YELLOWS DISEASE OF GLADIOLUS AND HYACINTH IN THE NETHERLANDS - 1) ADDITIONAL DATA ON FIELD CONTROL WITH SYSTEMIC INSECTICIDES AND EFFECTS OF TREATING CORMS AND BULBS IN HOT WATER - 2) DETECTION OF MYCOPLASMA-LIKE BODIES IN THE PHLOEM OF DISEASED HYACINTH LEAVES
A disease in hyacinths, characterized by pale-green leaves, malformations of the influorescence and a poor development of roots has been known in The Netherlands since the early 1930's. Plants with these symptoms have been given the name 'Lissers' by the bulbgrowers. The disease occurs only in some years as in 1971. After a two-week feeding period on 'Lissers', leafhoppers (M. sexnotatus) were transferred to Vinca rosea plants which developed the same symptoms as evoked after transmission of 'aster yellows' from gladiolus. Transmission from 'Lissers' to healthy gladiolus plants incited typical 'aster yellows' symptoms in the leaves and in the corms. Transmission from 'Lissers' to healthy hyacinths resulted in 57 bulbs out of 76 plants inoculated (75%) producing 'Lissers' whereas non-inoculated controls remained healthy. From these results published earlier (van Slogteren and Muller, 1972), it was concluded that 'aster yellows' in gladiolus and 'Lissers' in hyacinth are caused by identical or closely related mycoplasma-like disease agents.
Preliminary experiments have shown that spread in the field of 'aster yellows' in gladiolus can be reduced by using systemic insecticides against the leafhopper vector (van Slogteren, 1971b).
Infected gladiolus corms can be cured by a hot-water treatment (hwt) at 50°C for 1 hr (van Slogteren and Muller, 1969; van Slogteren, 1971b). A hwt should inflict the least possible harm to healthy corms. Therefore, in further experiments healthy corms have been used to study the effect of hwt on various dates and of different storage temperatures on the yield.