Compatibility of Entomopathogenic Nematodes with Chemical Insecticides for the Control of Drosophila suzukii (Diptera: Drosophilidae).

The spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a pest that reduces the productivity of small fruits. Entomopathogenic nematodes (EPNs) and chemical insecticides can suppress this pest, but the compatibility of the two approaches together requires further examination. This laboratory study evaluated the compatibility of Steinernema brazilense IBCBn 06, S. carpocapsae IBCBn 02, Heterorhabditis amazonensis IBCBn 24, and H. bacteriophora HB with ten chemical insecticides registered for managing D. suzukii pupae. In the first study, most insecticides at the recommended rate did not reduce the viability (% of living infective juveniles (IJs)) of S. braziliense and both Heterorhabditis species. The viability of S. carpocapsae was lowered by exposure to spinetoram, malathion, abamectin, azadirachtin, deltamethrin, lambda-cyhalothrin, malathion, and spinetoram after 48 h. During infectivity bioassays, phosmet was compatible with all the EPNs, causing minimal changes in infectivity (% pupal mortality) and efficiency relative to EPN-only controls, whereas lambda-cyhalothrin generally reduced infectivity of EPNs on D. suzukii pupae the most, with a 53, 75, 57, and 13% reduction in infectivity efficiency among H. bacteriophora, H. amazonensis, S. carpocapsae, and S. brazilense, respectively. The second study compared pupal mortality caused by the two most compatible nematode species and five insecticides in various combinations. Both Heterorhabditis species caused 78-79% mortality among D. suzukii pupae when used alone, and were tested in combination with spinetoram, malathion, azadirachtin, phosmet, or novaluron at a one-quarter rate. Notably, H. bacteriophora caused 79% mortality on D. suzukii pupae when used alone, and 89% mortality when combined with spinetoram, showing an additive effect. Novaluron drastically reduced the number of progeny IJs when combined with H. amazonensis by 270 IJs and H. bacteriophora by 218. Any adult flies that emerged from EPN-insecticide-treated pupae had a shorter lifespan than from untreated pupae. The combined use of Heterorhabditis and compatible chemical insecticides was promising, except for novaluron.

Pathogenicity and Virulence of Different Concentrations of Brazilian Isolates of Entomopathogenic Nematodes Against Drosophila suzukii.

The invasive pest Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) was recently recorded in Brazil and constitutes a threat to fruit growing, mainly for small, soft fruits. Recent advances in research on ways of controlling D. suzukii involve the use of entomopathogenic nematodes (EPNs). In this context, the objective of this study was to evaluate the pathogenicity and virulence of four isolates in different concentrations against D. suzukii pupae. The EPN isolates used in trials were Steinernema brazilense IBCBn 06, S. carpocapsae IBCBn 02, Heterorhabditis bacteriophora HB, and H. amazonensis IBCBn 24. Both H. amazonensis IBCBn 24 and H. bacteriophora HB were effective in controlling D. suzukii as they caused a mortality rate of 86.25% and 80.0%, and virulence of 549.75 IJs/pupae and 787.75 IJs/pupae in the concentrations of 1800 IJs/ml and 5400 IJs/ml, respectively. The lowest lethal concentrations (LC50) of juveniles were found in host pupae with 771.63 IJs/ml of H. bacteriophora HB and 1115.49 IJs/ml of H. amazonensis IBCBn 24. Results showed that both EPNs, H. amazonensis IBCBn 24 and H. bacteriophora HB, could be promising eco-friendly biological agents to control D. suzukii.

Effectiveness of Steinernema rarum PAM 25 (Rhabditida: Steinernematidae) Against Drosophila suzukii (Diptera: Drosophilidae).

Drosophila suzukii (Matsumura 1931) represents one of the main pests of small fruits. The use of biological agents is very promising for insect control. In the present study, the nematode Steinernema rarum PAM 25 was evaluated for the control of D. suzukii pupae, this species has not been evaluated previously. First, we evaluated the pathogenicity of S. rarum PAM 25 at the concentration of 1,000 infective juveniles (IJs) inoculated into D. suzukii pupae. In the second bioassay, we evaluated the influence of 1,500; 2,000; 2,500; 3,000; 4,000 IJs/ml nematode concentration and temperature on D. suzukii mortality. In the third bioassay, we evaluated the influence of the isolate S. rarum PAM 25 on D. suzukii adult lifespan following pupal infection, using the concentrations with the highest mortality rate of pupae at each temperature as determined in the second experiment. The S. rarum PAM 25 isolate is pathogenic to D. suzukii. The most effective temperature for S. rarum PAM 25 activity was 14°C at a concentration of 4,000 IJs/ml. Adults infected with S. rarum PAM 25 showed a significant reduction in longevity. The results confirmed the potential of S. rarum PAM 25 for the control of D. suzukii.

Effectiveness of Entomopathogenic Nematodes Against Ceratitis capitata (Diptera: Tephritidae) Pupae and Nematode Compatibility with Chemical Insecticides.

The Mediterranean fruit fly Ceratitis capitata (Wiedemann, 1824) (Diptera: Tephritidae) is among the main pests of fruit crops worldwide. Biological control using entomopathogenic nematodes (EPNs) may be an alternative to suppress populations of this pest. Thus, the aim of this study was to evaluate the pathogenicity and virulence of six EPN isolates (Heterorhabditis bacteriophora HB, H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47, and S. brazilense IBCB-n06) against C. capitata pupae. The compatibility of EPNs with different chemical insecticides that are registered for management of C. capitata was also assessed. Isolates of H. bacteriophora HB and S. brazilense IBCB-n06 at a concentration of 1,000 infective juveniles (IJ)/ml proved to be most pathogenic to C. capitata (70 and 80% mortality, respectively). In contrast, the isolates H. amazonensis IBCB-n24, Steinernema carpocapsae IBCB-n02, S. rarum PAM-25, S. glaseri IBCB-n47 provided pupal mortality of less than 60%. Bioassays to determine lethal concentrations indicated that concentrations of 600 IJ/ml (H. bacteriophora HB) and 1,000 IJ/ml (S. brazilense IBCB-n06) showed the highest virulence against C. capitata pupae. In contrast, the highest numbers of IJs emerged at concentrations of 1,200 and 200 IJ/ml. In compatibility bioassays, malathion, spinetoram, phosmet, acetamiprid, and novaluron were considered compatible with and harmless (Class 1) to H. bacteriophora HB and S. brazilense IBCB-n06, according to IOBC/WPRS. This information is important for implementing integrated management programs for C. capitata, using biological control with EPNs, whether alone or in combination with chemical insecticides.

First report of Meloidogyne javanica (Nematoda: Meloidogynidae) infecting Scoparia dulcis, a medicinal plant in Brazil.

Medicinal plants Scoparia dulcis showing symptoms caused by root-knot nematodes were detected in the municipality of Cachoeira do Sul, Rio Grande do Sul State, Brazil. Based on the morphological, esterase phenotypes, and molecular analyses of the mitochondrial DNA region between the cytochome oxidase subunit II and 16S rRNA genes (mtDNA) and species-specific sequence characterized amplified region (SCAR), the causal agent of the observed symptoms was identified as Meloidogyne javanica. Pathogenicity was confirmed by fulfilling a modified version of Koch's postulates. To our knowledge, this is the first report of M. javanica infecting S. dulcis in Brazil.

Entomopathogenic nematodes in agricultural areas in Brazil.

Entomopathogenic nematodes (EPNs) (Steinernematidae and Heterorhabditidae) can control pests due to the mutualistic association with bacteria that kill the host by septicemia and make the environment favorable for EPNs development and reproduction. The diversity of EPNs in Brazilian soils requires further study. The identification of EPNs, adapted to environmental and climatic conditions of cultivated areas is important for sustainable pest suppression in integrated management programs in agricultural areas of Brazil. The objective was to identify EPNs isolated from agricultural soils with annual, fruit and forest crops in Brazil. Soil samples were collected and stored in 250 ml glass vials. The nematodes were isolated from these samples with live bait traps ([Galleria mellonella L. (Lepidoptera: Pyralidae) larvae]. Infective juveniles were collected with White traps and identified by DNA barcoding procedures by sequencing the D2/D3 expansion of the 28S rDNA region by PCR. EPNs identified in agricultural areas in Brazil were Heterorhabditis amazonensis, Metarhabditis rainai, Oscheios tipulae and Steinernema rarum. These species should be considered pest biocontrol agents in Brazilian agricultural areas.

Oat, Wheat, and Sorghum Genotype Reactions to Meloidogyne incognita and Meloidogyne javanica.

Meloidogyne spp. are the most economically important species of plant-pathogenic nematodes. Plant resistance and crop rotation are the main nematode management methods. Thus, the objective was to evaluate the resistance of seven wheat genotypes, five oat genotypes, ten sorghum hybrids, and three sorghum-sudangrass genotypes to Meloidogyne incognita and Meloidogyne javanica. The crops were sowed in pots with an autoclaved substrate. A single plant/pot was left after thinning. The soil was infested with 5,000 eggs of the studied nematodes. Tomato (cv. Rutgers) plants were used as the standard for nematode susceptibility. The evaluations were conducted 60 d after inoculation. Gall and egg-mass indexes were obtained according to a 0-5 scale. Plants with a reproduction factor higher than 1.0 were classified as susceptible (S) and lower than 1.0 as resistant (R). Wheat and oat genotypes did not allow M. incognita and M. javanica reproduction, proving resistance to these organisms. Sorghum genotypes had different reactions to M. incognita and M. javanica. The tomato (cv. Rutgers) plants demonstrated the viability of the nematode inoculum for the three crops. The wheat and oat genotypes and the sorghum hybrids 'BRS-610', 'BRS-800', and '307.343' can be used in crop rotation systems for M. incognita and M. javanica management.