Phytophagous insects in cotton crop residues during the fallow period in the state of Mato Grosso do Sul, Brazil Rafael Azevedo da Silva(1), Paulo Eduardo Degrande(2), Carlos Eduardo Carducci Gomes(2), Ellen Patricia de Souza(2) and Mateus Fuchs Leal(2) (1)Instituto Federal de Mato Grosso do Sul, Campus Nova Andradina, Rodovia MS-473, Km 23, s/no, Fazenda Santa Bárbara, CEP 79750-000 Nova Andradina, MS, Brazil. E-mail: [email protected] (2)Universidade Federal da Grande Dourados, Faculdade de Ciências Agrárias, Rodovia Dourados/Itahum, Km 12, Caixa Postal 533, CEP 79804-970 Dourados, MS, Brazil. E-mail: [email protected], [email protected], [email protected], [email protected] Abstract – The objective of this work was to analyze the faunistic composition of the insect pests that occur during the fallow period in cotton (Gossypium hirsutum) crop residues in the state of Mato Grosso do Sul, Brazil. The study sites were the municipalities of Alcinópolis, Chapadão do Sul, Costa Rica, Aral Moreira, Dourados, and Sidrolândia. A sampling design with two replicates per municipality was used. Each replicate comprised 100 random points, and each point corresponded to a cotton plant that was entirely inspected, to count the insect pests on it. The obtained fauna was analyzed and a rarefaction curve of the species was generated. During the evaluation period, a total of 23 species were recorded in the cotton crop residue, and the most frequent and abundant were Bemisia tabaci, Aphis gossypii, Frankliniella schultzei, and Anthonomus grandis. The caterpillars were predominantly found on the non-Bt cotton crops in Dourados, and Chapadão do Sul was the municipality that exhibited the greatest species diversity. Despite being mandatory, the destruction of cotton stalks during the fallow period was not able to completely eliminate the insect pests during the study period; among these insect pests, A. grandis stands out, a species that affects the dynamics of cotton pest control. Index terms: Anthonomus grandis, Gossypium hirsutum, host plant, legislation, regrowth. Insetos fitófagos em restos culturais de algodoeiro durante vazio sanitário em Mato Grosso do Sul Resumo – O objetivo deste trabalho foi analisar a composição faunística de insetos-pragas que ocorrem durante o período de vazio sanitário em restos culturais de algodoeiro (Gossypium hirsutum) em Mato Grosso do Sul. Foram estudados os municípios de Alcinópolis, Chapadão do Sul, Costa Rica, Aral Moreira, Dourados e Sidrolândia. Utilizou-se um delineamento com duas repetições por município. Cada repetição foi composta por cem pontos aleatórios, e cada ponto correspondia a uma planta de algodão totalmente vistoriada, para contabilizar os insetos-pragas sobre ela. Realizaram-se a análise faunística e a curva de rarefação das espécies. Durante o período de avaliação, foi observado um total de 23 espécies em restos culturais de algodoeiro, sendo as com maior frequência e abundância Bemisia tabaci, Aphis gossypii, Frankliniella schultzei e Anthonomus grandis. O complexo de lagartas predominou sobre a variedade de algodoeiro não Bt em Dourados, e Chapadão do Sul foi o município com maior diversidade de espécies. Apesar de obrigatória, a destruição de soqueiras no vazio sanitário não conseguiu eliminar totalmente os insetos-pragas no ano deste estudo; dentre estes insetos-pragas, destaca-se A. grandis, que influencia a dinâmica do controle de pragas no algodoeiro. Termos para indexação: Anthonomus grandis, Gossypium hirsutum, hospedeiro, legislação, rebrota. Introduction 123,000 ha, representing only 8.8% of the total cotton cultivation area in the country. However, by 2017, it had In the early 1990s, the cotton cultivation and increased to 682,600 ha, corresponding to 72.7% of the production areas in Brazil were concentrated in the Southern, Southeastern, and Northeastern regions total cotton cultivation area, with an average cotton -1 (Stadler & Buteler, 2007). After this period, the yield of 4,046 kg ha (Acompanhamento…, 2017). cultivation of this fibrous plant shifted significantly to The observed increase in cotton cultivation area the Cerrado areas, in Midwestern region of Brazil. In was mainly due to the attacks by the boll weevils – 1990, this region had a total cotton cultivation area of Anthonomus grandis Boheman, 1843 (Coleoptera: This is an open-access article distributed under the Pesq. agropec. bras., Brasília, v.53, n.8, p.875-884, Aug. 2018 Creative Commons Attribution 4.0 International License DOI: 10.1590/S0100-204X2018000800001 876 R.A. da Silva et al. Curculionidae) before 1995. This species, in less than used diminishes, since the duration of application of five years of its advent, that happened in 1983, infested the herbicides is prolonged. This sometimes allows the more than 90% of the total cotton cultivation area in regrowth of plants and reappearance of insect pests in Brazil (Stadler & Buteler, 2007). One of the strategies most of the cultivated areas (Greenberg et al., 2007a, for the management of boll weevil populations is the 2007b). destruction of the cotton stalks during the fallow In addition to the presence of volunteer plants, period; it is considered useful. If this is not carried out, the continuous use of the same technologies in the under ideal environmental conditions, cotton plants extensive contiguous areas that are always cultivated can regrow, and consequently produce reproductive with a low diversity of species (corn, soybean, and structures, such as buds, flowers, and fruits, therefore, cotton) allows the formation of green bridges between hosting the species A. grandis during the off-season crops. The occasional association of green bridges with (Lu et al., 2010; Bianchini & Borges, 2013; Grigolli the misuse of chemicals has made agroecosystems et al., 2015). progressively susceptible to diseases and insect pests Destruction of the cotton stalks during the fallow (Silva & Ramalho, 2013). period is a prophylactic measure that must be done In Brazil, there are no studies on the composition efficiently soon after the harvest to avoid possible of insect pests during the fallow period in the cotton regrowth of the host plants. Furthermore, this is crop residues. Most of the studies deal with the a mandatory practice in the Brazilian territory considered most efficient cotton stalk destruction (Bianchini & Borges, 2013). methods (Bianchini & Borges, 2013); the crop residue In addition to the boll weevil, other insect pests destruction methods and survival of the boll weevil that thrive and feed on cotton crops include: Aphis (Ribeiro et al., 2015); and population dynamics of the gossypii (Hemiptera: Aphididae), Bemisia tabaci boll weevil (Grigolli et al., 2015; Pires et al., 2017) (Hemiptera: Aleyrodidae), Eutinobothrus brasiliensis (Coleoptera: Curculionidae), Pectinophora gossypiella and A. gossypii (Izeppi et al., 2011) in the crop residue (Lepidoptera: Gelechiidae), Chloridea virescens during the off-season. (Lepidoptera: Noctuidae), and caterpillar species The objective of this work was to analyze the of the genus Spodoptera (Lepidoptera: Noctuidae). faunistic composition of the insect pests that occur These species pose a risk not only to the successor during the fallow period in cotton crop residues in the crops, but also to the next set of cotton crops (Miranda, state of Mato Grosso do Sul, Brazil. 2010; Izeppi et al., 2011; Ribeiro et al., 2015). In 2013, Helicoverpa armigera was detected in Brazil and Materials and Methods added in the list. The study was conducted in the state of Mato Grosso The most commonly used method for the destruction of the cotton stalks in the Brazilian do Sul (Figure 1), in the municipalities of Alcinópolis, Cerrado regions involves two stages. First, the plants Chapadão do Sul, and Costa Rica in the north, and Aral are cut with a rotary cutter, and then they are destroyed Moreira, Dourados, and Sidrolândia in the south. These efficiently by means of mechanical action or the use of municipalities comprised 7.13, 22.64, 60.26, 0.62, herbicides (Bianchini & Borges, 2013). This practice 0.005, and 4.6% of the cultivation areas, respectively, is mandatory through the joint resolution of SEPAF/ representing 95.2% of the total cotton cultivation area IAGRO No. 1/2015 in the Cerrado regions of the states in the state. of Mato Grosso, Mato Grosso do Sul, and Goiás (Mato The areas that were considered for the present study Grosso do Sul, 2015). Moreover, this method exhibits cultivated cotton crops and showed cotton stalks (part of high efficiency and can be rapidly executed on small the stem that remains after the cotton plant destruction), crops and hydrated plants. However, the cotton crop and also exhibited their regrowth (regrowth of plants cultivation conditions in the Cerrado regions are after destruction of the cotton stalks). Moreover, the different. Here the plants are cultivated predominantly region showed volunteers plants (plants from the cotton in areas that are subjected to water stress and in large seeds that were not harvested, and had eventually properties. Therefore, the effectiveness of the herbicides germinated) (Miranda & Rodrigues, 2016). Pesq. agropec. bras., Brasília, v.53, n.8, p.875-884, Aug. 2018 DOI: 10.1590/S0100-204X2018000800001 Phytophagous insects in cotton crop residues during the fallow period 877 Figure 1. Map of the study areas in the state of Mato Grosso do Sul, Brazil, with the number of experimental replicates in 2015. The municipalities identified in the numerical sequence are: 1, Alcinópolis; 2, Costa Rica; 3, Chapadão do Sul; 4, Aral Moreira; 5, Dourados; and 6, Sidrolândia. Pesq. agropec. bras., Brasília, v.53, n.8, p.875-884, Aug. 2018 DOI: 10.1590/S0100-204X2018000800001 878 R.A. da Silva et al. The evaluations were carried out at 14-day intervals. Schreb.) as a cover plant. During the first of the two In the south of the state, the study period was from replicates in Sidrolândia, the mechanical destruction of June 1st to September 31, 2015. In the north, the period the crop residue was not performed.