Fungi such as Beauveria bassiana, Isaria fumosorosea, Metarhizium brunneum are pathogenic to mites and insects and are primarily used for pest management.  Some of these are known to endophytically colonize plants and offer protection against arthropod pests feeding on those plants.  Some studies have indicated that entomopathogenic fungi can also provide protection against plant pathogens.

In an effort to explore the endophytic potential of entomopathogenic fungi for strawberry pest management, studies were conducted in 2010 using commercial and California isolates of B. bassiana and M. brunneum where B. bassiana successfully colonized strawberry plants and persisted for up to 9 weeks in various plant tissues.  Observations during this study suggested that endophytic entomopathogenic fungi could be aiding in plant health probably through mycorrhizal activity by improving water and nutrient absorption.  Based on these observations, a small study was conducted to evaluate the impact of B. bassiana on strawberry plant health in comparison with a commercial product intended to promote plant growth, health, and yield.

This study was conducted in collaboration with Los Angeles County Pitchess Detention Center where inmates assisted in taking care of the plants and collecting data.  As a part of the MERIT (Maximising Education Reaching Individual Transformation) Masters program, some inmates were selected to participate in this project.  Since this was the first project in such collaboration, a simple experiment was designed for easy execution and data collection.

Treatments included i) Untreated control, ii) HYTA – which contains soil-based microorganisms that enhance nitrogen absorption, solubilize nutrients, and build soil organic matter, and iii) B. bassiana (Mycotrol –O).  Transplants of the strawberry variety Monterey were treated by applying HYTA or B. bassiana to the root system in transplant treys.  Planting was done 48 hours after treatment in 20X5X2' raised beds.  Plants were regularly watered and fertilized with fish emulsion.  Plant health was monitored for about three months starting from 4 weeks after planting.  Plants were periodically observed and their health was rated on a scale of 0-5 where 0= dead, 1=weak, 2 and 3=moderate, 4=good, and 5=very good.  

Strawberry plants were grown in 20X5X2' wooden beds.  (Photo by Adrianne Ferree)

Except for a few aphids on some plants, the trial did not have any pest infestations.  Plants treated with B. bassiana were rated higher than untreated control or those treated with HYTA throughout the observation period although differences were not statistically significant on all observations dates.  While the plant health rating ranged from 2.3 to 3.0 for untreated control, it was between 2.6 and 3.5 for those treated with HYTA and 2.9 to 4.1 for those treated with B. bassiana.  The average seasonal health rating was 2.8, 3.2, and 3.6 for untreated, HYTA, and B. bassiana, respectively.  Fruit yield could not be monitored due to some technical difficulties. 

Strawberry plant health from treating with HYTA and B. bassiana compared to untreated control

Beneficial microorganisms establish symbiotic relationship with plants and serve as extended root system improving the absorption of nutrients and moisture.  By colonizing the roots and other plant tissues, they can also provide protection against plant pathogens.  Several commercial formulations of fungus and bacteria based beneficial organisms are currently available for use on various crops.  This preliminary study demonstrates that B. bassiana promotes plant health and can play an important role in crop production in addition to the primary role of pest management.   Additional studies can further explore the potential of entomopathogenic fungi in promoting plant growth and improving yield as well as providing protection against pests and diseases.

Adrianne Ferree, Assistant Director, Jail Enterprises Unit collaborated in this project with the support of Chief Alex Yim.  One of the two inmates who participated in this project took an online Plant Science course and used this study as his class project.  He intends to pursue agronomy after his release.  It is a great experience for me to be involved in the Maximizing Education Reaching Individual Transformation (MERIT) Masters program and introduce agricultural research to the inmates.

Acknowledgements: Thanks to Mike Fahner, Cedar Point Nursery for providing transplants and Joe Coelho, DB Specialty Farms for providing drip tapes and plastic mulch. 

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References

Bisutti, I. L., S. Steen, and D. Stephan.  2013.  Does Metarhizium anisopliae influence strawberries in presence of pest and disease?  XLVI Annual meetings of the Society for Invertebrate Pathology, August 11-15, Pittsburgh, PA.

Dara, S.K. and S. R. Dara.  2010.  Endophytic colonization of entomopathogenic fungi in strawberry plants.  XLIII Annual meetings of the Society for Invertebrate Pathology, July 11-15, 2010, Trabzon, Turkey.

Dara, S. K., S. R. Dara,. and S. S. Dara.  2013.  Exploring the potential of Beauveria bassiana and azadirachtin for managing strawberry pests.  Proceedings of the II International Strawberry Congress, September 4-6, 2013, Antwerp, Belgium.

Miller T.C., W. D. Gubler, F. F. Laemmlen, S. Geng, and D. M. Rizzo. 2004.  Potential for using Lecanicillium lecanii for suppression of strawberry powdery mildew, Biocon. Sci. Technol., 14: 215-220.

Ownley, B.H., R.M. Pereira, W. E. Klingeman, N.B. Quigley, and B. M. Leckie. 2004. Beauveria bassiana, a dual purpose biocontrol organism, with activity against insect pests and plant pathogens. Lartey, R.T., Caesar, A.J., editors. Research Signpost, Kerala, India. Emeging Concepts in Plant Health Management. 2004. p. 255-269.

New UC short-day variety Benicia (Photo by Surendra Dara)

Different species of spider mites attack strawberry plants.  Spider mites feed on the underside of the leaves, scrape the tissue, and suck the plant juices.  As a result, corresponding area on the upper leaf surface initially shows yellow spots.  As the damage advances, these spots expand and gradually turn into brownish, dry patches of dead plant tissue.

Twospotted spider mite infestation and damage on the lower side of the leaves causes yellow discoloration on the upper side (above) in Albion.  Stippling of yellow spots on an infested foliage (below).  (Photos by Surendra Dara)

As the damaged tissue dies, brown, dry patches develop on the upper leaf surface in Albion. (Photo by Surendra Dara)

Spider mite damage symptom in Benicia, the new short-day (June-bearing) cultivar from University of California, seems to be different compared to other varieties.  While the upper leaf surface corresponding to the damaged lower surface shows initial yellow discoloration even at high mite densities in varieties such as Albion or San Andreas, it turns dark purple in Benicia even at low to moderate mite densities.  Physiological response of Benicia to mite damage probably contributes to this unique symptom.  Such a discoloration can be useful for early and easy detection of spider mite infestations.

Twospotted spider mite infestation on the lower side of the leaf (above) causes dark purple discoloration of the corresponding upper side (below) in Benicia.  
(Photos by Surendra Dara)

Foliar damage symptoms in Benicia by twospotted spider mites.
(Photo by Surendra Dara)

Benicia is adapted for early planting and produces larger fruits with excellent flavor compared to some other short-day varieties.

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Dead and dying strawberry plants with pallidosis-related decline in Santa Maria.  
Photo by Surendra Dara

Pallidosis-related decline or pallidosis disease of strawberries is a viral disease that appeared in several fields in the Santa Maria area early this year.  It is caused by a variety or viruses transmitted by insect vectors such as greenhouse whitefly, strawberry aphid, and thrips and other sources such as pollen, seed (not in the fruit production fields), and nematodes.  In addition to the routinely present strawberry aphids and thrips, increasing populations of greenhouse whitefly in strawberry fields contribute to the spread of the disease.  Severity of the symptoms varies depending on the strawberry cultivar, level of viral infection, and type of virus involved.

Good agricultural practices to obtain clean transplants, maintain and promote plant health, monitor and manage insect vectors are important to address the disease issue.  Since virus does not remain for too long in whiteflies, maintaining a host-free period of at least one month can reduce the risk of disease transmission by whiteflies which are occurring in large numbers in the recent years.  Timely disposal of crop residue, avoiding second-year crop, and effective and timely management of whiteflies to prevent their spread to new plantings are among recommended practices to address pallidosis disease.

Here is a short video to provide a quick overview of the disease.

Additional information on this disease can be found at:

Viral disease pallidosis-related decline confirmed in strawberries (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10773)

Possible pallidosis-related decline of strawberries in Santa Maria (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10523)

Increased whitefly risk to strawberries as a pest and a vector of the viral disease, pallidosis-related decline (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=10824)

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Compared to the number of queries I received last year, it has been fairly quiet about the Bagrada bug infestations.   Here is a brief update on the assays I conducted with some non-chemical control options and a short video I made to describe the biology, damage, and control of this pest.

Bioassays

Laboratory assays were conducted using various non-chemical pesticides that included entomopathogenic fungi, bacterial metabolites, pyrethrins, insecticidal soap, and essential oils.  Some of these may not have OMRI certification and these are only preliminary experimental results.  Products were used at field application rates.  Broccoli florets were treated with respective treatment materials and adult Bagrada bugs were released.  Assays were repeated three times.  Due to the lack of a laboratory colony of Bagrada bugs, additional assays could not be conducted to evaluate more control options.

Bagrada bug video

A short video was made to provide a quick overview about the Bagrada bug, its host range, life cycle, identification, damage symptoms, and control options.  While my previous articles and other resources provide several details, this video is intended to summarize basic information in less than 3 minutes.  Several people confuse harlequin bugs with Bagrada bugs and this video helps them compare these two species and see the difference.

A picture is worth a thousand words, but these days a short video is worth several pictures.

Previous articles on the Bagrada bug could be found at:

http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=4047

http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=8282

http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=8438

http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=9531

http://ucanr.org/blogs/blogcore/postdetail.cfm?postnum=9611