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.