ABSTRACT Synthetic insecticides used in the management of the mealybug Diaspis echinocacti (Bouché, 1833) (Hemiptera: Diaspididae) can contaminate co-products from this plant. The use of Agave extracts and/or mineral oil is a sustainable alternative to reduce the residual effect of these chemicals in the palm production chain. The objective here was to determine the effectiveness of Agave genotype extracts applied alone or mixed with mineral oil against the cactus scale mealybug D. echinocacti. Two experiments were carried out to achieve this goal. The first one aimed to select the most promising Agave genotype extract concentration (CL80) to kill 80% of the first instar mobile nymphs of D. echinocacti (Experiment 1), and the second to determine the effectiveness of the selected extract against nymphs, pupae, and adults of different ages of this mealybug in laboratory and greenhouse (Experiment 2). The extract of the genotype Agave fourcroydes cv. Cabinho with lethal concentration (LC80) of 10.9 mL/10 mL is the most efficient in causing mortality of D. echinocacti. The lethal concentration of the A. fourcroydes cv. Cabinho killed 80% of the first instar motile nymphs and more than 74% of the nymphs, pupae, and adults of different ages of D. echinocacti in the laboratory and greenhouse followed by Agave sisalana cv. Tatuí 3. Furthermore, the mortality of this scale mealybug was higher with applications of mineral oil (Assist), alone or mixed with sisal extracts.

ABSTRACT Caligo teucer (Linnaeus, 1758) is widely distributed in Argentina, Bolivia, Brazil and Ecuador. The objective was to study biological aspects of Caligo teucer japetus Stichel, 1903 with banana leaves, Musa sapientium L. (Zingiberales: Musaceae), in the butterfly garden, under environmental conditions, and in the laboratory of biological control of insects at the Universidade Federal de Viçosa in Viçosa, Minas Gerais state, Brazil at 24 ± 2 oC, 68 ± 10% relative humidity and 12 hours photophase. The duration of the egg incubation, larvae, pupa and egg to adult periods of C. teucer japetus were, respectively, 11.8 ± 0.1; 53.9 ± 0.9; 17.9 ± 0.3 and 82.6 ± 1.0 days for females, and 11.8 ± 0.1; 50.3 ± 0.6; 18.4 ± 0.3 and 79.4 ± 0.6 days for males in cages in the laboratory. The longevity of C. teucer japetus adults was 26.0 ± 10.4 and 47.5 ± 8.7 for females and 24.7 ± 3.5 and 35.4 ± 15.7 for males in the butterfly garden and in laboratory cages, respectively. The high survival and the relatively short period of development of its immature stages confirm that banana leaves are an adequate food substrate for the development and survival of Caligo teucer japetus.

Resumo: O objetivo deste trabalho foi determinar os parâmetros biológicos e morfológicos de Dysdercus maurus alimentado com sementes de algodão (Gossypium hirsutum) com alto ou baixo teor de óleo, bem como identificar genótipos a serem usados em programas de melhoramento como fontes de resistência a esse percevejo. O desenvolvimento, a sobrevivência e a reprodução do percevejo manchador de algodão foram determinados em delineamento experimental inteiramente casualizado. Os tratamentos consistiram de ninfas do inseto alimentadas com sementes de algodão da linhagem genética CNPA 2001-5581 (alto teor de óleo) ou CNPA 2001-5087 (baixo teor). Foram determinados a sobrevivência, o peso e os parâmetros morfológicos do percevejo. A sobrevivência das ninfas de segundo e terceiro ínstars e do estágio total de ninfas de D. maurus foi menor com sementes de algodão com baixo teor de óleo. O comprimento do corpo e a largura da cabeça dos adultos de D. maurus foram maiores, mas o comprimento e a largura do pronoto menores e as fêmeas mais pesadas com sementes de algodão com alto teor de óleo. Genótipos de algodão com baixo teor de óleo podem reduzir as populações do percevejo.

Abstract: The objective of this work was to determine the biological and morphological parameters of Dysdercus maurus fed with cotton (Gossypium hirsutum) seeds with a high or low oil content, as well as to identify genotypes to be used in breeding programs as sources of resistance to this stink bug. The development, survival, and reproduction of the cotton stainer bug were determined in a completely randomized experimental design. The treatments consisted of the insect nymphs being feed with cotton seeds of the CNPA 2001-5581 (high oil content) or CNPA 2001-5087 (low content) genetic line. Survival, weight, and morphological parameters of the bug were determined. The survival of second- and third-instar nymphs and of the total nymph stage of D. maurus was lower with cotton seeds with a low oil content. The body length and head width of D. maurus adults were greater, but pronotum length and width were smaller and the females heavier with cotton seeds with a high oil content. Low-oil cotton genotypes can reduce populations of the stainer bug.

ABSTRACT The objective of this study was to evaluate cotton cultivars based on the compensatory increase of cotton squares in response to the simulation of the boll weevil damage. The first experiment aimed to evaluate cotton cultivars with greater compensatory increase in squares removed artificially from the plant. The experimental design was in randomized blocks, in a 4 × 2 factorial scheme with 100% removal of cotton squares at 50, 70 and 90 days after the emergence of the FM975WS, TMG81WS, IMA6501B2RF and BRS432B2RF cotton cultivars and passive production (without removal) and active (with removal) of cotton squares, with four replications. In the second experiment, boll weevil damage in the TMG80WS and BRS432B2RF, with greater and lesser compensatory increase of cotton squares, after their removal at 50 days of age, was evaluated. The experimental design was in randomized blocks, in a 2 × 2 factorial scheme, with the former cultivars sprayed with carbamate or not (control). The compensatory increase of cotton squares, mainly after their artificial removal at 50 and 70 days of age, of the TMG81WS, was greater. The cotton square compensatory increase after being artificially removed in the cotton cultivars was higher during the period of exponential production of these reproductive structures and can be used to select cultivars tolerant to boll weevil damage.

RESUMO: Neste estudo, determinou-se a distribuição espacial e temporal dos botões florais e pequenas maçãs de algodoeiros caídas ao solo danificadas pelo bicudo e a eficiência de equipamentos para coletá-las. A distribuição espacial e temporal dos botões florais e pequenas maçãs de algodoeiros caídas ao solo danificadas pelo bicudo entre as fileiras de algodão foram determinadas em delineamento experimental de blocos ao acaso em arranjo fatorial 4x3, representado por faixas de superfície de solo localizadas entre 1-11cm; 12-22cm; 23-33cm e 34-44cm de distância da fileira de plantio em algodoeiros com 70, 85 e 100 dias de idade. A eficiência de coleta dos botões florais e pequenas maçãs caídas ao solo danificado pelo bicudo pelos rastelos plásticos em leque e reto, vassourão, catador modelo CNPA e aspirador de folhas “Trapp” foi determinado em delineamento de blocos ao acaso com cinco tratamentos e 10 repetições. Os resultados demonstraram que a coleta dos botões florais e pequenas maçãs caídas ao solo devem ser realizadas com maior atenção nas faixas de solo localizada abaixo da projeção da copa do algodoeiro e que o aspirador “Trapp” se mostrou mais adequado para essa operação porque gastou menos tempo para coletar essas estruturas vegetais, embora tenha apresentado eficiência semelhante aos demais equipamentos.

ABSTRACT: In this study, we determined the spatial and temporal distribution of fallen cotton squares and small cotton bolls fallen damaged by boll weevil and the efficiency and time interval of the equipment used to collect cotton samples. Spatial and temporal distribution of cotton squares and small cotton bolls fallen on the soil damaged by boll weevil among cotton rows was determined in an experimental design of randomized blocks in a factorial arrangement of 4x3, represented by soil surface tracks located at 1-11cm, 12-22cm, 23-33cm, and 34-44cm away from the planting row of cotton plants 70, 85, and 100 days of age. Efficiency and collection time interval of the cotton samples fallen on the soil infested by boll weevil by plastic rakes that were straight or fan-shaped, big broom, collector instrument model CNPA and aspirator of leaves ‘Trapp’ were determined in randomized block design with five treatments, 10 repetitions for each. Results demonstrated that the collection of cotton samples must be performed with greater attention to soil strips located below the cotton top projection and aspirator ‘Trapp’ of leaves was more appropriate for the operation as it used less time of collection with similar efficiency to other available equipment.

ABSTRACT The red spider mite Tetranychus neocaledonicus André (Acari: Tetranychidae) is commonly found on cotton and castor bean in Brazil, especially in the northeast, but to date it had not been found damaging cultivated peanut. The objective of this research was to record the occurrence of this mite on peanut plants and describe its damage on this Fabaceae. The peanut plants, when infested by this mite, exhibit initially small whitish spots on the leaves, which quickly develop to chlorotic spots, followed by silvering, drying and fall because of their feeding. The severity of the damage caused to peanut and the adaptability of the mite to warm and dry conditions indicate that this species has potential as peanut pest in northeastern Brazil.

Resumo: O objetivo deste trabalho foi avaliar a eficiência de métodos de destruição dos restos de cultura do algodoeiro (Gossypium hirsutum) para a redução da população remanescente do bicudo-do-algodoeiro (Anthonomus grandis). O experimento foi conduzido em blocos ao acaso, com quatro repetições e cinco tratamentos: roçagem, com aplicação de 2,4-D e beta-ciflutrina; roçagem, com aplicação de 2,4-D e glifosato; roçagem e gradagem; roçagem, com aplicação de 2,4-D e beta-ciflutrina, além de gradagem; e testemunha (sem destruição). A quantidade de bicudos foi determinada após a destruição dos restos de cultura do algodão, por contagem dos insetos capturados nas armadilhas de feromônio e daqueles encontrados dentro dos carimãs, no interior das gaiolas e na área externa. O número médio de bicudos adultos, capturados nas armadilhas de feromônio no interior das gaiolas, variou de 0,71 a 1,35 indivíduos. O maior número de carimãs e de bicudos dos carimãs, dentro e fora das gaiolas, foi observado na testemunha. Já o menor número de insetos foi observado nos tratamentos com gradagem e roçagem e naqueles com roçagem e gradagem com aplicação de 2,4-D e beta-ciflutrina, que são eficientes na redução de carimãs e de adultos do bicudo. Todos os métodos avaliados reduzem a quantidade de bicudos vivos no interior de carimãs.

Abstract : The objective of this work was to evaluate the effectiveness of methods for the destruction of cotton (Gossypium hirsutum) stalks on the remainder population of cotton boll weevil (Anthonomus grandis). The experiment was carried out in a randomized complete block design with four replicates and five treatments: mowing and application of 2,4-D and beta-cyfluthrin; mowing and application of 2,4-D and glyphosate; mowing and harrowing; mowing and application of 2,4-D and beta-cyfluthrin, besides harrowing; and a control without destruction. Boll weevil amount was determined after the destruction of cotton crop residues by counting the caught insects both in pheromone traps and within the dry bolls inside the cages and in the outer area. The average number of boll weevil adults captured in pheromone traps within the cages ranged from 0.71 to 1.35 individuals. The highest number of dry bolls and boll weevils from dry bolls, in and out of cages, was observed in the control. The lowest number of insects was observed in the treatments with harrowing and mowing and in those with mowing and harrowing with application of 2,4-D and beta-cyfluthrin, which are efficient in the reduction of dry bolls and boll weevil adults. All the evaluated methods reduce the amount of live boll weevils inside dry bolls.

Resumo:O objetivo deste trabalho foi determinar a concentração de caulim mais eficiente e econômica para a proteção de algodoeiro contra os danos causados pelo bicudo-do-algodoeiro (Anthonomus grandis). Utilizou-se o delineamento experimental de blocos ao acaso, com cinco tratamentos de pulverizações com caulim nas concentrações: 20, 40, 60, 80 e 100 g L-1. Determinaram-se os seguintes parâmetros: percentagem de botões florais com orifícios de oviposição por fêmeas do bicudo; resíduos de caulim depositados sobre as folhas e as brácteas do algodoeiro; média da produção; e receita líquida do algodão, por hectare, a partir da pesagem da pluma de algodão com caroço. As percentagens de botões florais com orifício de oviposição variaram de 13,6 a 30,8%; o resíduo médio de caulim depositado nas folhas, de 0,0010 a 0,0034 mg mm-2, e nas brácteas, de 0,0010 a 0,0034 mg mm-2; a produção variou de 348,1 a 717,8 kg ha-1; e a receita líquida de algodão de R$ 1.033,88 a R$ 2.098,86 por hectare. As concentrações de caulim mais eficientes para a proteção de algodoeiro contra o bicudo são as de 60, 80 e 100 g L-1; no entanto, a de 60 g L-1foi a mais econômica.

Abstract:The objective of this work was to determine the most effective and economical kaolin concentration to protect cotton against the injuries caused by the boll weevil (Anthonomus grandis). A randomized complete block design was used with five treatments of kaolin spraying at the following concentrations: 20, 40, 60, 80, and 100 g L-1. The following parameters were determined: percentage of punctured squares with oviposition by boll weevil females; the amount of kaolin residues on leaves and bracts of cotton square; average yield; and the cotton net income per hectare, measured from the weighing of cotton lint with seed. The percentages of oviposition-punctured squares ranged from 13.6 to 30.8%; kaolin residue, deposited on cotton leaves, ranged from 0.0010 to 0.0034 mg mm-2, and on bracts, from 0.0010 to 0.0034 mg mm-2; production ranged from 348.1 to 717.8 kg ha-1; and the net revenues from cotton ranged from R$ 1,033.88 to R$ 2,098.86 per hectare. The most efficient kaolin concentrations for cotton protection against damage caused by boll weevil are those of 60, 80, and 100 g L-1; however, the concentration of 60 g L1 is the most economic one.

Resumo: O objetivo deste trabalho foi avaliar a capacidade do caulim de afetar a oviposição e a alimentação de Alabama argillacea (Lepidoptera: Noctuidae) em algodoeiro. Determinou-se a preferência de oviposição, a viabilidade de ovos e o consumo das lagartas de primeiro instar de A. argillacea, em folhas de algodão tratadas ou não com caulim. A preferência de oviposição foi determinada por teste de escolha e confinamento, em delineamento experimental de blocos ao acaso, em arranjo fatorial 2x7, representado pelos tratamentos com caulim em água destilada (60 g L-1) ou somente água destilada (testemunha), e pela avaliação de sete estruturas vegetais da planta. O consumo pelas lagartas de primeiro instar foi determinado em delineamento experimental inteiramente casualizado, em arranjo fatorial 2x4, representado pelo tratamento com caulim em água destilada, pela testemunha e pelos quatro períodos de observação (6, 12, 24 e 48 horas). A oviposição das mariposas do curuquerê-do-algodoeiro foi reduzida nas plantas de algodão tratadas com caulim; no entanto, a viabilidade dos ovos não foi afetada. A folha da haste foi a estrutura preferida para oviposição. A sobrevivência e o consumo de lagartas de primeiro instar do curuquerê são menores nas plantas de algodão tratadas com caulim.

Abstract: The objective of this work was to evaluate the ability of kaolin to affect oviposition and feeding of Alabama argillacea (Lepidoptera: Noctuidae) on cotton. The oviposition preference, the egg viability, and the feed consumption of the first instar larvae of A. argillacea were determined on cotton leaves treated or not with kaolin. The oviposition preference was determined under choice test and confinement, in a randomized complete block design, in a 2x7 factorial arrangement, represented by the treatments with kaolin in distilled water (60 g L-1) or distilled water only (control), and by the evaluation of seven plant structures. The feed consumption by the first instar larvae was determined in a completely randomized design, in a 2x4 factorial arrangement, represented by the treatment with kaolin in distilled water, by the control, and by the four observation periods (6, 12, 24, and 48 hours). The oviposition of cotton leafworm moths was reduced in cotton plants treated with kaolin; however, the viability of eggs was not affected. Leaf stem was the preferred structure for oviposition. Survival and feed consumption of first instar larvae of cotton leafworm are lower on cotton plants treated with kaolin.

A cochonilha do algodão, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) tem sido registrada ocorrendo em vários países, causando perdas severas em diversas culturas de interesse econômico, incluindo o algodão. De acordo com informações relatadas por agricultores familiares do Sudoeste e Médio São Francisco, Bahia e também do Agreste e Semiárido da Paraíba, ocorreram altas infestações de cochonilhas de algodão nessas regiões durante as safras de 2007 e 2008. O inseto foi identificado como P. solenopsis e representa o primeiro registro deste inseto atacando algodão no Brasil.

The cotton mealybug, Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) has been reported occurring in several countries causing severe losses in economically important crops, including cotton. Based on information reported by farmers in the regions of the Southwest and Middle São Francisco, Bahia and also in the regions of the Agreste and Semi-arid of the Paraiba State, high infestations of cotton mealybugs have occurred in these regions during the cotton season of 2007 and 2008. The cotton mealybug was identified as P. solenopsis and this represents the first record of this insect attacking cotton in Brazil.

The development and survival of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) nymphs fed on larvae of Chlosyne lacinia saundersii Doubleday & Hewitson (Lepidoptera: Nymphalidae) was studied at 25 ± 1ºC, 68 ± 10% relative humidity and 12 h photo phase. P. nigrispinus developed until the adult stage when fed on C. lacinia saundersii caterpillars. However, the survival rate of P. nigrispinus during early instars allowed this predator to complement its diet with other preys and to maintain its populations in areas with the sunflower culture.

Objetivou-se determinar o efeito da defesa da presa Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) na taxa de predação por fêmeas de Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae). Podisus nigrispinus, predou 1,0; 1,4; 1,2; 3,8; 3,0 lagartas de terceiro estádio de S. frugiperda com defesa, respectivamente, nas densidades de uma, duas, quatro, seis e oito lagartas, enquanto esses valores foram de 0,4; 0,8; 1,6; 2,8; 3,2 lagartas sem defesa, respectivamente, nessas densidades. A taxa de ataque (a) e o tempo de manipulação (Th) foram, respectivamente, de 0,67 ± 0,39-h e 6,72 ± 2,88 horas para fêmeas de P. nigrispinus alimentadas com lagartas com defesa e de 2,51 ± 0,16-h e 0,51 ± 0,77 horas para aquelas sem defesa. A resposta funcional do predador P. nigrispinus varia com a defesa e a densidade da presa S. frugiperda, com maior consumo de presas sem defesa em altas densidades.

The effect of the defense of the prey Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) on predation rates of Podisus nigrispinus (Dallas) (Heteroptera: Pentatomidae) females was studied. P. nigrispinus preyed 1.0, 1.4, 1.2, 3.8 and 3.0 and 0.4, 0.8, 1.6, 2.8 and 3.2 third instars of S. frugiperda larvae with and without defense, respectively, with the densities of one, two, four, six and eight larvae. The attack rate and the manipulation time were, respectively, 0.67 ± 0.39-h and 6.72 ± 2.88 h for P. nigrispinus females fed with larvae with defense and 2.51 ± 0.16-h and 0.51 ± 0.77 h for those without defense. The functional response of the predator P. nigrispinus varies with the defense and the density of the prey S. frugiperda, with larger consumption of prey without defense at higher densities.

O desenvolvimento de Gargaphia torresi Lima em folhas de algodão foi estudado em câmara climatizada a 20, 23, 25, 28 e 30ºC, umidade relativa de 70±10% e fotofase de 12h. O período de incubação variou de 11 (20ºC) a 4 (30ºC) dias; o estágio ninfal de indivíduos que originaram fêmeas e machos variou de 20,8 (20ºC) a 8,3 (30ºC) dias e de 28,8 (20ºC) e 8,6 (30ºC) dias, respectivamente. O desenvolvimento dos estágios imaturos para indivíduos que originaram fêmeas e machos variou de 31,8 (20ºC) a 12,3 (30ºC) dias e de 31,5 (20ºC) a 12,6 (30ºC) dias, respectivamente. Os valores de longevidade e fecundidade foram inversamente proporcionais ao aumento da temperatura. As exigências térmicas (K) e temperaturas-base (Tb) foram estimadas para cada um dos estágios imaturos e de ovo à emergência de adultos (machos e fêmeas) de acordo com a Lei de Reamur e com o método de intercecção de X, respectivamente. Os estágios imaturos para indivíduos que originaram fêmeas e machos adultos requereram 209,4 e 220,3 graus-dia da oviposição à emergência do adulto, respectivamente, acima dos limites inferiores de 13,9 e 13,6ºC.

The development of Gargaphia torresi Lima on cotton leaves was studied in bioclimatic chambers at 20, 23, 25, 28 and 30ºC, relative humidity of 70±10%, and a 12h:12h (L:D) photoperiod. The incubation period varied from 11 (20ºC) to 4 (30ºC) days; nymphal stage of individuals that originated females and males varied from 20.8 (20ºC) to 8.3 (30ºC) days and from 20.8 (20ºC) to 8.6 (30ºC) days, respectively. Development of immature stages for individuals that originated females and males varied from 31.8 (20ºC) to 12.3 (30ºC) days and from 31.5 (20ºC) to 12.6 (30ºC) days, respectively. The values of longevity and fecundity were inversely proportional with increase of the temperature. The thermal constant (K) and theoretical lower threshold temperature of development (Tb) were estimated by Reamur law and intercession method of the X, respectively. The theoretical lower threshold temperature of development for individuals that originated adult females and males were 13.9ºC and 13.6ºC, respectively. The immature stages for individuals that originated adult females and males required 209.4 and 220.3 degrees-days from oviposition to adult emergence, respectively.

O objetivo deste trabalho foi estudar a biologia e as exigências térmicas de Tetranychus ludeni Zacher (Acari: Tetranychidae) em folhas de algodoeiro (Gossypium hirsutum L. r. latifolium (Hutch)). Foram utilizadas câmaras climatizadas, ajustadas nas temperaturas de 20, 23, 25, 28 e 30ºC, umidade relativa de 70% e fotófase de 12 horas. Os períodos de desenvolvimento de ovo a adulto variaram de 20,77 (20ºC) a 8,50 dias (30ºC), em fêmeas, e de 18,83 (20ºC) a 7,75 dias (30ºC), em machos. As temperaturasbase, estimadas pelo método da intersecção de X, para os períodos de desenvolvimento de ovoadulto, foram de 14,05ºC para fêmeas e 13,91ºC para machos, enquanto os valores da constante térmica estimados de acordo com a lei de Réamur foram de 138,34 grausdia, para fêmeas e 130,91 grausdia, para machos. Na temperatura de 30ºC foram observados os maiores valores de razão intrínseca de crescimento (0,418), número de ovos de fêmeas/dia (3,47), fecundidade (61,29) e taxa líquida de reprodução (48,00) e o menor valor para o tempo médio de uma geração (9,27).

The objective of this work was to study the biology and thermal requirement of Tetranychus ludeni Zacher (Acari: Tetranychidae) on leaves of cotton (Gossypium hirsutum L. r. latifolium (Hutch)). Bioclimatic chambers at 20, 23, 25, 28 and 30ºC, relative humidity of 70±10%, and a 12 hours:12 hours (L:D) photoperiod were utilized. Development period of eggadult, varied from 20.77 (20ºC) to 8.50 days (30ºC), for males and from 18.83 (20ºC) to 7.75 days (30ºC), for females. The threshold temperature of development, estimated by X intercession method for development period of eggadult were 14.05ºC, for females and 13.91ºC, for males. While those values of thermal constant estimated by Réamur law were 138.34 daydegrees for females and 130.91 daydegrees for males. At 30ºC of temperature, the highest values of the intrinsic rate of increase (0.418), number of eggs/females/day (3.47), fecundity (61.29), reproductive rate net (48.00), and minimum value to the mean generation time (9.27) were shown.

Objetivou-se selecionar isolados de Beauveria bassiana (Balsamo) Vüillemin provenientes de diferentes hospedeiros e regiões geográficas, patogênicos ao Anthonomus grandis, o bicudo-do-algodoeiro. Foram analisados 12 isolados em condições de laboratório. Os isolados obtidos originalmente de A. grandis foram pouco virulentos a essa praga. A mortalidade do bicudo teve início no segundo dia após a inoculação das suspensões fúngicas, variando de 15% a 83%, com TL50 entre 5,30 a 11,06 dias. Os isolados apresentaram variabilidade quanto à germinação dos conídios em meio de cultura artificial, e esta não se correlacionou com a patogenicidade. O isolado CG138 de B. bassiana destacou-se como um dos mais virulentos ao bicudo-do-algodoeiro.

The objective of this work was to screen pathogenic isolates of Beauveria bassiana (Balsamo) Vüillemin from different hosts and geographic regions, pathogenic to the cotton boll weevil. Twelve isolates were evaluated. Isolates originally obtained from boll weevil showed low pathogenicity against this host. Insect mortality began on the second day after inoculation by fungal suspension, ranging from 15% to 83%, with a TL50 of 5.30 to 11.06 days. Variability among isolates concerning conidial germination in artificial culture medium was verified, and TG50 did not correlate with pathogenicity. One of the most virulent isolates of B. bassiana against cotton boll weevil is CG138.