No Fungus Among Us

Fungi have been attacking termites for 300 million years. Now new observations reveal how termites may fend them off.This Formosan termite has been infected in the lab with the fungus Aspergillus spp. — a rare occurrence in nature. Photo: G. Henderson.more than 100 years termites have been trying to evade pest control operators, who attempt to stop their attacks on man-made structures, artwork, relics, and other cellulose-based materials. But termites and other soil-dwelling organisms, such as ants, have a more dangerous adversary than man: fungi.

Fungi are primitive, plant-like organisms that lack chlorophyll and require decaying or sometimes living matter for growth. It is everywhere, including between your toes, in your food, and in termite nests. Termites have been dealing with ways to stop the the attack from fungi for almost 300 million years. Fungi attack termites by attaching to their cuticle and growing into the internal tissues of their host. Since termites and ants are social animals that live together in large numbers, a successful fungus can enjoy a virtual smorgasbord if left unchecked.

Researchers discovered how ants deal with fungus invaders more than 20 years ago. A special gland located on the ant's back secretes an antifungal liquid that is spread over the ant's body by grooming. Because of this mechanism, the fungus cannot exploit the ant nest and its store of energy.

However, nothing is known about how termites inhibit fungal growth, though observations have suggested they do. We have observed that when termites are on their nest material, fungus will not grow. But remove the termites and a white fungal mat grows overnight.

We thought perhaps termites ate the fungus, and so we teamed up with a biochemist at Louisiana State University and set out to investigate this phenomenon. As a result, Dr. Jian Chen, a postdoctoral researcher in my lab has isolated and identified four chemicals that Formosan termites use to inhibit fungal growth. These chemicals are natural fumigants that work because termites live in a closed environment. Their atmosphere is largely controlled by their own emissions. One fungus appears to be specific to Formosan termite nests, and we are hoping to use our new discoveries against them. The most direct route to circumvent the colony's control over the fungus is to short-circuit this ability using biochemical or genetic manipulation. Long-term studies will be required to achieve this goal. However, an additional interesting twist we discovered about these emissions is that they are toxic to ants. Now our observations that ants tend not to penetrate termite shelter tubes, even when the tubes protrude through the ant mound, make sense.

We believe these new chemicals can be employed immediately in our fight against Formosan termites by incorporating them in baits. Termite baits are notorious for being favorable nesting sites for ants. Of course, once ants enter the bait, termites do not tread near. In addition these natural fumigants can control fungal growth on baits, reducing the frequency of inspections required by the operator. The directions need to be pursued, and we hope that manufacturers of baits see the value of providing funding in this direction.

Gregg Henderson is an associate professor at Louisiana State University's Agricultural Center in Baton Rouge, La.