Elsevier

Crop Protection

Volume 146, August 2021, 105651
Crop Protection

Root consumption and damage estimates caused by Phyllophaga capillata and Aegopsis bolboceridus (Coleoptera, Melolonthidae) larvae in soybean and maize in central Brazil

https://doi.org/10.1016/j.cropro.2021.105651Get rights and content

Highlights

  • White grubs are important soil pests in soybean and maize crops in Central Brazil.

  • Root consumption and damage by white grubs in soybean and maize were evaluated.

  • Third-instar larvae can consume 25% of soybean roots and 64% of maize roots.

  • Reduced productivity by white grubs can be 58.62% in soybean and 59.76% in maize.

Abstract

Phyllophaga capillata (Blanchard) and Aegopsis bolboceridus (Thomson) (Coleoptera, Melolonthidae) are important soil pests in soybean and maize crops in central Brazil. The aim of this study was to evaluate the capacity of root consumption by larvae of P. capillata in soybean and A. bolboceridus in maize under controlled conditions and to estimate the damage caused by these species in the field. Root consumption was evaluated in a screened nursery (Brasília/DF, Brazil). Pots with soybean and maize plants were infested separately with different instars and larval densities (0, 1, 2, 4, 6, 8, and 10 larvae/plant) of P. capillata or A. bolboceridus. After 24 h, the weight, area, and length of the roots were evaluated. Damage estimates were calculated for soybean (Brasília/DF, Brazil) and maize (Cabeceiras/GO, Brazil) production in fields with and without severe white grub infestations. In the crop production stage of the experiment, we evaluated the number of plants per linear meter, weight of 1000 grains, productivity, number of pods per plant (soybean), and weight and length of ears (maize). For the two species of white grubs, root consumption was relatively low for first-instar larvae, high for second-instar larvae, and especially high for third-instar larvae. The third instars reduced the root system by approximately 25% in soybean and 64% in maize. We observed that P. capillata and A. bolboceridus damaged all evaluated variables, reducing overall soybean productivity by 58.62% and maize productivity by 59.76%. Our results suggest that it is necessary to monitor the presence of these species by sampling and include them in the integrated pest management programs of these crops in the regions where these species occur.

Introduction

Insect pests are one of the main competitors of human beings for agricultural resources. The losses caused by these organisms have been favored by monocultures in extensive areas, the intensive use of fertilizers (Oerke and Dehne, 2004) and are important factors causing reduced productivity in several cultivated plant species (Cramer, 1967; Pimentel, 1976; Metcalf, 1996; Deutsch et al., 2018; Savary et al., 2019). In Brazil, insect pests are estimated to be responsible for an average annual loss in production of 7.18%. This represents a reduction in approximately 25 million tons of food, fiber, and biofuels. The total annual economic losses reached approximately $17.7 billion in 2014 (Oliveira et al., 2014).

Estimating losses caused by insect pests in agricultural production is necessary for food policy planning. Losses can influence the international prices of agricultural products and provide information to assist the resource allocation for pest and disease research and for decision making on the relative importance of these organisms in agriculture and the environment (Walker, 1983). These estimates are essential for the management of pest species and for evaluating the effectiveness of current plant protection practices (Oerke and Dehne, 2004).

Soybean [Glycine max (L.) Merril] and maize (Zea mays L.) are two of the most important agricultural commodities in Brazil. Together, they represent 89.2% of the grains harvested in 2020/2021. The Cerrado areas in central Brazil (Goiás and Federal District) account for 9.9% of soybean and 10.2% of corn produced in Brazil (CONAB, 2020). Since the 1990s, this region has experienced serious problems with soil pests, mainly due to white grub attacks on both crops (Oliveira et al., 2007, 2008). Advances in agriculture and livestock activities have been quickly evolving in the Cerrado biome since the 1970s (Dias, 2008; Bolfe et al., 2020). These advances have allowed these species to thrive the agricultural environment and become serious pests (Oliveira et al., 2008).

In central Brazil, Phyllophaga capillata (Blanchard) and Aegopsis bolboceridus (Thomson) (Coleoptera, Melolonthidae) are the main soil pests in soybean and maize crops (Oliveira et al., 2007, 2008; Oliveira, 2019). The geographical distribution of both species includes the states of Goiás, Minas Gerais, and the Federal District. Phyllophaga capillata also occurs in Pernambuco and A. bolboceridus is also distributed in the states of Mato Grosso do Sul and Paraná (Oliveira et al., 2007, 2008; Sobral et al., 2018). These species exhibit an annual cycle, with the most active phase synchronized with rain and spring/summer planting. Thus, larvae appear in the field at the beginning of spring, when soybean and maize are sown, and feed continuously on the roots of the plants until the end of summer when they enter diapause (Oliveira and Frizzas, 2013, 2019). Root consumption causes symptoms such as delayed growth, yellowing, and wilting, and can lead to plant death and reduce the total crop stand. These symptoms have direct consequences by reducing crop productivity (Oliveira et al., 2007, 2008). Although they are considered important pests and are difficult to control, no studies exist on the root consumption capacity or estimate of production loss caused by these species.

The study aimed to evaluate the capacity of root consumption by larval P. capillata in soybean and A. bolboceridus in maize under controlled conditions and to estimate the field damage caused by these species in central Brazil.

Section snippets

Estimated root consumption by white grubs in controlled conditions

The root consumption research on larvae (first, second, and third instar) of P. capillata in soybean and A. bolboceridus in maize were conducted in a screened nursery at Embrapa Cerrados (Brasília/Federal District, Brazil) between November 2010 and February 2011.

Larvae were obtained from eggs laid by adults collected in the field. The adult population peak of P. capillata and A. bolboceridus occurs between October and November, immediately after the first rains (Oliveira and Frizzas, 2013, 2019

Results

The first instar larvae of both P. capillata and A. bolboceridus demonstrated low root consumption. The percentage of roots consumed was up to 5.76% in weight, 7.23% in area, and 8.65% in root length. Consumption was only observed when the larval densities were higher than 6 larvae per plant in soybean and 10 larvae per plant in maize (Table 1). For the first instar larvae, the Kendall–Theil regression between larval density and root consumption showed no significant relationship for P.

Discussion

In Brazil, there are at least 1008 species of Melolonthidae with larvae living in the soil (Morón, 2004), most of the larvae feed on plant and animal organic matter and play an important role in ecosystems. Approximately 0.7% of these species feed on roots and can cause significant damage to several crops of economic interest (Oliveira, 2019) and mainly occur in the Midwest and South regions of the country (Santos et al., 1997; Oliveira et al., 1997, 2007, 2008; Santos and Avila, 2009). The

CRediT authorship contribution statement

Charles Martins de Oliveira: Conceptualization, Methodology, Validation, Formal analysis, Investigation, Resources, Writing - original draft, Visualization, Data curation. Marina Regina Frizzas: Conceptualization, Methodology, Writing - review & editing, Visualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

We thank the Embrapa Cerrados employees Sayuri Cristina Santos Takada, Janio Fonseca Silva, and João Alves da Silva for their assistance in conducting these studies. We thank Francisco Luçardo (Fazenda Sementes Primavera) and Vilmar (Fazenda Boa Vista) for allowing the studies to take place on their properties. CMO and MRF are recipients of fellowships (312050/2017-8 and 313952/2018-3) from the National Council for Scientific and Technological Development (CNPq).

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