This past fall we have had an awesome opportunity to work and collaborate with a Master’s student from Mexico. While here in the U.S. she has been able to discover what we believe are two different entomopathogen species in sugarcane aphid. This is great news because entomopathogens could play a critical role in colony collapse in aphids. The video below gives a quick summary of our work.
What is an Entomopathogen?
Entomopathogens are either bacteria, fungi or other microorganisms which infect insects and eventually kill them under the right conditions. The type of entomopathogens we have been studying are fungi species.
Entomopathogenic fungi infections begin by coming into contact with their host, in this case the sugarcane aphid. This happens when an aphid comes into contact with a spore (1).
Spores are living fungal particles that travel by wind. Once contacting sugarcane aphid and under favorable environmental conditions the spores grow string-like threads called mycellium. It is the mycellium that penetrates the exoskeleton of the aphid (2). The fungus grows inside of the aphid spreading throughout the body while attacking vital organs (3).
Once the host is fully consumed the fungi exits through the exoskeleton to release more spores and the cycle will be repeated when environmental conditions favor the pathogen (4-6).
This is Margarita Martinez, a Master’s student from Mexico. What she has been doing in the U.S. for us here in Texas over the last few months is awesome work. What Margarita has done is collected random samples of sugarcane aphids from volunteer sorghum along the Coastal Bend of Texas (see figure for counties where sugarcane aphid were collected) and then under specific laboratory conditions she has been able to find entomopathogenic fungi living inside of these aphids.
After she found fungal species living in the aphids she isolated them and began rearing them in colonies to determine what species they might be. In her opinion, the two species of fungi she has found so far that could affect the sugar cane aphid are Lecanicillium lecanii and an Isaria sp., but we are in the process of getting a final verification.
The significance of this is that both fungal entomopathogens have been found in infecting sugarcane aphid in Mexico. Almost all the aphids Margarita and I collected showed the presence of fungal entomopathogens.
Significance to Sorghum Managers
The widespread occurrence of these entomopathogenic fungi among sugarcane aphid in south Texas may make it possible for researchers to evaluate environmental conditions necessary for an epizootic (outbreak of the pathogen across an area). It may be possible that, as managers, we can predict sugarcane aphid colony collapse when environmental conditions favor an epizootic and adjust strategies for managing the aphid in south Texas sorghum.
We suspect epizootics as a possibility for sugarcane aphids to collapse across large areas following an extended period of cool and wet conditions. The widespread occurrence of these two sugarcane aphid fungal entomopathogens support our suspicion. It may be possible to develop biological insecticides from these pathogens to help control the sugarcane aphid without disrupting beneficial arthropods.
As managers and researchers it is critical for us to explore all options available and make use of all resources to control insect pests like the sugarcane aphid.