Miller Research LLC

Rupert, ID, United States

Miller Research LLC

Rupert, ID, United States

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Atkinson D.,Apple Inc | Thornton M.K.,University of Idaho | Miller J.S.,Miller Research LLC
American Journal of Potato Research | Year: 2010

Rhizoctonia solani may affect potato growth, yield and grade through lesions on stems and stolons and through development of black scurf on daughter tubers. R. solani inoculum can be found on seed potatoes and in the soil, although the relative importance of each inoculum source is unknown. Field studies at Parma and Aberdeen, Idaho, were conducted in 2004 and 2005 to evaluate the importance of each source of inoculum on the subsequent development of this disease. Seed of cultivars Ranger Russet (2004) and Russet Burbank (2005) was washed and sorted into three (2004) and two (2005) levels of black scurf. Prior to planting, the plots were inoculated with R. solani cultures mixed with vermiculite at low, medium and high rates. Each level of seed inoculum was planted at each level of soil inoculum. Significantly greater levels of disease on stems and stolons was consistently found on plants grown from high inoculum seed compared to low inoculum seed. However, significant effects of soil inoculum level on stem and stolon disease were rarely seen. In contrast, both seed and soil inoculum level influenced the development of black scurf on daughter tubers. The largest response to soil inoculum level was seen when seed inoculum was low. © 2010 Potato Association of America.


Miller J.S.,Miller Research LLC | Hamm P.B.,Oregon State University | Olsen N.,University of Idaho | Geary B.D.,Brigham Young University | Johnson D.A.,Washington State University
American Journal of Potato Research | Year: 2011

Silver scurf of potato, caused by Helminthosporium solani, can be a serious problem of potato tubers sold for table stock. The fungus originates primarily on seed and infects the periderm of daughter tubers, causing unsightly blemishes that reduce tuber quality. Secondary spread occurs in potato storage facilities when spores produced on infected tubers are moved through the air system. Depending on storage conditions and time, even a low initial disease incidence can result in significant losses through quality reductions. In the past, thiabendazole has been the most effective post harvest treatment in controlling this disease, but the development of fungicide resistance has made this product unreliable. Because of the lack of consistent alternatives, studies were conducted from 2001 to 2003 to examine the efficacy of various products in suppressing silver scurf incidence and severity when applied to tubers following harvest and prior to storage. Daughter tubers from a seed lot with high incidence of silver scurf symptoms were grown and then harvested 1 month after vine kill. After harvest, tubers were treated with a post-harvest application of various products, stored, and then evaluated for disease incidence and severity each year at two locations (Washington or Oregon and Idaho) and at two time periods (2 or 3 months and 6 months following storage). When treated tubers were stored from the fall of 2002 to spring of 2003, potassium sorbate and B. subtilis reduced disease severity after 6 months in storage at location 1, while azoxystrobin reduced incidence after 6 months in location 2. During the 2003-2004 storage season, azoxystrobin reduced silver scurf at both locations after 2 months of storage. Most products currently labeled for post-harvest silver scurf management were ineffective. While not currently registered, azoxystrobin used as a post- harvest, pre- storage treatment may be a significant method for commercial potato growers to suppress silver scurf in potato storage. © 2011 Potato Association of America.


Miller J.S.,Miller Research LLC | Hamm P.B.,Oregon State University | Dung J.K.S.,Oregon State University | Geary B.D.,Brigham Young University | And 3 more authors.
American Journal of Potato Research | Year: 2014

A three-year study was conducted in 1999, 2001, and 2002 to examine the influence of seed-borne inoculum and fludioxonil+mancozeb seed treatment on silver scurf (caused by Helminthosporium solani) development on progeny tubers at six locations under different potato rotations in the semi-arid U.S. Pacific Northwest. Disease-free pre-nuclear seed and diseased generation 3 seed was either treated or not treated with fludioxonil plus mancozeb, planted, and progeny tubers were harvested and then evaluated for silver scurf incidence and severity. Experiments were conducted in the southern Columbia Basin (Oregon), northern Columbia Basin (Washington), central Oregon, southern Oregon, western Idaho, and eastern Idaho under short (<3 years), normal (3-5 years), and long (>5 years) potato rotations over the three years for a total of 19 location-year-rotation combinations. Significant differences were observed among years and locations with disease incidence being highest in central Oregon. Progeny tubers from untreated generation 3 seed had significantly higher silver scurf incidence (18.4 %) and severity (1.3) compared to untreated progeny tubers from pre-nuclear seed (1.2 % and 0.04 for incidence and severity, respectively). Seed treatment with fludioxonil+mancozeb reduced incidence (3.8 %) and severity (0.2) significantly compared to the untreated control (15.8 % and 1.1 for incidence and severity, respectively). Significant (P < 0.0001) interactions between treatments and location-year-rotation were observed and additive main effects multiplicative interaction analysis discriminated those with high incidence, severity, and variability. These data indicate that seed, not soil, is the primary source of progeny tuber infection in the field in the Pacific Northwest. For long term storage, purchase of clean seed is an essential component for managing silver scurf. © 2014 The Potato Association of America.


Miller J.S.,Miller Research LLC | Johnson D.A.,Washington State University
American Journal of Potato Research | Year: 2015

Epidemics of late blight on potato in the semiarid Pacific Northwest since 1991 have been characterized by a prevalence of stem lesions in relation to leaf lesions. This study was conducted in 1997 to test the hypothesis that isolates representing immigrant strains of Phytophthora infestans were more adapted at causing stem lesions and more aggressive at higher temperatures than isolates representing the relatively older US-1 strain. A total of 23 Phytophthora infestans isolates representing US-1, US-8, and a new A1 compatibility type strain were tested for aggressiveness on leaflets and stems of whole potato plants (cv. Russet Burbank) in 11 trials. Plants in one set of trials were incubated at constant temperatures of 18, 23, and 28 °C for six days with a 16 h photoperiod. Plants in the second set of trials were incubated at the same three day temperatures but the night temperature in all treatments was reduced to 16 °C. Lesion establishment was recorded, and daily severity readings were used to calculate the area under the lesion expansion curve (AULEC). Lesion area, sporulation frequency, sporulation time, and sporulation capacity were also measured. Lesion establishment was higher on stems than on leaves for isolates of all strains. Isolates representing US-8 and new A1 strains often had higher AULEC values but had similar lesion establishment, sporulation frequency, sporulation time, and sporulation capacity values as US-1 isolates. A reduction in components of aggressiveness for all strains was noted at 28 °C, with leaflets being more affected than stems. Sporulation rarely occurred at 28 °C. Few differences in components of aggressiveness were observed between 18 and 23 °C. These findings indicate that isolates from the relatively newer strains (US-8 and new A1) were not better adapted in causing lesions on potato stems than isolates from the old US-1 strain, nor were they better adapted to higher temperatures. The relatively newer strains, however, were generally more aggressive as indicated by higher AULEC on stems and leaflets over the range of temperatures used in this experiment. © Potato Association of America 2014.

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