Zebra chip disease (ZC) is an emerging disease of potato in which tubers are produced with striped necrotic patterns that make them unmarketable. ZC is associated with the bacterium "Candidatus Liberibacter solanacearum" (Lso), which is transmitted by the potato psyllid, Bactericera cockerelli (Šulc; Hemiptera: Triozidae). First found in Idaho during 2011, ZC now contributes to increased production costs each season via additional insecticide sprays. To clarify the extent and severity of the threat of ZC in Idaho, we sampled potato psyllids in commercial potato fields across the state over four growing seasons (2012-2015). All life stages of psyllids were sampled using a combination of methods (yellow sticky traps, vacuum samples, and leaf samples), and adult psyllids were tested for the presence of Lso by Polymerase Chain Reaction (PCR). Abundance of potato psyllids initially increased gradually over each growing season, then exhibited a sharp late-season rise and a sharp decline as most fields were being harvested. Abundance of psyllids was higher at warmer, lower elevation sites, but infestation onset did not differ between growing regions. Fewer psyllids were collected in vacuum samples than in sticky trap samples. Nymphs and eggs were found only late season and during years with high abundance of adults. Overall incidence of Lso was similar among all years but one. The results presented here clarify our understanding of the seasonal phenology of potato psyllids and Lso in Idaho potato fields and will aid in developing integrated management strategies against this important pest of potato.

Many of the forest soils in the Intermountain West are deficient in several nutrients, including nitrogen (N), potassium (K), sulfur (S) and boron (B) and these deficiencies may impact tree resistance to insect attack. Two potential techniques for manipulating tree resistance are fertilization and thinning. We examined fertilization (both alone and in conjunction with stand thinning). Conifer resistance to bark beetles involves a three-step response, the first stage of which is resin flow. Rapid resin flow can prevent the colonization of bark beetles within a tree. Fertilization with low levels of N resulted in an increase in resin flow while high levels of N did not significantly increase resin flow in treated trees. Thinning did not result in higher concentrations of foliar K or B but did result in higher concentrations of foliar N and S. The highest concentrations of foliar N and S consistently occurred in the trees from thinned treatments, regardless of fertilization. There was a negative correlation between tree growth and resin flow one year following treatments. Increasing available nutrient levels to trees (either through fertilization or stand density management) may result in modified resistance parameters that must be considered when making management decisions.

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