Summary: In 2014, the authors evaluated fungicide products against a slate of several registered fungicides and an untreated control. Fungicides were tested for efficacy against gray mold caused by Botrytis cinerea and powdery mildew caused by Podosphaera aphanis.

Introduction: The authors have been engaged in studying fruit and foliar pathogens in strawberry since 2007. While this group of pathogens includes anthracnose caused by species of Colletotrichum, leather rot caused by Phytophthora cactorum and angular leaf spot caused by Xanthomonas fragariae, the fungicide screening of 2014 concentrated on the two most common problems: gray mold caused by Botrytis cinerea, and powdery mildew caused by Podosphaera aphanis. Year after year these diseases are the most important foliar/fruit concerns for growers, and subsequently garner the most attention from fungicide distributors and manufacturers.

Materials and Methods:

Powdery Mildew: The trial consisted of treatments (Table 1) arranged in a randomized complete block design with each treatment replicated four times, on the Holly Ranch managed by Dole on the variety Monterey. Applications of all materials were made in the equivalent of 150 gallons per acre with a motorized backpack sprayer and hand held boom configured with ten 8001 flat fan nozzles operating at 120 psi, which is intended to closely mimic the conditions of commercial application. Applications of all materials were made two weeks apart: May 16, May 28, June 16, and June 24, 2014.

Powdery mildew evaluations were done on June 5, June 19 and July 7 and consisted of taking ten strawberry leaflets (per plot) of young to mid-age and assigning a percentage on a scale of 0-100% (in 10% increments) to the level of powdery mildew severity on the underside.

Table 1: 2014 Powdery Mildew Treatments

Results for 2014 Trial

Table 2: 2014 Powdery Mildew Evaluation- Percent Leaf Disease by Treatment

Means followed by same letter do not significantly differ (P=0.05, LSD)

Botrytis Gray Mold: The trial consisted of treatments (Table 3) arranged in a randomized complete block design with each treatment replicated four times, on the Holly Ranch managed by Dole on the variety Monterey. Applications of all materials were made in the equivalent of 150 gallons per acre with a motorized backpack sprayer and hand held boom configured with ten 8001 flat fan nozzles operating at 120 psi, which is intended to closely mimic the conditions of commercial application. Applications of all materials were made two weeks apart May 16, May 28, June 16, and June 24, 2014.

Evaluations for Botrytis infected fruit were made during the weekly fruit harvest by a professional crew of research plot harvesters beginning May 21 and continuing until July 16. Culls were sorted and examined for symptoms and signs of gray mold disease, and a percentage of gray mold infected fruit was calculated from the total fruit harvested from that plot.  Data results (Table 4) is presented as a percentage of Botrytis infected fruit from the  total amount harvested.

Table 3: Test materials for Botrytis study

Table 4: Results for 2014 trial

 Means followed by same letter do not significantly differ (P=0.05, LSD)

Discussion of Results for 2014 Trial:

Powdery Mildew: Control of powdery mildew by both rates of Merivon and a rotation of Torino and Mettle was exceptional, with percentages of infection significantly lower than many treatments in each of the three evaluation dates.

Looking at the last rating date on July 7, neither formulation of Thiram controlled powdery mildew, but the inclusion of Procure together with Thiram 24/7 did result in disease percentages below the untreated control. Test compounds isofetamid and pyriofenone had lower percentages of mildew than the untreated control. Rally 40W did not have significantly lower percentages of mildew than the untreated control.

Botrytis: With the exception of the June 18 evaluation date, no significant differences were found between any of treatments. On June 18, both treatments of Merivon demonstrated lower levels of Botrytis infected fruit than the untreated control, Thiram 24/7, isofetamid @10.3 fl oz + IB8111 and Pristine.

Final Note: The use of fungicides, including unregistered materials, is the topic of this article. Before using any of these products, check with your local Agricultural Commissioner's Office and consult product labels for current status of product registration, restrictions, and use information.

Acknowledgments.

We thank Patty Ayala, Kat Kammeijer and Monise Sheehan for their assistance with this trial. We acknowledge the California Strawberry Commission and cooperating companies, in particular Dole, for supporting this work.

A few notes for people who couldn't attend the "Groundwater Recharge, Cover Crops and El Niño Preparation Field Day" this past Tuesday. 

First, you should have been there.  This was extension at its finest, with Richard Smith, Michael Cahn and Eric Brennan leading the charge on an immensely interesting and relevant meeting.

The upshot of the whole deal is that the use of cover crops on bare vegetable ground is really helpful in both managing erosion and retaining water which then goes back down into the water table - something we are sorely needing of after several years of drought.

For strawberries, which are of course grown in beds covered with plastic mulch, the use of a cover crop (the meeting focused on mustard) in the furrows will go a long ways in minimizing erosion and loss of soil during rainstorms.  Key point for establishment is the miniscule amount of water needed to establish it with the drip tape placed in the furrow, Eric shared that it was less than a quarter inch to get the crop to the point we saw on Tuesday - and this was during a hot spell to boot.

A more in-depth discussion of this important topic is here:

http://cesantacruz.ucanr.edu/files/221436.pdf

Finally, if you are interested Eric has 1600 lb of mustard seed to give away, and will even loan out his planter (seriously!) for anyone who is interested in planting cover crop this year.

September 2015 brought on record high temperatures in agricultural fields in California's central coast. Parts of the Salinas Valley, Pajaro Valley, and Watsonville experienced daytime high temperatures that are rarely seen here. Not surprisingly, various central coast crops exhibited symptoms that were associated with heat damage. Strawberry plantings also showed symptoms of heat damage. One particular manifestation of injury to strawberry resembled anthracnose disease. Strawberry runners had dark brown to black lesions (Photo 1) that initially measured from1/4 to 3/4 inch long. In some cases the lesions could be much longer and could cause the entire runner to wither and dry up (Photo 2).

Field examination and laboratory analysis clearly eliminated the anthracnose fungus (Colletotrichum acutatum) as a cause of this symptom. Strawberry runner lesions never developed any signs (fruiting structures) of any fungal pathogen. In affected fields, thousands of runners were damaged, which is far too many for an anthracnose case in summer and without any rain. 90% of the injured runners were hanging down along the sides of the beds (Photo 3) where direct sun exposure and temperatures would be the greatest; only a few runners on bed tops showed any lesions. Timing was important as a determinant: runner lesions occurred a few days after the maximum daily highs had passed. Finally, extensive testing by the UC Cooperative Extension diagnostic lab resulted in 100% complete negative results for pathogens. Therefore this abiotic damage symptom poses no threats to the plants and is not associated with anthracnose disease.

Labor easily takes top billing in most conversation concerning berry production today. While this is a very big deal for us, what does it look like outside of this industry?

A lot of the same actually.

Trucking: In spite of rising demand for freight shipment in our strengthening domestic economy, trucking businesses are hurting for drivers. Under the heading “Who's driving?” the August 28 trucking industry analysis by ValueLine, a leading stock advisory service, describes that a “worsening driver shortage is the biggest news affecting the industry today”. Truck fleets will have to either lower driver standards, raise pay or consolidate with other companies to purchase access to more drivers.

Housing: Likewise to trucking, what should come under the heading “Who's building?”, the September 21 quarterly earnings call of Lennar Corporation, one of the largest builders of single and multi-family homes in the US, alluded to labor as “having become a limiting factor” in being able to build houses. This has to be really frustrating, because the prospects for builders right now are really good – employment is up, demand is strong and consistent and Millennials, long understood to be on the sidelines of the market, are starting to form households. Nevertheless, according to the call, the entire labor market has tightened and rapid growth in the housing market will be limited by available labor.

So, are the worker shortages we face in the berry industry simply a reflection of a larger, secular shift in the labor situation in the USA? Given the above examples, one could say maybe so.