Giovanni Burgio

Estimation of mortality by entomophages on exotic Harmonia axyridis versus native Adalia bipunctata in semi-field conditions in northern Italy

A semi-field experiment was carried out in two peach orchards in northern Italy to assess mortality due to predators and parasitoids on the exotic coccinellid Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) in comparison with the native coccinellid Adalia bipunctata L. (Coleoptera: Coccinellidae). The experiments were conducted in cages to avoid the possible escape of the exotic ladybird (not yet established in Italy). Two kinds of cage experiments were included: ‘exclusion cages’ (access by walking predators impeded) and ‘free cages’ (walking predators free to enter). The cages, containing all the stages of the two ladybird species, were placed in two localities and left for 24xa0h. All ladybird stages used for the semi-field experiments came from a laboratory rearing. The eggs of H.xa0axyridis experienced less mortality than those of A.xa0bipunctata. The ant workers were the most frequent predators in ‘free cages’ but A.xa0bipunctata cannibalism on eggs was also detected. Larvae of both coccinellid species were predated equally but larval predation of L1 and L2 was higher in comparison to predation of L3 and L4. Pupae and adults of both exotic and native ladybirds were never attacked by predators. Predation on younger larval stages was higher in the ‘free cages’ in comparison with ‘exclusion cages’. No ladybird parasitisation was observed. The ‘free cage’ technique seems to provide a standardised and realistic estimation of predation impact but more studies are needed to evaluate ladybird parasitisation in semi-field conditions.

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

The potential non-target effects of genetically modified crops are some of the more debated topics within applied biotechnologies in agriculture and environmental risk assessment. The objective of the present research was to study the potential Bt-toxin uptake by the non-target herbivore Myzus persicae Sulzer (Hemiptera: Aphididae) feeding on transgenic oilseed rape plants (Brassica napus cv. Westar lines GT 2-4) expressing the Cry1Ac endotoxin. A specific aim was to replicate our previous experiment in controlled laboratory conditions to avoid or minimize the risk of contamination leading to potential false positive results. The toxin levels in vernalized (V) and not-vernalized (not-V) transgenic oilseed rape plants was also monitored to better clarify the role of physiological processes on Bt-toxin expression. Cry1Ac expression in not-V plants (mean concentration±SE=167.8±5.7 μg kg-1 FW) showed a pattern of large variability, in comparison with V plants whose expression (mean concentration±SE=227.7±1.9 μg kg-1 FW) was significantly more stable. Cry1Ac toxin was detected in three aphid samples reared on V plants with a mean toxin concentration±SE of 4.8±0.6 μg Kg-1 FW and in three out of six samples of aphids reared on not-V plants (mean toxin concentration±SE=7.1±1.2 μg kg-1 FW). The mean Bt-toxin concentration of all the positive aphid samples was 5.9±1.0 μg kg-1 FW. Our results confirmed the findings of our previous experiment and highlighted the potential for Cry1Ac toxin uptake by aphids feeding on transgenic oilseed rape plants.

Ostrinia nubilalis (Hb.) (Lep., Pyralidae) on sweet corn: relationship between adults caught in multibaited traps and ear damages

Infestation with Ostrinia nubilalis (Hb.), the European corn borer (ECB) can be detected by using different sampling techniques in the field and statistical models aimed to assess the development time of ECB larvae and crop damage. An appropriate monitoring for this polyphagous species to show a relationship between the kind of sampling or a model and the subsequent damage in a particular crop, is very difficult. Sex pheromone traps, generally, are also not reliable for monitoring ECB. The possibility of employing new types of traps baited with a sex pheromone and a maize kairomone, the phenylacetaldheyde (PAA) (multibaited traps) was investigated. In sweet corn, trapping experiments were conducted over a 2‐year period with two kinds of cone traps (XLa and XLb) set up at the borders of fields (four replicates). ECB attacks of first and second generation larvae were evaluated in the corn ears as a percentage of damage and using a damage index (DI). A correlation was found between the number of females caught per trap and either the percentage of damaged ears (ru2003=u20030.73 for XLa; ru2003=u20030.65 for XLb) and the DI (ru2003=u200370 for XLa; ru2003=u20030.60 for XLb). Conversely, the number of males caught per trap was not correlated with ECB larval damage. A linear model of multiple correlation fitted to the data of simultaneous captures of males and females showed that the coefficients were not higher than simple correlation. The correlation coefficients obtained by fitting a curvilinear response surface were higher (ru2003=u20030.81 for XLa and ru2003=u20030.84 for XLb, respectively, related to percentage of damaged ears; ru2003=u20030.79 for XLa and ru2003=u20030.76 for XLb, respectively, related to DI) thus indicating that the simultaneous counting of males and females in cone traps can be an efficient and simple monitoring tool.

Results of WCR monitoring plans and evaluation of an eradication programme using GIS and Indicator Kriging

This paper presents 3u2003years of GIS‐based monitoring of western corn rootworm (WCR –Diabrotica virgifera virgifera LeConte), a pest which invaded Northern Italy in 1998. The Veneto Region established a regional monitoring network to detect this important quarantine pest and to employ an eradication programme. Data were collected by means of sex pheromone PAL traps and analysed by Indicator Kriging, a geostatistics tool that determines the probability of data values in a given area being greater than a defined threshold value. Geostatistical analysis proved to be effective in mapping the spread of WCR. The temporal sequence of the probability maps was useful in interpreting the expansion of the insect. The detailed description of the pattern of WCR presence in 2006–2008 proves the temporary and local efficacy of the eradication programme carried out up to the 2006 season in Venezia province. An interpretation of the spatial pattern of WCR between the 2006 and 2008 seasons suggests that the pest colonized the eradication area coming from other invasion fronts. The large‐scale pattern of WCR dispersion can be accurately described by the spatial approach, thus optimizing the monitoring and subsequent control of this important insect pest of Northern Italy. Other data analyses, based on stochastic interpolations and a demographical approach are in progress. An interesting perspective would be to build predictive simulation models based on climatic and agronomic data taking into account the spatial representation of WCR patterns.

The Influence of Pine Volatile Compounds on the Olfactory Response by Neodiprion sertifer (Geoffroy) Females

Females of the pine sawfly Neodiprion sertifer (Hymenoptera Diprionidae) usually avoid Pinus pinea trees as host plants. In contrast, this sawfly species is highly attracted by P. sylvestris and P. nigra trees. Here, we investigated which pine volatiles might mediate this behavior by in situ sampling experiments and olfactometer laboratory tests. Volatiles emitted from P. pinea, P. sylvestris, and P. nigra foliage were sampled by solid-phase microextraction (SPME). Analysis of these volatiles by coupled gaschromatography/mass spectrometry revealed that the relative amounts of the compounds emitted by the three species were significantly different. A discriminant analysis showed that the amounts of limonene and myrcene significantly contributed to the species-specific volatile patterns. Pinus pinea emitted higher relative amounts of limonene than the other pine species. Pinus sylvestris emitted the highest relative amounts of myrcene. When testing the response of N. sertifer females to these pine terpenoids in an olfactometer bioassay, a low amount of limonene was attractive, while a repellent effect was evident when higher amounts were used. The sawfly females showed no significant olfactory response to myrcene. These data suggest that low relative amounts of limonene have a significant function in attracting N. sertifer females, while high amounts might contribute to avoidance of a tree.

Sex-Dispersal Differences of Four Phloem-Feeding Vectors and Their Relationship to Wild-Plant Abundance in Vineyard Agroecosystems

ABSTRACT n Sex-dispersal differences of four phloem-feeding vectors and their relationship to wild-plant abundance were analyzed over 2 yr in two vineyard agroecosystems. Adults of Euscelis lineolatus Brullè, Neoaliturus fenestratus (Herrich-Schäffer), Psammotettix alienus (Dahlbom), and Hyalesthes obsoletus Signoret were sampled by using yellow sticky traps at two heights (20 and 150 cm) above the ground in a regular geo-referenced grid. Wild vegetation was surveyed around each sampling point. The most abundant species collected was N. fenestratus, followed by P. alienus, H. obsoletus, and E. lineolatus. Low traps were more effective in capturing the females of N. fenestratus and P. alienus and the males of all of the species, except N. fenestratus at one site. Sex ratio was male-biased for N. fenestratus in both agroecosystems at both trap heights, and only in low traps for H. obsoletus and P. alienus at one site. Insect abundance, temporal population dynamics, and dispersal patterns showed considerable fluctuations according to vineyard agroecosystems and years. In the current study, all of the four phloem-feeding vectors were not found homogeneously in the vineyards, and they were aggregated in correspondence with their herbaceous wild-plant hosts. Insects tended to disperse from the borders toward the vineyard, or vice versa. Colonizing pattern was strongly affected by border vegetation, fallow fields, and vineyard ground-cover vegetation. Different plant communities were identified inside the agroecosystems, and significant correlations among insect and plant-species abundances were recorded. Data highlight the importance of understanding the dispersal patterns of vector species for the application of correct integrated pest-management strategies.

Control of European corn borer in sweet corn by Trichogramma brassicae Bezd. (Hym., Trichogrammatidae)

The biological control effectiveness of the indigenous egg parasitoid Trichogramma brassicae Bezd, reared continuously on Ostrinia nubilalis (Hb.) (ECB) eggs, was tested against ECB in sweet corn in 1991 (2 ha release plot) and 1992 (3.5 ha release plot). T. brassicae was reared for three‐four generations on the factidious host Ephestia kuehniella Zell. and then released on the crop; a 0.5 ha plot situated at 300–400m from the test plots was used as control in both years. Four releases, each totalling 250–300 000 individuals, were made the first year and three at the same rate per ha the second. ECB adult emergence was monitored using traps baited with sex pheromone and phenylacetaldehyde food attractant. The parasitoid activity was monitored via sentinel egg masses following each release. The parasitization rates of the sentinel egg masses was always higher in the release plot vs. control. The parasitization of natural egg masses sampled in both years before harvest was: 12.5 and 10.86% in control as against 87.5 and 68.58% in T. brassicae plots in the respective years. ECB damage was calculated on crop ear samples. The rate (%) of sentinel egg mass predation by wild predators showed no significant difference between control and release plots for both years. The low level of ECB damage to crop ears evinced the good search capacity, parasitization and control effectiveness of T. brassicae.