José Alexandre Freitas Barrigossi

Sex Attractant Pheromone from the Rice Stalk Stink Bug, Tibraca limbativentris Stal

The male-produced sex pheromone from the Brazilian rice stalk stink bug Tibraca limbativentris is reported. Olfactometer bioassays with sexually mature males and females showed that males attracted females, which suggests that males release a sex pheromone. Males were not attracted to either sex, nor were females attractive to conspecific females. Attraction of the females to males was highest at night. The headspace volatiles collected from male and female bugs were analyzed by gas chromatography (GC) and GC–mass spectrometry. Two male-specific compounds were identified as isomers of 1′S-zingiberenol, whereas a series of defensive compounds were identified in extracts from both sexes. Zingiberenol has three chiral centers, and the nonselective syntheses used produced two groups of isomers, zingiberenol I containing four isomers, namely (1RS,4RS,1′R)-4-(1′,5′-dimethylhex-4′-enyl)-1-methylcyclohex-2-en-1-ol, and zingiberenol II containing the other four isomers, namely (1RS,4RS,1′S)-4-(1′,5′-dimethylhex-4′-enyl)-1-methylcyclohex-2-en-1-ol. Both groups of stereoisomers were more attractive than hexane controls. The absolute configuration of the insect-produced pheromonal components remains to be elucidated, but the 1′S stereochemistry was established for at least one of the isomers.

Compatibility of conventional agrochemicals used in rice crops with the entomopathogenic fungus Metarhizium anisopliae

The toxicological impact of chemical pesticides on fungal entomopathogens and their use in tank-mixing can be directly measured through in vitro compatibility tests. This study reports the in vitro toxicity of eight insecticides, four fungicides and five herbicides in the conidial germination, vegetative growth and conidiation of Metarhizium anisopliae (strain CG 168). A conidial suspension containing the pesticide at recommended field dosage was subjected to constant agitation in a rotary shaker for 3h to simulate a tank mixing. Then, aliquots of each suspension were used to determine conidial germination, vegetative growth and conidiation on potato dextrose agar (PDA). The fungicides difenoconazole (69 mL ha-1), propiconazole (75 mL ha-1), trifloxystrobin (313 g ha-1) and azoxystrobin (56 mL ha-1) were the most harmful products to all biological stages of M. anisopliae and they should not be applied together with this fungus in tank mixing. The insecticides exhibited the least degree of toxicity to this fungal pathogen, whereas the herbicides had the greatest impact on mycelial growth. The agrochemicals compatible with M. anisopliae were the insecticides methyl parathion (240 mL ha-1), thiamethoxam (31 g ha-1), and lambda-cyhalothrin (6.3 mL ha-1) and the herbicides glyphosate (1560 mL ha-1), bentazon (720 mL ha-1), and imazapic+ imazapyr (84 g ha-1). The compatible pesticides could be simultaneously used with this bio-control agent for integrated pest management in rice production systems.

Parasitismo de ovos de Tibraca limbativentris Stal (Hemiptera: Pentatomidae) na cultura do arroz no Maranhão

The rice stem bug, Tibraca limbativentris Stal, is an important pest of rice in Brazil. This work evaluated the occurrence of parasitoids in eggs of T.limbativentris egg parasitism in rice crops in the Maranhão State. The eggs collected exhibited an average parasitism of 32%. The parasitoids collected were Telenomus podisi (Ashmead), Trissolcus urichi (Crawford) (Hymenoptera: Scelionidae) and Oencyrtus submetallicus (Howard) (Hymenoptera: Encyrtidae).

Efeito do armazenamento na compatibilidade de fungicidas e inseticidas, associados ou não a um polímero no tratamento de sementes de feijão

The compatibility of chemical products in dry bean seed coating associated to a polymer was studied in this work. Also, the maximum period of storage for these seeds coated with polymer and defensives was established. Dry beans, from cv. Perola were submitted to the following treatments: 1) control; 2) carbendazin + thiram + fipronil + polymer; 3) carbendazin + thiram + fipronil; 4) carbendazin + thiram + thiodicarb + polymer and 5) carbendazin + thiram + thiodicarb. The evaluated parameters included emergency, lesser cornstalk borer (Elasmopalpus lignosellus) efficiency control and seed pathology. For the parameters emergency and borer control the best results were obtained with the treatments including fipronil insecticide. As for seed pathology, treatments with thiodicarb insecticide were more efficient, indicating a suitable compatibility of this insecticide with the fungicides carbendazin + thiram until 150 days of storage. The products tested could be used in dry bean seed dressing, and the treated seeds could be stored up to hundred and twenty days prior to planting.

Consumption Rates and Performance of Erinnyis ello L. on Four Cassava Varieties

O consumo foliar de mandioca (Manihot esculenta Crantz) e a caracterizacao da injuria potencial por Erinnyis ello L. foram determinados em quatro variedades de mandioca. Lagartas de primeiro instar foram criadas individualmente em folhas de quatro variedades de mandioca. Foi usado o delineamento experimental de blocos ao acaso com nove repeticoes. Folhas frescas com areas previamente determinadas foram fornecidas as larvas diariamente. O consumo foliar em cada instar e o peso das lagartas e pupas foram registrados. Nao houve diferenca significativa no consumo foliar nas quatro variedades (P=0,82). O total de area foliar consumida (cm2) para as variedades testadas foi: 1030,5 (Fio de Ouro), 971,5 (Aipim Bravo), 968,6 (Urubu), 956,1 (Jaburu), sendo de 981,7 o consumo medio das quatro variedades. Aproximadamente 94% do consumo ocorreu durante os dois ultimos instares. Variedades nao afetaram o desenvolvimento larval (P=0,96). Os pesos medios de lagartas (g) em cada variedade foram: 4,9 (Jaburu), 4,8 (Fio de Ouro), 4,7 (Urubu), 4,6 (Aipim Bravo) e 4,8 (media das quatro variedades). Dois modelos, um relacionando a area foliar consumida e desenvolvimento larval (y=abx )e outro do crescimento larval (y=5/1+ea+bx), foram estabelecidos. Os dados obtidos indicam que as variedades testadas neste estudo foram nutricionalmente semelhantes para o desenvolvimento de E. ello. Como o consumo foliar de E. ello foi semelhante para todas as variedades, a mesma taxa de consumo pode ser usada para o calculo dos niveis de dano economico para manejar E. ello nessas variedades.

Spatial Distribution and Coexisting Patterns of Adults and Nymphs of Tibraca limbativentris (Hemiptera: Pentatomidae) in Paddy Rice Fields

Abstract The rice stem stink bug, Tibraca limbativentris Stål (Hemiptera: Pentatomidae), is a primary insect pest of paddy rice in South America. Knowledge of its spatial distribution can support sampling plans needed for timely decisions about pest control. This study aimed to investigate the spatial distribution of adults and nymphs of T. limbativentris and determine the spatial coexistence of these stages of development. Fifteen paddy rice fields were scouted once each season to estimate insect densities. Scouting was performed on regular grids with sampling points separated by ∼50 m. Morans I and semivariograms were used to determine spatial distribution patterns. Spatial coexistence of nymphs and adults was explored via spatial point process. Here, adults and nymphs had typically contrasting spatial distribution patterns within the same field; however, the frequency of aggregation was not different between these developmental stages. Adults and nymphs were aggregated in seven fields and randomly distributed in the other eight fields. Uniform distribution of adults or nymphs was not observed. The study-wide semivariogram ranges were ∼40 m for adults and ∼55 m for nymphs. Nymphs and adults spatially coexisted on 67% of the fields. Coexisting patterns were classified using one of the following processes: stage-independent, bidirectional attractive, unidirectional attractive, bidirectional inhibiting, or unidirectional inhibiting. The information presented herein can be important for developing sampling plans for decision-making, implementing tactics for site-specific management, and monitoring areas free of T. limbativentris.

First record of epizootics in the ocola skipper, Panoquina ocola (Lepidopera: Hesperiidae), caused by Isaria tenuipes in flooded rice fields of Central Brazil

We report the first occurrence of an epizootic of the ascomycete fungus, Isaria tenuipes (teleomorph Cordyceps takaomontana), on the ocola skipper Panoquina ocola (Lepidoptera: Hesperiidae), an insect pest affecting rice in Brazil.

Produtividade e danos por cupins em arroz com a compactação no sulco e o tratamento de sementes

The objective of this work was to determine the effects of soil compaction pressure on the sowing furrow and of seed treatments with insecticides on grain yield and on termite damage in upland rice plants under no-tillage, in the Center West region of Brazil. Three experiments were carried out, consisting of five seed treatments combined with three (first experiment) or four (second and third experiments) compaction pressures in a randomized complete block design, in a factorial arrangement. The seed treatments were: T0, without treatment; T1, imidacloprid+thiodicarb; T2, thiamethoxam; T3, carbofuran; and T4, fipronil+p yraclostrobin+thiophanate-methyl. The compaction pressures applied were: 25, 42, and 268 kPa, in the first experiment; and these same pressures plus 126 kPa in the second and third experiments. Seed treatment was effective in increasing rice grain yield, from 1,753 to 4,141 kg ha-1, especially in the lowest compaction pressure of 25 kPa. Soil compaction around 180 kPa in the sowing furrow results in higher rice grain yield and in fewer stems killed by termites. The use of soil compaction on the sowing furrow with seed treatment significantly increases rice grain yield under a no-tillage system.

Resistance of rice varieties to Sitophilus oryzae (Coleoptera: Curculionidae)

Abstract Rice, Oryza sativa L. (Poaceae), is one of the worlds most important food crops. Among the insects that damage rice grains, the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae), is the most important species. The objective of this study was to identify rice varieties with resistance to S. oryzae as measured by grain feeding damage and S. oryzae reproduction. The rice varieties evaluated were obtained from the germplasm bank of the National Center of Research Rice and Beans, Embrapa, Brazil. The experimental design was completely randomized with 3 replications and 22 treatments (varieties). The varieties Bonança, Esmeralda, and Rio Verde had the antibiosis and/or antixenosis type of resistance, providing high rates of mortality, low rates of adult emergence, and low rates of grain consumption by S. oryzae. The varieties Pepita and Progresso were susceptible, with a high rate of S. oryzae adult emergence and grain consumption. The presence or absence of a fissure in the grain was a major morphological characteristic determining susceptibility or resistance to S. oryzae in rice varieties.

A Field technique for infesting rice with Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) and evaluating insecticide treatments

Uma tecnica para produzir lagartas Elasmopalpus lignosellus (Zeller), no laboratorio, infestar plantas em campo e avaliar tratamentos foi descrita e testada em arroz. A acao de inseticidas para tratamento de sementes no controle da lagarta elasmo, utilizando infestacao artificial e natural, tambem foi avaliada em experimentos de tres datas de plantios. O delineamento experimental foi quadrado latino 6x6. A unidade experimental era formada de sete fileiras de arroz de 4 m de comprimento, espacadas de 0,4 m. Os tratamentos consistiram dos seguintes inseticidas e doses: tiametoxam (52,5; 70 e 105 g i.a./100 kg sementes), furatiocarbe (320 g i.a./100kg sementes), carbofuram (525 g i.a./100 kg sementes) e testemunha nao tratada. Infestacoes artificiais foram realizadas em dois grupos de tres colmos, selecionados nas fileiras bordadura das parcelas e confinados em cilindros de PVC, em tres datas de cada plantio. Colmos de cada cilindro foram infestados com tres lagartas de E. lignosellus com sete dias de idade. Imediatamente apos as infestacoes, os cilindros contendo tres colmos de arroz foram protegidos do efeito das chuvas sobre as lagartas. Os danos foram avaliados 20 dias apos as infestacoes. Infestacoes artificiais usadas neste estudo aumentaram o dano em 32 vezes, em relacao a infestacao natural das testemunhas. Inseticidas reduziram significativamente a sobrevivencia de larvas ate 60 dias apos o plantio, comparados com a testemunha.