Silicon as resistance inducer to control black apphid Aphis craccivora Koch, 1854 in cowpea beans [Vigna unguiculata (L)] Walp

The black aphid Aphis craccivora (Koch, 1854) stands out between the bugs considered cowpea pests. The objective of this study was to evaluate the effects of silicon application on the resistance induction of cowpea plants to the black aphid A. craccivora. The experiment was conducted in the Entomology Laboratory of the Phytosanitary sector of the Centro de Ciências Agrárias at the Universidade Federal do Piauí. The effects of the application of silicon on biological aspects were evaluated using a completely randomized design, with four treatments and 40 repetitions, being: silicon in soil (T1), silicon in soil + leaf (T2), silicone leaf (T3), and control (T4). The following biological variables were evaluated: generation period, reproductive period, fecundity, and daily average of nymphs per female. The silicon and lignin contents were also evaluated in the plants. The silicic acid was applied in a 1% solution around the stem of the plants (soil), 15 days after emergence, by diluting 2 g of the product in 200 mL of water. However, the leaf application was carried out with sprayer five days after application in soil. The non-preference of A. craccivora on bean was also evaluated. The evaluations were performed after 24, 48 and 72 hours of infestation by counting nymphs at 24, 48 and 72 hours and adults at each leaf session. The application of silicon promotes the reduction of the production of nymphs, interfering in the biological aspects of A. craccivora, and has potential to be used in a cowpea pest management program in cowpea.

Degradation and Mobility of Pesticides in Norwegian Soils

In this report the following topic of pesticides and fate in Norway has been outlined covering: 1. Factors influencing degradation of pesticides. 2. Description and update of datasets on soil and climate in agricultural areas. 3. Normalization of field degradation data as input for modelling fate. 4. Use of degradation data from Norway in model scenarios. Norwegian laboratory degradation studies indicate that increased soil organic carbon content enhances degradation rates of pesticides that show low sorption (e.g. metalaxyl, bentazone) ,due to increased microbial activity. Whereas pesticides that sorb moderately to strongly to soil (e.g. boscalid, propiconazole), display reduced degradation as organic carbon increases as a consequence of sorption and reduced bioavailability. Recent DegT50 field studies display a large variation in fungicide degradation rates from Klepp in the south to Tromsø in the north. For the mobile herbicide bentazone, no effect of climate was observed, as degradation rates were coherent at all sites, probably due to rapid leaching. The climate (temperature) seems to be more determinate for fungicide degradation rates than the soil type. Fungicide degradation was slow at two northern sites having low soil temperatures, even though microbial biomass was hugely different at the sites. How soil temperature and moisture affects microbial activity and diversity in various soils, climates and crops is important for the understanding of degradation capacity in Norwegian soils and fields. Microbial activity could be related to both soil, climate and crops/cropping regime – as well as to the nature of the soil organic matter. The fact that DegT50 values are very much shorter than laboratory values at the same reference conditions, may point to some systematic error in the normalization procedure (e.g. the default simplifications in the Walker and Arrhenius equations), or that the parameters affecting degradation in the laboratory are different from the parameters that affect degradation in the field. Consequently, lab-derived and field-derived DegT50matrix values should be compared and interpreted with care. The large variations in normalized DegT50 values obtained in field studies in Norway as well as in other regions in Norway cannot be explained by differences in the associated parameters characterizing the soil and microbial community. It is therefore not possible to determine if a certain field study is more or less representative for “Norwegian conditions”. As a conservative approach, the highest, normalized DegT50 from the European field studies should be selected for the Norwegian risk assessment independent on geographic vicinity. As an alternative, when a sufficient number of data are available, a high percentile (e.g 80 or 90-percentile) should be used rather than the geomean. Each agricultural region in Norway is dominated by one specific soil type for each region. Albeluvisol, Cambisol, Umbrisol, Stagnosol and Histosol in respectively Eastern Norway south, Eastern Norway north, Rogaland, Trøndelag and North of Norway. New updates for Norway include especially Umbrisols and Histosols rich in organic matter. Albeluvisols, Cambisols and Stagnosols are representing the main soil types in the agricultural area in Norway. These are also included in the groundwater (Rustad and Heia) and surface water scenarios (Syverud) developed for Norway. Experience from pesticide fate in the organic rich soils on the south west coast and north of Norway is limited. Compared to the “normal” temperature and precipitation from 1961 to 1990 with a “new normal” from 1991 to 2014, the climate has changed. For the five described agricultural areas in Norway, annual temperature has increased in average 1 degrees for all five regions and seasons for the new normal. The rainfall has increased for all seasons and regions except for the Northern Norway (Holt in Tromsø) and summer season at Kvithamar (Trøndelag) with lower precipitation in June to September. Annually the precipitation has increased approximately 100 mm in average. The existing Norwegian scenarios in groundwater and surface water seem to be representative in the meaning of covering the main soil types in the central agricultural areas in South Eastern Norway. However there are no scenarios covering areas of South West and North of Norway containing soil with high organic content, slow degradation and heavy rainfall. Vulnerable areas are not included in these scenarios as the idea of the representativity of soil was to include the main soil types covering the most of the agricultural production areas. The vulnerable areas deals with smaller areas and has to be treated separately. Vulnerable areas are areas with high groundwater levels and sandy soil and mobile pesticides. Hilly areas with clay soil represent high risk of surface runoff with strongly sorbed pesticides. We are lacking experience from areas with high content of organic matter causing slow degradation, combined with heavy rainfall. A database with representative soils and climates for various crops should be established in Norway and utilized in a targeted risk assessment approach. Then, the degradation of pesticides to be used in for example fruit/berry cropping, could be evaluated in respect to representative and vulnerable soils and climates in fruit/berry regions in Norway. A correct risk assessment of pesticide degradation in Norwegian agricultural soils should take the varying climatic zones, the diversity in agricultural soils and crops in Norway into consideration before formulated pesticides are approved. Risk assessment should be based on soils and climates most prevalent for the crop to which the pesticide is to be applied, in addition, vulnerable areas with slow degradation and/or high leaching/runoff risk should be recognized.

Use of the arbuscular mycorrhizal fungus Glomus intraradices as biological control agent of the nematode Nacobbus aberrans parasitizing tomato

The plant-parasitic nematode Nacobbus aberrans is an endoparasite that induces gall formation in the roots and causes severe losses to diverse crops. Some populations of this nematode show preference for certain hosts, revealing the existence of "races/groups" with different behaviour and making nematode management difficult. A possible biological control alternative to reduce the damage caused by this species may be the use of arbuscular mycorrhizal fungi (AMF). In the present work, the effect of Glomus intraradices on tomato plants inoculated with the nematode at transplanting and three weeks later was tested. At 60 days, the following parameters were estimated: percentage of AMF colonization, root and aerial dry weight, number of galls and egg masses, and reproduction factor (RF=final population/initial population) of N. aberrans. AMF colonization was higher in the presence of the nematode. The use of AMF favoured tomato biomass and reduced the number of galls and RF on the plants inoculated with the nematode at transplanting.

Mecanismos de defensa y respuestas de las plantas en la interacción micorrícica: una revisión / Plant defense mechanisms and responses in the arbuscular mycorrhizal symbiosis: a review

El establecimiento de la simbiosis planta-hongos formadores de micorrizas Arbusculares (HFMA) requiere procesos armónicos a nivel espacio-temporal, que dependen de señales para el reconocimiento, colonización e intercambio bidireccional de nutrientes. Las plantas presentan respuestas de defensa frente a posibles organismos invasores; sin embargo, frente a HFMA estas son débiles, localizadas y no impiden la colonización del hongo. Los beneficios de la simbiosis generalmente se asocian a nutrición vegetal, aunque, también está relacionada con el incremento de la tolerancia-resistencia de plantas a los estreses bióticos. La resistencia inducida HFMA (MIR) es importante en el control de patógenos foliares, comedores de hojas y necrótrofos, encontrándose protección de plantas micorrizadas tanto a nivel local como sistémico, relacionada con los niveles de ácido jasmónico en tejidos. Un mecanismo en la MIR está asociado con el “priming”, que permite una rápida y eficiente respuesta de defensa de plantas micorrizadas. Se han planteado posibles mecanismos de atenuación de las respuestas de defensa, considerando: activación de supresores de defensa; plantas que producen respuestas de defensa frente a HFMA y otras que no las producen, y plantas que suprimen las respuestas de defensa en la simbiosis. Aunque el control de la simbiosisestá regulado básicamente por la planta, aún se desconoce el papel de los HFMA en el debilitamiento de las respuestas de defensa. Recientemente, se ha dado un avance importante en entender los mecanismos mediante los cuales se establece y mantiene la biotrofía del hongo, al describirse la proteína SP7 que interactúa con el factor de transcripción PR, ERF19 en el núcleo de la célula vegetal. Se ha sugerido que SP7 es un efector que actúa oponiéndose al programa de inmunidad de la planta.

Harmonic processes between plant and arbuscular mycorrhyzal fungi (AMF) are required for the symbiosis formation between the two organisms. These processes depend on specific signalling for the plant-fungus recognition, colonisation and bidirectional nutrient exchange. Plants show defence responses against invasive organisms, however they react weakly and localised when challenged by AMF. The benefits derived from the mycorrization are described for the nutritional aspect; however, it is known that mycorrhized plants are more tolerant to biotic stresses. Mycorrhizal induced resistance (MIR) is especially important for the control of foliar pathogens, leaf cutters and necrotrophs. There has also been found that mycorrhizal plants are protected both locally and systemically and their protection is related with jasmonic acid levels at their tissues. One of the most important mechanisms for MIR is the so called “priming” that allows plants to exert a fast and efficient defence response. Possible mechanisms to unravel mycorrhizal plants lower defence systems include: defence suppressor activation, differential plants response towards AMF from inexistent to low, and plant defence response suppression during the AMF symbiosis. The symbiosis control is known to be regulated by the plant, however, no role has been assigned to the AMF for the weakening of the plant defence system. Recently, a big step towards understanding of the fungal role has been made. A protein SP7 that interacts with a PR transcription factor ERF19, in the plant nucleus, has been described. This discovery indicates a possible mechanism to establish and maintain the biotrophic status of the AMF counteracting the immune plant system.

First report of the red palm mite, Raoiella indica Hirst (Acari: Tenuipalpidae), in Brazil

The presence of the red palm mite, Raoiella indica Hirst, is reported for the first time in Brazil. This invasive mite was found in July 2009 infesting coconut palms and bananas in urban areas of Boa Vista, State of Roraima, in northern Brazil. Comments on the possible pathways of R. indica into the country, present and potential impact of its introduction and mitigating measures to prevent or to delay the mite spread in Brazil are presented.

Silício como indutor de resistência no controle do tripes do prateamento Enneothrips flavens Moulton, 1941 (Thysanoptera: Thripidae) e seus reflexos na produtividade do amendoinzeiro / Silicon as a resistance inducer controlling the silvering thrips Enneothrips flavens Moulton, 1941 (Thysanoptera: Thripidae) and its effects on peanut yield

O tripes do prateamento, Enneothrips flavens Moulton, 1941, é considerado a principal praga do amendoim no Brasil, por sua ocorrência generalizada, pelos elevados níveis populacionais e pelos danos causados a cultura. Objetivou-se, com este trabalho, avaliar o efeito do silício sobre a população de E. flavens e sobre a produtividade do amendoinzeiro. Avaliaram-se, semanalmente, 10 folíolos abertos ou semi-abertos no terço superior das plantas do cultivar IAC 886, por parcela. Os tratamentos foram constituídos por: uma aplicação foliar de silício realizada aos 20 dias após a emergência, duas aplicações foliares de silício realizadas aos 20 e 55 dias, e o controle. Uma aplicação de silício proporcionou proteção às plantas de amendoim, reduzindo o número de adultos e ninfas do tripes de E. flavens e aumentou a produtividade da cultura em 31,30 por cento de amendoim em casca e 28,85 por cento em grãos.

The silvering thrips, Enneothrips flavens Moulton, 1941 is considered the major pest on peanuts in Brazil, due to its widespread occurrence, high population levels, and high damage to the crop. The objective of this study was to evaluate the effect of silicon on E. flavens populations and on peanuts yield. Ten fully-opened or semi-opened leaflets per plant were sampled weekly from the peanut cultivar IAC 886. The following treatments were tested: leaf spraying of silicon at 20 days after plant emergence, two leaf spraying of silicon at 20 and 55 days, and the control check. A single silicon spraying provided protection to peanut by reducing the number of E. flavens adults and nymphs and by increasing the yield of peanut pods by 31.30 percent and peanut grains by 28.85 percent.

First report of the citrus hindu mite, Schizotetranychus hindustanicus (Hirst) (Prostigmata: Tetranychidae), in Brazil

The citrus Hindu mite, Schizotetranychus hindustanicus (Hirst), is reported for the first time in Brazil and for the second time in South America. Mite specimens were collected from citrus in the municipality of Boa Vista, State of Roraima, northern Brazil. Symptoms associated with S.hindustanicus infestations on citrus are described. The importance of avoiding dissemination of this mite to the main citrus production areas in Brazil is discussed.

Sistema de previsão de ocorrência de requeima em clones de batata suscetíveis e resistentes / Forecasting system of late blight occurrence in susceptible and resistant potato clones

Sistemas de previsão e cultivares resistentes à requeima são importantes ferramentas para reduzir a quantidade de fungicidas utilizados e os custos de produção da batata. O objetivo deste trabalho foi avaliar a utilização do sistema de previsão Blitecast e de clones suscetíveis e resistentes no manejo da requeima da cultura da batata na região produtora de Santa Maria, Rio Grande do Sul (RS). Os experimentos foram conduzidos na Universidade Federal de Santa Maria, na primavera de 2006 e no outono de 2007, sendo os dados meteorológicos medidos continuamente acima do dossel das plantas. Foram utilizados 10 tratamentos arranjados no delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram diferenciados pelos valores de severidade acumulados, calculados pelo sistema Blitecast, e pelos clones SMIJ461-1 e SMINIA793101-3, caracterizados como resistentes à requeima, e Macaca (suscetível). Verificou-se que o sistema Blitecast não foi eficiente para prever o momento de aplicação de fungicida no controle da requeima. Portanto, este deve sofrer ajustes para ser utilizado em clones suscetíveis. Nos clones considerados resistentes, a aplicação de fungicidas com base na utilização do sistema Blitecast não tem efeito sobre a severidade da requeima e a produtividade da cultura da batata.

Forecasting systems and late blight resistant cultivars are important tools to reduce the amount of fungicides and the production cost of a potato farm. The objective of this study was to evaluate the Blitecast forecasting system for late blight occurrence and susceptible and resistant potato clones for managing late blight in Santa Maria, RS, Brazil. Experiments were conducted at the Federal University of Santa Maria during the Spring 2006 and Autumn 2007. Meteorological data were measured continuously above the crop canopy. Ten treatments were used in a completely randomized design, with four replications. Treatments were different values of accumulated severity, calculated by the Blitecast forecasting system and by the potato clones SMIJ461-1 and SMINIA793101-3, characterized as resistant, and the clone Macaca as susceptible to late blight. The Blitecast forecasting system was not effective for predicting the time of fungicide spraying for the control of late blight and, therefore, to be used in susceptible clones it has to be adjusted. For resistant clones, the fungicide spraying based on the Blitecast system has no effect on late blight occurrence and potato productivity.

A genomic approach to characterization of the Citrus terpene synthase gene family

Terpenes are a very large and structurally diverse group of secondary metabolites which are abundant in many essential oils, resins and floral scents. Additionally, some terpenes have roles as phytoalexins in plant-pathogen relationships, allelopathic inhibitors in plant-plant interactions, or as airborne molecules of plant-herbivore multitrophic signaling. Thus the elucidation of the biochemistry and molecular genetics of terpenoid biosynthesis has paramount importance in any crop species. With this aim, we searched the CitEST database for clusters of expressed sequence tags (ESTs) coding for terpene synthases. Herein is a report on the identification and in silico characterization of 49 putative members of the terpene synthase family in diverse Citrus species. The expression patterns and the possible physiological roles of the identified sequences are also discussed.

Protection of Vochysia elliptica (Vochysiaceae) by a nectar-thieving ant

Vochysia elliptica (Vochysiaceae) is a shrubby plant, which does not have EFNs. Camponotus ants thieve nectar, and can decrease plant fitness by making flowers less attractive to pollinators. However, ants remove herbivores, wich can be beneficial. Results show that plants from which ants were excluded had lower rates of termite (simulated herbivore) removal than did plants visited by ants. Plants accessible to ants showed higher rates of termite removal in the base of leaves and in the inflorescence, than in the tip of leaves. This occurs because ants must pass through the principal axis to reach the inflorescence. Conclusive results of this cost/benefit analysis of the Camponotus sp. presence for V. elliptica can be obtained, with experimental manipulations.

Vochysia elliptica (Vochysiaceae) é uma planta arbustiva que não porta NEFs. Formigas Camponotus roubam néctar e podem diminuir a aptidão da planta, tornando as flores menos atrativas para polinizadores. O efeito das formigas na remoção dos herbívoros, no entanto, pode ser benéfico. Resultados evidenciaram que plantas cujas formigas foram excluídas tiveram menor taxa de remoção de cupins (herbívoros simulados) do que plantas visitadas por formigas. Plantas com acesso às formigas apresentaram maior taxa de cupins removidos na base das folhas e na inflorescência do que na ponta das folhas. Isso ocorre porque formigas devem passar através do eixo principal para alcançar a inflorescência. Resultados conclusivos dessa análise de custo/benefício da presença de Camponotus sp. para V. elliptica deverão ser obtidos no futuro, com manipulações experimentais.