Key Points:
- A study has identified a lethal fungus combination responsible for the decline of fig trees.
- The fungi is frequently transmitted by ambrosia beetle adult females, who spread fig-wilting disease.
- The findings provide important clues toward improving integrated pest management methods.
Many countries around the world are seeing a decline in the number of fig trees. Among the leading causes of their mass decline is fig-wilting disease often caused by Ceratocystis ficicola—a fungus often transmitted by an ambrosia beetle called Euwallacea interjectus. In a study published in Microorganisms, a group from Nagoya University in Japan has identified another fungus, Fusarium kuroshium, which by itself is harmless, but when found together with C. ficicola makes a deadly combo on fig trees.
C. ficicola, along with F. kuroshium and other fungi, are believed to be important in fig-wilting disease. Since these fungi are frequently found on the heads of wild and reared E. interjectus adult females, it has long been suspected that they are responsible for the spread of disease.
To determine whether the fungi are related to the damage of the fig trees, Zi-Ru Jiang and Associate Professor Hisashi Kajimura inoculated fig saplings with various combinations of fungi collected from E. interjectus. As a control, they also included Neocosmospora metavorans, which is found in a wide range of plant hosts.
Some saplings received only one of the three fungi, and one group received a combination of F. kuroshium and C. ficicola. As expected, the saplings infected with C. ficicola wilted, whereas the other two groups infected with only N. metavorans or only F. kuroshium did not, suggesting that these two fungi are not harmful to fig trees.
“A combination of the ambrosia beetle and its fungi may lead to symptoms of fig-wilting disease in the case of mass beetle attacks and decreased resistance in host trees. Therefore, understanding the relationship between C. ficicola and its symbionts may be useful in developing suitable disease control strategies,” explained Kajimura.
Kajimura said this study may provide important clues to improve integrated pest management methods in the future.