Comparative virulence of blue-stain fungi isolated from Japanese red pine

 We made inoculations to determine the comparative virulence of blue-stain fungi isolated from Japanese red pine (Pinus densiflora Sieb. & Zucc.). Based on the symptoms caused by each fungus, the most virulent fungus was Leptographium wingfieldii. Also, Ophiostoma minus was relatively virulent while lesions induced by some species did not differ from those in the control treatment. Based on the results, we concluded that the pathogenicity of the blue-stain fungi varied widely, and thus their impact on the host most likely varies too. Received: June 7, 2002 / Accepted: October 4, 2002 Present address: JST Domestic Research Fellow, Forest Pathology Laboratory, Tohoku Research Center, Forestry and Forest Products Research Institute, 92-25 Nabeyashiki, Shimo-Kuriyagawa, Morioka 020-0123, Japan Tel +81-19-648-3961; Fax +81-19-641-6747 e-mail: H_masu@hotmail.com Acknowledgments We thank Drs. Ohtaka and Usuki, Plant Pathology and Mycology Laboratory, Institute of Agriculture and Forestry, University of Tsukuba, for technical assistance. Contribution No. 174, Plant Pathology and Mycology Laboratory, Institute of Agriculture and Forestry, University of Tsukuba. Correspondence to:H. Masuya     

Factors influencing mansonone induction in elm callus by culture filtrate elicitors of Qphiostoma ulmi

Mansonone F (phytoalexin) production in elm callus induced by elicitors of Ophiostoma ulmi is affLited by cultural and experimental conditions. These factors include different fun gal isolates, fungal culture age, elicitor concentration, the time of elicitor treatment, the callus cu Ytured with or without light and the callus subculturing frequency.     

Dutch elm disease in New Zealand: impacts from eradication and management programmes

Ophiostoma novo‐ulmi, the cause of the current pandemic of Dutch elm disease, is considered one of the 20 worst pests to have been introduced to New Zealand. An attempt to eradicate the pathogen came close to success, but was eventually stopped and replaced by management programmes. These programmes are slowing the spread of the pathogen. If left uncontrolled it is likely that New Zealand will lose 90% of its elm trees. Although elms are exotic trees in New Zealand, the loss of such a large number of popular amenity trees is likely to have numerous social, cultural, environmental and economic effects. It is estimated that this disease could cost public and councils over NZD $350 million in tree removal and replacement costs. Control of O. novo‐ulmi is limited, but biological control using d‐factor viruses has been proposed. Although O. novo‐ulmi was not eradicated from New Zealand, the eradication programme had many successes; in particular, the effective interaction of good management and science in the early years of the campaign. Also highlighted in this review are several tactics and steps that could be applied to eradication attempts for other species.     

切梢小蠹伴生真菌发生及病害特征的初步研究

小长喙霉 ( Ophiostoma minus Hedgc.)于 190 6年作为新种定名为 Ceratostomella minorHedgc,1981年更名为 Ophiostoma minus Hedgc.,此后一直沿用至今 [1]。小长喙霉以小蠹虫( Tomicus spp.)为媒介 ,通过小蠹虫对树木的蛀害 ,被携带进入到寄主植物组织内 ,进行自身生命过程并危害寄主植物[2 ] ,故也被称为小蠹虫伴生真菌 [3,4] 。该菌的寄主植物主要是松树( Pinus spp.) [4] ,它在协助小蠹虫蛀害松树树木中扮演着重要的角色 [3,4]。80年代以来 ,纵坑切梢小蠹 ( Tomicus piniperda Linnaeus)在云南 8个地州大面积暴发成灾 ,10余万 hm2 …     

Control of Dutch elm disease by the sterol biosynthesis inhibitors fenpropimorph and fenpropidin

Sterol biosynthesis inhibitors that inhibit the yeast-hyphae conversion inOphiostoma ulmi suppressed Dutch elm disease development in two elm clones. After curative treatment with fenpropimorph-sulphate of 27 Vegeta elms which had previously been inoculated withO. ulmi, 25 trees did not show disease symptoms by the end of the second season. All 41 control trees, inoculated withO. ulmi only, were clearly diseased. In an experiment with Commelin elms three fenpropimorph salts and thiabendazole were compared. Injection of the trees three weeks after inoculation withO. ulmi gave by the end of the second season no symptoms of Dutch elm disease in any of the trees injected with fenpropimorph-phosphate or thiabendazole, and in most trees injected with fenpropimorph-acetate or-sulphate. Similar treatments with the free base of fenpropimorph and fenpropidin-sulphate were less effective due to insufficient uptake of the fenpropimorph emulsion and phytotoxicity of fenpropidin-sulphate, respectively. Injection of fenpropimorph-sulphate or thiabendazole six weeks after inoculation withO. ulmi did not result in significant differences from the control group inoculated withO. ulmi only.Fenpropimorph-phosphate and-sulphate completely suppressed Dutch elm disease upon injection of only 7.5 or 10 g per tree (average tree diameter 28 cm). Residue analyses showed only a slow decrease in concentration of the fungicide over two growing seasons and an apparent transport into the new annual ring, other prerequisites for a possible future use for control of Dutch elm disease.Samenvatting De iepeziekte kan onderdrukt worden door sterolbiosyntheseremmers die de overgang vanOphiostoma ulmi van de gistvorm in de hyfevorm remmen. Aan het eind van het tweede seizoen na een curatieve behandeling van 27 Vegeta iepen met fenpropimorfsulfaat bleken 25 bomen geen symptomen van iepeziekte te vertonen. Alle controlebomen, die alleen metO. ulmi geïnoculeerd waren, waren duidelijk ziek. In een proef met Commelin iepen werden drie fenpropimorfzouten en thiabendazool vergeleken. De zouten werden drie weken na de inoculatie metO. ulmi geïnjecteerd. Aan het eind van het tweede seizoen vertoonden geen van de bomen die met fenpropimorffosfaat of thiabendazool geïnjecteerd waren en slechts enkele bomen die met fenpropimorfacetaat of-sulfaat geïnjecteerd waren iepeziektesymptomen. Behandelingen met fenpropimorf (vrije base) en fenpropidinsulfaat werkten minder goed door de slechte opname van de fenpropimorfemulsie en de fytotoxiciteit van fenpropidin. Injectie met fenpropimorfsulfaat of thiabendazool zes weken na inoculatie leidde niet tot significante verschillen met de controlegroep die alleen metO. ulmi geïnoculeerd was.Een dosis fenpropimorffosfaat of-sulfaat van 7.5 of 10 g per boom met een gemiddelde boomdiameter van 26 cm bleek de iepeziekte volledig te kunnen onderdrukken. Uit residue-onderzoek bleek dat de concentratie van het fungicide gedurende de twee groeiseizoenen slechts langzaam afnam en dat het middel naar de nieuwe jaarring werd getransporteerd, twee voorwaarden voor een toepassing op praktijkschaal van fenpropimorf voor de bestrijding van de iepeziekte.     

Pseudomonas for biological control of dutch elm disease. I. Labeling,detection and identification of pseudomonas isolates injected into elms; comparison of various methods

To understand the mechanisms involved in biological control of Dutch elm disease byPseudomonas, data were needed on the distribution of the introduced bacteria within elm and on the development of the bacterial population over a period of time.As traditional biochemical identification techniques are not suitable for distinguishment between individualPseudomonas isolates, three alternative approaches were compared.

Pseudomonas for biological control of Dutch elm disease. III. Field trials at various locations in the Netherlands

The prophylactic effect in elm of one treatment with aPseudomonas isolate was monitored in two types of field trials. In one type only natural Dutch elm disease infections were monitored and hence large numbers of trees were necessary due to the low incidence of natural occurring infections. In the other type trees were artificially infected.The large-scale field trials in which only natural infections were monitored, were based on expected annual losses due to Dutch elm disease of approximately 2%. As a result of the Dutch sanitation program, which was based on the prompt removal of every weakened or diseased elm, the actual losses were generally threefold lower. Dutch elm disease incidence was 22–45% lower in the trees treated with aPseudomonas isolate in the year of treatment and the year after. The results of the biocontrol treatment were negatively influenced because on several locations trees were felled that showed initial signs of Dutch elm disease, which probably would have disappeared during the season.The advantage of artificial infections withOphiostoma ulmi was a reproducable development of symptoms and the possibility to maintain diseased trees, at least till the first signs of elm bark beetle breeding. For Commelin elms an increase in symptoms was observed with increasingO. ulmi dose till 3000 conidia per tree; the standard 500 000 conidia used for most experiments was well above this critical value. No decrease in effectiveness of the bacterial pre-treatment was observed with increasingO. ulmi inoculum. Different bacterial treatments suggested that injections at a smaller interval (i.e. more injections per tree) may result in a better prophylactic effect, but the significance of the correlation remained doubtful. A comparison of several elm species and clones showed the importance of the host tree. Prophylaxis as a result of one bacterial treatment was shown repeatedly in Commelin elms; the numbers of trees showing symptoms by the end of the second year were 10 to 85% lower in the bacteria-treated groups in comparison with the controls. Also in one experiment with Belgica elms prophylaxis was observed, resulting in a 84% decrease in the number of trees showing symptoms by the end of the second year after the prophylactic treatment followed by inoculation withO. ulmi. In Vegeta symptom development was only less severe and in field elms (Ulmus carpinifolia) some prophylactic effect was observed in one experiment, but no effect in two others.Samenvatting De mogelijke bescherming tegen de iepeziekte, verkregen door injectie van de boom met bacteriën van het geslachtPseudomonas, werd gemeten in twee soorten experimenten. In het ene soort werden natuurlijke infecties gemeten, waardoor grote proefgroepen nodig waren. In het andere soort werden de iepen kunstmatig geinfecteerd.De grootschalige veldexperimenten waarbij natuurlijke iepeziekte-infecties werden gemeten, waren gebaseerd op een verwachte jaarlijkse uitval van 2%. Als gevolg van de landelijke bestrijdingscampagne bleken de verliezen slechts ongeveer een derde hiervan te zijn. Er kwam minder iepeziekte voor in de metPseudomonas geïnjecteerde bomen in het jaar van injectie en in het jaar daarna. Een storende invloed op de resultaten had het effect dat ook met bacteriën geïnjecteerde bomen soms beginnende symptomen vertonen na infectie metOphiostoma ulmi, symptomen die in de loop van het seizoen soms weer verdwijnen. Als gevolg van de bestrijdingscampagne werden zulke bomen toch geveld.Het voordeel van kunstmatige infecties metO. ulmi was een voorspelbaar verloop van de symptoomontwikkeling en de mogelijkheid om zieke bomen te laten staan tot er iepespintkevers in kwamen. In Commelin iepen bleken de symptomen toe te nemen met een tot 3000 conidiën per boom toenemende dosisO. ulmi. De gebruikelijke 500000 conidiën die in de meeste experimenten werden gebruikt lagen ver boven deze kritische waarde. Er werd geen effect van een toenemende dosisO. ulmi op de effectiviteit van een bacteriebehandeling waargenomen.Uit variaties in de diverse bacteriebehandelingen kwam naar voren dat injecties met een kleinere tussenruimte (dus meer injecties per boom) mogelijk het effect verbeterden, maar de significantie van deze correlatie bleef twijfelachtig.Vergelijken van diverse iepen toont dat soort en kloon type een belangrijke rol speelt bij deze bestrijdingsmethode. Bescherming tegen de iepeziekte als gevolg van een bacteriebehandeling werd diverse malen aangetoond in Commelin iepen; het aantal bomen met iepeziekte-symptomen was aan het eind van het tweede seizoen in de met bacteriën behandelde groepen 10 tot 85 % lager dan in de controlegroepen. Ook in een experiment met Belgica iepen werd een goede bescherming gemeten. In Vegeta werd slechts een verminderde symptoomontwikkeling gemeten en in veldiepen (U. carpinifolia) werd enige bescherming gevonden in één experiment, maar geen effect in twee andere.     

Fungi associated with the spruce bark beetle Ips typographus in an endemic area in Norway

To investigate the fungal flora associated with the spruce bark beetle Ips typographus in an endemic area, beetles were collected during the flight period in six locations in Tr?ndelag, Norway. The beetles were inoculated into fresh Norway spruce logs, and the frequency of different species was monitored by fungal isolation from bark and wood. The most common species were Ophiostoma bicolor, O. penicillatum, O. polonicum and a previously undescribed Graphium species, the same species which were the most important associates of I. Typographus in an epidemic area in southeastern Norway. The frequency of the primary invader, O. polonicum, was, however, lower in Tr?ndelag, which may indicate that this species is less frequent in endemic areas than in epidemic areas.     

Evaluating Verticillium dahliae for biological control of Ophiostoma novo-ulmi in Ulmus minor

The ability of isolate Vd-48 of Verticillium dahliae to induce resistance against subsequent challenge with Ophiostoma novo-ulmi was examined in Ulmus minor . In the first experiment, conditioning inoculation of 5-year-old elm trees (2–3 m in height) with Vd-48 15 days prior to challenge inoculation with O. novo-ulmi significantly reduced wilting ( P  ≤ 0·05) compared with trees not conditioned with Vd-48. However, in another experiment on 6-year-old trees (2–3·5 m in height), no protection was achieved when the length of time between conditioning and challenge inoculations was 45 or 60 days. In a further experiment, inoculations with Vd-48 alone resulted in severe wilting in 22 out of 118 trees (6–10 years old and 4–7 m in height). Across the 2 years of this last trial, nine trees showed massive feeding wounds made by Scolytus sp., while O. novo-ulmi strains were isolated from six trees. Vd-48 provided a variable prophylactic effect against O. novo-ulmi in U. minor . Major difficulties with this approach to control Dutch elm disease are discussed.     

Comparisons of Ophiostomatoid fungi associated withTomicus piniperda andT. minor in Japanese red pine

Five species ofOphiostoma, twoLeptographium species and aGraphium species were isolated from two morphologically and ecologically similar bark beetle species,Tomicus piniperda andT. minor, and their infested Japanese red pine (Pinus densiflora) in Yamanashi Prefecture, central Honshu, Japan. An underscribedOphiostoma species andO. minus were isolated mainly fromT. piniperda and its galleries.Ophiostoma canum which was found for the first time in Japan was mainly fromT. minor and its galleries. Specific relationships between the beetles and fungal species are suggested. Contribution No.140, Laboratory of Plant Pathology and Mycology, Institute of Agriculture and Forestry, University of Tsukuba. Part of this study was presented at 108th Annual meeting of Japanese Forestry Society, April 2, 1997, Fukuoka, Japan.