Lucas Silva de Faria

The distribution of entomopathogenic nematodes (EPNs) in agricultural soils is influenced by complex interactions between edaphic factors and crop management practices, yet these relationships remain poorly understood under tropical conditions. This study evaluated the spatial distribution of EPNs and their association with soil chemical attributes in five crop systems in southeastern Brazil. A total of 82 soil samples were collected and analyzed using insect-baiting techniques and geospatial tools, including kernel density and interpolation methods. EPN occurrence varied across crops and was positively associated with higher concentrations of potassium and iron, while an inverse pattern was observed for copper. These results suggest that micronutrients may indirectly influence EPN distribution by modulating soil microbial communities and plant–soil interactions. Although causal relationships cannot be definitively established, the spatial patterns identified highlight the importance of soil chemical composition in structuring beneficial soil fauna. The integration of geospatial analysis provides a valuable framework for optimizing the application of biological control agents in Integrated Pest Management (IPM) programs. These findings contribute to a better understanding of soil ecological dynamics and support the development of more sustainable agricultural practices.

Summary: The corn leafhopper, Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae), was considered a secondary pest in Brazilian corn crops. However, from 2015 onwards, there was a significant increase in its population and a high incidence of both pale and red wilt diseases. This species transmits these phytopathogens, elevating its status to a major agricultural pest. It has a high dispersal capability, significant reproductive potential, and adapts to adverse conditions, result in damage to crops by inhibiting plant growth and decreasing yield, leading to financial losses for farmers due to challenges in its control. Accordingly, the study aimed to evaluate the virulence of seven isolates of entomopathogenic nematodes belonging to the Heterorhabditis and Steinernema genera against adult D. maidis , as well as the lethal concentration (LC50), compatibility with insecticides and herbicides used in corn cultivation, and the nematode life cycle within the insect. There was no significant difference between the isolates, and they displayed a mortality rate exceeding 50%. The lethal concentration for H. amazonensis MC01 was 75 IJs adult ⁻¹ , and for S. feltiae IBCB 47, it was 25 IJs adult ⁻¹ . No phytosanitary product was found to be harmless to H. amazonensis MC01. The herbicide tembotrione did not affect the viability and infectivity of S. feltiae IBCB 47. The H. amazonensis MC01 and S. feltiae IBCB 47 isolates completed their life cycle in D. maidis adults, with the S. feltiae IBCB 47 isolate showing a longer life cycle than H. amazonensis MC01.

One of the obstacles to the cultivation of coffee trees is the occurrence of the mealybug Planococcus citri. These insects occur in clusters, and can infest branches, leaves, flower buds, and fruits, reaching all the rosettes of the plant and leading to partial drying or total loss of these branches. This study determined the use of low-cost multispectral images to identify coffee plants infested with P. citri. Two study areas were used in the municipality of Coromandel, Minas Gerais, Brazil. One had a high infestation rate of mealybugs and the other had no mealybugs. Another area, in the municipality of Monte Carmelo, Minas Gerais, Brazil, had mealybugs on some plants and not on others. In each study area, 50 plants were randomly sampled, with a minimum distance of 10 m between them. Then, we counted the number of mealybugs in two plagiotropic branches in the middle third portion of the plants. The images were obtained using a drone attached to a Mapir Survey 3W camera at a height of 100 m. The classifications were made using Artificial Neural Networks (ANN), Support Vector Machine (SVM), and Random Forest algorithms. The results confirmed the possibility of distinguishing between healthy and P. citri infested plants using algorithms based on machine learning. The best differentiation of healthy and infested plants was achieved using the Random Forest algorithm in areas with variable infestation (EG = 90% and K = 0.80), followed by SVM (EG = 83.34% and K = 0.67), and ANN (EG = 73.34% and K = 0.47).

The cornstalk borer, Elasmopalpus lignosellus (Lepidoptera: Pyralidae), reduces the productive potential of maize crops and is a difficult pest to manage. A management program using different methods could improve the control of E. lignosellus. Considering the potential of entomopathogenic nematodes (EPN) in reducing insect pest populations in soil, the objective of this study was to evaluate the virulence of these EPN and adjust their concentration for controlling E. lignosellus larvae under laboratory and greenhouse conditions. In the laboratory, the virulence of five EPN populations was tested; then, Heterorhabditis amazonensis MC01 was tested at four concentrations. In the greenhouse, H. amazonensis MC01 was tested at four concentrations and was applied to vessels containing maize plants and six larvae. After five days, mortality was evaluated, and means were compared using Tukey’s test (p-value < 0.05). Heterorhabditis amazonensis MC01 and S. carpocapsae All were equally virulent, reducing the larva population by more than 90%. The concentration of H. amazonensis MC01 that caused the highest mortality of larvae in the laboratory was 182 infective juveniles (IJ) larva^-1. In the greenhouse, the nematode was also considered virulent to E. lignosellus since all concentrations tested caused larval mortality greater than 70%.

Helicoverpa armigera (Hübner) is a polyphagous insect of difficult control and maize is an important host crop of this insect. Entomopathogenic nematodes (EPNs) are control agents of soil pests. This study aimed to verify the action of EPNs for the control of H. armigera pupae. Laboratory and greenhouse bioassays were conducted to select the concentration of nematode application and subsequently field test were conducted. It was obtained that Heterorhabditis amazonensis MC01 at the concentration of 400 infective juveniles (IJs) ·pupa-1 caused the highest mortality in a lower concentration, whereas for H. amazonensis JPM4, concentrations of both 200 and 400 IJs ·pupa-1 were similar causing pupae mortality. In the greenhouse, H. amazonensis MC01 caused mortality reached values of 80% after 10 days, at concentrations of 600 and 800 IJs ·pupa-1. The highest mortality caused by Steinernema carpocapsae was observed at eight days after the juvenile application, at a concentration of 600 IJs ·pupa-1, also reaching 80% mortality. In the field test, both forms of application were considered appropriate for H. amazonensis MC01, causing mortality rates of up to 80%.

O uso de plantas transgênicas com tecnologia Bt para controle de Helicoverpa armigera (Hübner, 1805) (Lepidoptera: Noctuidae) tem sido uma ferramenta adotada dentro do plano de manejo da praga, no entanto, é necessário verificar a presença de populações resistentes do inseto. Teve-se por objetivo avaliar a atratividade, o consumo e a preferência alimentar de lagartas de H. armigera em cultivares de soja Bt. Para a avalição de atratividade e consumo foram liberadas lagartas de H. armigera em placas de Petri contendo quatro discos foliares, sendo dois discos de cultivar Bt e dois discos não-Bt. Na avaliação da preferência alimentar, uma lagarta foi disposta na área central da placa juntamente com dois discos de cada cultivar colocados equidistantes, resultando em doze discos foliares por placa. Em ambos os testes foram observadas lagartas em todas cultivares de soja. No teste de atratividade verificou-se que as cultivares Desafio IPRO e LG 60162 foram consideradas atrativas para H. armigera, enquanto a M 7739 IPRO foi considerada pouco atrativa para alimentação de lagartas de H. armigera. Na avaliação de consumo foliar, as cultivares Desafio IPRO e LG 60162 IPRO foram consideradas atrativas para o consumo. Em relação ao teste de preferência alimentar, a cultivar M 7739 IPRO foi a que teve menor preferência para alimentação de H. armigera. Trabalhos futuros devem ser desenvolvidos a fim de verificar em condições de campo se há preferência alimentar de H. armigera por diferentes cultivares de soja Bt, já que fatores ambientais podem interferir no comportamento do inseto.

Among the main problems for coffee production, it is possible to mention the occurrence of coffee borer, Hypothenemus hampei. In order to seek alternatives to control the pest, the objective of this study was to evaluate the interaction between Beauveria bassiana and Heterorhabditis amazonensis MC01 on the control of coffee borer. Therefore, four experiments were set. In the first, B. bassiana, H. amazonensis MC01 and both entomopathogens associated were applied in bored fruits displaced in vermiculite. In the second experiment, the methodology was similar to the previous one; however, the fruits were immersed in the suspensions. In the third experiment was evaluated the transport of B. bassiana conidia by H. amazonensis, checking the mortality of Tenebrio molitor. In the fourth experiment, the fungus and the nematode were added to Petri dishes containing agar-water. It was found that, when entomopathogens were applied to vermiculite, treatments using B. bassiana and H. amazonensis alone caused the highest mortality of H. hampei adults. For larvae, there was no difference among treatments. The same was observed when the fruits were dipped in the suspensions, with no difference among treatments. As for T. molitor mortality, it was observed that there was no difference among treatments. However when applied in combination, there was a higher mortality caused by B. bassiana compared to H. amazonensis. In the last experiment, juveniles and conidia were found on the opposite side of the dish, and it can be inferred that the presence of conidia was due to transport by infective juveniles. Key words: Biological control; Coffea; Entomopathogenic fungus; Entomopathogenic nematode.

Chemical insecticides are widely used to control soil pests but not always effective. Entomopathogenic nematodes (NEPs) are found in the soil and depend on host insects to complete their life cycle, and therefore have the potential to control soil pests. Thus, we aimed to investigate the possible joint use of these control methods by assessing the compatibility of two nematodes (Heterorhabditis amazonensis GL and Heterorhabditis amazonensis MC01) with five crop protection products used for maize seed treatment (Maxim®, Cruiser 350 FS®, Fortenza 600 FS®, Avicta 500 FS®, and Amulet®), as well as one neem-based product (NeenMax®). The experimental design was completely randomized with five replicates, six treatments, and one control, in which only distilled water was added to nematode suspension. Each replicate consisted of a test tube containing 1 mL suspension with 2,000 infective juveniles (IJs) and 1 mL of diluted product, following the manufacturer's recommendation. The evaluated parameters were viability, infectivity on Tenebrio molitor larvae and IJs production after exposure to products. Both nematodes were compatible with NeenMax® and Fortenza 600 FS® since they did not differ from the control and were classified as innocuous. Cruiser 350 FS ® was also compatible with the nematodes since the effect value of the product was lower than 30%. Amulet® was classified as slightly noxious, reducing H. amazonensis MC01 and H. amazonensis GL infectivity by 17.5% and 28.5%, and production by 18.2% and 22.3%, respectively. Despite not having reduced viability, Avicta 500 FS® and Maxim® were considered harmful. This is because Avicta 500 FS® and Maxim® reduced productivity by 70.0% and 72.5% and production by 66.1% and 65.4% for H. amazonensis MC01, respectively. For H. amazonensis MC01, both Avicta 500 FS® and Maxim® reduced infectivity by 76.19%, and production by 63.7% and 62.3%, respectively.

Stenoma catenifer is considered the main pest of avocado, making impossible to commercialize the infested fruits. This study was conducted with the objective of evaluating the potential of Heterorhabditis amazonensis MC01 in the field control of avocado borer, as well as the nematode release method. Two treatments were tested, namely: release of dead Tenebrio molitor infected with the nematode and hydraulic nematode spraying; hydraulic application of chemical insecticides was used as a control. The experiment was set up in a randomized complete block design with 15 replicates. The concentration of suspension distribution was 5,500 infective juveniles per m². At the experimental area traps with sex pheromone were installed to capture adult males. The number of borer fruits was evaluated in the two central plants of each plot, sampling 4 fruits per plant. There was a reduction in the percentage of borer fruits from 15 days of application for all control methods. After the release of nematodes, the adult population was similar to the control, and it can be inferred that, even without chemical control, there was no increase in the number of adults. Thus, H. amazonensis was considered promising under field conditions, reducing the populations of S. catenifer, in all release methods.

Entomopathogenic nematodes are effective in controlling soil insects and they are used in agricultural systems. The virulence of entomopathogenic nematodes on crickets (Gryllus L.) (Orthoptera: Gryllidae) was evaluated under different conditions in order to select populations for application in the field. Virulence tests with Heterorhabditis amazonensis RSC05, H. amazonensis MC01, Steinernema carpocapsae All (Weiser) and H. amazonensis GL were performed. Evaluations were then made of the concentrations of infective juveniles (100, 200, 400 and 600 infective juveniles per insect); feeding preference with or without choice; and field tests using traps to evaluate insect sampling. All isolates were found to cause mortality in Gryllus sp., and H. amazonensis MC01 and S. carpocapsae All were selected; an increase in concentration resulted in increased insect mortality. Regarding the feeding preference tests, after 16 h there was no feeding in any of the treatments. In treatments with a chance of choice, it was verified that the crickets fed, independently of the presence of the nematodes. In the field tests, 19 live crickets were found in the traps, and, after application of entomopathogenic nematodes in aqueous suspension, 2 live crickets were found. Results suggested that H. amazonensis MC01 was promising in the control of Gryllus sp. under the tested conditions.