We evaluated the comparability of culture and PCR tests for detecting Ichthyophonus in Yukon River Chinook salmon Oncorhynchus tshawytscha from field samples collected at 3 locations (Emmonak, Chena, and Salcha, Alaska, USA) in 2004, 2005, and 2006. Assuming diagnosis by culture as the 'true' infection status, we calculated the sensitivity (correctly identifying fish positive for Ichthyophonus), specificity (correctly identifying fish negative for Ichthyophonus), and accuracy (correctly identifying both positive and negative fish) of PCR. Regardless of sampling locations and years, sensitivity, specificity, and accuracy exceeded 90%. Estimates of infection prevalence by PCR were similar to those by culture, except for Salcha 2005, where prevalence by PCR was significantly higher than that by culture (p < 0.0001). These results show that the PCR test is comparable to the culture test for diagnosing Ichthyophonus infection.

We examined the impacts of Ichthyophonus infection on spawning success of Yukon River Chinook salmon Oncorhynchus tshawytscha at spawning grounds of the Chena and Salcha Rivers, Alaska, USA. During the period 2005 to 2006, 1281 salmon carcasses (628 male, 652 female) were collected throughout the spawning season and from the entire spawning reaches of the Chena and Salcha Rivers. For each fish, infection status was determined by culture method and visual inspection of lesions of heart tissue as uninfected (culture negative), infected without lesions (culture positive with no visible lesions), and infected with lesions (culture positive with visible lesions), and spawning status was determined by visually inspecting the percentage of gametes remaining as full-spawned (<10%), partial-spawned (10−50%), and unspawned (> 50%). Among the 3 groups, the proportion of full-spawned (i.e. spawning success) females was lower for those infected without lesions (69%) than those uninfected (87%) and infected with lesions (86%), but this did not apply to males (uninfected 42%, infected without lesions 38%, infected with lesions 41%). At the population level, the combined (infected and uninfected) proportion of female spawning success was 86%, compared to 87% when all females were assumed uninfected. These data suggest that while Ichthyophonus infection slightly reduces spawning success of infected females, its impact on the spawning population as a whole appears minimal.

Using a spray tower to simulate aerially applied liquid sprays, three doses of Spinosad (a bacteria derived product) were each applied to grasshoppers and pots of growing grass separately on 7 Sept. For each dose, untreated grasshoppers were confined on treated grass, treated grasshoppers were confined on untreated grass and treated grasshoppers were confined on treated grass. Untreated grasshoppers were confined on untreated grass as a control. Grasshoppers treated with Fyfanon ULV (malathion) were confined on grass treated with Fyfanon as a standard for comparison. All spray treatments were applied at an equivalent total volume of 32 fluid oz/acre. Spinosad treatments were applied in distilled water and Fyfanon was diluted and applied in oil. The study design consistedof 10 replicates per treatment. Each replicate consisted of a caged pot of grass containing five fourth instar grasshoppers. Pots were 4 inches X 4 inches square with a 9 inch high cage attached and contained grass approximately 4 inches high at time of treatment. Caged grasshoppers were held at 78°2±°F and a photoperiod of 14:10 (L:D). Dead grasshopperswere removed from the cages and mortality recorded daily.

An upland site on the South Dakota State University Agronomy Farm, Brookings, SD, was chosen to evaluate the efficacy of several foliar-applied rescue insecticide treatments for control of RWA. Soil on the site was classified as a Barnes clay loam (mixed Udic Haploboroll).

for data not supporting the conclusions of 'PCR testing is as accurate as culture…', but they neither pointed out what part of our data did not support our conclusion, nor did they provide any contrary scientific evidence supporting their argument that PCR testing is less accurate than culture. In the absence of any contradictory data, we stand by our data and our conclusion: PCR test is as suitable as culture as a diagnostic and field surveillance tool.