Emanuele Mazzoni

Field control of Fusarium ear rot, Ostrinia nubilalis (Hübner), and fumonisins in maize kernels

BACKGROUND A 6 year study was conducted to evaluate the possible support of pesticides in mitigating mycotoxin contamination in maize grown in northern Italy. Different pesticides to control Ostrinia nubilalis (Hübner) (ECB), Fusarium verticillioides (Sacc.) Nirenb. and Aspergillus flavus Link were considered to check their efficacy and the best schedule to reduce fumonisin and aflatoxin contamination. RESULTS Fumonisin B1 (FB1) contamination at harvest has been reduced by ECB control, while the addition of ingredients targeted to F. verticillioides gave a limited advantage, mainly with low FB1 contamination; nevertheless, fusaria control is relevant in high-risk conditions, when FB1 is likely to exceed the legal limit. The combination of fungal and pest control in a single spray at silk browning stage (BBCH 67) is the best way of application. These results are robust because they were obtained in a 6 year trial, with relevant differences in meteorological conditions, ECB and fungal presence and mycotoxin contamination. CONCLUSION Insecticides have been shown to give advantages in their application, while the low FB1 contamination in the final years of the study did not lead to conclusive data on the advantage of adding a fungicide. Chemicals applied did not modify A. flavus incidence or aflatoxin contamination (only detected in trace amounts).

Detecting the presence of target-site resistance to neonicotinoids and pyrethroids in Italian populations of Myzus persicae

BACKGROUND Myzus persicae is a key pest of peach, which in commercial orchards is mainly controlled by chemical treatments. Neonicotinoids represent the main control strategy, but resistance monitoring programmes in Southern Europe have shown the widespread presence of populations highly resistant to this insecticide class in peach orchards. Moreover, in Italy reports of neonicotinoid application failures are increasing. This work describes the status of the main target-site mutations associated with neonicotinoid and pyrethroid resistance in Italian populations collected in 2012. RESULTS R81T mutation linked with neonicotinoid resistance was found in 65% of analysed aphids (35.5% with a homozygous resistant genotype). For the first time, R81T was found in samples collected from herbaceous hosts. Bioassays on a few genotyped populations also revealed the involvement of P450-based metabolic resistance. Only a few individuals without kdr (L1014F) and s-kdr (M918T) target-site mutations were collected. A new single nucleotide polymorphism in the s-kdr locus producing M918L substitution was found. CONCLUSION Target-site resistance to neonicotinoids is common in specialised peach-growing areas, and it is spreading in other Italian regions and on herbaceous hosts. The high frequency of target-site mutations and data obtained from bioassays confirm the presence of multiple resistance mechanisms and suggest the importance of coordinated control strategies.

Differing morphology and ultrastructure of the male copulatory apparatus in species-groups of Anagrus Haliday (Hymenoptera: Mymaridae).

Male genitalia of 13 members of the mymarid wasp genus Anagrus have been studied: Anagrus (Anagrella) mymaricornis (Bakkendorf), Anagrus (Paranagrus) unilinearis Soyka, A. (Anagrus) ustulatus Haliday, A. (A.) erythroneurae Trjapitzin and Chiappini, A. (A.) atomus (Linnaeus), A. (A.) aegyptiacus Soyka, A. (A.) vilis Donev, A. (A.) sensillatus Viggiani and Jesu, A. (A.) breviphragma Soyka, A. (A.) incarnatus Haliday, A. (A.) obscurus Förster sensu Soyka, A. (A.) fennicus Soyka and A. (A.) avalae Soyka. Taxonomically significant differences between subgenera and the atomus and incarnatus species-groups are described. The functional significance of various features, and in particular, the arrangment of sensilla are discussed.

Cytogenetic characterization of the holocentric chromosomes in the aphids Myzus varians and Myzus cerasi

Cytogenetic investigations on the holocentric chromosomes of Myzus varians and Myzus cerasi have been carried out using silver staining and C-banding followed by chromomycin A3 (CMA3) and DAPI staining in order to improve our knowledge of these pest crop species and facilitate their identification. In M. varians C-banding pattern is pecu-: liar of each chromosome pair thus allowing the identification of all homologues and the reconstruction of a reliable karyotype whereas in M. cerasi, C-positive regions result to be limited to both the telomeric regions of the X chromosomes. In both species, silver staining localizes rDNA genes on one telomere of each X chromosome; such telomeres are the unique brightly fluorescent C-positive regions after CMA3 staining, whereas all other heterochro-matic bands result DAPI positive.

Wax Production in Adults of Planthoppers (Homoptera: Fulgoroidea) with Particular Reference to Metcalfa pruinosa (Flatidae)

Abstract Although wax characteristics, wax-producing structures, and their probable functions in planthopper juveniles have been summarized in recent articles, very little has been published regarding the morphology of these structures in adults. In the Nearctic flatid Metcalfa pruinosa (Say), most wax is secreted on the forewings of both sexes and on the anal tube of females. There is also a sparse powdery layer of wax that lightly covers most of the body. Along most of the body surface and forewings many small glandular ring-shaped areas occur, delimiting a pore, from which single thin filaments of wax emerge. Moreover, numerous moniliform glandular pore-plates are randomly scattered on the surface of the forewings. On each plate, 8–50 subcircular pores are symmetrically arranged in one or two lines around a long central sensory hair. An internally hollow cylindrical wax ribbon emerges from each pore. In addition, many prominent glandular plates occupy the ventral surface of the female anal tube. Each plate is nearly circular and is marginally perforated by seven to eight pores from which long, hollow, cylindrical wax tubules emerge. These plates are not present on the anal tube of the male. Although the function of the anal tube wax is unknown, the wax layer that covers the body and forewings may play an important role in protection against abiotic factors and prevent smearing the cuticle with honeydew.

Presence and impact of allelic variations of two alternative s-kdr mutations, M918T and M918L, in the voltage-gated sodium channel of the green peach aphid Myzus persicae

BACKGROUND Pyrethroids have been widely employed in order to control several agricultural pests, including Myzus persicae. Target-site resistance is the main mechanism that confers insensitivity to this class of compounds, and the most common amino acid substitutions are kdr (L1014F) and s-kdr (M918T), but recently another mutation in the s-kdr locus (M918L) has been described in French and Korean populations of M. persicae. RESULTS Molecular analysis of several Italian populations of M. persicae by pyrosequencing revealed the presence of the new s-kdr mutation (M918L) in different forms. It was found in two different nucleotide polymorphisms (a/t or a/c substitution), in heterozygous or homozygous status, and also in combination with the classic kdr and s-kdr. Bioassays on populations carrying the M918L mutation show that it strongly affects pyrethroid efficacy, particularly of type II pyrethroids such as lambda-cyhalothrin, while it has no effect against DDT. CONCLUSION This work provides more information about the new s-kdr M918L mutation in M. persicae, describing a more complicated situation arising from the possible combination with the classic L1014F and M918T. Our data open new questions concerning the origin of these new genotypes with different combinations of target-site mutations, and also their possible influence on control strategies.

A1-3 chromosomal translocations in Italian populations of the peach potato aphid Myzus persicae (Sulzer) not linked to esterase-based insecticide resistance

Esterase-based resistance in the peach-potato aphid, Myzus persicae (Sulzer), is generally due to one of two alternative amplified carboxylesterase genes, E4 or FE4 (fast E4). The E4 amplified form is distributed worldwide and it is correlated with a particular translocation between autosomes 1 and 3, whereas the FE4 form, which has hitherto not been found to be associated with chromosomal rearrangements, is typical of the Mediterranean regions. In this study, we present for the first time cytogenetic and molecular data on some M. persicae parthenogenetic lineages, which clearly show a chromosomal A1-3 translocation associated with esterase FE4 genes and unrelated to high levels of esterase-based resistance.

Karyotype variations in Italian populations of the peach-potato aphid Myzus persicae (Hemiptera: Aphididae)

In this study, we present cytogenetic data regarding 66 Myzus persicae strains collected in different regions of Italy. Together with the most common 2n = 12 karyotype, the results showed different chromosomal rearrangements: 2n = 12 with A1-3 reciprocal translocation, 2n = 13 with A1-3 reciprocal translocation and A3 fission, 2n = 13 with A3 fission, 2n = 13 with A4 fission, 2n = 14 with X and A3 fissions. A 2n = 12-13 chromosomal mosaicism has also been observed. Chromosomal aberrations (and in particular all strains showing A1-3 reciprocal translocation) are especially frequent in strains collected on tobacco plants, and we suggest that a clastogenic effect of nicotine, further benefited by the holocentric nature of aphid chromosomes, could be at the basis of the observed phenomenon.

Use of the synergist piperonyl butoxide can slow the development of alpha-cypermethrin resistance in the whitefly Bemisia tabaci

The development of insecticide resistance in insect pests of crops is a growing threat to sustainable food production, and strategies that slow the development of resistance are therefore urgently required. The insecticide synergist piperonyl butoxide (PBO) inhibits certain insect detoxification systems and so may delay the evolution of metabolic resistance. In the current study we characterized resistance development in the silverleaf whitefly, Bemisia tabaci, after selection with either a neonicotinoid (thiacloprid) or pyrethroid (alpha‐cypermethrin) insecticide alone or in combination with PBO. Resistance development was significantly suppressed (> 60%) in the line selected with alpha‐cypermethrin + PBO compared to the line selected with alpha‐cypermethrin alone. RNA sequencing (RNAseq) analyses revealed an increase in frequency of a knock‐down resistance mutation but no differentially expressed genes were identified that could explain the sensitivity shift. No significant difference was observed in the level of resistance between the thiacloprid and thiacloprid + PBO selected lines, and RNA sequencing (RNAseq) analyses revealed that the cytochrome P450 monooxygenase CYP6CM1, known to metabolize neonicotinoids, was significantly upregulated (>10‐fold) in both lines. The findings of this study demonstrate that PBO used in combination with certain insecticides can suppress the development of resistance in a laboratory setting; however, the mechanism by which PBO supresses resistance development remains unclear.

Genetic variability among different Italian populations of the aphid Myzus persicae

Abstract Aphids life cycle includes cyclical or obligate parthenogenesis, therefore low genetic variation is expected in these insects. Genetic diversity in crop pest aphids such as Myzus persicae, is also influenced by the extensive use of insecticides which favoured the selection of few resistant strains. In the present work, 18 M. persicae populations collected in different Italian regions, were studied by RAPD-PCR (Random Amplified Polymorphic DNA) to assess genetic variability among populations. Twelve different random primers, selected out of 24 previously investigated, were employed for genomic DNA amplification. A total of 150 fragments from the aphid M. persicae populations, and 31 fragments in two outgroups were identified. An UPGMA cluster analysis based on NEI and Lis genetic distance revealed that the M. persicae populations could be divided into two groups: aphids from Central and Southern Italy were generally located in the same cluster, while aphids from Northern Italy were more often located in the other. The presence of a positive correlation between genetic and geographical distance suggests that at least a portion of the interpopulation polymorphism evidenced could be caused by restricted gene flow.