Effectiveness of field-exposed attract-and-kill devices against the adults of Popillia japonica (Coleoptera: Scarabaeidae): a study on duration, form and storage.

BACKGROUND: The Japanese beetle Popillia japonica Newman is an insect pest native to Japan that has spread into North America, the Azores and, recently, into continental Europe. Here, we present a study assessing the effectiveness of a long-lasting insecticide-treated net (LLIN), assembled in semiochemical-baited attract-and-kill devices (A&Ks) as a low environmental impact means to control P. japonica in the field. We compared the attractiveness of three different forms of A&Ks that were left outdoors throughout the summer, and the residence time of P. japonica landing on them. Moreover, we performed a preliminary study testing the effectiveness of new LLINs after storage. Collected data also allowed us to investigate the beetles' diel flight patterns in relation to meteorological conditions. RESULTS: Killing effectiveness of the field-exposed A&Ks declined steadily over the flight season (from 100% to 37.5%) associated with a decrease in residues of α-cypermethrin, the active ingredient in the LLINs. The different A&K forms (pyramidal, octahedral and ellipsoidal) attracted similar numbers of beetles. Individual beetles' residence time ranged from 75 to 95 s and differed slightly between A&K forms. Effectiveness of LLINs decreased by ≈30% after 1 year storage. Based on numbers landing on A&Ks, the beetles' flight activity peaked about 14:30 h and was inversely correlated with relative humidity. CONCLUSION: This study indicates that semiochemical-baited A&Ks are effective for controlling P. japonica in the field. Because of active ingredient decay, the LLINs should be replaced after 30-40 days of field exposure to ensure that the A&Ks remain fully functional. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Genetic variability of Metarhizium isolates from the Ticino Valley Natural Park (Northern Italy) as a possible microbiological resource for the management of Popillia japonica.

The natural occurrence of entomopathogenic fungi (EPF) was investigated along the Ticino River (Ticino River Natural Park, Novara Province, Piedmont, Italy), at the center of the area of the first settlement of the invasive alien pest Popillia japonica. Using Zimmermann's "Galleria bait method", EPF were successfully isolated from 83 out of 155 soil samples from different habitats (perennial, cultivated, or uncultivated meadows, woodlands, and riverbanks). Sequencing of the 5' end of the Translation Elongation Factor 1 alfa (5'-TEF) region allowed the assignment of 94% of the isolates to Metarhizium spp., while 8% and 7% were assigned to Beauveria spp. and Paecilomyces spp., respectively. Four Metarhizium species were identified: Metarhizium robertsii was the most common one (61.5% of the isolates), followed by M. brunneum (24.4%), M. lepidiotae (9%), and M. guizhouense (5.1%). Microsatellite marker analysis of the Metarhizium isolates revealed the presence of 27 different genotypes, i.e., 10 genotypes among M. robertsii, 8 among M. brunneum, 5 among M. lepidiotae, and 4 among M. guizhouense. Metarhizium brunneum appeared to be associated with woodlands and more acid soils, while the other species showed no clear association with a particular habitat. Laboratory virulence tests against P. japonica 3rd instar larvae allowed the identification of one M. robertsii isolate that showed efficacy as high as 80.3%. The importance of this kind of study in the frame of eco-friendly microbiological control is discussed.

Evaluation of Indigenous Entomopathogenic Nematodes as Potential Biocontrol Agents against Popillia japonica (Coleoptera: Scarabaeidae) in Northern Italy.

The natural presence of entomopathogenic nematodes (EPNs) has been investigated in the Piedmont region (Northern Italy) in areas infested by the Japanese beetle Popillia japonica. Thirty-nine out of 155 soil samples (25.2%) were positive for EPNs. Most of the samples contained only steinermatids (92.3%), 5.1% contained heterorhabditids, and one sample (2.6%) contained both genera. All the recovered isolates were identified at species level both morphologically and molecularly. Steinernema carpocapsae was the most abundant and it was mainly distributed in open habitats, such as perennial meadows, uncultivated soils, and cropland, characterized by sandy loam soil texture and acidic pH. Steinernema feltiae has been found associated mainly with closed habitats such as coniferous and deciduous woodland, characterized by sandy loam-texture and extremely acidic soil. The three isolates of Heterorhabditis bacteriophora were collected only in open habitats (perennial meadows and uncultivated fields) characterized by strongly acidic soils with sandy loam texture. The virulence of all EPN natural strains was evaluated by laboratory assays against P. japonica third-instar larvae collected during two different periods of the year (spring, autumn). The results showed that larval mortality was higher for pre-wintering larvae than post-wintering ones. The five more promising EPN isolates were tested in the semi-field assay in which H. bacteriophora natural strains have been shown to be more efficient in controlling P. japonica grubs. All of these results are finally discussed considering the use of these natural EPNs as biological control agents against P. japonica, within an eco-friendly perspective of management.

Long-lasting insecticide-treated nets: A new integrated pest management approach for Popillia japonica (Coleoptera: Scarabaeidae).

The Japanese beetle Popillia japonica Newman is a US and EU quarantine insect pest that has recently invaded northern Italy. Its ability to rapidly spread in new areas makes this insect a threat to agriculture. In the last decades, several trials on biological control of the Japanese beetle by entomopathogenic nematodes and fungi have been carried out with variable efficacy. However, the necessity of an integrated pest management approach to improve control has arisen. Long-lasting insecticide-treated nets (LLINs) have been used to control other agricultural pests with an attract-and-kill strategy. Here, we present results from laboratory evaluation of 2 LLINs, Storanet® (BASF™) and ZeroFly® (Vestergaard™), against P. japonica adults. Both were effective in killing the beetles; however, some differences emerged if different exposure times were compared: ZeroFly® always gave 100% mortality in tests from 5-s to 30-min exposure; Storanet® showed 100% mortality only with 30-min exposure and going down to 89%-99% mortality for 5-s to 15-min exposure. A description of the paralysis process occurring at 5-s exposure is given. Possible field application of LLINs within programs of integrated pest management is discussed. Integr Environ Assess Manag 2019;15:259-265. © 2018 SETAC.

Cuticle-degrading proteases and toxins as virulence markers of Beauveria bassiana (Balsamo) Vuillemin.

Beauveria bassiana is one of the most known entomopathogenic fungal species and its entomopathogenic mechanism involves several bioactive metabolites, mainly cuticle-degrading enzymes and toxic molecules, which are predicted to play a key role as virulence factors. In this study six Beauveria bassiana strains (B 13/I03, B 13/I11, B 13/I49, B 13/I57, B 13/I63, and B 13/I64) were assayed against Tenebrio molitor larvae. Enzymatic activity of total proteases and specifically Pr 1 and Pr 2, as well as the production of toxic compounds were investigated in each fungal strain. Toxins were detected both in vitro-in medium filtrates and mycelia-and in vivo-in Tenebrio molitor larvae infected by the fungal strains tested. B 13/I11 and B 13/I63 strains showed the most significant entomopathogenic activity against Tenebrio molitor larvae (cumulative mortality rate 100 and 97%, respectively; average survival time 5.85 and 6.74 days, respectively). A widely variable and fungal strain-dependent enzymatic activity of total proteases, Pr 1 and Pr 2 was found. Beauvericin, beauvericin A and bassianolide resulted the most prevalent toxins detected in the substrates analyzed. It has been found that an increase of beauvericin content in vivo resulted significantly correlated to a decrease of Tenebrio molitor larvae average survival time in entomopathogenic bioassay (inverse correlation). The involvement of beauvericin in B. bassiana entomopathogenic process is confirmed; in vitro analysis of cuticle degrading proteases activity and toxins production in relation to the methods adopted resulted insufficient for a rapid screening to determine the virulence of B. bassiana strains against Tenebrio molitor larvae.