Role of semiochemical in host finding, oviposition and sexual communication in Guatemalan potato moth Tecia solanivora

Semiochemicals are important cues in the interaction between plant and insects and between conspecific insects. Volatile compounds emitted by plants provide herbivorous insects with cues for host finding, selection and discrimination. In moths, female emitted sex pheromones enable conspecific males to find them for mating. This thesis investigated the role of semiochemicals in the behaviour of the Guatemalan potato moth Tecia solanivora (Lepidoptera: Gelechiidae), a pest insect of potato. Identification of odours of foliage, flowers, and tubers of potato, Solanum tuberosum, were done with coupled gas chromatography-mass spectrometry and with high-performance liquid chromatography for non-volatile compounds in tubers. Antennal activity of potato volatiles was tested with electroantennographic recordings. Attraction of T. solanivora to potato volatile compounds was investigated through olfactometer, wind tunnel and field bioassays. Male behavior towards two different synthetic pheromone blends was similarly tested, to clarify their mode of action in mating disruption management. Potato emits structure-specific volatile blends that change during the development of the plant. Tuberization stage was the preferred stage for oviposition while foliage released deterrent compounds. A three-component flower-odour mimic attracted males and females, virgin and mated, and enhanced the number of eggs laid. Female oviposition in the soil, during the tuberization stage might be guided by odours from spatially separated flowers, as an indication of suitable host vicinity. Larval survival was low in tubers with high concentrations of glycoalkaloids. This study demonstrates that odours from qualitatively different sites guide female to oviposit on tubers with high suitability for larval performance. Mating disruption was obtained with pheromone-permeated air with the two blends, but the disruption mechanism were different between them. This first study on chemical communication between T. solanivora and its host plant showed that potato volatile compounds are perceived by the moth and act as cues in host location and oviposition. It highlights the possibility of using semiochemicals to manipulate the behavior of the moths and provides a base for further investigation and development of odour-based pest management

Control of Whiteflies (Aleurotrachelus socialis) in Cassava (Manihot esculenta) : physically acting pesticides : mortality and application

The study was performed in southwest of Colombia in close collaboration with the interna-tional centre of tropical agriculture, CIAT and supervised from the university of Valle, Uni-valle, Cali, Colombia and from the Department of Landscape Management and Horticultural Technology, SLU, Alnarp, Sweden. The main purpose of this thesis was to evaluate six different non-conventional insecticides and their ability to control whitefly Aleurotrachelus socialis in cassava Manihot esculenta. The aim was also to evaluate the most appropriate application technique for these products which were: Agronim, Biomel, Bioneem, EcoSwing, Coco soap + chilli and L´Ecomix. The products are mainly based on vegetable oil, soap and plant extract and cause primarily a physical contact effect which affirm that it is fundamental to obtain a high coverage of the underside of the leaves, where A. socialis is present. Initial greenhouse trials were made, comparing four different stages of A. socialis; eggs, nymphs of first and second instars and adults. Mortality for each stage was measured for three concentrations of each product, by dipping leaves into the treatments. Additionally two spray equipments and four different nozzles were evaluated, measuring per-centage coverage of the lower surfaces of the leaves and calculating the dispersion in three levels in the foliage of cassava, in relation to the liquid amount used by the spray equipment and the nozzles. The differences in the coverage between the four nozzles were not signifi-cant; ~60% coverage was obtained in all three levels in the foliage. However, the flow rate (l/min) for the traditional nozzle was approximately three times higher than for Albuz ATR (size: lilac), Goizper 50/0,2/3 and TX SS 3, which also differ in droplet size. The different products were observed to reduce the number of A. socialis, especially in the nymphal stages. It was observed that oil in combination with soap probably could be used as a control method for A. socialis. Treatments with Biomel and Coco soap + Chilli had the high-est mortality for the four stages. Eventually a field trial was conducted with Biomel 5ml/l and Coco soap 7g/l + Chilli 10g/l simultaneously with two different nozzles. The differences in number of A. socialis between the different treatments, in the field trial, were not significant due to a low incursion in the field, in combination with an exceptionally high precipitation. The results show potential for reducing the amount of spray required by using nozzles produc-ing fine droplets and in the same time obtain a good coverage of the products to control A. socialis in cassava. SPANISH ABSTRACT: ABSTRACTO Términos claves: Aleurotrachelus socialis, Manihot esculenta, insecticidas con efecto físico, técnicas de aplicación, boquillas La presente investigación de Tesis de Maestría fue realizada en el sur occidente de Colombia en colaboración con el Centro Internacional de Agricultura Tropical, CIAT, el Departamento de Biología de la Universidad del Valle, Cali, Colombia y el Departamento de Manejo de Paisajes y Tecnologías de Horticultura, SLU, Alnarp, Suecia. El propósito principal fue evaluar la efectividad de seis diferentes insecticidas no convencionales en el control de la mosca blanca Aleurotrachelus socialis en el cultivo de yuca Manihot esculenta. Adicionalmente se buscó determinar la técnica de aplicación más apropiada para los productos evaluados: Agronim, Biomel, Bioneem, EcoSwing, Jabón de coco + ají y L´Ecomix. Los productos están basados de aceites vegetales, jabones y extractos de plantas y causan principalmente un efecto físico de contacto lo cual implica que es fundamental obtener una cobertura alta en el envés de las hojas, donde se encuentra la mosca blanca. Inicialmente, se realizaron ensayos en invernadero comparando cuatro estados de A. socialis; (huevos, adultos y ninfas del primer y segundo instar) para evaluar la mortalidad de cada estado frente a tres concentraciones de cada producto. Se observó que los diferentes productos redujeron en forma estadísticamente significativa el número de A. socialis, especialmente en el estado de ninfas. Los tratamientos Biomel y Jabón de coco + ají causaron mortalidades encima de 75% en el primer estado. Las concentraciones recomendadas de Biomel (5 cc/l) y de Jabón de coco + ají (7 g/l + 10 g/l) causaron mortalidades más altas en los cuatro estados, mientras otros productos tuvo un efecto bajo, especialmente en control de huevos. La combinación aceite y jabón desplegó posibilidades para control de A. socialis. Al comparar dos equipos de aplicación y cuatro boquillas, midiendo el porcentaje de la cobertura en el envés de las hojas y calculando la dispersión en tres niveles del follaje de yuca, de acuerdo con el caudal no se registraron diferencias significativas en cobertura entre las cuatro boquillas, obteniendo alrededor de 60% de cobertura en los tres niveles. El caudal de la boquilla tradicional fue tres veces mayor que con las boquillas Albuz ATR (tamaño: lila), Goizper HC50/0,2/3) y TX SS 3, diferenciándose también en el tamaño de las gotas. Se pudo constatar que es posible mantener la misma cobertura disminuyendo el volumen asperjado con la bomba de espalda al cambiar la boquilla tradicional con una boquilla de gotas finas y flujo menor. Finalmente, al realizar un ensayo de campo con Biomel 5ml/l y Jabón de coco 7g/l + ají 10g/l en tratamientos cruzados con dos boquillas diferentes, no se registraron diferencias significativas entre los tratamientos en cuanto a las poblaciones de A. socialis, probablemente a causa de una incursión baja y una precipitación alta.För att öka odlingssäkerheten, förbättra kvalitet och minska miljöbelastningen krävs det att användningen av syntetiska pesticider i lantbruket minskar. Detta gäller främst i grödor där användningen av pesticider är hög och speciellt i bekämpning där resistens utvecklats och pesticiderna har låg verkan. Fysikaliskt verkande insektsmedel baserade på oljor och såpor bekämpar insekter främst genom att täppa till spirakler och/eller bryta ned kutikulan. Dessa medel kan i vissa fall även ha andra effekter, speciellt med tillsats av växtextrakt som ger avstötande effekt eller tillväxtstörningar. Det krävs mer kunskap om appliceringstekniken (duschkvalitet, täckning etc.) för nämnda produkter för att uppnå en tillförlitlig och godtagbar bekämpningsnivå. På olika håll bedrivs forskning inom de två områdena, fysikaliskt verkande insektsmedel för bekämpning av vita flygare samt appliceringsteknik. Det finns hundratals arter av vita flygare, men endast ett fåtal är skadeinsekter, främst i varmare klimat och i växthus. Vita flygare Aleurotrachelus socialis är en av de dominerande skadeinsekterna i kassava i Colombia, Ecuador och Venezuela. Skördebortfallet kan bli upp till 90 % vid långvariga attacker som påbörjats på unga plantor. I Colombias kassavaodlande distrikt bekämpas för närvarande vita flygare med, i huvudsak, syntetiska insektsmedel. Alternativ tas nu fram och bland dem kan nämnas resistenta sorter, predatorer, parasitoider samt biologiska- (svampar, bakterier) och fysikaliskt verkande insektsmedel, de senare ofta med tillsats av växtextrakt. Detta examensarbete strävar att sammanfoga dessa områden för att skapa en gemensam lösning; en fungerande appliceringsteknik för ett effektivt fysikaliskt verkande insektsmedel mot vita flygare. Produkter som undersöktes var: Agronim, Biomel, Bioneem, EcoSwing, L´Ecomix och Kokossåpa+Chili, son i huvudsak är baserade på oljor och såpor med tillsats av växtextrakt. Inledningsvis jämfördes tre koncentrationer av varje produkt på fyra stadier av A. socialis; ägg, första och andra nymfstadiet samt vuxenstadiet. Försöken genomfördes i växthus på CIAT, Cali, Colombia. Växthusförsöken visade att det finns fysikaliskt verkande insektsmedel med växtextrakt som orsakar hög mortalitet av vita flygare A. socialis. Det kommersiella insektsmedlet Biomel med koncentrationen 5 ml/l gav en mortalitet omkring 90 % för nymf- och vuxenstadierna då de doppades i sprutvätskan. Kokossåpa orsakade hög mortalitet i flera stadier; kring 80 % i nymf- och vuxenstadierna med koncentrationen 3,5 g/l observerades. Agronim var den produkt som gav högst mortalitet i äggstadiet och visade även en ökad mortalitet med ökande koncentration i detta stadium. Även i första nymfstadiet observerades hög mortalitet med Agronim. Ett par av produkterna, EcoSwing och L´Ecomix, visade mycket låg mortalitet och Bioneem visade en hög mortalitet endast i andra nymfstadiet. För fysikaliskt verkande insektsmedel är hög täckningsgrad och en jämn spridning viktig. Bekämpning av vita flygare kräver en täckning av bladens undersidor på de nivåer i bladverket där de befinner sig. Täckningsförsök genomfördes, med hjälp av vattenkänsligt papper, i fält för att jämföra avsättningen för ett urval av spridare. Parametrar som mättes var vätskefördelningen på undersidan av bladen i ett etablerat bestånd av kassava samt vätskemängd och inträngning i bladverket. Försöket genomfördes med en hydraulisk ryggspruta och en roterande spridare. Även ett fältförsök genomfördes med syftet att avgöra om de observerade effekterna från växthuset även kunde observeras i fält, om produkterna tolererade en utomhusmiljö med stark sol och värme och samtidigt kunde ge upphov till hög mortalitet. Intentionen var också attjämföra om effekten var beroende av de olika spridarna genom att observera populationen av vita flygare i fält. Fältförsöket genomfördes i kassava med de två produkter som visat högst mortalitet, Biomel och Kokossåpa+Chili i kombination med två spridare anslutna till en rygg-spruta. Försöksmodellen som användes var ett traditionellt blockförsök med fyra upprepning-ar. Två kontrolled ingick, ett med ett kemiskt insektsmedel (tiametoxan) och ett obehandlat led. Utvärderingen i fält skedde visuellt genom att skatta antalet vuxna individer, nymfer och puppor som urskiljdes i olika nivåer i bladverket. Dessutom bedömdes graden av skada orsa-kad av vita flygare. Dessvärre var skillnaderna mellan kontrolled och de olika behandlingarna inte signifikanta, detta beroende av låg inflygning av A. socialis i kombination med onormalt hög nederbörd. Om dödligheten i fält liknar mortaliteten i växthusen kan man emellertid för-vänta sig en relativt hög dödlighet även i fält. Täckningen i växthusförsöken var 100% till följd av att bladen doppades fullständigt och i fält bedömdes att med spridare som bildar fina droppar; mindre än 100μm och det traditionella munstycket som bildar grova droppar, uppnådde en täckning över 60%. Genom att använda det traditionella munstycket används 2-3 gånger större volym än vid användning av ett munstycke med små droppar (<100μm) men med de olika munstyckena uppnåddes ändå en liknande täckningsgrad. Fysikaliskt verkande insektsmedel med växtextrakt har potential att användas för bekämpning av vita flygare. De moderna spridarna förmodas ge en tillräcklig täckning, möjliggöra användning av en lägre vätskemängd och kunna användas vid applicering av exempelvis Biomel och Kokossåpa+Chili vid bekämpning av vita flygare i kassava

Interactions between the omnivorous bug Nesidiocoris tenuis (Heteroptera: Miridae) and the tomato pests Helicoverpa armigera (Lepidoptera: Noctuidae) and Phthorimaea absoluta (Lepidoptera: Gelechiidae): predation, phytophagy, and prey preference

Nesidiocoris tenuis (Reuter) (Heteroptera: Miridae) is a zoophytophagous bug that can derive nutrients from 3 trophic levels: plants, herbivorous arthropods, and other predators. On tomato, besides damaging the plants as they feed, might the mirid also forage on pest species and repel pests. In greenhouse and laboratory experiments, we investigated the functional response of the bug, its prey preference, and its influence on the oviposition potentials of 2 major pest species Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae) and Phthorimaea absoluta Meyrick (Lepidoptera: Gelechiidae) on tomato Solanum lycopersicum L. (Solanaceae). Nesidiocoris tenuis showed a Type II functional response to both prey species. The estimated handling time was higher for H. armigera eggs than for P. absoluta yet N. tenuis attack rates did not differ between the 2 prey species. Nesidiocoris tenuis did not show a preference for 1 species when prey eggs were provided in equal proportions. The feeding on tomato plants by N. tenuis did not affect oviposition by the 2 moth species, as neither species showed a preference for clean or N. tenuis-adult-damaged plants and clean or N. tenuis-nymph-damaged plants. This study shows that N. tenuis can prey upon eggs of both moth species as the 3 species co-occur in tomato fields. However, because of the shorter handling time of P. absoluta eggs by the predator and the higher number of eggs laid by H. armigera, the co-occurrence might be less detrimental to the H. armigera populations compared to P. absoluta

Pathogenicity of Beauveria bassiana (Balsamo-Crivelli) and Metarhizium anisopliae (Metschnikof) isolates against life stages of Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae)

Background Entomopathogenic fungi are primary pathogens that naturally afect insect pests by suppressing their populations and considered as an ecofriendly agents. The present study aimed to evaluate in vitro activity of diferent isolates of Beauveria bassiana and Metarhizium anisopliae against the development of larval stages of the Cucurbit fruit fy, Zeugodacus cucurbitae (Coquillett) (Diptera: Tephritidae). Results Larval mortality was signifcantly high with B. bassiana isolate Bb337 (5.82–21.70%) and with the lowest in M. anisopliae isolate MaD (1.49–6.33%). Pupal mortality rate was comparatively higher with more than 50%. The cadavers of all host instars produced conidia (sporulation). Sporulated dead larvae were signifcantly higher in Bb337 (61.10%) than at the least in MaD (18.60%) at 105 conidia/ml. At 108 conidia/ml, MaD induced the highest pupal cadavers with mycosis (32.42%). Regardless of applied fungal species, host instars mortality signifcantly increased with increasing concentration of B. bassiana isolates, suggesting a concentration-dependent response of Z. cucurbitae. Conclusion The tested isolates demonstrated their pathogenicity through vertical transmission of mycosis from one instar to another, regardless of the concentrations used

First report of Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) in the Republic of Benin

Tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a serious pest of tomato Solanum lycopersicum L. (Solanaceae) originating from South America. Due to previous outbreaks in neighbouring West African countries, surveillance was ongoing since 2014 in Benin. Tomato plants were regularly inspected and pheromone traps placed in tomato-producing localities in northern, southern and central Benin, including fields close to the border with Niger and Nigeria. In late 2017 and beginning of 2018 Gelechiidae moths were obtained from both the traps and the reared plant material. Morphological examination and molecular analysis of the gained specimens allowed to confirm the presence of the pest in the northern and central regions of Benin. We hence confirm the presence of T. absoluta in yet another West African country

Exotic or Native? Interspecific Competition in the Parasitization of the Fruit Fly Ceratitis cosyra

Fopius arisanus Sonan and Fopius caudatus Szèpligeti (Hymenoptera: Braconidae) are two solitary endoparasitoids of tephritid fruit flies that parasitize eggs of fruit flies infesting the same fruits. We studied intraspecific competition between these two parasitoids species in the mango fruit fly Ceratitis cosyra (Walker) (Diptera: Tephritidae). Based on previous documentation of the equal chance of survival between F. arisanus and Fopius ceratititvorus Wharton (Hymenoptera: Braconidae) while co-parasitizing (Bokonon-Ganta et al., 2005), we hypothesized that we would not find a superior competitor between the two parasitoids

Basal conditions at Engabreen, Norway, inferred from surface measurements and inverse modelling

Engabreen is an outlet glacier of the Svartisen Ice Cap located in Northern Norway. It is a unique glacier due to the Svartisen Subglacial Laboratory which allows direct access to the glacier bed. In this study, we combine both sub- and supraglacial observations with ice-flow modelling in order to investigate conditions at the bed of Engabreen both spatially and temporally. We use the full-Stokes model Elmer/Ice and satellite-based surface-velocity maps from 2010 and 2014 to infer patterns of basal friction. Direct measurements of basal sliding and deformation of lower layers of the ice are used to adjust the ice viscosity and provide essential input to the setup of our model and influence the interpretation of the results. We find a clear seasonal cycle in the subglacial conditions at the higher elevation region of the study area and discuss this in relation to the subglacial hydrological system. Our results also reveal an area with an overdeepening where basal friction is significantly lower than elsewhere on the glacier all year round. We attribute this to either water pooling at the base, or saturated sediments and increased strain heating at this location which softens the ice further

Hyaluronic Acid Levels Predict Risk of Hepatic Encephalopathy and Liver-Related Death in HIV/Viral Hepatitis Coinfected Patients

Whereas it is well established that various soluble biomarkers can predict level of liver fibrosis, their ability to predict liver-related clinical outcomes is less clearly established, in particular among HIV/viral hepatitis co-infected persons. We investigated plasma hyaluronic acid's (HA) ability to predict risk of liver-related events (LRE; hepatic coma or liver-related death) in the EuroSIDA study

A longitudinal analysis of trends in the number of positive cases and swabbing activities during the first eighteen months of the COVID-19 pandemic in Malta

In March 2020, at the onset of the COVID-19 pandemic teams were set up to execute the processes needed to implement COVID-19 related activities. The Helpline team was responsible for the booking of appointments for swabbing, the first step in the process. The Helpline also received calls from the public for other reasons.peer-reviewe

The national helpline during the COVID-19 pandemic : a pillar of support for the public

Soon after the onset of the COVID-19 pandemic in Malta in March 2020, the number of calls from the public escalated so much that a helpline service, Helpline 111, was set at a private call centre. Calls from the public were answered by a team of trained agents, supported onsite by officials from the Public Health Response Team. The reasons for the calls varied and guidelines for answering the calls were continuously updated in line with the current standards and mitigation measures.peer-reviewe