Seasonal variation of pest mite populations in relation to citrus scion cultivars in northeastern Brazil

Pest populations in a given agroecosystem may be influenced by several abiotic and biotic variables, including the host plant cultivar. We compared the population fluctuation of pest mites in twenty citrus scion cultivars grafted on Rangpur lime (Citrus limonia). Adults of citrus rust mite Phyllocoptruta oleivora (Acari: Eriophyidae), Texas citrus mite Eutetranychus banksi and Tetranychus mexicanus (Acari:Tetranychidae) were monthly counted in each scion cultivar from April 2011 to February 2013 in Sergipe state, northeastern Brazil. Larger E. banksi population peak was recorded on sweet orange ‘Valência Montemorellos’ in February 2012 compared to the other cultivars and larger populations of T. mexicanus were found on sweet orange ‘Lima’ in January 2013 in comparison to acid limes ‘Tahiti IAC 5’ and ‘IAC 5-1’. The population of P. oleivora, however was not different among scion cultivars and varied only with time. Abiotic and biotic variables were important mechanisms underlying such responses. We conclude that the abundances of the mites E. banksi and T. mexicanus were influenced by scion cultivars only in some periods, suggesting putative resistance mechanisms in some genotypes to these pests

Eficiencia de tres especies de ácaros depredadores (Acari: Phytoseiidae) para el control de Raoiella indica (Acari: Tenuipalpidae)

In this work, the efficiency of Amblyseius largoensis (Muma), Typhlodromus (Anthoseius) ornatus Denmark e Muma and Iphiseiodes zuluagai Denmark ( Muma for controlling Raoiella indica Hirst (Acari: Tenuipalpidae) was assessed by comparing their functional and numerical responses to increasing densities of R. indica eggs. The three predatory mites exhibited a type II functional response, indicating that they can assist in the control of R. indica, especially at low to moderate densities of this pest. However, A. largoensis consumed the highest number of preys with the shortest handling time and showed a superior reproductive potential when fed upon R. indica eggs. A. largoensis proved to be the most efficient of the three predatory mites.En este trabajo se evaluó la eficiencia de Amblyseius largoensis (Muma), Typhlodromus (Anthoseius) ornatus Denmark ( Muma e Iphiseiodes zuluagai Denmark & Muma para controlar Raoiella indica Hirst (Acari: Tenuipalpidae) mediante la comparación de sus respuestas numéricas y funcionales con densidades crecientes de huevos de R. indica. Los tres ácaros depredadores mostraron una respuesta de tipo II, lo que indica que pueden ayudar en el control de R. indica, especialmente en densidades de bajas a moderadas de esta plaga. Sin embargo, A. largoensis consumió el mayor número de presas en menor tiempo, así como presentó un potencial reproductivo superior cuando se alimentó de huevos de R. indica. A. largoensis demostró ser el más eficiente de los tres ácaros depredadores

Nest Architecture and Colony Growth of Atta bisphaerica Grass-Cutting Ants

Atta grass-cutting ants (Formicidae: Myrmicinae: Attini) are found in the Cerrado biome and build giant nests with hundreds or thousands of large chambers. We assessed for Atta bisphaerica grass-cutting ants whether the total volume of fungus chambers and other nest parameters grow at close or similar proportions to worker numbers in the colony. Data on fungus garden biomass, population, external area, number of entrance holes, number of fungus chambers, total fungus chambers volume, and nest depth were obtained during colony growth/nest development. Our results reveal that the fungus garden biomass, external area, and total fungus chamber volume increased at rates similar to the increase in the number of workers. The total volume of chambers, and external area increased at a similar proportion to the increase in number of workers, probably due to the fungus garden allocation needs of the colony. The number of fungus chambers, number of entrance holes, and nest depth increased less than 4-fold for every 10-fold increase in the worker number. In addition, the height of the fungus chambers increased as the width increased, a pattern not observed for tunnel height and length, and the chamber volume increased according to worker number. Thus, this study demonstrates for A. bisphaerica that nest development in terms of chamber volume is similar to the increase in number of colony workers, and this contributes to a better understanding of Atta nest architecture

Dinâmica populacional e parasitismo natural de Diaphorina citri Kuwayama (Hemiptera: Liviidae) em pomares de citros em Sergipe

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Liviidae), which is the vector of the Hunglongbing (HLB) bacterium, has become a key citrus pest in Brazil. In addition to citrus, the ornamental plant known as Orange Jasmine, Murraya paniculata (L.) Jack, also hosts the psyllid. The present work aimed at studying the population dynamics of the psyllid in citrus orchards and its parasitism in citrus and M. paniculata in the state of Sergipe, the fourth largest citrus-producing state in Brazil. The evaluations were performed fortnightly for eleven months in seven Pera Citrus sinensis (L.) Osbeck orange orchards located in two municipalities of Sergipe state (Boquim, and Umbauba). The populations of eggs, nymphs and adults of D. citri were compared among all orchards and all developmental stages were related to the abiotic factors temperature, relative humidity and precipitation, in each locality. The psyllid was classified as an accessory species (not very abundant) in the orchards of Sergipe, showing a higher population density in November, December and March. Precipitation was the only abiotic factor that contributed to the population increase of adults of the psyllid. High rates of parasitism (55%) of psyllid nymphs by the exotic parasitoid Tamarixia radiata Waterston (Hymenoptera: Eulophidae) were detected in M. paniculata plants. Based on the results, if the HLB bacterium is detected in Sergipe, shorter samplings should be performed in the spring and summer months aiming at vector management. In addition, T. radiata could be released inundatively in integrated vector management programs.O psilídeo, Diaphorina citri Kuwayama (Hemiptera: Sternorrhyncha: Liviidae), por ser vetor da bactéria causadora do Hunglongbing (HLB), tornou-se uma praga-chave dos citros no Brasil. Além dos citros, a planta ornamental conhecida como murta-de-cheiro, Murraya paniculata (L.) Jack, também é hospedeira do psilídeo. O presente trabalho teve como objetivo estudar a dinâmica populacional do psilídeo em pomares de citros e o seu parasitismo em citros e murta-de-cheiro no estado de Sergipe, o quarto maior produtor de citros do Brasil. As avaliações foram realizadas quinzenalmente durante onze meses em sete pomares de laranjeira Pera Citrus sinensis (L.) Osbeck localizados em dois municípios (Boquim, e Umbaúba). As populações de ovos, ninfas e adultos de D. citri foram comparadas entre todos os pomares e todas as fases de vida foram relacionadas com os fatores abióticos, temperatura, umidade relativa e precipitação de cada localidade. O psilídeo D. citri foi classificado como espécie acessória (pouco abundante) nos pomares de Sergipe, apresentando maior densidade populacional nos meses de novembro, dezembro e março. A precipitação foi o único fator abiótico que contribuiu para o aumento populacional de adultos do psilídeo. Altas taxas de parasitismo (55 %) de ninfas do psilídeo pelo parasitoide exótico Tamarixia radiata Waterston (Hymenoptera: Eulophidae) foram detectadas em plantas de murta-de-cheiro. Com base nos resultados, caso a bactéria seja detectada em Sergipe, para o manejo do vetor, amostragens de menor intervalo deverão ser realizadas nos meses da primavera e verão. Adicionalmente, o parasitoide T. radiata poderia ser liberado inundativamente em programas de manejo integrado do vetor

Bioactividad de aceites vegetales a Orthezia praelonga (Hemiptera: Sternorrhyncha: Orthezidae) y selectividad a su predador Ceraeochrysa caligata (Neuroptera: Chrysopidae)

Vegetable oils are abundant in oleaginous plants and they can be an alternative for the pest control in integrated management systems. Fatty acids present in these oils are bioactive to pests and they can be an alternative to the use of insecticides suggested to crops of citrus. Although these oils are of natural origin, the impact on beneficial species must be widely evaluated. Here, we evaluated the toxicity and repellency of crude oils of cotton, palm, soybean and coconut to a key citrus pest, Orthezia praelonga (Hemiptera: Sternorrhyncha: Ortheziidae), and its selectivity to Ceraeochrysa caligata (Neuroptera: Chrysopidade). Bioassays of concentration-mortality were performed under laboratory conditions and lethal concentrations of oils were estimated on O. praelonga adult females were estimated. Additionally, the repellent effect of each oil to the LC50 and LC80 was evaluated after 1.24, and 48 h. The four vegetable oils showed toxicity to O. praelonga: cotton LC50 = 1.92 μl/ml, palm oil LC50 = 2.54 μl/ml; soybean LC50 = 3.18 μl/ml and coconut LC50 = 5.02 μl/ml; and its selectivity to C. caligata was verified (CLs50 >80 % alive). Repellent effects of cotton oil (LC50 = 1.92 μl/ml, LC80 = 5.99 μl/ml), and palm oil (LC80 = 10.22 μl/ml) were demonstrated for one hour of exposure. In contrast, the soybean oil (LC80 = 12.50 μl/ml) repelled O. praelonga after 24 and 48 h of exposure. Results of toxicity, repellence and selectivity show the cotton, palm, and soybean oils as the most suitable for the control of O. praleonga.Los aceites vegetales abundan en plantas oleaginosas y pueden ser una alternativa para el control de plagas en sistemas de manejo integrado. Los ácidos grasos presentes en estos aceites muestran bioactividad a plagas y pueden ser una alternativa al uso de insecticidas recomendados para plantaciones de cítricos. Aunque estos aceites son de origen natural, el impacto en especies benéficas debe ser extensamente evaluado. Este estudio fue conducido a fin de evaluar la toxicidad y la repelencia de aceites crudos de algodón, dendé, soja desgomado y coco a una plaga clave de cítricos, Orthezia praelonga (Hemiptera: Sternorrhyncha: Ortheziidae), y su selectividad al predador Ceraeochrysa caligata (Neuroptera: Chrysopidae). Se realizaron bioensayos de concentración-mortalidad en condiciones de laboratorio y se estimaron concentraciones letales de los aceites sobre hembras adultas de O. praelonga. Adicionalmente, se evaluó el efecto repelente de cada aceite a la CL50 y CL80 después de 1, 24 y 48 h. Los cuatro aceites vegetales presentaron toxicidad a O. praelonga: algodón CL50=1,92 µl/ml, dendé CL50=2,54 µl/ml, soja CL50=3,18 µl/ml y coco CL50=5,02 µl/ml; su selectividad a C. caligata fue verificada (CLs50 >80 % de vivos). Se demostró el efecto repelente del aceite de algodón (CL50=1,92 µl/ml; CL80=5,99 µl/ml) y dendé (CL80=10,22 µl/ml) con una hora de exposición. Contrariamente, el aceite de soja desgomado (CL80=12,50 µl/ml) repelió a O. praelonga con 24 y 48 horas después de haber sido expuesta. Los resultados de toxicidad, repelencia y selectividad muestran al aceite vegetal de algodón, dendé y soja desgomado como los más adecuados para el control de O. praleonga