Organic flower bulb growers are selecting cultivars from the regular assortment. It is not clear whether these cultivars are suitable for organic cultivation. Experimental station Zwaagdiijk tested several cultivars in a Value for Use test. Tulip gall mite and Botrytis are the most threatening pathogens of the crop. But in 2009 hail caused damage as well. Yields in 2008 as well as in 2009 were disappointing, average marketable 265 in 2008 and 180 in 2009.
Growing season 2007-2008
The 2007/2008 season was unfavourable for bulb cultivation. An early emergence in February was followed by a cold spring through to April. A dry warm period from May restricted crop growth. Friendship and India yielded most kilograms of planting material.
Botrytis tulipae developed in the field as from April. Especially Royal Love was found to be susceptible to Botrytis. After harvest and during storage the bulbs were tested for the presence of dry rot caused by Fusarium oxysporum. Directly after harvest (10 days) no dry rot was found in Erna Design, Euro Vivi and Jive.
Growing season 2008-2009
Yields in the 2008/2009 growing season were even lower, caused by tulip gall mite infestations. Although the bulbs came from ULO storage, infestation levels were high. This resulted in a strong inhibition of root growth. Highest losses were found for the standard cultivar Leen van der Markt and Friendship, resulting in very low yields. Royal Love and Jazz produced most kilograms of planting material.
Gall mites were also found during forcing, despite the preceding ULO treatment; in the first forcing of Royal love and Friendship, but in later forcings also in the other cultivars. Besides tulip gall mites, straw mites -possibly also causing damage- were found as well.
The following cultivars have been tested in the Value for Use test: Leen van der Mark, Bolroy Silver, Cerise Parrot, India, Jazz, Royal Love, Friendship, Erna Design, Euro Vivi, Jive
Click here for the report 'Biologische bolbloemen- en bollenteelt, daar gebeurt het!: Gebruikswaarde onderzoek biologische tulp, verslag van eerste serie cultivars'. (Organic flower bulb and bulb flower cultivation; that’s where it happens. Value for Use test organic tulip; report on a first series of cultivars)
Source: www.biokennis.nl