Various soilborne, fruit and foliar diseases can affect strawberry crop and fruit yields.  Chemical fumigants and a variety of fungicides are typically used for managing the disease issues.  In addition to the environmental and human health concerns with chemical control options there is a need to improve current disease management with alternatives that include beneficial microbes.  Previous studies showed some promise with some of the treatments, but additional studies are required to evaluate the efficacy, which is more evident especially when there is disease incidence. 

A study was conducted in summer-planted conventional strawberries in 2016 at Manzanita Berry Farms to evaluate the impact of various beneficial microbial treatments on plant growth, health, and fruit yield.  Untreated control and the grower standard practice (Healthy Soil treatment) were compared with MycoApply EndoMaxx (Glomus intraradices, G. aggregatum, G. mosseae, and G. etunicatum), Actinovate AG (Streptomyces lydicus WYEC 108), and Inocucor Garden Solution (Saccharomyces cerevisiae and Bacillus subtilis) applied in the following treatments:

1. Untreated control

2. Grower Standard-Healthy Soil; transplant dip in Switch 62.5WG 5 oz in 100 gal

3. MycoApply EndoMaxx 2 gpa transplant dip (TD)

4. MycoApply EndoMaxx 2 gpa drip at planting (DrP)

5. MycoApply EndoMaxx 2 gpa transplant dip + 2 gpa drip at planting

6. MycoApply EndoMaxx 4 gpa transplant dip

7. MycoApply EndoMaxx 4 gpa drip at planting

8. MycoApply EndoMaxx 4 gpa transplant dip + 4 gpa drip at planting

9. Actinovate AG 6 oz/ac transplant dip + 6 oz drip at planting + 6 oz drip monthly (DrM)

10. Inocucor Garden Solution 1 gpa drip at planting + 1 gpa drip monthly

Transplanting was done on 21 May, 2016 with appropriate treatments administered at the time of planting and thereafter.  Study had two blocks of 10 strawberry beds (300' long) and treatments were randomly applied to a bed within each block.  Two 15' long plots were marked within each bed for sampling.  Canopy growth was measured on June 21, July 5 and 20; powdery mildew severity on August 3, September 1, October 10 and November 16; botrytis severity 3 and 5 days after harvest (DAH) for berries harvested on September 13 and 27, and October 11 and 18; and dead and dying plants were counted on September 16 and October 23.  Yield data were collected from August 20 to November 18.  Powdery mildew and botrytis fruit rot severity was measured on a scale of 0 to 4 where 0=No disease, 1=1-25%, 2=26-50%, 3=51-75%, and 4=76-100% severity.  Data were analyzed and means were separated using LSD test.

Strawberry field and plots on June 9 (above) and August 31 (below).

Two sampling plots were set up within each bed to collect plant growth, health, and yield data.

Canopy growth: MycoApply EndoMaxxat 2 gpa either as a transplant dip with or without drip application at planting appeared to promote significantly higher growth (P <0.0001) than MycoApply EndoMaxx at 2 and 4 gpa as drip at planting, untreated control, and grower standard.  Inoculating the entire transplant with Glomus spp. through a dip appears to be better than application through drip irrigation system.

Powdery mildew: Disease incidence and severity was low during the observation period.  When the average of four observations period was compared, the grower standard, MycoApply Endomaxx at 2 and 4 gpa as drip at planting, and the Actinovate treatments had the lowest incidence (P = 0.0271).

Botrytis fruit rot: There was no difference (P >0.05) among the treatments on botrytis when the mold growth on fruit was compared 3 and 5 days after harvest.

Unknown issue: Some wilting and dead plants were found throughout the field during the study.  Although symptoms suggested some kind of wilt, laboratory testing did not identify any pathogens.  The total number of dead and dying plants was the lowest in Actinovate treatment, but it was significantly different (P = 0.0429) only from the grower standard Healthy Soil treatment.

*Means followed by the same or no letter are not significantly different at the P value indicated in the table.

Fruit yield: There were no statistically significant difference among the treatments and the seasonal total of marketable yield varied between 66 lb/plot in the grower standard and about 76 lb/plot in MycoApply EndoMaxx applied as a transplant dip at 4 gpa.

Total and marketable berry yields and their proportion among different treatments.

We need to continue to evaluate beneficial microbial products and their potential benefit in improve crop health and yields.

Acknowledgements: Thanks to Chris Martinez and Tamas Zold for technical assistance, and Valent USA and Inocucor Technologies for the financial support of the study.

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