Entomopathogenic fungi have recently been seen attacking citrus whitefly and cloudywinged whitefly nymphs in North Florida citrus groves. Muhammad Shahid, Mujahid Hussain and Danielle Sprague, all with the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS), wrote about the “friendly” fungi in the October UF/IFAS Cold Hardy Citrus Connection newsletter. Shahid is a horticulturalist and Hussain is a graduate assistant, both at the UF/IFAS North Florida Research and Education Center (NFREC). Sprague is an Extension agent in Gadsden County.
The authors report that at first glance, the fungi attacking the whiteflies make it appear the grove is being plagued with a new citrus disease or a new species of scale.
The citrus whitefly (Dialeurodes citri) and the cloudywinged whitefly (Singhiella citrifolii) are two pest species that occasionally cause injury in citrus. Adults are small, white and resemble tiny moths. Adults lay eggs on the underside of leaves, and eggs hatch into nymphs.
Nymphs cause injury to the plant by feeding and consuming large quantities of sap. As a result of the large amount of sap consumed, nymphs excrete honeydew, which causes growth of sooty mold fungi. Severe sooty mold infestations give plants an unhealthy appearance and can reduce plant photosynthesis.
Fortunately, the populations of whitefly nymphs are being suppressed by the entomopathogenic fungi.
In Florida, there are two major strains of entomopathogenic fungi: the red strain (Aschersonia aleyrodis) and the yellow strain (Aschersonia goldiana). The red strain infects the citrus whitefly (as well as other species), and the yellow strain infects the cloudywinged whitefly. Both strains have been seen in various groves in North Florida.
At the NFREC, the red strain has been observed in several varieties, including UF Dawn, Fallglo, UF Sunrise and Bingo. Both strains have also been seen in commercial groves of Owari and Brown Select.
These friendly fungi are normally observed from mid-August to mid-September after the rainy season. The fungi can be clearly seen from a distance with their bright red and/or yellow spots.
While it may be a scary sight to see, the entomopathogenic fungi does not harm the tree and is making a bad situation better by attacking whitefly nymphs.