Host–pathogen interaction between Phytophthora infestans and Solanum nigrum, S. villosum, and S. scabrum

Potato and tomato are the two major hosts for Phytophthora infestans causing late blight. The susceptibility of leaves and whole plants of Solanum nigrum, S. villosum, and S. scabrum to infection by P. infestans was tested under laboratory conditions. Out of 39 plants representing 38 different S. nigrum accessions, 16 were highly resistant (seven accessions did not show any symptoms of infection, nine were highly resistant showing necrotic lesions in the place of infection), and 23 plants of S. nigrum were colonized by, at least, 1 of the 2 isolates of P. infestans (17 accessions were infected with two P. infestans isolates, and 6 accessions showed different reactions depending on the isolate used for inoculation). Three accessions of S. villosum, and one accession of S. scabrum were tested and did not show any symptoms of infection. The majority of S. nigrum accessions infected by P. infestans in a detached leaf assay were also infected in the whole plant assay. The reaction of field- and greenhouse-grown plants to inoculation with P. infestans in detached leaf assays was similar, but in some cases leaves from field-grown plants reacted as resistant in comparison with the leaves from greenhouse-grown plants, which were susceptible.     

1977 British Crop Protection Conference —Pests and Diseases,Brighton, November 1977

Abstract

The golden apple snail, Pomacea canaliculata (Lamarck, 1822) (Mesogastropoda: Pilidae), has recently been introduced to several Asian countries where it has unexpectedly developed into a pest of rice. Reasons for the introduction as well as the economic and ecological impact of the snail are described. Most farmers have resorted to chemical control, with implications for human health and the environment. Integrated snail management practices are summarized including the use of the snail as a valuable aquatic resource. It is concluded that research on control strategies is urgently needed but requires sound knowledge of the ecology of the snail in its natural habitat.     

The organisation and practice of vertebrate pest control,Elvetham Hall,Hampshire, August–September 1982

Abstract

The evaluation of an electrostatic sprayer developed by ICI, the Electrodyn® sprayer, for use in the residual treatment of dwellings for the control of malaria vectors is detailed, and the advantages of using an ultra‐low volume technique for this type of mosquito control are discussed. The impact of this new technology on malaria control programmes is also considered.     

Pest control by pathogens — fungi,viruses and bacteria

Integrated pest control on chrysanthemum is once again becoming a possibility.Verti-cillium lecanii is one of the key components as, under the right conditions, it will provide good control of several pest species. High humidity for a number of nights per week is critical for reliable pest control with this fungal pathogen. These conditions can be obtained easily and safely by fogging water over the crop at night. Four consecutive nights of high humidity per week or a cycling two nights of high humidity and two nights ambient have given excellent pest control with no adverse effect to the crop.     

Genetic Diversity of Xylella fastidiosa Strains from Costa Rica, São Paulo, Brazil, and United States

ABSTRACT The diversity of 42 Xylella fastidiosa strains from Costa Rica, S?o Paulo, Brazil, and the United States were analyzed using the sequence of the 16S rRNA gene by variable number of tandem repeat (VNTR) fragment analysis and by restriction fragment length polymorphisms (RFLP) of a specific polymerase chain reaction (PCR)-amplification product using enzyme CfoI. Limited variability in the sequence of the 16S rRNA gene was observed and, although the separation was not absolute, most strains from Costa Rica clustered with strains from the United States and not with strains from S?o Paulo. The PCR-RFLP produced different patterns of DNA bands. The same pattern was shared by strains from Costa Rica, the United States, and two coffee strains from S?o Paulo, but a different pattern was observed in six coffee and orange strains from Brazil. In all, 32 amplification products were scored in the VNTR fragment analysis. The total variation observed among the X. fastidiosa strains had significant (P < 0.001) contributions from both geography and host origin as inferred by Nei's values of genetic diversity and WINAMOVA statistics. The strains from Costa Rica were isolated from diseased grapevines, coffee, and sweet orange and these strains grouped together and could be distinguished from strains from grapevine from the United States or from either coffee or sweet orange from S?o Paulo. The strains tested from Costa Rica are most likely of local origin, although the possibility that they have been introduced along with horticultural crops cannot be excluded. In either case, they are examples of independent selection of strains of X. fastidiosa affecting coffee and sweet orange. Greater genetic similarity was observed between strains from Costa Rica and the United States than with those from S?o Paulo.     

Predation and parasitism on eggs of two pod‐sucking bugs,Nezara viridula and Piezodorus hybneri in soybean

Abstract

Cohorts of newly laid egg masses of two pod‐sucking bugs, Nezara viridula and Piezodorus hybneri (Hemiptera: Pentatomidae), were exposed to naturally occurring predators and parasitoids on soybean in unsprayed fields at four sites in Northern Sumatra. The fate of the young stages was recorded until the late first instar, before the nymphs start to disperse and feed. Partial life tables showed that mortality of N. viridula until the late first instar was 50–87%, of which 18–65% occurred during the egg stage and was mainly caused by predation; 2–26% of the eggs died of parasitism. P. hybneri which was present at only two sites, showed a 73–89% mortality until the late first instar, of which 69–85% was during the egg stage and, again, mainly caused by predation; 15–24% of the eggs died of parasitism. To evaluate the role of individual egg predator species in the field, we conducted hourly observations of exposed egg masses of the two pests. Dolichoderus sp., Solenopsis geminata (Hymenoptera: Formicidae), Paederus sp. (Coleoptera: Staphylinidae) and several gryllids (Orthoptera) were most commonly encountered feeding on the eggs. An index of ‘predation pressure”; was calculated from the densities of predators in the field and from an estimate of their attack rate based on field observations of predator feeding. Two sites with low predator pressures had low predation rates, while the two sites with high predation pressures had considerably higher predation rates. The implications of the findings for IPM training in soybean are discussed.     

Effect of α tocopherol and selenium on antioxidant status, lipid peroxidation and hepatopathy induced by malathion in chicks

The objective of the present study was to investigate the role of α tocopherol and selenium on malathion induced hepatic damage, and antioxidant defense in chicks. The chicks were divided into three groups. First group received malathion 10 mg/kg BW, orally for 60 days, the second group received the same dose of malathion but was supplemented with α tocopherol and selenium for 60 days and the third group served as the control. A compromised antioxidant capacity as evidenced by increased levels of erythrocytic lipid peroxidation and decreased concentration of vitamin E and decreased activity of glutathione peroxidase was observed in chicks following the administration of malathion. An improved antioxidant status was observed in chicks of second group with α tocopherol and selenium supplementation including higher concentration of vitamin E, increased activity of glutathione peroxidase and lower levels of lipid peroxidation. Histopathological studies of liver in the chicks which received malathion exhibited, moderate to severe degenerative and necrotic changes in the hepatocytes. The correlation of decreased antioxidant status of chicks with degenerative changes in liver suggests that lipid peroxidation may be one of the important mechanism in the chronic toxicity of malathion. The results indicate that α tocopherol and selenium were effective in partially alleviating degenerative changes induced by malathion in the liver of chicks by attenuating processes leading to lipid peroxidation.     

Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China

The Dunhuang–Golmud railway passes through different deserts in arid areas, especially drifting-sand desert and sandy-gravel Gobi. The near-surface wind environment and wind-sand transport process vary due to different external factors, such as topography, vegetation, and regional climate, resulting in evident spatial differences in surface erosion and deposition. Consequently, the measures for preventing wind-sand hazards will differ. However, the mechanism and control theory of sand damage rem...     

Characterization of the defence response to Venturia inaequalis in ‘Honeycrisp’ apple,its ancestors,and progeny

The apple cultivar Honeycrisp exhibits genetic resistance to apple scab. The characterization of the macroscopic and microscopic responses on leaves infected by the pathogen Venturia inaequalis is described. The macroscopic resistance reactions observed in ‘Honeycrisp’, its parent ‘Keepsake’, and grandparents ‘Frostbite’ and ‘Northern Spy’ ranged from 0 (no reaction) to chlorotic flecking, stellate chlorosis, necrotic flecking, and sporulation. No hypersensitive response was observed. The resistance response occurred as early as 7 days post inoculation (dpi) at the same time that susceptible plants exhibited macroscopic signs of the disease. The resistance reactions were similar in the progeny population of ‘Honeycrisp’ × ‘Twin Bee Gala’, although they were delayed to 10–14 dpi possibly due to variable greenhouse conditions. This population segregated 3 resistant:1 susceptible, which suggests the presence of two genes in ‘Honeycrisp’ and agrees with the finding that different responses within ‘Honeycrisp’ to mixed inoculum are due to differential recognition of pathogen effectors.     

Region-wide glacier area and mass budgets for the Shaksgam River Basin,Karakoram Mountains,during 2000–2016

The Karakoram Mountains are well known for their widespread surge-type glaciers and slight glacier mass gains.On the one hand,glaciers are one of the sensitive indicators of climate change,their area and thickness will adjust with climate change.On the other hand,glaciers provide freshwater resources for agricultural irrigation and hydroelectric generation in the downstream areas of the Shaksgam River Basin(SRB)in western China.The shrinkage of glaciers caused by climate change can significantly affect the security and sustainable development of regional water resources.In this study,we analyzed the changes in glacier area from 2000 to 2016 in the SRB using Landsat TM(Thematic Mapper)/ETM+(Enhanced Mapper Plus)/OLI(Operational Land Imager)images.It is shown that the SRB contained 472 glaciers,with an area of 1840.3 km2,in 2016.The glacier area decreased by 0.14%/a since 2000,and the shrinkage of glacier in the southeast,east and south directions were the most,while the northeast,north directions were the least.Debris-covered area accounted for 8.0%of the total glacier area.We estimated elevation and mass changes using the 1 arc-second SRTM(Shuttle Radar Topography Mission)DEM(Digital Elevation Model)(2000)and the resolution of 8 m HMA(High Mountain Asia)DEM(2016).An average thickness of 0.08(±0.03)m/a,or a slight mass increase of 0.06(±0.02)m w.e./a has been obtained since 2000.We found thinning was significantly lesser on the clean ice than the debris-covered ice.In addition,the elevation of glacier surface is spatially heterogeneous,showing that the accumulation of mass is dominant in high altitude regions,and the main mass loss is in low altitude regions,excluding the surge-type glacier.For surge-type glaciers,the mass may transfer from the reservoir to the receiving area rapidly when surges,then resulting in an advance of glacier terminus.The main surge mechanism is still unclear,it is worth noting that the surge did not increase the glacier mass in this study.     

Root lesion nematode,Pratylenchus penetrans,in ‘Fire King’ lilies: attack and control with aldicarb

In field trials on fumigated sandy soil planted with stock of Fire King lilies lightly infested withPratylenchus penetrans, nematode control with aldicarb did not influence growth and yield of the lilies in the first growing season, perhaps because of the low initial number of nematodes. In the second season, however, a clear relation appeared between yield and nematode control by aldicarb.In such a biennial crop, yields after aldicarb treatment at planting were almost as good as after treatment in both years, 3 kg aldicarb a.i./ha (1.6 mmol.m^–2) being optimum.Samenvatting Bij de bestrijding van wortellesieaaltjes moet niet alleen rekening worden gehouden met de in de grond aanwezige aaltjes maar ook met die in de wortels van het plantgoed. Aan de wortels van het plantgoed is de aanwezigheid van deze aaltjes niet altijd duidelijk te zien. In als goed gekwalificeerd plantmateriaal van de leliecultivar Fire King werden gemiddeld 15Pratylenchus penetrans per bol gevonden en in slecht plantgoed 9.De aaltjes in de grond kunnen effectief worden bestreden door toepassing van grondontsmetting met een aaltjesdodend middel. In een tweejarige teelt van licht besmet plantmateriaal is dit echter onvoldoende om schade te voorkomen. Dit bleek uit een proef met Fire King in vooraf ontsmette zandgrond op de proeftuin Ens. In het tweede jaar was de groei van de lelies na toepassing van aldicarb ongeveer drie maal beter dan zonder dit middel. In de wortels van de onbehandelde lelies werden ongeveer twintig keer zoveel wortellesieaaltjes gevonden als in die van de behandelde planten.Om dit tweedejaarseffect nader te analyseren en de toepassing van aldicarb beter te preciseren werd het onderzoek op de proeftuin in 1975 en 1976 voortgezet, waarbij vooral aandacht werd besteed aan de dosering en de toedieningswijze van aldicarb in de vorm van Temik 10 G.Uit het pouplatieverloop van de wortellesieaaltjes gedurende de tweejarige teelt (Fig. 3) kan worden afgeleid dat pas merkbare schade optreedt bij meer dan 300P. penetrans per 10 g wortels en meer dan 20P. penetrans per 100 ml grond in mei, wanneer de ontwikkeling van de stengelwortels plaats vindt. De gevonden besmettingen blijven in het eerste jaar in alle objekten beneden deze schadegrens en komen in het tweede jaar daarboven in de objekten waar minder dan 3 kg aldicarb a.i./ha (1,6 mmol.m^–2) is toegediend in het eerste jaar. Dit is in overeenstemming met de opbrengstresultaten (Tabel 2).Uit het verband tussen de toegediende hoeveelheid aldicarb en de relatieve opbrengst blijkt eveneens dat een hogere dosering dan 1,6 mmol.m^–2 nog slechts weinig effectiever is en mogelijk zelfs groeiremmend kan werken. Het maakt daarbij weinig verschil of de toediening plaats vindt bij het planten in de vore of kort voor de opkomst van de lelies in de rug (Tabel 1). Uit praktische overwegingen moet de voorkeur worden gegeven aan de toediening in de plantvoor.De toediening van aldicarb in beide jaren had slechts een geringe produktieverhogend effect boven toediening uitsluitend in het eerste jaar (Tabel 2). Blijkbaar is de effectiviteit van dit nematicide veel groter tegen de lichte aanvangsbesmetting met aaltjes in de wortels van het plantgoed dan wanneer het in de rug wordt toegediend aan de veel hogere, verspreide besmetting aan het begin van het tweede jaar.Wat betreft de bewortelingskwaliteit van de bollen valt het op (Tabel 3) dat ook hogere doseringen dan 1,6 mmol.m^–2 nog verbetering geven en dat toediening in beide jaren een betere bewortelingskwaliteit geeft dan wanneer alleen in het eerste jaar aldicarb wordt toegediend. Het nematicide aldicarb heeft slechts een werkingsduur van 1 à 2 maanden, zodat de aaltjes zich later in het seizoen weer sterk kunnen vermeerderen waardoor de kwaliteit van de wortels snel kan teruglopen. Om een betere bewortelingskwaliteit te bereiken wordt dan ook een veel effectievere bestrijding van de wortellesieaaltjes gevraagd dan voor het veiligstellen van de groei en de opbrengst van lelies.Aangezien de bolwortels van ondergeschikte betekenis zijn voor de groei en de opbrengst van deze lelies lijkt het niet verantwoord hogere doseringen dan 1,6 mmol.m^–2 toe te passen.     

Endo-1,3-β-glucanase and cellulase from Trichoderma harzianum: purification and partial characterization, induction of and biological activity against plant pathogenic Pythium spp.

There were indications that endo-1,3--glucanase (1,3-(1,3;1,4)--D-Glucan 3(4)-glucanohydrolase (EC 3.2.1.6)) and cellulase (1,4-(1,3;1,4)--D-Glucan 4-glucanohydrolase (EC 3.2.1.4)) activity of Trichoderma harzianum Rifai isolate T3 were induced in sphagnum peat moss cultivations and dual culture experiments by the presence of Pythium ultimum. Further, P. ultimum stimulated the germination of Trichoderma conidia. Endo-1,3--glucanase and cellulase were purified from T. harzianum isolate T3, known to control Pythium damping-off of cucumber seedlings. The enzymes were purified from the culture filtrate of the fungus by gel filtration and isoelectric focusing. The purified endo-1,3--glucanase was a small protein with a molecular mass of 17 kilodaltons and a pI of 5.0. Two cellulases were purified to homogeneity and had molecular masses of 40 and 45 kilodaltons respectively, and pI's of 6.4 and 7.6 respectively. Germination of encysted zoospores and elongation of germ tubes of a plant pathogenic Pythium isolate were inhibited by low concentrations of the purified enzymes. A strong synergistic effect was observed on the inhibition of cyst germination by a combination of the endo-1,3--glucanase and the fungicide Fongarid. Finally, a time-course study of colonization of the rhizosphere of cucumber seedlings showed that the active fungal mycelial biomass of a GUS-transformant of T. harzianum isolate T3 increased over four weeks. Trichoderma appeared to colonize healthy roots only superficially, whereas the mucilage of the root hairs and of distal parts of wounded areas or broken parts of the roots, were extensively colonized.     

Neoproterozoic I-type granites in the Central Tianshan Block (NW China):geochronology,geochemistry,and tectonic implications

The Central Tianshan Block is one of numerous microcontinental blocks within the Central Asian Orogenic Belt(CAOB)that overlies Precambrian basement rocks.Constraining the evolution of these ancient basement rocks is central to understanding the accretionary and collisional tectonics of the CAOB,and their place within the Rodinia supercontinent.However,to date,the timing and tectonic settings in which the basement rocks in the Central Tianshan Block formed are poorly constrained,with only sparse geochemical and geochronological data from granitic rocks within the northern segment of the block.Here,we present a systematic study combining U-Pb geochronology,whole-rock geochemistry,and the Sr-Nd isotopic compositions of newly-identified granitic gneisses from the Bingdaban area of Central Tianshan Block.The analyzed samples yield a weighted mean Neoproterozoic 206Pb/238U ages of 975-911 Ma.These weakly-peraluminous granitic rocks show a common geochemical I-type granite affinity.The granitic gneisses are calc-alkaline and enriched in large ion lithophile elements(LILEs)and light rare earth elements(LREEs),but they are depleted in high field strength elements(HFSEs);these characteristics are similar to those of typical subduction-related magmatism.All samples show initial(⁸⁷Sr/⁸⁶Sr)(t)ratios between 0.705136 and 0.706745.Values forεNd(t)in the granitic gneisses are in the range from-5.7 to-1.2,which correspond to Nd model ages of 2.0-1.7 Ga,indicating a role for Mesoproterozoic to Paleoproterozoic rocks in the generation of the granitic protoliths.The documented geochemical features indicate that the protoliths for the gneisses have a similar petrogenesis and magmatic source,which may reflect partial melting of thickened crust with the addition of small amounts of mantle-derived material.The Central Tianshan Block probably constitute part of an exterior orogen that developed along the margin of the Rodinian supercontinent during the Early Neoproterozoic and underwent a transition from subduction to syn-collision compression at 975-911 Ma.     

Effects of nC24 and nC27 petroleum spray oils on oviposition and egg survival of Ostrinia nubilalis Hübner (Lepidoptera,Pyralidae) and Trichogramma brassicae Bezdenko (Hymenoptera,Trichogrammatidae) adults on maize plants

Abstract

The study determined the effectiveness of nC24 and nC27 petroleum spray oils (PSOs) to reduce oviposition of Ostrinia nubilalis and survival of O. nubilalis eggs and Trichogramma brassicae adults. Under choice and no-choice tests, maize treated with 3, 5 and 10% (v/v) of both oils deter O. nubilalis oviposition on maize. The study also showed that treatment of 1 – 3-day-old O. nubilalis eggs with 1 and 2% (v/v) nC24 oil caused 6% mortality compared with 99.5% when treated with 3, 5 and 10% (v/v) oil. In contrast, treatment with 1 – 10% (v/v) nC27 oil caused 99% mortality. Trichogramma brassicae is a major parasitoid of O. nubilalis. The mortality of T. brassicae 24 h after exposure to maize sprayed with 2% (v/v) nC24 and nC27 oils was 8.3 and 12.7%, respectively. At 5% (v/v), the mortalities were 24.9 and 23.5%, respectively. Therefore, application of 3% (v/v) PSO may deter O. nubilalis egg lay, egg mortality and survival of T. brassicae on maize.