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In September 2011, potato (Solanum tuberosum) tubers grown in Nicaragua outside of Estelí and Jinotega were observed with internal discoloration suggestive of zebra chip (ZC); and the plants showed foliar symptoms of chlorosis, leaf scorching, wilting, vascular discoloration, swollen nodes, twisted stems, and aerial tubers (3). Disease incidence ranged from 50 to 95% in eight fields ranging from 5 to 12 ha in the Estelí and Jinotega regions of Nicaragua. Leaf samples and psyllids were collected from two fields, and total DNA was purified from the leaves of 17 symptomatic and 10 asymptomatic plants. DNA was also extracted from 20 individual potato psyllids. Primers specific for 16S rDNA (OA2 and OI2c) and the surface antigen gene (OMB 1482f and 2086r) of Candidatus Liberibacter solanacearum (CLs) were used to confirm the presence of the pathogen in infected potatoes and insects (2). All symptomatic potato leaf samples tested positive for the presence of CLs using both primers, and no asymptomatic plants had positive results. Seven insects tested positive for the presence of CLs. 16S rDNA sequences obtained for all positive samples (1,071 bp) were identical and showed 99 to 100% identity to a number of rDNA sequences of CLs in GenBank (Accession Nos. HM246509 and FJ957897). 16S rDNA sequences from two CLs-infected plants, one from Estelí, Nicaragua (JX559779) and one from Jinotega, Nicaragua (JK559780), were deposited in GenBank. Identity of insects was done using a morphological key, and then verified as Bactericera cockerelli using a real-time PCR assay with melt temperature analysis of the cytochrome c oxidase 1 gene, as described by Chapman et al. (1). Sequencing of the amplified DNA yielded an approximately 63-bp read, with 100% homology to reference sequences of B. cockerelli (AY971886) and those obtained from psyllids collected in McAllen, TX, in 2010. B. cockerelli samples were collected from both locations. Similar to previous reports of ZC in new locations, foliar and tuber symptoms associated with ZC were observed in all eight fields in these two Nicaraguan potato-growing regions, specific PCR amplification with two primer pairs was completed, 16S rDNA sequence analyses showed 100% similarity to reference sequences of CLs, and the presence of potato psyllids which tested positive for the presence of CLs provide evidence that ZC is now present in Nicaragua. Potatoes rank in the top 20 commodities produced in Nicaragua, resulting in >$4.5M annual revenue. Because CLs has caused significant economic damage to potatoes in the United States, Mexico, Guatemala, and Honduras, this finding has significance for potato production in Central America. References: (1) R. I. Chapman et al. Southwest. Entomol. 37:475, 2012. (2) J. M. Crosslin. Southwest. Entomol. 36:125, 2011. (3) L. W. Liefting et al. Internat. J. Syst. Evol. Microbiol. 59:2274, 2009.

We evaluated the effectiveness of alternative fumigants on weed control, soil pests, plant growth and marketable roots production in a commercial nursery located at high-elevation and low latitude (Ciudad Guzman, Jalisco) during 2013 and 2014. Treatments were: Methyl bromide with chloropicrin (MB:CP); 1,3-dichloropropene:CP (1,3D:CP); CP alone; metam sodium (MS) alone; dimethyl disulphide with CP (DMDS:CP); and sequentially applied CP and MS (CP+MS). A Rotary Spading Machine was used for MS and CP followed by MS. All treatments except MS and CP+MS in 2014 controlled Rhizoctonia and all controlled Phytophthora in 2013, but none controlled Fusarium in soil. No significant nematode, Verticillium and Pythium populations were detected in nursery soil before treatments. No diseased plants were observed throughout the cultivation cycle. Densities and fresh weights of graminoid weeds were significantly reduced by MB:CP and CP+MS, but none of the fumigants controlled all forbs. Only Echinochloa crus-galli, Digitaria spp., Sonchus oleraceus, and Amaranthus hybridus densities and biomass were reduced 50-78% by all fumigants. The highest commercial yield of raspberry roots and plant emergence were recorded with MB:CP and 1,3D:CP, while CP and MS only increased plant emergence. Finally, two years of work on MB alternatives were not sufficient to provide reliable recommendations on this critical need, therefore MBTOC recommended CUN for MB in 2015.

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