De overbrenging van een virusziekte van zure kers op komkommer

Summary Cucumber seedlings were infected with a virus from sour cherry by rubbing the cotyledons with sap from young sour cherry leaves, showing shock effect symptoms of a virus infection (probably necrotic ringspot). The symptoms on cucumber consisted of necrosis of vegetation point, yellow spots in the leaves and rosette formation, thus showing the resemblance of this infection to the oneMoore, Boyle andKeitt effected in cucumber by using a mixture of necrotic ringspot and yellows virus.     

Cnephasia longana,een beschadiger van de scheuttoppen van fruitgewassen

In the Netherlands, the polyphagous larvae ofCnephasia longana Haworth occur locally on apple and pear trees, damaging the growing shoot-tips. They are also observed on red currant bushes, strawberry, beet, clover, lucerne and creeping thistle. A useful degree of control has been obtained with organo-phosphorus sprays.     

Onderzoekingen over een virusziekte bij stoppelknollen (Brassica Rapa var.Rapifera)1)

European Journal of Plant Pathology - Beschreven worden de eigenschappen van een virus, behorende tot de groep van “turnip virus 1”, dat in 1949 ernstige schade in stoppelknollen...     

Kurkwortel verschijnselen van tomaat,veroorzaakt door een steriel mycelium. II

Ohne Zusammenfassung

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With a summary: Corky root of tomato caused by a sterile mycelium. II

     

Enkele waarnemingen over het opreden van de verwelkingsiekte bij luzerne in Zeeland in 1957

Summary Some observations have been made on lucerne wilt disease during the growing season in 1957, and in experimental inoculation tests in a glasshouse in 1958. In the province of Zeeland the disease does harm to the crop and prevents many farmers from keeping their crops longer than two years.In a survey data have been collected on soil type, preceding crops, green manuring and manuring with stable dung, pH, structure and weeds. No correlations between these factors and the degree of attack by the disease could be proved, except that on heavy soils the disease was less severe than on lighter soils (as a mean of all observations).Development of the disease is facilitated by damage caused by mechanical equipment to the crop. Damage to the crown of the plants should be avoided as much as possible. The disease is distributed extensively after frequent mowing. On attacked leaves left behind on the mowed stalks, and on decayed leaves dropped to the soil, masses of spores ofVerticillium albo-atrum are produced, which form a potential source of infection in a weakened crop.It seems that the disease is more air-borne than soil-borne, since one year old crops are seldom attacked.From attacked lucerne plants in the field the following fungi have been isolated:Verticillium albo-atrum Reinke & Berth.,Gliocladium roseum Bain andFusarium avenaceum (Fr.) Sacc. (table 1).Isolations have been made from 50 different species of weeds, out of which the following fungi were obtained:Verticillium albo-atrum Reinke & Berth. fromCapsella bursa-pastoris Med. andPlantago major L.,V. dahliae Kleb. fromPrunella vulgaris L.,Capsella bursa-pastoris Med. andThlaspi arvense L., andV. lecanii (Zimm.) Viegas fromPlantago major L.In inoculation experiments with all these isolates, in roots, stalks and on cut plants of lucerne, onlyV. albo-atrum, both from lucerne and weeds, andV. lecanii proved to be able to cause wilting of leaves and stalks. WithGliocladium, Fusarium andVerticillium dahliae no such symptoms could be obtained. The results were the same whatever method of inoculation was used.     

Bij het begin van de een en zestigste jaargang

Ohne Zusammenfassung     

Het stippelstreep van de boon (Phaseolus vulgaris), een ziekte veroorzaakt door een virus,dat in de grond overblijft

Summary It has been shown in a field experiment that stipplestreak — a virus disease of haricot beans (Phaseolus vulgaris) — is carried by the soil. Keeping the infected soil at 100°C. for 30 minutes destroys the virus.Young haricot bean plants may become infected naturally with the stipplestreak virus within the first week after sowing the seeds in infected soil. The stipple-streak symptoms, however, do not appear until considerably later; for example, in 1947, they did not appear until about six weeks after the seedlings had been transferred (one week after seed sowing) from infected to non-infected soil.According toHubbeling, whose experimental results it was possible to confirm, the properties of the virus in freshly expressed sap are: — thermal inactivation point, between 85° and 90°C; solution end point, between 10^–5 and 10^–6. The virus resists drying out.The virus causes local necrotic spots — often in the form of concentric rings —on the leaves of tobacco (Nicotiana tabacum).Gaarne wordt ook op deze plaats dank betuigd aan de heren A. J. van Velzen, Assistent bij de Rijkstuinbouwvoorlichtingsdienst en Jac. van der Meer, tuinder, beiden te Roelofarendsveen voor hun zorg besteed aan het koken van de grond en aan het proefveld aldaar.Onderzoek, verricht voor de afd. Tuinbouwkundig Onderzoek van de Directie van de Tuinbouw.