Ficus (fig trees, Moraceae) is one of the most important plant genera of tropical and sub-tropical forests, with over 800 species worldwide. Fig trees are entirely dependent on a mutalistic association with host-specific pollinating fig wasps for reproduction. They are widely planted as ornamental trees outside their native ranges and several have become significantly invasive in natural and semi-natural habitats in situations where their associated pollinator is also established.
Ficus benjamina is indigenous to Asia and Australasia and is commonly planted, both within its native range and elsewhere. It is widely planted in cities or gardens as an ornamental plant, both in China and elsewhere. Since its pollinator has not become widely established, F. benjamina mainly represents a potential threat at present.
Dr. PENG Yanqiong of Xishuangbanna Tropical Botanical Garden (XTBG) and her colleagues examined the biological control potential of an undescribed gall midge that utilizes the figs of F. benjamina within the plant's natural range in Xishuangbanna, south-western China, focusing on its impact on pollinators, premature fig fall, seed production and seed quality.
The study found that the gall midge decreased the numbers and quality of its host's seeds. The gall midges have a major impact on the reproductive success of the figs they colonize, substantially reducing the numbers of both pollinators and viable seeds, primarily by causing premature abortion of the developing figs. It is also independent of the pollinating fig wasp, being able to develop in figs that no pollinators have entered.
The researchers thus concluded that the host specific gall midge is an excellent candidate biological control agent, available as and when F. benjamina becomes of more widespread conservation concern.
The research entitled “The impact of a gall midge on the reproductive success of Ficus benjamina,a potentially invasive fig tree” has been published online in Biological Control, doi:10.1016/j.biocontrol.2011.07.007