The Scotch thistle, Onopordum acanthium (Asteraceae) has the Eurasian origin
and represents an invasive weed in the USA and Australia. It is a serious
problem in pastures, along roadsides, rangeland, etc. The weed is very common
in Bulgaria and in 2009-2010 several sites with large populations of O.
acanthium have been located. The weekly surveys of some of the sites, mainly
in the region of Plovdiv, revealed a significant diversity of phytophagous
insect species, some of which had very high population density. More than 30
species have already been identified and observations on the phenology and
biology of some of them have been conducted. For some of the species, such as
endophagous Larinus latus, Lixus cardui, Eublemma amoena, Trichosirocalus
briesei, or ectophagous Cassida rubiginosa etc. found during our surveys,
there are reports in the literature describing them as having been already
introduced as successful biocontrol agents in Australia. Endophagous species
like lepidopteran Myelois circumvoluta and Pyroderces argyrogrammos which
feed on the stems and the head, and the tephritid flies Tephritis postica and
Chaetostomella cylindrica which feed on the capitula, seem quite destructive
for the weed, but need to be further studied regarding host specificity.
Species like Vanessa cardui and Brachycaudus cardui were found regularly, but
in low population density, mainly due to the high rate of parasitism.
Species of Phytophagous Insects Associated with Strawberries in Latvia
