Grower Notes and Pest News
Early symptoms of downy mildew - stunted growth and yellowing compared to healthy leaf (right).
(Photo by Margery Daughtrey, Cornell University)
One of California's most adored flowering plants, impatiens, is being threatened by a serious pest. You may have noticed the common garden impatiens missing from nurseries, retail store shelves, and landscapes, parks, and gardens this year.
Impatiens are dying from a relatively new plant disease called impatiens downy mildew, caused by the fungus-like, oomycete pathogen Plasmopara obducens. The pathogen primarily affects varieties of Impatiens walleriana, or hybrids with an I. walleriana parent and wild impatiens (I. balsamina). Note that this pathogen does not affect New Guinea impatiens (Impatiens hawkeri) or other bedding plant genera. This disease develops rapidly, with a few leaves on apparently healthy impatiens beginning to show slight yellowing and stunting followed by development of white, powdery spores on the undersides of leaves, and later, by leaf and flower drop. Plants are likely to become completely defoliated within several weeks. The pathogen produces airborne spores, which can travel for many miles, as well as swimming zoospores and oospores, which can survive within soil and plant debris for long periods and infect healthy plants when replanted in the same area.
White, powdery fungal growth on the lower side of leaves (Photo by Margery Daughtrey, Cornell University)
Early detection is especially critical for this disease since chemical control has been shown to be ineffective once sporulation begins. Scout routinely to identify and remove diseased plants before epidemics can result. Removing infected plants may limit spread to other areas of the landscape.
Consider growing alternative bedding plants that will grow well in shady areas of the landscape but that will not be affected by the disease. Some examples include Bergenia hybrids, Caladiums, Coral bells, Lobelia, New Guinea impatiens, Sweet alyssum, and wax begonias.
This article was originally published in the December 2013 issue of the UC IPM Green Bulletin. Read the entire article at http://www.ipm.ucdavis.edu/greenbulletin/
Bagrada bug adults on grass (Photos by Bryan Jones, San Francisco)
Invasive Bagrada bug continues to spread to various counties in California. Compared to previous years, reports of Bagrada bug infestations came in quite late in 2013. They also seemed to survive cold winters. How they survive cold temperatures when there are no cultivated or weed hosts is not clear, but they can hide under vegetation, in the crop debris, or the top layer of soil.
Bryan Jones of San Francisco just reported seeing a Bagrada bug on his backyard grass. This is probably the first report of its spread to San Francisco. It was also reported from Fresno, Monterey, San Benito, and San Bernardino Counties, suspected to be present in Santa Cruz County in 2013, and appears to be in Kern County for a couple of years or more. Out side California, it is present in La Paz, Maricopa, Pinal, and Yuma Counties in Arizona, Luna, Santa Fe, Socorro, and Valencia Counties in New Mexico, and some parts of Utah and Texas. Unlike other invasive pests such as the brown marmorated stink bug or the Asian citrus psyllid which moved to the west coast from eastern parts of the US, Bagrada bug is moving to the east.
Bagrada bugs on Brussels sprouts (above) and radish in Bakersfield (Photo by Surendra Dara)
Regular monitoring, timely treatments during the early stages of plant development, crop rotation with non-host plants are some of the available management options. Using sweet alyssum or other hosts as trap crops does not seem to be an effective strategy accordingly to some research.
Bagrada bug Pest Alert can be downloaded from: http://www.ipm.ucdavis.edu/PDF/pestalert/bagradabug.pdf
Do you know how to check your hotel room for bed bugs before you settle in for the night? Can you tell the difference between yellowjackets, paper wasps, and other common wasps? What’s in that bottle of pesticide you are thinking of using on your plants? New videos from UC IPM can help answer these questions!
Adult western yellowjacket
Thanks in part to funding from the Western IPM Center, the UC Statewide Integrated Pest Management Program has recently created a series of short, 2-3 minutes videos to help you identify, monitor, manage or prevent some pests from becoming problems around your home and garden!
Find out how to use a bed bug detector and inspect your bedroom or hotel room for bed bugs. Protect yourself from mosquito bites and West Nile virus by eliminating mosquito-breeding sites around your yard. Watch how you can hose aphids off plants instead of spraying pesticides. Discover the difference between yellowjackets and other wasps and find out how to find, trap, and treat yellowjackets around your yard or property.
You can also learn about common garden spiders and how to catch them or clean up webs. Are snails and slugs eating your plants? Learn how to recognize whether plant damage was caused by snails or insects with similar feeding habits, and how to trap snails or apply baits. If ants have invaded your home, find out why they are there, how to get rid of them, and how to prevent future infestations.
Watch all our videos by visiting UC IPM’s YouTube channel or by going to the video library page on the UC IPM web site, where you can find these as well as other videos covering pests and related topics.
UC IPM’s new Pest Alert helps you identify Bagrada bug, an invasive stink bug spreading through western Arizona and southern California causing severe crop, nursery, and landscape losses. In agriculture, Bagrada bug is a pest of cole crops and other mustard family plants. In home gardens it feeds on these same vegetables and on ornamental plants such as sweet alyssum and candytuft.
Bagrada bugs use their needlelike mouthparts to pierce and feed on plants and their seeds. Damage includes leaf spotting, wilting, stunting, multiple branches or crowns, and death of the whole plant.
The Pest Alert was produced by UCCE advisors Eric Natwick and Surendra Dara, John Palumbo from the University of Arizona, and the UC IPM team.
Preliminary agricultural management information is also available.
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
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 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.
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.