Candidatus Liberibacter solanacearum" (Lso) (="Candidatus Liberibacter psyllarous") is an uncultured, phloem-limited bacterium that is associated with zebra chip disease (ZC) in potato (Solanum tuberosum L.) and transmitted by the potato psyllid (Bactericera cockerelli (Šulc)). Vector density and timing of infection have been shown to affect ZC prevalence at harvest; however, little work has been done on disease development during storage. Here we confirm with field-cage trials that ZC prevalence at harvest was greater with increased time between inoculation and vine kill. Moreover, we show that with Pacific Northwest growing conditions, ZC can develop over time during storage. Plants inoculated 2 to 3 weeks before vine kill showed little or no ZC symptoms in tubers at harvest, but higher prevalence of symptoms after 3 months in storage. For plants inoculated at 4 to 5 weeks before vine kill, tubers exhibited notable symptoms at harvest, but still showed evidence of symptom development after storage. Plants inoculated within 1 week before vine kill exhibited little or no risk of ZC in tubers at harvest or after storage. Higher vector density tended to contribute to ZC prevalence, but was far less important than timing of infection. These results underscore the potential danger of underestimating ZC prevalence at harvest for tubers being stored long term, and suggest that plants at risk of Lso infection should be protected from potato psyllids until at least 2 weeks before vine kill.

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Strip tillage, in which tillage and seedbed preparation are limited to a narrow band where the subsequent crop is planted, provides many potential agronomic benefits, including reduced fuel and labor costs, reduced erosion, and improved soil tilth. Lower soil disturbance and enhanced water retention associated with strip tillage also may affect density and diversity of predatory arthropods, which have been little studied in sugar beet. We examined the effects of tillage (conventional versus strip) on the predatory epigeal arthropod fauna in sugar beet. Studies were conducted over three growing seasons (2010–2012) in Idaho using both fenced and unfenced pitfall traps to sample arthropods. Unfenced pitfall traps often captured a greater activity density and richness of predators, and showed no bias of higher captures in conventionally tilled plots as has been shown elsewhere. Total density of predators was higher in strip tillage only during 2011. Density and species richness of carabid beetles did not differ between tillage treatments during the course of the study. Density of the other major taxa (staphylinid beetles, spiders, and Opiliones) was higher under strip tillage during some years, especially early in the season, but richness showed little or no relationship with tillage. Predaceous arthropods might be favored by enhanced ground cover, higher humidity, more moderate temperatures, and/or less habitat disturbance associated with strip-tilled plots. The results suggest that certain groups of soil-dwelling predatory arthropods can be favored by strip tillage in sugar beet, which further adds to the benefits of conservation tillage in this system.

Despite the many agronomic benefits of conservation tillage, little is known regarding the effects of reduced tillage on the pest complex in sugar beet. We examined the effects of two types of tillage (strip till versus conventional) and different irrigation rates on yield as well as densities of insect pests, weeds, and a soil-borne plant pathogen in sugar beet. Yields were similar between tillage treatments for two of the three years, but were greater for conventional tillage during one year in which a wet spring may have slowed seedling development in strip-tilled plots. The low irrigation treatment exhibited lower yields in one of three years, regardless of tillage treatment. Eggs of beet leafminer flies were more abundant in conventional tillage on three of eight observation dates, but larval densities did not differ by tillage treatment. Bean aphid incidences generally were positively related to irrigation rate. Total weed counts within beet rows did not