A systematic approach to biological control agent exploration and prioritisation for prickly acacia (Acacia nilotica ssp. indica)

Agent selection for prickly acacia has been largely dictated by logistics and host specificity. Given that detailed ecological information is available on this species in Australia, we propose that it is possible to select agents based on agent efficacy and desired impact on prickly acacia demography. We propose to use the 'plant genotype' and 'climatic' similarities as filters to identify areas for future agent exploration; and plant response to herbivory and field host range as 'predictive' filters for agent prioritisation. Adopting such a systematic method that incorporates knowledge from plant population ecology and plant-herbivore interactions makes agent selection decisions explicit and allow more rigorous evaluations of agent performance and better understanding of success and failure of agents in weed biological control.

The distribution and spread of citrus canker in Emerald, Australia

Citrus canker is a disease of citrus and closely related species, caused by the bacterium Xanthomonas citri subsp. citri. This disease, previously exotic to Australia, was detected on a single farm [infested premise-1, (IP1). IP is the terminology used in official biosecurity protocols to describe a locality at which an exotic plant pest has been confirmed or is presumed to exist. IP are numbered sequentially as they are detected] in Emerald, Queensland in July 2004. During the following 10 months the disease was subsequently detected on two other farms (IP2 and IP3) within the same area and studies indicated the disease first occurred on IP1 and spread to IP2 and IP3. The oldest, naturally infected plant tissue observed on any of these farms indicated the disease was present on IP1 for several months before detection and established on IP2 and IP3 during the second quarter (i.e. autumn) 2004. Transect studies on some IP1 blocks showed disease incidences ranged between 52 and 100% (trees infected). This contrasted to very low disease incidence, less than 4% of trees within a block, on IP2 and IP3. The mechanisms proposed for disease spread within blocks include weather-assisted dispersal of the bacterium (e.g. wind-driven rain) and movement of contaminated farm equipment, in particular by pivot irrigator towers via mechanical damage in combination with abundant water. Spread between blocks on IP2 was attributed to movement of contaminated farm equipment and/or people. Epidemiology results suggest: (i) successive surveillance rounds increase the likelihood of disease detection; (ii) surveillance sensitivity is affected by tree size; and (iii) individual destruction zones (for the purpose of eradication) could be determined using disease incidence and severity data rather than a predefined set area.

Austropleospora osteospermi gen. et sp nov and its host specificity and distribution on Chrysanthemoides monilifera ssp rotundata in Australia.

Hendersonia osteospermi was found for the first time in Australia on leaf spots of the introduced invasive plant Chrysanthemoides monilifera ssp. rotundata (bitou bush) in coastal regions of New South Wales. Pathogenicity tests on species from 11 tribes in the family Asteraceae, demonstrated that H. osteospermi caused severe necrosis on leaves and stems of C. monilifera ssp. rotundata and its congener C. monilifera ssp. monilifera (boneseed). Small necrotic spots also developed on Osteospermum fruticosum and Dimorphotheca cuneata in the Calenduleae and on Helianthus annuus (sunflower) in the Heliantheae. None of the other plant species tested developed leaf spots, although H. osteospermi was re-isolated from senescent leaves of Cynara scolymus (globe artichoke) in the Cynareae and Vernonia cinerea in the Vernonieae. Single ascospores from ascomata of a Pleospora-like fungus found on diseased stems of bitou bush produced H. osteospermi in culture, which proved the anamorph/teleomorph connection. The ITS region of both a single-ascospore isolate and a single-conidium isolate were sequenced and found to be identical. The taxonomic status of H. osteospermi is re-examined and Austropleospora osteospermi gen. et sp. nov. is described as its teleomorph based on morphology, host range tests and DNA sequence analysis. The potential of A. osteospermi for the biological control of bitou bush and boneseed in Australia is discussed.

Outbreak of angular leaf spot, caused by Xanthomonas fragariae, in a Queensland strawberry germplasm collection.

Strawberry (Fragaria (x) ananassa) plants exhibiting leaf lesions consistent with angular leaf spot (ALS, caused by Xanthomonas fragariae Kennedy and King 1962) were identified in the Queensland strawberry germplasm at Bundeberg in May 2010. Water suspensions of bacterial ooze tested positive using a previously described primer set. However, the slow growth rate of X. fragariae and the presence of a fast-growing, non-pathogenic, undescribed Xanthomonas species presented problems that were overcome by dilution plating and DNA sequence analysis. Sequencing of the gyrB locus of putative colonies of X. fragariae indicated 100% sequence similarity to other X. fragariae isolates. A new set of diagnostic primers for X. fragariae based on the gyrB locus is presented.

Impact of a biological control agent, Chiasmia assimilis, on prickly acacia (Acacia nilotica ssp. indica) seedlings

A leaf-feeding geometrid, Chiasmia assimilis (Warren), was introduced into northern Queensland from South Africa in 2002 as a biological control agent for the invasive woody weed, prickly acacia, Acacia nilotica subsp. indica (Bentham) Brenan. The insect established in infestations in coastal areas between the townships of Ayr and Bowen where the larvae periodically cause extensive defoliation at some localities during summer and autumn. The impact of this herbivory on a number of plant parameters, including shoot length, basal stem diameter, root length, number of leaves, number of branches, and above and below ground biomass was investigated at one coastal site through an insect exclusion trial using potted seedlings and regular spray applications of a systemic insecticide to exclude the biological control agent. Half the seedlings, both sprayed and unsprayed, were placed beneath the prickly acacia canopy, the other half were placed in full sunlight. Larvae of C. assimilis were found on unsprayed seedlings in both situations. The effects of herbivory, however, were significant only for seedlings grown beneath the canopy. At the end of the five-month trial period, shoot length of these seedlings was reduced by 30%, basal stem diameter by 44%, root length by 15%, number of leaves by 97%, above ground biomass by 87%, and below ground biomass by 77% when compared to sprayed seedlings. Implications are that the insect, where established, may reduce seedling growth beneath existing canopies and in turn may help limit the formation of dense infestations. Crown Copyright (C) 2012 Published by Elsevier Inc. All rights reserved.

Life history of Anomalococcus indicus (Hemiptera: Lecanodiaspididae), a potential biological control agent for prickly acacia Vachellia nilotica ssp indica in Australia

Babul scale Anomalococcus indicus Ramakrishna Ayyar, a major pest of Vachellia nilotica (L.f.) P.J.H. Hurter & Mabb. on the Indian subcontinent, has been identified as a potential biocontrol agent for prickly acacia V. nilotica subsp. indica (Benth.) Kyal. & Boatwr. in Australia and was imported from southern India for detailed assessment. The life history of A. indicus under controlled glasshouse conditions was determined as a part of this assessment. Consistent with other scale species, A. indicus has a distinct sexual dimorphism which becomes apparent during the second instar. Females have three instars, developing into sexually mature nymphs after 52 days. The generation time from egg to egg was 89 days. Females are ovoviviparous, ovipositing mature eggs into a cavity underneath their body. An average of 802 +/- 114 offspring were produced per female. Reproductive output was closely associated with female size; larger females produced more than 1200 offspring. Crawlers emerged from beneath the female after an indeterminate period of inactivity. They have the only life stage at which A. indicus can disperse, though the majority settle close to their parent female forming aggregative distributions. In the absence of food, most crawlers died within three days. Males took 62 days to develop through five instars. Unlike females, males underwent complete metamorphosis. Adult males were small and winged, and lived for less than a day. Parthenogenesis was not observed in females excluded from males. The life history of A. indicus allows it to complement other biological control agents already established on prickly acacia in Australia.

Biological management of the invasive Vachellia nilotica ssp. indica (Benth.) Kyal. & Boatwr. (Fabales: Mimosoideae) in tropical Australia: stress-inducing potential of Anomalococcus indicus Ramakrishna (Insecta: Hemiptera: Coccoidea: Lecanodiaspididae), an agent of promise

Vachellia nilotica ssp. indica (hereafter, V. n. indica) is an important tree weed in Australia. Its dense populations induce undesirable changes in the vast areas of northern Australia. Because chemical and mechanical management options appear unviable for various reasons, biological management of this tree is considered a better option. Among the many trialled arthropods in Australian context, Anomalococcus indicus, a lecanodiaspid native to India, has been identified as a potent-candidate, since in India, its native terrain, it is the most widespread and occurs throughout the year. Severe infestations of A. indicus cause defoliation, wilting and death of branches, and occasionally the tree. Populations of A. indicus have been brought into Australia and are being tested for its host specificity under quarantine conditions. This article reports the physiological damage and stress it inflicts in the shoots of V. n. indica. Younger-nymphal instars of A. indicus feed on cortical-parenchyma cells of young stems, whereas the older instars and adults feed from the phloem of old stems. Two conspicuous responses of V. n. indica arising in response to the feeding action of A. indicus are changes in the cell-wall dynamics and irregular cell divisions. The feeding action of A. indicus elicits a sequence of reactions in the stem tissues of V. n. indica such as differentiation of thick-walled elements in the outer cortical parenchyma, differential thickening of cells with supernumerary layers of either suberin or lignin, proliferations of parenchyma and phloem, wall thickening and obliteration of inner lumen of phloem cells, and the sieve plates plugged with callosic deposits. The responses are the culminations of interaction between the virulence factor (one or more of the salivary proteins?) from A. indicus and the resistance factor in V. n. indica. We have analysed structural changes in the context of their functions, by comparing the feeding action of A. indicus with that of other hemipteroids. From the level of stress it induces, this study confirms that A. indicus has the potential to be an effective biological management of V. n. indica in Australia. © 2014 © 2014 Taylor & Francis and Aboricultural Association.

Timotein (Phleum pratense ssp. pratense L.) alkuperän vaikutus kylmänkestävyyteen, vernalisaatiovaatimukseen sekä kasvuun ja kehitykseen

Nurmiheinien merkitys maailmanlaajuisesti on merkittävä, sillä noin 69 % maapallon peltopinta-alasta on pysyvää laidunmaata tai niittyä. Suomessa nurmien osuus on noin 29 %, ja tuotanto perustuu pääosin intensiiviseen säilörehuntuotantoon. Yleisin nurmiheinälaji Suomessa on timotei (Phleum pratense ssp. pratense L.). Timotei on talvenkestävä ja soveltuu siksi pohjoisiin kasvuoloihin. Timoteilajikkeita jalostettaessa pohjoista alkuperää olevia vanhempaislinjoja käytetään hyvän talvenkestävyyden varmistamiseksi, eteläisiä tavoiteltaessa nopeaa kasvurytmiä. Ilmaston muutoksen ennustetaan lisäävän erilaisia äärioloja kuten myrskyjä ja sateita. Vuorokauden keskilämpötila nousee ja kasvukausi pidentyy. Lisäksi talvet muuttuvat sateisemmiksi. Muutokset näkyvät erityisesti pohjoisissa kasvuympäristöissä. Tutkimuksessa haluttiinkin selvittää eri alkuperää edustavien timoteilajikkeiden ja linjojen kylmänkestävyyttä, kasvu-, ja kehitysnopeutta sekä vernalisaation vaikutusta. Lisäksi tutkittiin syysviljojen vernalisaatiovasteen mittaamiseen käytettyjen menetelmien soveltuvuutta nurmille. Tutkimukseen kuului kaksivuotinen peltokoe sekä kasvatuskaappikoe. Vernalisaatio nopeutti timotein kasvua ja kehitystä. Tutkimuksen perusteella eteläistä alkuperää olevilla lajikkeilla kasvu- ja kukintavalmius oli olemassa ilman vernalisaatiota. Pohjoisilla lajikkeilla oli suurempi vernalisaatiovaste ja niiden kukkiminen ja kasvu nopeutui vernalisaation myötä. Vernalisaatiolla oli vaikutusta myös kasvuston rakenteeseen. Generatiivisten versojen määrä lisääntyi vernalisaation myötä, kun taas vegetatiivisten versojen määrä väheni. Kylmänkestävyys oli tutkimuksen perusteella riippuvainen syksyn karaistumisjakson pituudesta sekä jakson lämpösummasta (FH-COLD). Korkea keskilämpötila ja lyhyt karaistumisjakso heikensivät kylmänkestävyyttä. Vastaavasti karaistumiskauden lämpötilan ollessa välillä 0 °C:ta ja + 5 °C:ta ja jakson pituuden kasvaessa kylmänkestävyys lisääntyi. Tutkimuksen perusteella vernalisaatiolla oli selvä vaikutus timotein kasvuun ja kehitykseen. Pohjoista alkuperää olevat timoteit reagoivat vernalisaatioon eteläisiä enemmän. Osa pohjoisista linjoista vaati vernalisaation generatiivisten versojen muodostumiseen. Syysviljojen vernalisaatiovasteen mittausmenetelmät soveltuvat osin myös puhtaiden timoteilajikkeiden vernalisaation seurantaan.

Incidencia de mosca blanca (Bemisia tabaci Genn) y Picudo (Anthonomus eugenii cano) en cinco genotipos de chile (Capsicum ssp)

Este trabajo se realizó en el período comprendido entre noviembre 2003 y abril 2004, en el área experimental del programa de Recursos Genéticos Nicaragüenses(REGEN), de la Universidad Nacional Agraria, ubicado en el km 12 ½ Carretera Norte con el objetivo de evaluar cinco genotipos de chile (Capsicum ssp.), a la infestación natural de las principales plagas. Los genotipos evaluados fueron CANICA1, CANICA2, ALFILERILLO, DIENTE PERRO Y MIRASOL; se utilizó un diseño de Bloques Completos al Azar (BCA). Las variables evaluadas fueron: incidencia de mosca blanca, incidencia y severidad de virosis, incidencia de picudo,número de frutos por planta, número de frutos anormales y rendimiento (kg ha-1).Para identificar características entre los genotipos, se realizó análisis de varianza y separación de medias (Tukey α=0.05). Los resultados indicaron que para todas las variables evaluadas existen diferencias significativas. El mayor promedio de mosca blanca la obtuvo el genotipo CANICA2 y el menor el genotipo MIRASOL. En cuanto a la incidencia de virosis el menor valor lo presentó CANICA1 y el mayor DIENTE PERRO. El genotipo con mayor severidad por infección viral fue MIRASOL y el menor valor promedio en CANICA1. Para la variable número de frutos por planta, los genotipos MIRASOL y ALFILERILLO promediaron los menores y mayores valores promedio, respectivamente. En cuanto a frutos deformes el menor promedio lo obtuvo CANICA1 y el mayor DIENTE PERRO. Los mayores rendimientos fueron alcanzados por los genotipos DIENTE PERRO (944.4 kg ha-1) y CANICA2 (941 kg ha-1) y el menor valor al genotipo ALFILERILLO con un rendimiento de 368.8 kg ha-1.

Tolerancia de diferentes variedades de repollo (Brassica oleracea L.) a la bacteriosis causada por Xanthomonas campestris pv. campestris P.

Con el objetivo determinar el grado de tolerancia de diferentes variedades de repollo a la bacteriosis (xanthomonas campestri pv. Campestri) y evaluar su adaptabilidad y rendimiento en la zona de la concepción , Masaya, se establecieron ensayos en invernadero y campo en el periodo comprendido entre el 17 de abril al 17 de noviembre de 1989. Se evaluaron 10 variedades de repollo bajo las condiciones de inoculación artificial en el invernadero de las cuales la variedad superette resulto la más susceptible a la bacteriosis; las variedades yasseng e izalco resultaron las más tolerantes. Otras variedades como King kole, Premium y potye resultaron menos susceptibles. A nivel de campo se evaluaron 5 variedades seleccionadas de acuerdo a su grado de tolerancia a bacteriosis y representatividad en el país de las cuales fueron superette, izalco resulto más tolerante a la bacteriosis mientras que la variedad superette mostro alta susceptibilidad seguido por King kole, Premium y copenhagen. Los rendimientos en las variedades susceptibles a la bacteriosis resultaron bajos comparados con izalco.

Comportamiento agronómico e industrial de ocho variedades de Caña de Azúcar; (Saccharum ssp. Hibrido), en un vertisuelo oscuro plástico, (Suelo negro)

Ocho variedades de caña de azúcar (sacoharum ssp), fueron estudiadas en la estación experimental de caña de azúcar del complejo azucarero agro-industrial victoria de julio planteado en enero de 1987, tomando como diseño experimental el de bloque completo al azar, con cuatro repeticiones evaluando los durante la primera cosecha, por los caracteres, crecimiento, desarrollo, rendimiento agrícola, rendimiento industriales y rendimiento agro-industrial. Los resultados demostraron que existió diferencia significativa entre las variedades salvo en cuanto al contenido de sacarosa en caña, en donde las variedades se comportaron de igual forma. Las variedades L .72-3 y CP.63-588 se obtuvieron un rendimiento de 151.07 y 146.60 ton. /ha. Respectivamente, obteniendo el último lugar, asimismo dicha variedades obtuvieron los más bajo rendimiento con 17.76 y 17.13 ton. De azúcar por HA, donde el resto de las variedades evaluadas se comportaron con similar rendimiento agrícola a agro-industrial. Ubicándose en el primer lugar.

Efecto de tratamiento de semilla sobre la incidencia de tizón común (Xanthomonas campestris p.v. phaseoli) en frijol (Phaseolus vulgaris L.)

En las pruebas de calidad de semilla, ocho diferentes variedades de frijol común colectadas de una parcela experimental infectada por tizón común mostraron la presencia de Xanthomonas campestri pv. Phaseoli . Las variedades Revolución 799ª, Revolución 79 y Revolución 84 mostraron menos grado de infección bacteriana mientras las variedades ICA-PIJAO, Honduras -46, Revolución 81 y Revolución 85 mostraron alto grado de infección: El grado de infección bacteriana en las semillas afecto adversamente su capacidad germinativa: los tratamientos físicos como Agua caliente (50º C) por 10,15 y 20 minutos y tratamientos químicos como Agrimicia (100 y 200 ppm), Formalina 5% y Sulfato de cobre 200 ppm no mostraron ser efectivos para reducir el grado de infección significativamente: Los mismos tratamientos aplicados a la semilla infectada no resultaron efectivos para reducir el grado de infección significativamente: Los mismos tratamientos aplicados a la semilla infectada no resultaron efectivos para reducir la severidad de tizón común en el campo donde las condiciones climáticas eran favorables para l desarrollo de la enfermedad y se realizó control mecánico de malezas: La alta severidad de tizón común registrada durante el ciclo trajo como consecuencia rendimientos muy por debajo del rendimiento potencial: La obtención de sillas de los campos libres o con baja incidencia de tizón común es la única práctica que puede asegurar semillas libre de este patógeno y por lo tanto una buena cosecha.