Chrysanthemums (Chrysanthemum sp.) are native to east Asia, but have been cultivated in China for millennia, apparently since the 15th century BC, or even earlier. Later they became very popular in Japan, and the monarchy there is known still as the Chrysanthemum Throne.Although most chrysanthemums are grown for their beauty, some species can be drunk as a tea, or boiled and eaten in dishes such as Chinese hotpot. Conversely, the seed pots of some species have been used for centuries to make permethrin, an effective insecticide and the ancestor of modern synthetic pyrethroids.
So why am I talking about chrysanthemum's in a blog about Brazilian nature? Because they are part of it, being grown mainly in the state of Sao Paulo. Especially around Holambra, where Dutch immigrants established a flourishing horticultural industry and today there is an important flower auction system, the Veiling Holambra. The ornamental flower industry has grown rapidly in Brazil, with Ibraflor (the Brazilian Institute of Floriculture) reporting in 2021 an annual average growth rate of 10-12 per cent over the previous 10 years. Roses are the most popular, followed by chrysanthemums, alstroemerias, lilies and lisianthus, and orchids. 97% of domestic demand for chrysanthemums is supplied by domestic production (Gobatto et al 2019).
A survey of virus infections in chrysanthemum greenhouses and the weeds present in and around those greenhouses gives a snapshot of an ecosystem in Sao Paulo (and Colombia, but I'll just talk about Brazil) (Gobatto et al 2019).
The chrysanthemums are grown in greenhouses, but they can interact with the environment outside. A survey of weeds in and around greenhouses in Sao Paulo found 51 different species, which were consequently tested for the commercially important RNA viroid, Chrysanthemum stunt disease (CSVd). The only one found to have a natural infection was Oxalis latifolia (in Brazil "trevo"), which not only contained virus particles but also showed symptoms. Originally from Central America, O. latifolia is a very common weed, and in fact has been introduced around the world as a garden flower, and even, in India, as rabbit food.
Oxalis latifolia (Wikimedia Commons) Of the other species of weeds tested, 17 were found to be possible hosts of CSVd. ie. they didn't have virus infections, but could be infected in lab conditions. The most widespread in and around greenhouses was Cardamine bonariensis ("griãozinho") a kind of cress. C. bonariensis seems to have originated in Europe, probably entering Brazil with imported plants. Although no natural infections were found, or have been reported, evidence that it can support CSVd is worrying.
And of course there are insects. The most important pests of chrysanthemums in Brazil are aphids and thrips (Bueno et al, 2003). One of the commonest thrips is Frankliniella occidentalis, a very polyphagous species that has spread from the southern USA around the world, and can feed on practically everything (well, at least 500 species). F. occidentalis has been shown to transmit another chrysanthemum virus Chrysanthemum stem necrosis virus (Goretti & Lima 2019).
Frankliniella occidentalis (author's collection)
So there we have it. An ecosystem, a world, of mainly expats
in the same place and time. An artificial ecosystem for sure, but how many
ecosystems are completely "natural" these days?
Bueno, V.H.P.; Lenteren, J.C. van; Silveira, L.C.P.;
Rodrigues, S.M.M. (2003). An overview of biological control in greenhouse
chrysanthemums in Brazil. Bulletin OILB/SROP 26(10), 1-5.
Gobatto, D., de Oliveira, L.A., de Siqueira Franco, D.A.,
Velásquez, N., Daròs, J.A., Eiras, M. (2019). Surveys in the chrysanthemum production
areas of Brazil and Colombia reveal that weeds are potential reservoirs of
Chrysanthemum Stunt Viroid. Viruses. 2019 Apr 17;11(4):355.
Goretti, Maria & Lima, Élison (2019). Tripes -
ornamentais. Pragas e doenças associados aos cultivos na Serra de Baturité, CE (pp.123-130).
Publisher: Liceu.
