Effect of green manure crops and organic amendments on incidence of nematode-borne tobacco rattle virus

Tobacco rattle tobravirus (TRV) may infect several ornamental bulb crops and is transmitted by trichodorid nematodes. Paratrichodorus teres, P. pachydermus and Trichodorus similis are the main vectors in the Netherlands. In field experiments the effects of various pre-crops and organic amendments on the TRV Infection Potential of Soils (TRV-IPS) and on disease level in tulip and gladiolus were studied. Organic matter amendment of soil at a rate of 1% dry weight has been shown to reduce the host finding activity of P. teres under laboratory conditions. In a field containing viruliferous P. teres dahlia, italian ryegrass, white mustard and fodder radish were grown or the soil was kept fallow and the resulting TRV-IPS prior to the bulbous test crops was measured by a soil dilution bait test method. The application of organic matter was tested after dahlia as pre-crop. Household waste compost (GFT compost) was applied as a soil mix or planting furrow treatment at 12 tons dry weight per ha for tulip and gladiolus. Spent mushroom compost (Champost) was added as planting furrow treatment at 17 or 12 tons dw/ha, respectively, for tulip and gladiolus. The percentage of TRV diseased plants was determined at flowering in all pre-crop and organic amendment treatments. Champost in the planting furrow and fodder radish as a preceding crop reduced the percentage infection in tulip under favourable conditions for TRV infection. In gladiolus most organic amendments, fodder radish as pre-crop and keeping the soil fallow reduced the TRV infection rate of the plants during the first growing season, but not of the plants grown from the corms in the next year

Verslag naar aanleiding van een studiereis naar Japan van 24 april - 15 mei 1986

Reisindrukken met o.a. raadgevingen voor de Nederlandse bloembollenexporteur

Control situation of virus diseases in narcissus in the Netherlands

The control situation of virus diseases in narcissi grown in the Netherlands was studied. The viruses, viz., narcissus latent virus (NLV), narcissus mosaic virus (NMV), potyviruses differentiated in narcissus yellow stripe virus (NYSV) and narcissus silver streak virus (NSSV), tobacco rattle virus (TRV), Arabis mosaic virus (ArMV), narcissus tip necrosis virus (NTNV), and tobacco ringspot virus (TRSV) reflect half of those known in literature. In the chain of control factors the symptoms of single and multiple virus infections play a predominant part which results in the roguing of undesirably diseased plants. Arbitrarily the symptoms are differentiated in various syndromes, e.g., streaking, early mosaic, late mosaic, leaf grey, tip- and leaf edge grey, tip brown, leaf brown, tip- and leaf silver streak, tip silver, and healthy appearance. The bulb yield reduction by different virus diseases may be up to 30%. The routine testing of numerous samples by ELISA is not applicable yet. Therefore, the elimination of high virus-source rates by the roguing of plants is amply applied to reduce virus spread indirectly. The control of spread above soil level is not always purposeful if the additional cause of a syndrome will be due to a virus transmitted below soil level, or to a virus where the mode of transmission is unknown. Soil disinfestation is occasionally applied. Additionally the complexity of virus control in its efforts for further improvement is discussed

Incidence and control of viruses in Gladiolus in the Netherlands

The control situation of virus diseases in Dutch-grown gladioli was studied. Bean yellow mosiac virus (BYMV), narcissus latent virus (NLV), tobacco rattle virus (TRV), cucumber mosaic virus (CMV), and an unidentified corky pit viruslike agent (UCPVA) were found apart from tobacco mosaic virus (TMV) only found once and from the ca. 20 viruses reported in the literature. Symptoms are extensively described as these affect the mode of control to discard undesirably diseased plants and cultivars. The conn yield reduction by BYMV was little. The virus detection by visual means is considered much more important than the ELISA-testing used for diagnostics only. The BYMV-tested culture of a series of cultivars was unsuccessfull because of the rapid BYMV-spread inefficiently controllable by mineral-oil sprays, and the harmful effect of current-season infection on the quality of cut flowers. The incidence of other viruses, e.g., NLV, CMV, TRV, and the UCPVA is considered effectively reducible by the roguing of plants and the rejection of lots for further use, apart from the soil disinfestation to limit TRV-infection. The general control situation of all viruses apart from BYMV, and the perspectives of virus-tested culture are discussed.</p