Not known to transmit any human or animal pathogens.

"Candidatus Phytoplasma solani" is vectored by numerous planthoppers in the Cixiid and Cicadellid families (See the CAPS Pest Datasheet for a complete listing). The most important vector is Hyalesthes obsoletus, which transmits "Ca. P. solani" to grape. Another important vector is Reptalus panzeri, which transmits "Ca. P. solani" to both grape and corn.

Follow instructions in Phytoplasma Sample Screening and Confirmation

If you have completed phytoplasma specific training or proficiency testing for DNA extraction and real-time PCR from S&T Plant Pathogen Confirmatory Diagnostics Laboratory (PPCDL, formerly Beltsville lab), you can screen your own phytoplasma samples. Note: You will still have to follow the protocol in the linked document for confirmations.

No specific signs are present.

Symptoms vary by host. See the CAPS pest datasheet for a complete list of hosts, associated symptoms, and images.

          Grape

Typical symptoms of Bois noir (BN) disease in grapevines (Vitis vinifera L.) include discoloration of leaves and veins, downward curling of the leaf blade often forming a triangular shape, shorter internodes, lack of or incomplete lignification of shoots, which later turn black, abortion of fruit clusters and shriveling of the ripening fruit. In most cultivars, the symptoms of BN disease remain restricted to the infected vines for several years. The disease does not usually kill the infected vines, but grape production can be significantly reduced. Extended remission of visual symptoms and even complete recovery of infected vines are known phenomena, although very unpredictable and still not fully understood.

In red grape cultivars, the phytoplasma infection causes premature leaf reddening and in white grape cultivars it causes leaf yellowing and the development of necrotic veins. Shriveled grape clusters occur in both red and white grape cultivars. 

          Corn

Symptoms of "Ca P. solani" in field corn (Zea mays L.), commonly known as maize redness disease, include midrib, leaf, and stalk reddening, followed by drying out of the entire plant, abnormal ear development, and incomplete kernel set. Environmental factors play a role in both the intensity and incidence of MR, with more severe disease being associated with early-planted fields and hot, dry summers.

          Weeds
Bindweed (Convolvulus arvensis L.) plants infected by "Ca. P. solani" exhibit symptoms of stunting, shoot proliferation, leaf color change and yellowing. We found no description of typical symptoms in Urtica dioica (stinging nettle).

Surveys should take place when symptoms are most likely to be apparent, which will depend on the specific host plant being surveyed. Symptoms in grapes and corn are usually most visible from July to October, although they can appear at different periods of the year according to the cultivar and latitude. 

Survey for "Ca. P. solani" in grapes and corn, searching for symptoms (as described in the sections above). Two of the most important weed reservoirs, Convolvulus arvensis (bindweed) and Urtica dioica (Stinging nettle) are good targets for survey if they are inside or adjacent to vineyards or corn fields. 

Follow instructions in Phytoplasma Sample Screening and Confirmation

1. British Columbia Wine Council, Canada. 2024. Grape Diseases in the Southern Interior of British Columbia
2. Canadian Food Inspection Agency, Canada. 2024. Grapevine Yellows: Flavescence dorée and Bois noir - Identification Guide.
3. EPPO. 2024. "Candidatus Phytoplasma solani"(PHYPSO)
4. USDA. 2024. Grapevine Diseases.

Other phytoplasmas cause similar symptoms in these hosts and they can only be distinguished by molecular methods. There are several phytoplasmas known to be present outside the U.S. that also cause grapevine yellows including "Ca. P. australiense", "Ca. P. vitis", and Buckland Valley grapevine yellows phytoplasma.

North American grapevine yellows (NAGY) disease is caused by strains related to "Ca. P. asteris" and "Ca. P. pruni". NAGY is known to occur in Arkansas, Kansas, Maryland, Michigan, Minnesota, Missouri, New York, Ohio, Pennsylvania, and Virginia.

Both maize bushy stunt disease and corn stunt spiroplasma disease are present in the United States and can be mistaken for "Ca. P. solani". Maize bushy stunt phytoplasma (MBSP) is associated with "Ca. P. asteris" and "Ca. P. pruni"-related strains and symptoms in field corn include leaf chlorosis, reddening in older leaves, shortening of the internodes, and stunting. Corn stunt spiroplasma (CSS) disease is caused Spiroplasma kunkelii and symptoms include stunting, short internodes, leaf reddening and streaking, and multiple small ears.