De rijpingsvraat van de eikensp intkever,scolytus intricatus ratzeb

Summary The oak barkbeetle,Scolytus intricatus Ratz., is, in normal times, a rather uncommon insect in the Netherlands. After the outbreak of the war, however, it developed in large numbers in oak trees, damaged bij direct war action. The presence of the beetle is indicated bij its maturation feeding, consisting in affecting and killing a large number of spur shoots during May. Bij their boring activity the young beetles nearly cut off these shoots near their base, soon they wither and fade becoming clearly visible in the green canopy. Stormy weather causes them to drop off green so that the ground may become densily covered with these shoots.A rectification is added concerning the maturation feeding ofSc. laevis Bechst., as described formerly by the same author. The identification of the beetle in question proved to be wrong. The maturation feeding described refers to the commonSc. rugulosus Ratz.     

Aantasting van bladeren van rhododendron DoorChaetapiospora rhododendri (Tengw.) v. Arx

Summary Two fungi were isolated from diseased leaves ofRhododendron ponticum: Botryosphaeria foliorum (Sacc.)v. Arx etMüll enChaetapiospora rhododendri (Tengw.) v. Arx. With the latter inoculation-experiments were performed. It became clear that this fungus can only invade the leaves ofRhododendron ponticum through wounds, causing dead areas. These spots enlarged quickly when the leaves were detached from the branches. Perithecia developed in the dead tissues.     

Aantasting in frambozen door Pratylenchus penetrans (Cobb.) Sher et Allen

Summary Raspberries and strawbereis planted several years after a previous crop of raspberries were found attacked byPratylenchus penetrans. Raspberries planted in places where appled trees had been taken out showed slightly stunted growth and a moderate attack of the roots byP. penetrans.The symptoms of heavily infested raspberries were: severely stunted growth of above ground parts without other particular symptoms; a very poor root system, parts of which are completely dead and blackened or show dead, blackened bark, and the absence of fine feeding roots. In cases of light attack the root system is more normal but there is a number of rather large black lesions.Raspberries should not be planted after raspberries, after fruit trees susceptible to attack byP. penetrans, after strawberries or on possibly infested soil (in general light soils) unless a determination of the degree of infestation in the plant sites has shown that the place is safe. In case of infestation suitable measures to eradicate the nematodes should be taken. It may be expected that a fairly light degree of infestation of the soil is sufficient to cause appreciable damage.     

Solanum dulcamara L. (Bitterzoet) als mogelijke bron voor bladrolvirus

Summary Dijkstra (1933) demonstrated thatSolanum dulcamara (Bittersweet, Woody Nightshade) can be a host plant of potato leaf-roll virus. It was, however, not known whether this wild growing plant in nature contains the virus. AsS. dulcamara is the only common perennial Solanacea in the Netherlands its role as a virus reseroir was investigated.At 25 localities plants ofS. dulcamara were collected, and tested for the presence of leaf-roll virus by transferring virus-freeMyzus persicae (Sulz.) after 24 hrs feeding to groups ofPhysalis floridana, where they fed for 24 hrs before being killed. All plants ofS. dulcamara appeared to contain leafroll virus, though they did not show symptoms. Also seedlings ofS. dulcamara from seed of a leafroll infested plant showed no symptoms before or after infection with leafroll bij transmission withMyzus persicae (Sulz.).The virus could be transmitted fromS. dulcamara to potato (var. Bintje) byMyzus persicae (Sulz.) and by graftingS. dulcamara on potato.Seedlings, grown from seed obtained from a plant which was shown to have leaf-roll, all appeared to be infected with leaf-roll. As so far no plants were found or obtained which had no leaf-roll virus, it is possible that inS. dulcamara leaf-roll virus is invariably transmitted with seed. But as the virus does not appear to be pathogenic inS. dulcamara, one might assume that what in potatoes and other plants is called leaf-roll virus, inS. dulcamara is an integral, natural component of the organism.     

Een interessante waarneming over het schadelijk optreden van de zuringbladwesp (Ametastegia glabrata Fall.)

Summary The apple-crop from one part of a bush-orchard with a cover crop of vetch was seriously damaged by the larvae ofAmetastegia glabrata Fall. In the other part of the same orchard planted with an under-crop of potatoes there was no damage at all. The difference was attributed to the presence in the vetch of the weedPolygonum Convolvulus L., a known host-plant of the sawfly larvae. This weed, which climbed into the trees, was absent from that part of the orchard where the potatoes were grown. An experiment is planned with different greenmanuring plants in the infested orchard to investigate their effects on the development of the weed and consequently on the damage by the sawfly larvae.     

Bacterial community associated with the ambrosia beetle Platypus cylindrus on declining Quercus suber trees in the Alentejo region of Portugal

In Portugal, the oak pinhole borer Platypus cylindrus and its mycobiota have been associated with cork oak (Quercus suber) death, but no knowledge exists regarding the associated bacterial community. However, it is known that some bacteria are important for ambrosia beetle symbiosis and play a role in oak tree health. To explore the bacteria associated with this beetle and its host, with the ultimate goal of highlighting potential roles in oak decline, this study used a culture-dependent approach for strain isolation and phylogenetic identification using 16S rRNA gene sequencing and multilocus sequence analysis (MLSA). The bored galleries of different cork oak trees from a cork stand in Alentejo, together with the body and mycangia of adult beetles, were investigated. The samples revealed a diverse community comprising 500 isolates with 64 distinct types of bacterial colonies. Sixty-eight strains were selected for sequencing and used for phylogenetic analysis, 40 from wood galleries and 28 from beetles. Thirty-two genera of bacteria were identified, 18 of which were described for the first time within oak–beetle interactions. Major taxonomic groups were Actinobacteria in beetles and Enterobacterales in wood galleries. Although specific oak bacterial pathogens were not detected, a group of distinct strains detected in wood galleries, potentially belonging to a new Pectobacteriaceae species, were able to produce mild symptoms on cork oak plantlets. This study reports for the first time the biodiversity of culturable bacteria associated with the Q. suber–P. cylindrus interaction, their relevance to both organisms and the possible contribution to oak decline.     

Carbon Fixation and Partitioning in Coffee Seedlings Infested with <Emphasis Type="Italic">Pratylenchuscoffeae</Emphasis>

The objective was to study CO₂ fixation and photoassimilate partition in coffee (Coffea arabica) seedlings infested with the lesion nematode Pratylenchus coffeae. Seedlings infested with 0, 1000 and 8000 Pratylenchus coffeae nematodes were exposed to ¹⁴CO₂ and the incorporation and distribution of radioactivity were followed in the roots, stems and leaves. Fresh mass, pigments, soluble sugars, sucrose and specific radioactivity of sucrose in the plant parts were determined. At the highest level of infestation almost all the parameters were significantly changed showing the carbon fixation in the leaves and partitioning to the roots were decreased. Since lesion nematodes are not sedentary and do not form feeding sites that could be characterised as metabolic sinks, it is suggested that their damage is more readily expressed by the leaves, through a reduction in photosynthesis and phloem transport.     

Inoculum availability and seasonal survival of Potebniamyces pyri in pear orchards

Potebniamyces pyri (anamorph Phacidiopycnis piri) is the causal agent of Phacidiopycnis rot, a postharvest disease of pear fruit (Pyrus communis). Infections of pear fruit by P. pyri occur in the orchard, and symptoms develop after harvest during storage or in the market. P. pyri also is the cause of a canker and twig dieback disease of pear trees. To determine inoculum availability of P. pyri, dead bark and dead fruit spurs were periodically collected in two commercial ‘d’Anjou’ pear orchards and examined for the presence and viability of fruiting bodies of P. pyri. To determine seasonal survival of P. pyri, 2-year-old twigs of ‘d’Anjou’ pear in a research orchard were inoculated approximately monthly over 2 years with P. pyri and monitored for canker development. Inoculated twigs were removed from the trees 6 months post inoculation and examined for formation, viability of pycnidia of P. pyri, and reisolation of the pathogen. In both commercial orchards, all sampled trees were infected by P. pyri; viable pycnidia of P. pyri were observed on 42–78 % of the sampled bark and 5–32 % of the sampled fruit spurs; and viable conidia were observed at all sampling times during the fruit growing season. Apothecia of P. pyri also were observed on sampled dead bark and fruit spurs, but at a frequency ranging from 0 % to 19 %. P. pyri was recovered from inoculated twigs 6 months after inoculation at all sampling times during the 2-year study, but recovery frequency varied. P. pyri formed pycnidia on most cold-injured and inoculated twigs. The results suggest that: i) the conidial state of P. pyri is the main type of inoculum in pear orchards in the region; ii) viable inoculum of P. pyri for potential fruit infections is available during the pear fruit-growing season; iii) P. pyri can form pycnidia on cankers of twigs infected by the fungus at different seasons during the year; and iv) P. pyri can survive as mycelium in diseased pear twigs year round in the orchard.     

Een virus inAtropa belladonna

Summary In a bgarden at Baarn, The Netherlands,Atropa belladonna plants, grown from seed, showed symptoms similar to those described bySmith (1946, 1957) for Belladonna mosaic. After inoculation of solanaceous test plants with sap from diseased plants, the following species showed symptoms:Atropa belladonna L.,Capsicum annuum L.,Hyoscyamus niger L.,Nicandra physaloides Gaertn.,Nicotiana glutinosa L.,Nicotiana tabacum L. var. Samsun,Petunia hybrida andPhysalis floridana Rydb. The symptoms suggest that the virus may be identical with that described bySmith. A high virus concentration was found inHyoscyamus niger. Nicandra physaloides, Petunia hybrida, Physalis floridana, in the roots and the pericarp of diseasedAtropa plants, and also inSolanum nigrum L. andDatura stramonium L. The latter two species showed hardly any symptoms. A. low virus concentration was found inCapsicum annuum, though this plant showed severe symptoms.The dilution end point of the virus was between 10^–3 and 10^–4; virusinactivation occurred between 70° and 80°C.In electron micrographs the rod-shaped virus particles appeared similar to those of rattle virus.Virus could be detected in the roots of tobacco plants after the leaves had been inoculated with sap of diseasedAtropa-plants (Table 1). The reverse did not occur. Following immersion of the roots of tobacco plants in virus-containing sap these plants were potted in steamed soil. Subsequently the roots proved to be infected but the stems and leaves contained no virus. However,Atropa plants treated in the same way, did show leaf symptoms.It appeared, that the roots of young, healthy tobacco plants could become infected with virus, when grown in naturally infested soil for only tow days (Table 2). Fungus cultures isolated from diseased roots did not show any infectivity. Nematodes are probably the vectors of this virus (Sol, Van Heuvel & Seinhorst, 1960).Met medewerking van Merr.J. M. Dekhuyzen-Maasland, Dr. S. Gayed (Karthoum), Mej.C. van Heuven, C. de Vooys en Mej.R. van Wessem.     

Het parasitaire karakter van Septotinia populiperda Waterman & Cash

Summary Mature apothecia ofSeptotinia populiperda Waterman andCash are formed in spring and early summer on leaves shed the previous autumn. The ascospores ofS. populiperda produce an infection in the form of leafblotches only when an injury of the leaf is present.P. candicans Ait. is more susceptible to the parasite thanP. marilandica Bosc. andP. brabantica Houtz. Leafblotches are produced in equal numbers when the ascospores are sprayed with an atomizer upon the upper or the lower leafsurface. The germination of the ascospores is inhibited in vitro at a concentration of 7 to 8 mg copper per liter, when copper is used as Bordeaux mixture, or as coppersulfate (CuSO₄5H₂O).     

Influence of altitude on adult emergence and dynamics ofKaltenbachiola strobi (Winnertz) (Diptera: Cecidomyiidae) populations and its parasites in the Tatra National Park, Poland

A field study onKaltenbachiola strobi (Winnertz) (Diptera: Cecidomyiidae), was carried out between 1987 and 1993 in the highest mountain range in the Western Carpathians located within the Tatra National Park, in southern Poland. Rearing and analysis of 5 780 cones ofPicea abies (L.)Karst., collected from trees growing at different altitudes, yielded 30,478 individuals ofKaltenbachiola strobi, which infested 89.10% of the cones. In case of 29.81% of cones there were more than 20 larvae ofK. strobi per cone. It was shown thatK. strobi in the Tatra Mts. is more abundant in spruce stands of the upper mountain forest zone. Significant connections between the time of cone infestation byK. strobi and its parasitoids and characteristic phenophases in spruce foliage and cone development, and also the development of selected vegetation of the forest floor at different heights above sea level were determined. It was shown that the population dynamics ofK. strobi had tendency to alternate the increase and decrease in numbers every two years. It was also discovered that every two years spruce cones were inhabited by the population ofK. strobi with increased percentage of individuals having prolonged diapause. In total, the parasitoids reduced the population ofK. strobi by about 16–22.63%. Parasitism ofK. strobi in the lower mountain forest zone was higher than in the upper zone.Triplatygaster contorticornis Ratz. (Hymenoptera: Platygasteridae),Torymus azureus Boheman (Hymenoptera: Torymidae) andTetrastichus strobilanae Ratz. (Hymenoptera: Eulophidae) were most effiecient in reduction of the population ofK. strobi, and in the lower mountain forest zoneT. azureus was the dominant parasitoid species, while in the upper zoneT. contorticornis andT. strobilanae. It was shown that a considerable part of the populations ofT. azureus, T. contorticornis andT. strobilanae have their diapause prolonged and highly synchronized with the diapause of their host.     

Het toetsen van stammen vanNectria cinnabarina (Tode) fr. op levende takken in vitro

Summary Some types of elm hybrids resistent to the Dutch elm disease turned out to be susceptible toNectria cinnabarina (Tode) Fr. This fungus may behave as a parasite, killing branches. Virulent and non-virulent strains are known. A method is described for cultivatingNectria-strains in vitro on living desinfected branches ofAcer and ofUlmus. Three weeks after inoculation with a virulent strain the branches were killed. They were covered all over by a thick layer of mycelium. The mycelium of non-virulent strains could not kill the branches. It developed only sparsely. By this method it will be possible to select the most virulent strains out of a collection of isolates in order to use them for testing elm hybrids on their resistence toNectria cinnabarina.     

“Zwartbenigheid” bij tulp en iris,veroorzaakt doorSclerotium wakkerii nov. spec.

Samenvatting Aansluitend op een vorige publikatie over de z.g. zwartbenigheid bij tulpen (Boerema, 1960) zijn in dit artikel nadere gegevens medegedeeld over deze ziekte en de veroorzakende schimmel. Een 23-tal bloembolgewassen zijn door uitplanting op zwaar besmette grond getoetst op hun gevoeligheid voor deze ziekte. Daarbij kon het typische ziektebeeld van de zwartbenigheid alleen worden verkregen bij tulpen en bolirissen. De uit de praktijk afkomstige stelling dat ook krokussen voor deze ziekte gevoelig zijn (Silver & Slootweg, 1959), kon niet worden bewezen.De kenmerkende eigenschappen van de sclerotiën vormende schimmel die deze zwartbenigheid veroorzaakt, zijn uitvoerig besproken. Daar de schimmel onbekend blijkt te zijn, is deze beschreven als een nieuwe soort:Sclerotium wakkerii. Deze schimmel is nauw verwant aanSclerotium denigrans Pape, die een zwarte verkleuring vanConvallaria-kiemen veroorzaakt (Pape, 1943).Summary After reference to an earlier paper on black leg of tulips (Boerema, 1960) the present paper gives further data on the disease and the causal fungus. Besides affecting tulips, the disease is also found in the field on bulbous irises. The disease symptoms are shown in figs. 1, 2, 3 and 4.The susceptibility to black leg of 23 bulb species was tested in heavily contaminated soil. In agreement with experience in practice, only tulips and irises developed the typical black leg symptoms. In other bulb species a black discoloration of the dead membraneous bulb or tuber tunic was sometimes found, but no disease symptoms appeared above ground. This applied also to crocus, for which susceptibility to black leg in the field has been claimed (Silver & Slootweg, 1959).The black leg-fungus is easily isolated on cherry agar at 20 °C (fig. 5a), after treating the attacked tissue with a detergent and rinsing with tap water. Growth of the fungus was studied on malt agar, as this medium favours good and rapid growth. The relation between the growth rate on malt agar in the dark and temperature is shown in fig. 6. In the early stage a white flat mycelium is formed; later this turns brownish-black, secreting a typical dark pigment in the medium (fig. 7a and 7b). The hyphae (fig. 5d) vary in width from 1.8 to 7.5 , the walls being rather thick, 0.4 to 0.8 . The hyphae are often anastomosed and branched. After 2 or 3 weeks in culture the fungus develops brownish-black round or flattened irregular sclerotia 2–5 mm in diameter and 0.5–1.5 mm thick, consisting of a compact mass of hyaline hyphae surrounded by thick-walled dark coloured cells (fig. 5a and 5c). When the fungus is grown at low temperatures sclerotia sometimes develop in the aerial mycelium. These are always somewhat spherical and at first white in colour (fig. 5b). In an old culture of the fungus grown on malt agar microconidia formed in phialides were found in 1960 (Boerema, 1960). This has not been observed again, however, so possibly a contamination was concerned.The black leg fungus differs from all other known sclerotia producing fungi.¹ It is therefore described as a new species,viz. Sclerotium wakkerii Boerema & Posthumus nov. spec. We take pleasure in naming this species after Dr.J. H. Wakker (1859–1927), originator of scientific work on bulb diseases. Living cultures of the fungus have been placed at the disposal of the Centraalbureau voor Schimmelcultures at Baarn (type culture) and at the Commonwealth Mycological Institute at Kew. Dried plate cultures were sent to the Commonwealth Mycological Institute at Kew and the Rijksherbarium at Leyden. Sclerotium wakkerii closely resemblesSclerotium denigrans Pape, the cause of a black discoloration of the shoots of lily of the valley (Pape, 1943). However, the sclerotia ofSclerotium denigrans are considerably smaller than those ofSclerotium wakkerii.     

Indole-3-acetic acid biosynthesis in <Emphasis Type="Italic">Aciculosporium take</Emphasis>, a causal agent of witches' broom of bamboo

 Aciculosporium take (Ascomycota; Clavicipitaceae) is a causal agent of witches' broom of bamboo plants. The symptoms of this disease are believed to be induced by plant hormones, particularly auxins. Indole-3-acetic acid (IAA) was identified in cultures of this fungus in an l-tryptophan-supplemented liquid medium. IAA production was confirmed on 30 isolates of A. take from various hosts and locations at levels up to 1 mg/l. The biosynthetic pathway of IAA in A. take culture was examined by analyzing intermediate products and by feeding experiments. The results showed that the indole-3-pyruvic acid pathway (l-tryptophan → indole-3-pyruvic acid → indole acetaldehyde → IAA) was the dominant pathway in A. take. Received: June 3, 2002 / Accepted: July 25, 2002     

The effect of soil type and farm size on the variability of weed infestation in maize (Zea mays L.) fields in the south-west region of Poland

Weeds are a primary factor limiting maize yield. Their occurrence and abundance are affected considerably by environmental factors and farming practices. The variability of weed number in maize depending on the soil type and farm size was investigated. Farms of different sizes vary in farming practices, which affects weediness. Based on this assumption, farm size was considered as indirect factor affecting weed abundance. An investigation of 45 farms that differed in size (5–15 ha, 15–50 ha, >50 ha) and soil type (chernozem, distric cambisol, haplic luvisol) was conducted. Thirteen dominant weed species persistently occurring in maize fields in south-western Poland were examined. Regardless of the soil type and farm size, the most abundant weed species were Echinochloa crus-galli and Chenopodium album. In addition to these species, the most numerous weeds on chernozems were Setaria viridis and Solanum nigrum, while on haplic luvisols and distric cambisols, the most numerous were Viola arvensis and Elymus repens. Additionally, on haplic luvisols, Anthemis arvensis was abundant. Small farms were stronger infested by weeds than large farms due to the implementation of extensive weed-supressing practices, especially low herbicide use. Soil type affected the number of weeds to a greater extent than did farm size.     

Het optreden van plaatselijke rassen bij Helopeltis antonii Sign. op Java

Summary Helopeltis antonii was bred at different constant temperatures at the experimental station at Semarang in 1939 and 1940. Some of the results concerning the duration of development from hatching of the egg untill the imaginal stage are recorded in the table and the graph. By comparing these data with those published byLeefmans (1916) (Helopeltis bred on tea in West Java) andZehntner (1901) (Helopeltis bred on cocoa in Central Java) we find that the time of development mentioned by these authors is shorter. In accordance with the experiments ofBonnemaison (1946) this probably can be attributed to the breeding ofHelopeltis at alternating temperatures (day and night). The duration of development at 19°C, mentioned byLeefmans (19 days), however, differs so much from the duration found in this investigation (32–34 days) that this explanation seems improbable. Other experiments at constant temperature, that will be published elsewhere, show that the population used for breeding was well adapted to the average temperature at the estate, Djati Rungo, from where this population came. This extreme adaptation suggests that this may also occur at other localities. Therefore it is probable that the populations ofH. antonii from different localities do not have the same genetical composition. The differences mentioned above can probably be attributed therefore to this fact. Data are given to strengthen this supposition. The existence of genetically different populations has already been suggested by ProfessorRoepke in 1909. He called them biological races. The occurrence of the varietybradyi ofH. antonii is probably caused by such a difference too and thus could better be considered as a subspecies.Helopeltis theobromae Mill. is without doubt only a subspecies ofH. theivora.Thus we suggest:Helopeltis antonii subspec.bradyi Wat. new comb. Helopeltis theivora subspec.theobromae Mill. new comb.

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Deventer     

Research activities focused on management of red palm weevil at the UJI‐IVIA Associated Unit (Region of Valencia,Spain)

During the past 5 years, the Associated Unit between Institut Valencià d’Investigacions Agràries (IVIA) and Universitat Jaume I (UJI) has been working on the management of Rhynchophorus ferrugineus. The host status of Washingtonia filifera, Chamaerops humilis and Phoenix theophrasti was established, and complete resistance via antibiosis was described for W. filifera. A thermal constant (egg to adult) of 989.3 degree‐days has been established for R. ferrugineus when feeding in live P. canariensis. Based on this result, less than one annual generation is expected in areas with mean annual temperature below 15°C, and more than two if above 19°C. Assays on chemical control showed that a dose of 1.14 g aluminium phosphide m^?3 for 3 days is enough to kill all stages of R. ferrugineus in infested palms. The efficacies of imidacloprid and a microencapsulated paint containing chlorpyrifos and pyriproxyfen were also studied. Imidacloprid had high efficacies when applied as a drench either as a preventive or a curative treatment, whereas the paint was effective as a preventive treatment only. Biological control by use of entomopathogenic nematodes and fungi has been explored. Steinernema carpocapsae resulted in high efficacies when applied in a chitosan formulation. Beauveria bassiana also gave very good results, and new assays are under way to improve its use.     

Over enige insecten in lisdodden

Summary Observations on the biology ofLimnaecia phragmitella Stt. (fam. Momphidae, Lepid.) — made in the Netherlands — are mentioned.The species was previously considered as being rare but now is known to be numerous in a few areas. The caterpillars live in the heads of Typha where they feed on the seeds and later on the core. They hibernate when halfgrown, develop further in the spring and early summer and pupate in June; the moths appear during July.The species has a worldwide distribution: England, Central and Southern Europe, Northern Africa, Australia, New Zealand and the United States of America. In the latter country it was studied byP. W. Claassen together with a number of other Typha-insects occurring in the U.S.A. (Cornell Un. Memoir 47, Oct. 1921).The present author has found an hemipteron,Chilacis typhae Perris (Lygaeidae), in Typha heads occurring together with the caterpillars ofLimnaecia. This insect has also been reported in the literature as being rare in the Netherlands. It is suspected of living on the caterpillars but this has not been shown.     

Enkele gegevens omtrent sclerospora in Indonesië

Samenvatting De gevoelige periode van de maisplant voor infectie doorSclerospora maydis (Rac.) Butler werd bepaald, alsmede de incubatietijd (grafieken 1 en 2). Behalve deze soort komt sinds 1947 op Noord CelebesSclerospora philippinensis Weston voor, die daar aanzienlijke schade aan mais toebrengt. De verschillen van deze schimmel metSclerospora sacchari zijn slechts gering en een nader onderzoek dienaangaande is dan ook zeer gewenst.De eerste oögoniën-vorm vanSclerospora in Indonesië werd gevonden en wel vanSclerospora northii Weston op eenErianthus spec. op het eiland Soemba.Summary The nomenclature ofSclerospora maydis (Rac.) Butler is discussed. The susceptible period of the host and the time of incubation of this fungus (graphs 1 and 2) were determined.Since 1947 a species ofSclerospora has caused considerable damage on maize in North Celebes. It is stated to beSclerospora philippinensis Weston. The differences between this fungus andSclerospora sacchari T. Miyake are very slight. AsSclerospora sacchari is still unknown in Indonesia, it is very important for the culture of sugarcane on Java to investigate by means of inoculation trials, ifSclerospora philippinensis can attack sugarcane. Sclerospora northii Weston has been found onErianthus spec. on the isle of Sumba; it is the only knownSclerospora species in Indonesia which forms oögonia.Vroeger verbonden aan het Instituut voor Plantenziekten te Bogor, Indonesia, thans aan het Inst. v. Plantenziektenkundig Onderzoek (I.P.O.) te Wageningen.     

Selective media for <Emphasis Type="Italic">Fusarium oxysporum</Emphasis>

Selective media without pentachloronitrobenzene were developed for quantitative assays of Fusarium oxysporum in soils. Media Fo-G1 and Fo-G2 were effective for naturally infested soils, Fo-W1 and Fo-W2 for wild-type isolates in soils containing a nitrate-nonutilizing (nit) mutant, and Fo-N1 and Fo-N2 for nit mutants. Selective media were made using ammonium citrate dibasic, l-sorbose, econazole nitrate, 25% iminoctadine triacetate solution and 50% tolclofos-methyl wettable powder for soil dilutions of 100-fold or more (Fo-G1, FoW1 and Fo-N1) and 10-fold (Fo-G2, Fo-W2 and Fo-N2). Potassium chlorate was added to Fo-N1 and Fo-N2. The efficacy for selectively isolating F. oxysporum was confirmed using six soils naturally infested with one of six formae speciales of F. oxysporum and with soil dilutions containing conidia of wild-type strains or nit mutants from the six formae speciales. On Fo-G1 and Fo-G2, most colonies of F. oxysporum were compact and round with purplish or reddish pigment in the reverse. Cylindrocarpon sp. formed colonies as large as those of F. oxysporum but were distinguishable by their colony morphology. Other contaminants such as F. solani, F. moniliforme, and Trichoderma were suppressed by medium ingredients and colonies of F. oxysporum. On Fo-W1 and Fo-W2, colony morphology of F. oxysporum and contaminants corresponded to that on Fo-G1 and Fo-G2, although F. oxysporum failed to produce the pigment. On Fo-N1 and Fo-N2, nit mutants formed clear colonies from 100- and 10-fold soil dilutions, respectively, and contaminants seldom formed large colonies.