both pest and parasitoid stages. The slope of each regression was significantly >1 for L. huidobrensis mines and larvae, and endoparasitoid and ectoparasitoid larvae, indicating a clumped distribution of both pest and parasitoids. Constant precision level stoplines for mines and larvae of L. huidobrensis and for endoparasitoid and ectoparasitoid larvae were calculated, by using the common a and b derived from Taylor’s power law. Wilson and Room binomial sampling was used to estimate the mean number of L. huidobrensis mines or live larvae from the ratio of leaves with mines. In this way, it is possible to estimate the mean density of L. huidobrensis by counting the leaves with mines, an index parameter easy to obtain in field sampling. Validation of the presence-absence sampling plan by using field data collected in 2002 and 2003 seasons, showed that the Wilson and Room model fits very well empirical data. Statistical analysis does not show any significant difference between observed and predicted data.

Faunistic Study of the Agromyzidae (Diptera) on Weeds of Marginal Areas in Northern Italy Agroecosystems

Abstract Extensive surveys of weedy plant species among hedgerows of different complexity and floristical composition were conducted with the aim to evaluate the role of weeds as reservoirs of agromyzids and to study the trophic relationships between these Diptera and noncrop plants. Field samplings were carried out weekly collecting foliage infested by leafminers from the representative weedy plants in three sites located in Bologna province, Italy. During 1998–1999, a total of 646 agromyzid specimens were reared, representing eight genera and 24 species. The most abundant species were Chromatomyia horticola (Goureau), Phytomyza lappae Goureau, Phytomyza ranunculi Schrank, Phytomyza plantaginis Robineau-Desvoidy, Liriomyza trifolii (Burgess), and Ophiomyia pulicaria (Meigen). C. horticola was the dominant species accounting for 35.76% of adults reared. Agromyzids mined 25 plant species belonging to nine families. The Asteraceae, in particular Cirsium arvense (L.) Scopoli and Sonchus asper (L.) Hill, were the most important sources of leafminers considering both species richness and population densities. Shannon–Weaver (H′), Simpson (D), and Berger–Parker (d) indices all pointed out that agromyzid species diversity was higher in the site characterized by the highest floristic richness, the highest complexity of ecological net and nonintensive agriculture. Most of the weeds sampled proved to be reservoirs for noneconomically important agromyzids in open-field crops in Italy.

Area‐wide monitoring of potato tuberworm (Phthorimaea operculella) by pheromone trapping in Northern Italy: phenology, spatial distribution and relationships between catches and tuber damage

The potato tuberworm (PTW) Phthorimaea operculella (Zeller) (Lepidoptera: Gelechiidae) is key pest of potato in tropical and subtropical regions. From 2002 onward, PTW has emerged as a problem in the Bologna province, the main potato production area in Northern Italy. Field investigations were performed to study the temporal and spatial dynamics of PTW. Adult moths were monitored using pheromone‐baited traps over 3 years (2009–2011). Traps were georeferenced and catches were analyzed by geostatistical maps. Each year, the percentage of damaged tubers at harvest was assessed. Pheromone trapping, integrated with temperature‐dependent developmental times, showed that PTW completed two generations throughout the potato‐growing season; the remaining generations developed in the noncrop season. Maps showed a clumped distribution of PTW at the landscape scale. The hot spots of infestation corresponded to the areas most intensively cropped with potato. Trap catches from hilling to harvesting were linearly and positively correlated with the percentage of damage in 2 out of 3 years and in the pooled data set. The present study demonstrated the widening of PTW areal to Northern Italy. In this area, georeferenced pheromone traps were validated as a useful monitoring technique for describing the phenology and distribution of PTW, thus providing crucial knowledge for the rational management of this pest.

Interactions between the Multicolored Asian Lady Beetle Harmonia axyridis and the Parasitoid Dinocampus coccinellae

Harmonia axyridis (Pallas) has been introduced either intentionally or accidentally in different areas outside its native range, where it is often regarded as invasive. Dinocampus coccinellae (Schrank) has been recorded to parasitize H. axyridis in the field, both in the native and introduced areas, Italy included. The percent of parasitism found in our field investigation was low (four percent). The effect of exposure time of H. axyridis to D. coccinellae and the impact of parasitization on host longevity, oviposition capacity and egg fertility were evaluated in the laboratory. The acceptance and suitability of H. axyridis as host for D. coccinellae were then studied, in comparison with the native coccinellid Adalia bipunctata (L.), which shares the same ecological niche. The effects of parasitization on female longevity and reproduction capacity in the exotic vs. the indigenous lady beetle were also investigated. The overall results showed that D. coccinellae negatively affected the fitness of H. axyridis, more than that of A. bipunctata. The parasitoid may thus play a marginal role in controlling the populations of the Asian lady beetle, without representing a threat to A. bipunctata.

Lethal and Sub-lethal Effects of Four Insecticides on the Aphidophagous Coccinellid Adalia bipunctata (Coleoptera: Coccinellidae)

Abstract Conventional insecticide assays, which measure the effects of insecticide exposure on short-term mortality, overlook important traits, including persistence of toxicity or sub-lethal effects. Therefore, such approaches are especially inadequate for prediction of the overall impact of insecticides on beneficial arthropods. In this study, the side effects of four modern insecticides (chlorantraniliprole, emamectin benzoate, spinosad, and spirotetramat) on Adalia bipunctata (L.) (Coleoptera: Coccinellidae) were evaluated under laboratory conditions by exposition on treated potted plants. In addition to investigation of acute toxicity and persistence of harmful activity in both larvae and adults of A. bipunctata, demographic parameters were evaluated, to provide a comprehensive picture of the nontarget effects of these products. Field doses of the four insecticides caused detrimental effects to A. bipunctata; but in different ways. Overall, spinosad showed the best toxicological profile among the products tested. Emamectin benzoate could be considered a low-risk insecticide, but had high persistence. Chlorantraniliprole exhibited lethal effects on early instar larvae and adults, along with a long-lasting activity, instead spirotetramat showed a low impact on larval and adult mortality and can be considered a short-lived insecticide. However, demographic analysis demonstrated that chlorantraniliprole and spirotetramat caused sub-lethal effects. Our findings highlight that sole assessment of mortality can lead to underestimation of the full impact of pesticides on nontarget insects. Demographic analysis was demonstrated to be a sensitive method for detection of the sub-lethal effects of insecticides on A. bipunctata, and this approach should be considered for evaluation of insecticide selectivity.