High Quality Beverage Raw Materials for the Craft Brewing Industry

Hop Disease Research:

Hypothesis 1: Late winter/spring air and soil temperature data was collected using a Spectrum 1000 Series weather station and Spectrum soil temperature probes at four collaborating hop yards.  Hop yards were visited weekly/biweekly from late March to late April and scouted for hop shoots showing characteristic downy mildew symptoms.  These shoots are classified as ‘basal spikes’.  The date at which the first basal spikes were observed was recorded.  This data collection occurred from 2015-2017.  Weather data was processed using “R” (https://www.R-project.org) statistical software.  Accumulated degree-days were calculated using several base temperatures for each location/year/emergence date combination.  Degree-day calculations for each base temperature were averaged over all years and used for model selection based on certain statistical parameters such as range, variance, and coefficient of variation.  The day-of-year (DOY) at which these newly calculated degree-day thresholds occurred was also calculated and compared to actual emergence dates. 

Hypothesis 2: Experiments were performed to artificially “manipulate” the soil temperature at two collaborator hop yards over the winters of 2016/17 and 2017/18.  Treatments consisted of snow removal to remove insulation and lead to colder soil temps, a mulch layer to add insulation and warm soil, and an unaltered control.  Treatment plots were five feet long within a hop row with five foot buffers between each plot.  Treatments were replicated five times with a randomized complete block design.  Experiments were conducted with ‘Nugget’ variety hops of similar ages at both hop yards.  Spectrum button loggers measuring temperature were buried at 4 and 10 cm in one of each treatment plots at both locations to ensure the appropriate temperature changes occurred.  Mulch was applied as intact straw bales.  Snow removal was performed by grower collaborators as accumulation occurred.  In the spring, counts of healthy hop shoots and basal spikes in each plot were made at time of emergence, then 3, 7, 10, and 14 days post-emergence.  Data was analyzed for differences in the number of infected basal spikes between treatments and the timing of this spike emergence.  

Hypothesis 3: Healthy and infected leaf and stem hop plant tissue was screened for the presence of P. humuli oospores.  Plant tissue was cleared by boiling in ethanol followed by a 10% bleach soak for several hours.  Cleared tissue was visualized under a light microscope for characteristic double-walled oospores.  Soil samples were collected from four hop yards at spring, summer, and fall time points in 2016.  At each collection, ten samples of soil taken from the top 2-3 inches of soil at the base of hop plants were gathered from arbitrary locations within the hop yard.  10 g from each of the ten samples per time/location were aggregated and homogenized with a mortar and pestle.  The resulting 100 g aggregate sample was suspended in water and sonicated for 5 minutes at 70% duty cycle.  The resulting slurry was strained sequentially through sieves 250, 75, 50, and 25 um in size.  The material remaining on the 25 um sieve was collected and layered onto 20 ml of a 70% sucrose solution and centrifuged to separate oospores from soil.  The supernatant, which would contain any present oospores, was sieved again through a 25 um sieve and rinsed.  The remaining material was collected in a 15 ml tube.  Six 30 ul subsamples from this solution were observed under the microscope and oospores were counted in each.  Based on these counts, the total number of oospores in each soil sample was back-calculated. 

Hypothesis 4: Colony isolates of P. humuli were collected from 8 hop yards in 6 counties in 2014-2017.  These isolates were tested for insensitivity to a commonly used and highly effective fungicide chemistry utilized for hop downy mildew control: mefenoxam.  This screen was performed as a leaf disk assay based on previously performed work in the Pacific Northwest.  In short, leaf disks were cut from hop leaves from greenhouse-grown plants.  Leaf disks were placed onto Petri plates with water agar or water agar amended with a discriminatory dose of mefenoxam (25 ug/ml).  Seven leaf disks were placed on each plate, with the top leaf surface in contact with the agar.  Fourteen total leaf disks were each inoculated in three discrete locations with a standardized suspension of P. humuli sporangia collected from the field.  After incubating for 5-7 days, each inoculation site on both control and treatments plates was observed for the presence of P. humuli sporulation.  An isolate was determined to be resistant if the amount of sporulation on fungicide treatment plates was at least 50% the amount of sporulation on control plates.  Further assays conducted on a range of fungicide concentrations were performed to calculate ED50 values for each isolate.  These values are useful for tracking sensitivity changes within a population over time.  A total of 80 isolates grew sufficiently for full analysis. 

Hop Soil Fertility Research:  the first year, 2016 that we studied hop soil fertility, we only looked at the biomass produced in the whole plant and in the hop cones alone.  We did this for 3 hop varieties in two locations (farm cooperators).  In 2017 we expanded this research by adding 3 different nitrogen rates. See the following for the protocol used: Hop N fertility protocol_051817

Malting Barley Research trials were in cooperative with UW-Madison Extension and the University of Minnesota.  All plots were planted using a randomized block design.  see fungicide example 17213 Buffalo Co. Barley Trial  

• 28 - 38 winter malting barley varieties were planted in October, 2015, 2016, and 2017 and about 70% did very well.  Proteins seemed a little high for craft brewing malting quality, but more test years are needed to understand their true characteristics.  The unusually late freeze allowed these plants to grow larger than desired, and as of this report 85% of the varieties seemed to have survived the winter.  Farmers are very excited about the possibility for winter barley as they seem to yield higher, have less disease issues, fit better into the rotation, and provide better cover on steeper soils than spring barley.  One Buffalo County farmer did contract with a malter to grow 45 acres of a winter malting barley.
• Spring varieties were planted in two locations, Buffalo County and Chippewa County.  Nine varieties were included in 2015, 2016, and 2017 replicated variety plots.  All were malted by the USDA Cereal Grains Unit in Madison, WI.  Six of the varieties showed good malting qualities, two varieties seem to have consistently high protein levels undesirable in brewing, and one heritage variety had many agronomic characteristics that made it suffer to a point that it was not suitable to harvest.
• A fungicide plot was also included in two locations in 2016 and 2017.  Plots included no fungicide, fungicide for leaf diseases only, fungicide at heading only and two fungicide applications.  All were replicated with two different varieties of barley (Pinnacle and Genesis) and each was replicated four times.  Data is still being analyzed, but preliminary data looked like there may be some advantage to the Genesis variety and maybe just fungicide at heading.  
• A nitrogen fertilizer trial was conducted in 2015, 2016, and 2017 with Pinnacle and Genesis barley with rates from 0 to 120 pounds of nitrogen.  
•  Four graduate students from the University of Minnesota attended the seminar and explained their major areas of research.