Population parameters as a way to evaluate the risk of attack of Aphis craccivora (Hemiptera: Aphididae) on cowpea / Parâmetros populacionais como forma de avaliar os riscos de ataque de Aphis craccivora (Hemiptera: Aphididae) em feijão-caupi

The objective of this research was to develop fertility life tables in order to estimate the population parameters of black aphid (Aphis craccivora Koch) in cowpea (Vigna unguiculata) varieties, aiming to propose a risk scale for its use. The experiment consisted of six treatments and six replicates (five varieties plus the cultivar VITA 7 as a susceptible control). A cohort was formed with six adult females distributed in six replicates of each genotype, and the insects were observed daily. Based on the data, fertility life tables were drawn for each variety and the population parameters were estimated. The different values of the finite growth rate (λ) were considered to propose a risk scale for the use of the genotypes. The results obtained give the dimension of the variability of V. unguiculata in respect to the character, resistance to A. craccivora, with antibiosis as the main mechanism of resistance. Considering all the results, the varieties studied can be classified according to their suitability as a plant favorable to the development of the black aphid as follows: VITA 7 > CE-13 > CE-51 > CE-08 = CE-07. The proposal of a risk scale for the use of V. unguiculata genotypes against the A. craccivora population, based on the finite growth rate (λ) values, was adequate to discriminate the varieties studied.(AU)

Objetivou-se nesta pesquisa elaborar tabelas de vida de fertilidade com o intuito de estimar os parâmetros populacionais de pulgão-preto (Aphis craccivora Koch) em variedades de feijão-caupi (Vigna unguiculata), visando propor uma escala de risco para o seu uso. O experimento constituiu-se em seis tratamentos (cinco variedades mais o cultivar VITA 7 como padrão de suscetibilidade) com seis repetições. Formou-se uma coorte com seis fêmeas adultas distribuídas em cada genótipo, sendo todos os indivíduos observados diariamente. De posse dos dados, foram elaboradas tabelas de vida de fertilidade para cada variedade e estimados os parâmetros populacionais. Para propor uma escala de risco de uso de genótipos, ponderou-se sob os diferentes valores da razão finita de crescimento (λ). Os resultados obtidos dão a dimensão da variabilidade de V. unguiculata com relação ao caráter da resistência a A. craccivora, sendo a antibiose o principal mecanismo de resistência associado. Considerando-se todos os resultados, foi possível hierarquizar as variedades estudadas segundo sua aptidão como planta favorável ao desenvolvimento ao pulgão-preto conforme segue: VITA 7 >> CE-13 > CE-51 > CE-08 = CE-07. A proposta de uma escala de risco do uso de genótipos de V. unguiculata frente à população de A. craccivora, baseada nos valores da razão finita de crescimento (λ), foi adequada para discriminar as variedades estudadas.(AU)

Distribuição espacial da cigarrinha Empoasca kraemeri Ross & Moore (Hemiptera: Cicadelidae) no feijão-de-corda e cálculo do número de amostras / Spatial distribution of leafhopper Empoasca kraemeri Ross & Moore (Hemiptera: Cicadelidae) in cowpea and calculation of number of samples

Objetivou-se estudar a dispersão espacial da cigarrinha Empoasca kraemeri Ross & Moore (Hemiptera: Cicadelidae) na cultura de feijão-de-corda Vigna unguiculata (L.) Walp. e estabelecer o número de amostras necessárias para a estimativa da população da praga para o uso em programas de manejo integrado de pragas. Foram cultivados dois campos experimentais na Universidade Federal do Ceará, em Fortaleza. O primeiro campo com área de 216 m2 composta de 15 parcelas. O segundo campo com área de 576 m2 dividida em 25 parcelas. O cultivar utilizado foi Vita 7 com plantas espaçadas em 0,25 x 0,8 m. Foram realizadas três coletas de dados no Campo I e quatro no Campo II, sendo avaliadas dez plantas por parcela. Foi contado o número de adultos e ninfas de cigarrinha presentes em toda a planta. Os resultados obtidos nos índices de agregação utilizados indicam que a dispersão da E. kraemeri no campo é do tipo agregada, o que foi confirmado pelo ajuste dos dados à distribuição de frequência binomial negativa. Para aplicação em programas de manejo integrado de pragas, 30 é o número de amostras estatisticamente adequado para a estimativa da população de E. kraemeri em campos de V. unguiculata.(AU)

The objective was to study the spatial dispersion of the leafhopper Empoasca kraemeri Ross & Moore (Hemiptera: Cicadelidae) on culture of cowpea Vigna unguiculata (L.) Walp. and to establish the number of sample necessary to estimate the population of the pest for use in integrated pest management programs. Two experimental fields were cultivated at the Federal University of Ceará, in Fortaleza, Brazil. The area of the Field I was 216 m2, composed of 15 plots. The area of the Field II was 576 m2, divided into 25 plots. The cultivar used was Vita 7 with plants spaced 0.25 x 0.8 m. We performed three separate collections of data in Field I and four in Field II; in each plot ten plants were assessed. Th number of leafhopper nymphs and adults present in the plant was counted. The aggregate indexes used indicate that the dispersion of E. kraemeri in the fi is of the aggregate type, which was confirmed by fi the data to the negative binomial frequency distribution. To be used in integrated pest management programs, 30 is the sample number statistically suitable for the estimation of E. kraemeri population in V. unguiculata fields.(AU)

Aphid antixenosis in cotton is activated by the natural plant defence elicitor cis-jasmone.

Upon insect herbivory, plants can release blends of volatile organic compounds (VOCs) that modify herbivore and natural enemy behaviour. We have shown recently that cotton, Gossypium hirsutum, emits a blend of defence VOCs that repels the cotton aphid, Aphis gossypii, upon herbivory by this notorious crop pest, including (Z)-3-hexenyl acetate, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), methyl salicylate and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT). In this study, we investigated changes in the defence VOC profile of G. hirsutum induced by the naturally-occurring plant elicitor cis-jasmone (CJ) and whether these changes modify the behaviour of A. gossypii. In four-arm olfactometer assays, VOCs from untreated plants were significantly attractive (P<0.05), whilst VOCs from CJ-treated plants were significantly repellent (P<0.05). The VOCs induced by CJ appeared to comprise (Z)-3-hexenyl acetate, DMNT, methyl salicylate and TMTT. In quantitative VOC collection studies, sustained release of DMNT and TMTT was observed in CJ-treated plants over a period of five days, with levels becoming statistically significantly higher than for control treated plants on the fifth day in most cases. Despite earlier indications, no statistically significant differences were observed in levels of (Z)-3-hexenyl acetate or methyl salicylate between CJ and control treatments on any day. Furthermore, DMNT and TMTT emissions from CJ-treated plants were further enhanced by subsequent addition of A. gossypii. CJ treatment induced statistically significantly higher DMNT and TMTT expression levels as early as day three, when A. gossypii was present. The results in this study show that CJ can induce the production of A. gossypii-induced VOCs from G. hirsutum, with potential for deployment in novel crop protection strategies.

Identification of semiochemicals released by cotton, Gossypium hirsutum, upon infestation by the cotton aphid, Aphis gossypii.

The cotton aphid, Aphis gossypii (Homoptera: Aphididae), is increasing in importance as a pest worldwide since the introduction of Bt-cotton, which controls lepidopteran but not homopteran pests. The chemical ecology of interactions between cotton, Gossypium hirsutum (Malvaceae), A. gossypii, and the predatory lacewing Chrysoperla lucasina (Neuroptera: Chrysopidae), was investigated with a view to providing new pest management strategies. Behavioral tests using a four-arm (Pettersson) olfactometer showed that alate A. gossypii spent significantly more time in the presence of odor from uninfested cotton seedlings compared to clean air, but significantly less time in the presence of odor from A. gossypii infested plants. A. gossypii also spent significantly more time in the presence of headspace samples of volatile organic compounds (VOCs) obtained from uninfested cotton seedlings, but significantly less time with those from A. gossypii infested plants. VOCs from uninfested and A. gossypii infested cotton seedlings were analyzed by gas chromatography (GC) and coupled GC-mass spectrometry (GC-MS), leading to the identification of (Z)-3-hexenyl acetate, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), methyl salicylate, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT), which were produced in larger amounts from A. gossypii infested plants compared to uninfested plants. In behavioral tests, A. gossypii spent significantly more time in the control (solvent) arms when presented with a synthetic blend of these four compounds, with and without the presence of VOCs from uninfested cotton. Coupled GC-electroantennogram (EAG) recordings with the lacewing C. lucasina showed significant antennal responses to VOCs from A. gossypii infested cotton, suggesting they have a role in indirect defense and indicating a likely behavioral role for these compounds for the predator as well as the aphid.

[Monitoring the susceptibility to insecticides in Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) populations from Brazil]. / Monitoramento da suscetibilidade a inseticidas em populações de Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) no Brasil.

Monitoring the susceptibility of a pest population to pesticides is essential for resistance management programs. The objective of this research was to evaluate the genetic variability in pesticide susceptibility in populations of Bemisia tabaci (Gennadius) collected from different Brazilian agricultural regions through the use of two different tests. Four whitefly populations, two from Goiás state (GO-1 and GO-2) e two from Bahia state (BA-1 and BA-2), were tested against a susceptible reference one (SusIAC). A residual contact bioassay was used to evaluate the pesticide susceptibility of each population by using diagnostic concentration bioassays and by estimating the baseline susceptibility data to each one of the tested insecticides, acetamiprid, imidacloprid, thiamethoxam, chlorpyrifos and endosulfan. Adult insects of unknown age and sex were tested. Evaluations were performed after 24h for endosulfan and 48 h for the other chemicals. Both procedures showed significant differences in the susceptibility to the pesticides among B. tabaci populations. However, the discrimination among B. tabaci populations was more evident with the use of diagnosis tests. The population GO-2 was significantly less susceptible to the tested pesticides than SusIAC, mainly to neonicotinoids. The most critical resistance situation of B. tabaci was detected to thiamethoxam, followed by imidacloprid.

Monitoramento da suscetibilidade a inseticidas em populações de Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) no Brasil / Monitoring the susceptibility to insecticides in Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) populations from Brazil

O monitoramento da suscetibilidade de pragas a praguicidas é essencial para programas de manejo da resistência. O objetivo deste trabalho foi verificar a variabilidade genética de populações de Bemisia tabaci (Gennadius), oriundas de diferentes áreas agrícolas, quanto a suscetibilidade a inseticidas no Brasil, por meio de dois testes diferentes. Quatro populações de mosca-branca foram testadas em relação a uma população suscetível de referência (SusIAC); duas oriundas de Goiás (GO-1 e GO-2) e outras duas da Bahia (BA-1 e BA-2). Uma técnica de bioensaio do tipo contato residual foi empregada para realização dos testes: 1) teste diagnóstico da resistência; e 2) teste para obtenção das linhas de suscetibilidade das populações. Os produtos utilizados foram acetamipride, imidaclopride, tiametoxam, clorpirifós e endosulfam. Utilizaram-se insetos adultos não separados por sexo e nem por idade nos testes. As avaliações foram realizadas em 24h, para o teste com endosulfam, e em 48h, para os demais produtos. Ambos os testes revelaram variabilidade genética quanto à suscetibilidade de mosca-branca aos inseticidas. No entanto, a discriminação entre as populações de B. tabaci foi mais evidente com o uso de testes diagnósticos. A população GO-2 foi significativamente menos suscetível aos produtos testados que a SusIAC, principalmente em relação aos neonicotinóides. A situação mais crítica de resistência de mosca-branca foi com tiametoxam, seguida pelo imidaclopride.

Monitoring the susceptibility of a pest population to pesticides is essential for resistance management programs. The objective of this research was to evaluate the genetic variability in pesticide susceptibility in populations of Bemisia tabaci (Gennadius) collected from different Brazilian agricultural regions through the use of two different tests. Four whitefly populations, two from Goiás state (GO-1 and GO-2) e two from Bahia state (BA-1 and BA-2), were tested against a susceptible reference one (SusIAC). A residual contact bioassay was used to evaluate the pesticide susceptibility of each population by using diagnostic concentration bioassays and by estimating the baseline susceptibility data to each one of the tested insecticides, acetamiprid, imidacloprid, thiamethoxam, chlorpyrifos and endosulfan. Adult insects of unknown age and sex were tested. Evaluations were performed after 24h for endosulfan and 48h for the other chemicals. Both procedures showed significant differences in the susceptibility to the pesticides among B. tabaci populations. However, the discrimination among B. tabaci populations was more evident with the use of diagnosis tests. The population GO-2 was significantly less susceptible to the tested pesticides than SusIAC, mainly to neonicotinoids. The most critical resistance situation of B. tabaci was detected to thiamethoxam, followed by imidacloprid.

Preferência de Bemisia tabaci biótipo B em linhagens mutantes de algodoeiro / Bemisia tabaci biotype B preference in mutant cotton lines

Os efeitos de caracteres mutantes morfológicos do algodoeiro (Gossypium hirsutum L. r. latifolium Hutch.): folha okra, bráctea frego e planta vermelha, em relação à resistência à mosca-branca (Bemisia tabaci biótipo B Hemiptera: Aleyrodidae), foram avaliados em experimentos com ou sem chance de escolha. Os experimentos foram conduzidos em casa-de-vegetação, no delineamento de blocos ao acaso, em fatorial 23 + 1, com quatro repetições. O mutante com a característica planta vermelha foi menos atrativo e menos preferido para oviposição, em relação à planta verde, em ambos os ensaios, com ou sem escolha. Não houve preferência quanto à forma da folha e ao tipo de bráctea.

The effects of cotton lines (Gossypium hirsutum L. r. latifolium Hutch.) with mutants morphologic characteristics: okra leaf, frego bract and red plant in relation to host plant resistance to whitefly (Bemisia tabaci bioyipe B Hemiptera: Aleyrodidae), were evaluated in choice or no choice assays. The assays were carried out in the greenhouse conditions, according to a completely randomized block design, in a 23 + 1 in a factorial arrangement with four replications. The mutant with red plant characteristic was less attractive and less preferred for oviposition than the normal green plant does, in both, whit or without choice tests. It did not have preference in relation to the form of the leaf and bract type.

Preferência do pulgão-preto, Aphis craccivora Koch, a diferentes genótipos de feijão-de-corda, Vigna unguiculata (L) Walp / Black aphid, Aphis craccivora Koch, preference to different cowpea, Vigna unguiculata (L) Walp. cultivars

Este trabalho foi desenvolvido visando a avaliar a resposta de cultivares de feijão-de-corda, Vigna unguiculata (L.) Walp., à presença do pulgão-preto (Aphis craccivora Koch). Os experimentos foram conduzidos de agosto a outubro de 2004, em casa-de-vegetação da Universidade Federal do Ceará (UFC). As cultivares foram: "Epace-10", "Epace-11", "Patativa", "Pingo de Ouro", "Pitiúba", "BR-10 Piauí", "BR-12 Canindé", "BR-14 Mulato" e "BR-17 Gurguéia". O experimento constou de três ensaios, cada um com cinco tratamentos e seis repetições, sendo o delineamento estatístico inteiramente casualizado. Os genótipos foram cultivados em copos plásticos de 300ml e mantidos em gaiolas protegidas por tela antiafídeos. As plantas foram infestadas após doze dias do plantio através da liberação de cinco fêmeas adultas do pulgão-preto por planta. As avaliações foram realizadas após o terceiro e o quinto dia da infestação, constando da contagem direta das formas adulta e jovem do inseto presentes nas plantas. Os dados obtidos foram analisados através de análise de variância e pelo teste de Tukey em 5 por cento de probabilidade de erro. As cultivares "Epace-10" e "Patativa" foram as menos preferidas por A. craccivora.

This research was conducted with the intention of evaluating the response of different cowpea, Vigna unguiculata (L.) Walp, cultivars to the black aphid (Aphis craccivora Koch). The bioassays were conducted from August through October of 2004 in a greenhouse at the Ceará Federal University (UFC) campus. The cowpea cultivars used were: Epace-10, Epace-11, Patativa, Pingo de Ouro, Pitiúba, BR-10 Piauí, BR-12 Canindé, BR-14 Mulato and BR-17 Gurguéia. Each assay had five treatments and six replications in a completely randomized block design. The genotypes were raised in a 300ml plastic cup and maintained in cages protected by an insect proof net. Plants were infested twelve days after planting with five adult females per plant. Evaluations were performed three and five days after infestation by visual counting of the adults and nymph forms present on the plants. A variance and Tukey analysis were done with the obtained data at a 5 percent level of probability. The Epace 10 and Patativa cultivars were less preferred by A. craccivora.