Survival and preference of cotton boll weevil adults for alternative food sources / Sobrevivência e preferência para exploração de recursos de adultos do bicudo do algodoeiro

Abstract Plants that have potential as alternative food source (floral nectar, pollen and plant tissues) to the boll weevil during the intercropping season were evaluated considering the prevalent conditions of Cerrado in the Central Brazil. Initially, we tested the nutritional adequacy for the survival of the insect of flower resource (pollen and nectar) provided by eight plant species (fennel, mexican sunflower, castor bean, okra, hibiscus, sorghum, pigeonpea and sunn hemp). Subsequently, we tested if the resources provided by the selected plants continued to be exploited by the boll weevil in the presence of cotton plant, its main food source average longevity of boll weevil adults was significantly longer when they were fed on hibiscus’ flowers (166.6 ± 74.4) and okra flowers (34.7 ± 28.9) than when they fed on flowers of other six species. Subsequently, the preference of the boll weevil in the use of resources was compared between okra or hibiscus and cotton plants, in dual choice experiments. Boll weevils preferred plants of the three species in the reproductive stages than those in vegetative stages. Although the cotton plant in the reproductive stage was the most preferred plant of all, boll weevils preferred flowering okra and hibiscus than cotton at the vegetative stage.

Resumo Plantas que podem ser uma fonte potencial de recursos alimentares (néctar floral, pólen e tecidos vegetais) para o bicudo do algodoeiro durante a entressafra foram avaliadas, considerando as condições ambientais prevalentes na região de Cerrado do Brasil Central. Primeiro, testamos a adequação nutricional dos recursos (pólen e néctar) fornecidos por oito espécies de plantas (erva-doce, margaridão, mamona, quiabo, hibisco, sorgo, feijão guandu e crotalária) como único recurso alimentar para a sobrevivência do inseto. Posteriormente, nós avaliamos se os recursos fornecidos pelas plantas selecionadas continuaram a serem explorados pelo bicudo na presença do algodoeiro, seu recurso alimentar principal. A longevidade média do bicudo do algodoeiro foi significativamente maior quando eles foram alimentados com flores de hibisco (166,6 ± 74,4) e quiabo (34,7 ± 28,9) do que quando alimentados com flores das outras seis espécies. Em seguida, a preferência do bicudo no uso de recursos foi comparada contrastando o quiabo e o hibisco com o algodão, em experimentos de dupla escolha. Os bicudos preferiram as plantas das três espécies na fase reprodutiva em relação àquelas em estádios vegetativos. Embora a preferência por plantas de algodão na fase reprodutiva tenha sido maior, os bicudos preferiram plantas em floração de quiabo e hibisco quando estas foram contrastadas com o algodão na fase vegetativa.

Aplicabilidad de estadística multivariada para estudios nutricionales: bioensayo con el gorgojo de arroz (Sitophilus oryzae L) / Applicability of Multivariate Statistics for nutritional studies: bioassay rice weevil (Sitophilus oryzae L)

El análisis de componentes principales (PCA), escalamiento multidimensional no-métrico (MDS) y el análisis de similaridad (ANOSIM) son técnicas estadísticas multivariadas, las dos primeras representan gráficamente de manera simultánea las unidades estadísticas y las variables que las caracterizan, evaluando similaridades entre las unidades y correlaciones entre las variables, la última técnica dota de un test estadístico no paramétrico para comparar agrupaciones de las unidades. Este trabajo evaluó la aplicabilidad de estas técnicas para valorar la calidad nutricional de la dieta, utilizando el bioensayo del gorgojo de arroz. Las dietas ensayadas fueron: almidón de maíz; almidón de papa; 5% glucosa; arvejas; ayuno y ayuno con agua. Se estudiaron las variables supervivencia, variación de peso y composición corporal. El PCA y MDS mostraron relaciones positivas de la supervivencia y variación de peso con los parámetros corporales grasa y carbohidratos, siendo mayor para dietas de almidón, similares al control positivo. En el PCA se observaron diferencias en las poblaciones mantenidas con las diferentes dietas; el MDS no distingue claramente entre ellas, aún cuando logra diferenciar la dieta definida por el ayuno de las restantes. Ambos estudios definieron un gradiente del valor nutritivo de las dietas, en el eje de las abscisas. El ANOSIM indicó diferencias significativas (p<0,05) entre grupos de insectos sustentados con estas dietas. Esta prueba refuerza los resultados obtenidos en el PCA y MDS. La aplicación de estas herramientas estadísticas son promisorias para analizar procesos complejos, como la interacción de distintas variables que midan la calidad nutricional de diferentes dietas.

The principal component analysis (PCA), non-metric multidimensional scaling (MDS) and analysis of similarity (ANOSIM) are multivariate statistical techniques that graphically represent numerical measures of several factors and display multiple relationships that may exist between them. In this study, we evaluated the applicability of these techniques to analyze the nutritional quality of diet, using as model, the bioassay rice weevil. The diets tested were: corn starch, potato starch, 5% glucose, peas, starved and starved with water supply. The variables studied were: survival, weight change and body composition. The PCA and MDS showed positive relationships of survival and weight change with body fat and carbohydrate parameters. Fat and carbohydrates were greater in starches diets, similar to the positive control. The PCA showed differences between populations fed with different diets, whereas the MDS showed similarity between diets. Both studies defined a gradient of the nutritive value of diets in the x-axis. The ANOSIM indicate significant (p<0, 05) differences between groups. This test is necessary to support the results obtained in the PCA and MDS. The application of these statistical tools is promising to analyze complex processes such as interaction of differents variables to measure the nutritional quality of diets.

Alternative food sources and overwintering feeding behavior of the boll weevil, Anthonomus grandis boheman (coleoptera: curculionidae) underthe tropical conditions of central Brazil

The boll weevil causes serious damage to the cotton crop in South America. Several studies have been published on this pest, but its phenology and behavior under the tropical conditions prevailing in Brazil are not well-known. In this study the feeding behavior and main food sources of adult boll weevils throughout the year in Central Brazil was investigated. The digestive tract contents of insects captured in pheromone traps in two cotton fields and two areas of native vegetation (gallery forest and cerrado sensu stricto) were analyzed. The insect was captured all through the year only in the cerrado. It fed on pollen of 19 different plant families, on Pteridophyta and fungi spores and algae cysts. Simpson Index test showed that the cerrado provided greater diversity of pollen sources. In the beginning of the cotton cycle, the plant families used for pollen feeding were varied: in cotton area 1, the weevil fed on Poaceae(50 percent), Malvaceae and Smilacaceae (25 percent each); in cotton area 2 the pollen sources were Malvaceae (50 percent), Asteraceae (25 percent) and Fabaceae and Clusiaceae (25 percent each); in the cerrado they were Chenopodiaceae (67 percent) and Scheuchzeriaceae (33 percent). No weevils were collected in the gallery forest in this period. After cotton was harvested, the family Smilacaceae was predominant among the food plants exploited in all the study areas. These results help to explain the survivorship of adult boll weevil during cotton fallow season in Central Brazil and they are discussed in the context of behavioral adaptations to the prevailing tropical environmental conditions.

Atração de adultos de Sphenophorus levis Vaurie (Coleoptera: Curculionidae) a fragmentos vegetais em diferentes estados de conservação / Attraction of Sphenophorus levis Vaurie adults (Coleoptera: Curculionidae) to vegetal tissues at different conservation levels

The occurrence of the sugarcane weevil Sphenophorus levis Vaurie is important in sugarcane in some regions in Brazil. Damage is caused by the larvae as they bore into the nodes and can reach 30 ton/ha/year. Many control alternatives have been attempted, but none were satisfactory, except for the use of toxic baits. Therefore, it is necessary to optimize their efficiency or to propose new techniques. The objective of the current study was to evaluate the attractiveness of adults of S. levis to sugarcane nodes and pineapple peelings in an "Y" tube olfactometer. The sugarcane internodes were treated with 10 percent molasses, and tested after different periods of fermentation (24, 48 e 72h), at different times of the day (diurnal and nocturnal) and with both sexes. These tests were carried out in order to correlate the response of S. levis to ethyl acetate and ethanol release as a result of the fermentation process. The release of both compounds was monitored by gas chromatography-mass spectrometry (GC-MS). Our data indicated that sugarcane internodes mixed with 10 percent molasses fermented for 24h and 48h were the most attractive to S. levis (up to 90 percent). Pineapple peelings attracted 62.5 percent of the tested insects. The olfactory response was higher during the day, and no differences were found between the sexes. The production of ethanol in all plant substrates was higher than ethyl acetate, but we could not establish a clear correlation with the insect response to baits.

A ocorrência do besouro da cana-de-açúcar, Sphenophorus levis Vaurie, é importante em algumas regiões do Brasil. O dano é causado pelas larvas que perfuram os colmos, ocasionando perdas de até 30 ton /ha/ano. Várias alternativas de controle têm sido utilizadas, embora nenhuma delas com resultados satisfatórios, à exceção do uso de iscas tóxicas. Sendo assim, há necessidade de otimizar sua eficiência ou propor novas técnicas. O objetivo do presente estudo foi avaliar a atratividade dos adultos de S. levis a toletes de cana e casca de abacaxi por meio de olfatômetro em "Y". Os entrenós foram tratados com melaço a 10 por cento e foram testados depois de diferentes tempos de fermentação (24, 48 e 72h), em diferentes horários (diurno e noturno) para ambos os sexos. Os testes foram conduzidos na tentativa de relacionar a resposta de S. levis ao acetato de etila e etanol produzidos pela fermentação. A produção de ambos compostos foi determinada por cromatografia gasosa de massa (GC-MS). Os dados obtidos indicaram que os entrenós da cana-de-açúcar misturados com melaço a 10 por cento e fermentados por 24h e 48h foram os mais atrativos a S. levis (acima de 90 por cento). A casca de abacaxi só atraiu 62,5 por cento dos insetos testados. A resposta olfativa foi maior durante o dia e não houve diferenças entre os sexos. A produção de etanol em todos os substratos foi maior do que a do acetato de etila, embora não tenha sido possível estabelecer uma relação clara com a resposta dos insetos às iscas.

Persea schiedeana (Lauraceae), nuevo hospedero de Heilipus lauri Boheman (Coleoptera: Curculionidae) en Veracruz, México / Persea schiedeana (Lauraceae), a new host of Heilipus lauri Boheman (Coleoptera: Curculionidae) in Veracruz, Mexico

The presence of the Molytinae Heilipus lauri Boheman is reported for the first time attacking fruits of Persea schiedeana, commonly called "chinene" in Huatusco and Zongolica, state of Veracruz, Mexico.

Se reporta por primera vez la presencia del Molytinae Heilipus lauri Boheman atacando frutos de Persea schiedeana, comúnmente conocidos como "chinene" in Hustusco y Zongolica, Veracruz, México.

Flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch (Coleoptera: Curculionidae) and its relationship with susceptibility to insecticides / Atividade de vôo de Sitophilus oryzae (L) e Sitophilus zeamais Motsch (Coleoptera: Curculionidae) e a sua relação com a susceptibilidade a inseticidas

Insect-pest mobility can influence insect susceptibility to the insecticides used to control them. The objective of this work was to evaluate the flight activity of Sitophilus oryzae (L) and Sitophilus zeamais Motsch populations reared on corn and wheat grains, and its relationship with insecticide susceptibility. Unsexed adult insects with ages between 10 and 20 days were placed on a plastic tray. A 40-watt incandescent light bulb was positioned at a 50 cm height relative to the tray. Flight activity was evaluated during 30 min. In the LC50 estimation bioassays, the insects were exposed to dry residues of the organophosphorus insecticide fenitrothion and of the pyrethroid insecticide esfenvalerate on the internal surface of glass vials. Mortality was evaluated 24h after installation of the experiments. Sitophilus zeamais showed greater flight activity when compared with S.oryzae; likewise, insects reared on corn had greater flight activity than those reared on wheat. Sitophilus oryzae was less susceptible to the insecticides studied than S. zeamais. Adults reared on wheat were more susceptible to the insecticides than those reared on corn. This study demonstrates that the lower flight activity of S. oryzae is related to its greater tolerance to insecticides.

A mobilidade de insetos pragas pode influenciar sua susceptibilidade aos inseticidas usados no seu controle. O objetivo do presente trabalho foi avaliar a atividade de vôo em populações de Sitophilus oryzae (L) e Sitophilus zeamais criadas em grãos de milho e trigo, e a sua relação com a susceptibilidade a inseticidas. Insetos adultos não-sexados, com idades entre 10 e 20 dias, foram colocados sobre bandeja plástica. Uma lâmpada de luz incandescente de 40 watts foi posicionada a 50 cm de altura em relação à bandeja. A atividade de vôo foi avaliada durante 30 min. Nos bioensaios para estimar a CL50 os insetos foram expostos a resíduos secos do organofosforado fenitrotiom e do piretroide esfenvalerato sobre a superfície interna de tubos de vidro. A avaliação da mortalidade foi feita 24h após a instalação dos experimentos. Sitophilus zeamais apresentou maior atividade de vôo quando comparada a S. oryzae; outrossim, os insetos criados no milho apresentaram maior atividade de vôo do que aqueles criados no trigo. Sitophilus oryzae foi menos susceptível aos inseticidas estudados do que S. zeamais. Os adultos procedentes da criação em trigo foram mais susceptíveis aos inseticidas do que aqueles procedentes da criação em milho. O presente trabalho demonstra que a menor atividade de vôo de S. oryzae está relacionada a sua maior tolerância a inseticidas.

Parisoschoenus obesulus Casey (Coleoptera: Curculionidae) não é praga de frutos novos do coqueiro / Parisoschoenus obesulus Casey (Coleoptera: Curculionidae) is not a pest of young coconut tree fruits

Este estudo teve por objetivo avaliar se Parisoschoenus obesulus Casey só ataca frutos em processo de abortamento natural e, portanto, não é praga de frutos jovens do coqueiro. Para testar a hipótese, inflorescências em diversos estágios de desenvolvimento fisiológico foram oferecidas a indivíduos de P. obesulus. Os resultados mostraram que somente frutos abortivos foram colonizados por P. obesulus aceitando-se, portanto, a hipótese estabelecida.

This study aimed to evaluate if Parisoschoenus obesulus Casey only attacks naturally aborting coconuts and, consequently, is not a pest of young fruits of coconut tree. Aiming to test this hypothesis, inflorescences at diverse stages of physiological development were offered to individuals of P. obesulus. The results showed that only aborting fruits were colonized by P. obesulus corroborating the established hypothesis.

Infestação de Pseudopiazurus papayanus (Marshall) (Coleoptera: Curculionidae) em genótipos de Carica spp. e Vasconcella spp. / Infestation of Pseudopiazurus papayanus (Marshall) (Coleoptera: Curculionidae) on Carica spp. and Vasconcella spp. genotypes

The papaya borer weevil, Pseudopiazurus papayanus (Marshall), is generally considered a secondary pest, but it has been reported in high infestations in Northeast Brazil. This work aimed at evaluating the occurrence of P. papayanus and reporting its infestation level in papaya genotypes kept at the germplasm bank of Embrapa Cassava & Tropical Fruits (Cruz das Almas, Bahia, Brazil). The number of larvae, pupae and adults found in each plant of 65 Carica spp. genotypes and of three Vasconcella spp. genotypes was registered in three to five plants of each genotype, by cutting the exsudating trunks lenghtwise. Papaya borer weevil was found in C. papaya and V. cauliflora but not in those of V. quercifolia. Among the evaluated genotypes, 52.4 percent of those belonging to the Solo group were infested, against 25.0 percent of the Formosa group. Larval infestation was the best criterion for sorting out genotypes concerning this insect infestation. This is also the first occurrence of the papaya borer weevil on V. cauliflora.

A broca-do-mamoeiro, Pseudopiazurus papayanus (Marshall), é considerada praga secundária da cultura; entretanto, altas infestações têm sido registradas no Nordeste do Brasil. O objetivo deste trabalho foi avaliar a infestação de P. papayanus em genótipos de mamoeiro do banco ativo de germoplasma de Carica spp. da Embrapa Mandioca e Fruticultura Tropical, em Cruz das Almas, BA. Registrou-se o número de larvas, pupas e adultos em 68 genótipos, amostrando-se de três a cinco plantas/genótipo. As amostragens foram feitas em caules com exsudações. A broca-do-mamoeiro infestou plantas de C. papaya e V. cauliflora, mas V. quercifolia não foi atacada. Entre os acessos de C. papaya infestados, 52,4 por cento e 25,0 por cento pertenciam, respectivamente, aos grupos Solo e Formosa. A amostragem de larvas foi o melhor critério para distinguir os acessos com relação à infestação pelo inseto. Esta é também a primeira ocorrência da broca-do-mamoeiro em V. cauliflora.

Defoliation levels of oriental spruce by Ips typographus (L.) in relation to elevation and exposure.

A study concerning the effects of elevation and exposure of the spruce forests on defoliation levels of oriental spruce (Picea orientalis (L.) Link.) by Ips typographus L. was carried out during 2005 and 2006 in Artvin-Hatila National Park, Turkey Nine spruce stands were selected at 3 zones of elevations (1000-1350 m, 1350-1700 m and 1700-2000 m) and at different aspects to assess the role of elevation and exposure in the crown defoliation level and body length of beetles. Influence of bark thickness and trunk diameter at 1.3 m on the damage caused by the pest was investigated as well. The results of the study were as follows: (1) The mean defoliation level was highest at 1700-2000 m following by 1350-1700 m and 1000-1350 m. (2) The highest defoliation levels occurred on southern slopes following by eastern and northern slopes at 1700-2000 m. (3) No statistical differences were found in the mean bark thickness between tree defoliation levels 1, 2, 3 and 4. (4) Mean trunk diameters of dead trees (level 4) were significantly greater than those with defoliation levels 0, 1 and 2. (5) Mean body length of I. typographus at upper zones was significantly higher than those at middle and lower zones.

Pollination of Anthurium (Araceae) by derelomine flower weevils (Coleoptera: Curculionidae)

Cyclanthura flower weevils (Coleoptera: Curculionidae: Derelomini) are identified for the first time as pollinators of multiple species of Anthurium (Araceae) in Costa Rica. The weevils are present on the inflorescences in small numbers during the pistillate and staminate phase of anthesis, and consume plant tissues and pollen. The individuals of one species of Cyclanthura can visit several Anthurium species within the same locality. They also engage in reproductive activities and are likely to oviposit into the flowers. The mating strategies suggest that sperm precedence selects males that are able to secure their position as the last partner prior to oviposition.