A recent study in Japan found that bred ragweed beetles, Euwallacea interjectus, may have symbiotic fungi that differ from those found in the wild. These findings suggest biocontrol implications for pest beetles that damage valuable crop trees such as fig trees.
The ragweed beetle is an insect that burrows through the bark and deep into the wood of trees. With few nutrients in its environment, the beetle lives in symbiosis with fungi that serve as a food source. However, in addition to food fungi, these can also be harmful fungi, such as Ceratocystis ficicola, which can cause wilt of host trees. Wilt causes damage to valuable crop trees by blocking the flow of water into the tree, causing leaves to wilt and eventually death.
A research group led by associate professor Hisashi Kajimura and Dr. Zi-Ru Jiang of the Graduate School of Bioagricultural Sciences at Nagoya University, in collaboration with the Forestry & Forest Products Research Institute, evaluated fungi living with ragweed beetles grown on a artificial diet composed of coniferous sawdust, potato starch, dried yeast, sugar and distilled water. To better understand the beetle-fungi symbiosis, they compared the fungi in farmed beetles with those in the wild. The researchers found that the dominant species of symbiotic fungi differed between cultivated and wild beetles. They published their results in the magazine diversity.
Nine filamentous fungi and one yeast were identified as symbionts. These include a previously undescribed genus of Fusarium fungi. The researchers also found that the dominant species in wild ragweed beetles was Fusarium kuroshium, while for bred beetles it was Neocosmospora metavorans. These findings suggest that the beetle’s fungal symbiote changes when raised on an artificial diet.
“Our results represent a major paradigm shift in understanding beetle-fungus interactions, as they show that specific symbiote exchanges can take place at different breeding grounds,” explains Jiang. “The results suggest that the symbiotic relationship between insects and fungi is dynamic, offering a new perspective.”
Understanding this complex symbiotic relationship of ragweed beetles with fungi could aid artificial control efforts. “We have obtained results that are a starting point for pest control,” says Kajimura. “To give an example, it may be possible to replace the insect’s symbiotic fungi with a species or strain that causes less disease in plants.”
The origin of agricultural insects
Zi-Ru Jiang et al, Fungal flora in adult females of the rearing population of Ambrosia beetle Euwallacea interjectus (Blandford) (Coleoptera: Curculionidae: Scolytinae): is it different from the wild population?, diversity (2022). DOI: 10.3390/d14070535
Quote: Symbiotic Fungi Suggest Biocontrol Implications for Pest Beetles (2022, September 27) Retrieved September 27, 2022 from https://phys.org/news/2022-09-symbiotic-fungi-biocontrol-implications-pest.html
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