2013 Annual Report
Objective 2: Factorial experiments will determine interacting roles of insect vector density and potato plant growth stage on disease symptoms. Experiments will evaluate beet leafhoppers as vectors of the purple top disease pathogen and potato psyllid as vectors of the zebra chip disease pathogen. We will determine the time needed for an uninfected psyllid to acquire the Liberibacter pathogen from foliage, and the time needed for an infected psyllid to transmit the pathogen to an uninfected plant. We will determine the relative susceptibility of potato cultivars to zebra chip disease by comparing disease incidence and severity in varieties of potato in field cages, with timed numbers of infective potato psyllids.
Objective 3: We will develop a toxicant bait for attracting and killing wireworm larvae when applied to potato fields at spring planting to provide protection of tubers at the end of the season. Baits will be tested in the field to determine efficacy against wireworms.
Potato psyllid was shown to be surprisingly cold-hardy, which forces scientists and growers to seriously consider that the insect may be able to overwinter under local winter conditions. Animal proteins were found to be highly stimulatory to feeding wireworms. Efforts to incorporate animal proteins into baits for use as monitoring tools or in attract-and-kill programs are ongoing.
Field studies further confirmed that zebra chip-infected potato tubers do not significantly contribute to the disease spread as these tubers generally do not sprout and if they do, usually produce disease-free and short-lived potato plants. This information will greatly benefit seed certification agencies and promote national and international trade of fresh potatoes.
For a second year, it was determined that asymptomatic potato tubers produced by plants infected with liberibacter late in the season could develop zebra chip symptoms in storage. This is particularly important for the Pacific Northwest where the potato psyllid colonizes fields late in the season and where most of the potatoes are stored for several months pending processing. This information will help potato producers make informed decisions on whether to store tubers from fields impacted by zebra chip.
In collaboration with several private and public potato breeders, potato clones were screened for zebra chip resistance. Six of the advanced potato breeding lines showed some tolerance to zebra chip. This information enables the development and adoption of better and sustainable management strategies for zebra chip.
It was found that applications of Cyazypyr are effective in killing the potato psyllid rapidly. However, although Cyazypyr insecticide effectively suppressed psyllid populations, it did not prevent transmission of liberibacter to potatoes. Information from this research will be incorporated in integrated pest management programs for potato psyllid.
In collaboration with ARS and university scientists, the zebra chip bacterium was found on several important crops in Central America (Nicaragua, Honduras, and El Salvador), including tomato, pepper, eggplant, and tobacco. The genetic variants of the potato psyllid in U.S., Mexico, and Central America were identified and their spatial and temporal distributions described.
Nelson, W.R., Sengoda, V.G., Alfaro-Fernandez, A.O., Font, M.I., Crosslin, J., Munyaneza, J.E. 2013. A new haplotype of 'Candidatus Liberibacter solanacearum' identified in the Mediterranean region. European Journal of Plant Pathology. 135:633-639. DOI:10.1007/s10658-012-0121-3.
Munyaneza, J.E., Buchman, J.L., Sengoda, V.G., Goolsby, J., Ochoa, A.P., Trevino, J., Schuster, G. 2012. Impact of potato planting timing on potato zebra chip disease incidence in the Lower Rio Grande Valley of Texas. Southwestern Entomologist. 37:253-262.
Davis, T.S., Horton, D.R., Munyaneza, J.E., Landolt, P.J. 2012. Experimental infection of plants with an herbivore-associated bacterial endosymbiont influences herbivore host selection behavior. PLoS One. 7(11):e49330. doi:10.1371/journal.pone.0049330.
Horton, D.R., Guedot, C., Landolt, P.J. 2012. Identification of feeding stimulants for Pacific coast wireworm by use of a filter paper assay (Coleoptera: Elateridae). Journal of British Columbia Entomological Society. 109:38-47.
Munyaneza, J.E., Henne, D.C. 2012. Leafhopper and psyllid pests of potato. In: Giordanengo, P., Vincent, P., Alyokhin, A., editors. Insect Pests of Potato: Global Perspectives on Biology and Management. San Diego, California:Academic Press. p. 65-102.
Munyaneza, J.E. 2012. Zebra chip disease of potato: biology, epidemiology, and management. American Journal of Potato Research. 89:329-350.
Swisher, K.D., Munyaneza, J.E., Crosslin, J. 2012. High resolution melting analysis of the cytochrome oxidase I gene identifies three haplotypes of the potato psyllid, Bactericera cockerelli, in the United States. Environmental Entomology. 41:1019-1028.
Swisher, K.D., Munyaneza, J.E., Crosslin, J. 2013. Temporal analysis of potato psyllid haplotypes in the United States. Environmental Entomology. 42:381-393.
Liu, Q., Chen, J., Munyaneza, J.E., Civerolo, E.L., Wallis, C.M. 2013. Scanning electron microscopy and in vitro cultivation of endophytic bacteria from potato tubers related to Zebra Chip disease. Canadian Journal of Plant Pathology. 35:192-199.
Bextine, B., Aguilar, E., Rueda, A., Caceres, O., Sengoda, V.G., Mc Cue, K.F., Munyaneza, J.E. 2013. First report of 'Candidatus Liberibacter solanacearum' on tomato in El Salvador. Plant Disease. 97:1245.
Munyaneza, J.E., Sengoda, V.G., Aguilar, E., Bextine, B., Mc Cue, K.F. 2013. First report of 'Candidatus Liberibacter solanacearum' associated with psyllid-affected tobacco in Nicaragua. Plant Disease. 97:1244.
Aguilar, E., Sengoda, V.G., Bextine, B., Mc Cue, K.F., Munyaneza, J.E. 2013. First report of 'Candidatus Liberibacter solanacearum' associated with psylllid-affected tobacco in Honduras. Plant Disease. http://dx.doi.org/10.1094/PDIS-04-13-0453-PDN.
Aguilar, E., Sengoda, V.G., Bextine, B., Mc Cue, K.F., Munyaneza, J.E. 2013. First report of 'Candidatus Liberibacter solanacearum' on tomato in Honduras. Plant Disease. 97:1375.
Horton, D.R., Lewis, T.M., Dobbs, T.T. 2013. Interceptions of Anthocoridae, Lasiochilidae, and Lyctocoridae at the Miami Plant Inspection Station (Hemiptera: Heteroptera). Florida Entomologist. 96(2):482-497. DOI:http://dx.doi.org/10.1653/024.096.0214.
Guedot, C.N., Horton, D.R., Landolt, P.J. 2012. Age at reproductive maturity and effect of age and time of day on sex sttraction in the potato psyllid Bactericera cockerelli. Insect Science. 19:585-594. DOI 10.1111/j.1744-7917.2011.01498.x.
Munyaneza, J.E., Sengoda, V.G., Aguilar, E., Bextine, B.R., Mc Cue, K.F. 2013. First report of "Candidatus Liberibacter solanacearum" infecting eggplant in Honduras. Plant Disease. 97:1654 http://dx.doi.org/10.1094/PDIS-06-13-0641-PDN.