|Munyaneza, Joseph - Joe|
Submitted to: Subtropical Plant Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/21/2007
Publication Date: 7/1/2007
Citation: Goolsby, J., Bextine, B., Munyaneza, J.E., Setamou, M., Adamczyk Jr, J.J., Bester, G. 2007. Seasonal abundance of sharpshooters, leafhoppers, and psyllids associated with potatoes affected by zebra chip disorder. Subtropical Plant Science. 59:15-23. Interpretive Summary: In Texas, more than 15,000 acres of potatoes were planted in 2006, with a value more than 73 million dollars. Potatoes grown for the chipping industry are primarily located in, Dalham, Frio, Hartley, Hidalgo, Lamb, and Winkler counties. A bacteria-like disease, called “zebra chip” is impacting the potato production and quality with losses of more than 15 million dollars in both 2005 and 2006. The disorder is called zebra chip (ZC) because of the stripped pattern of necrosis in the tubers which becomes more prominent when chipped and fried for chips from affected plants. Potato plants initially exhibit scorch symptoms similar to Pierce’s Disease in grapes. The causal pathogen(s) or vector(s) of the ZC disorder are not known, but are under investigation. Most likely the cause of ZC is a “complex” of pathogens; including bacteria-like organisms and Phytoplasmas. The “vector” or “vectors” have not been firmly identified; one of the possible vector, “potato psyllid,” is the most likely vector which is associated with the disease in the U.S. and Mexico and prevalent in field surveys conducted in the Lower Rio Grande Valley in 2006. The potato psyllid and several other leafhoppers were positive for the pathogen Xyllela fastidiosa, which may be associated with zebra chip disease.
Technical Abstract: A survey of psyllids, leafhoppers, and sharpshooters in commercial potatoes near McAllen, TX in the Lower Rio Grande Valley was conducted using yellow sticky traps. Species from these groups that were collected in the survey were evaluated for the presence of Xylella fastidiosa, the suspected causal agent of zebra chip disorder in potatoes. Potato psyllids, Bactericera cockerelli, were the most common species collected in the study, entering the fields in mid-January and reaching a peak in mid March. More than 87 % of the psyllids tested positive for X. fastidiosa. Leafhoppers were less common, with populations peaking in mid-February. Several species tested positive including; Empoasca spp., Schaphytopius sp., Ceratogallia sp., Penestragania sp., Erythroneura sp., Graminella sp., and Dikranuera sp. Sharpshooters were rare, including Homalodisca vitripennis, but nearly all were positive for X. fastidiosa. It is not known if these species are capable of vectoring X. fastidiosa, but they should be further investigated in transmission studies. Thirteen common species of plants in the vicinity of the potato fields were evaluated as potential reservoirs of X. fastidiosa, with only Funastrum clausum, climbing milkweed vine testing positive.