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Grower Notes and Pest News

Be on the Lookout for Spotted Wing Drosophila

Adult male spotted wing drosophila.  Note the dark spot on the tip of its wings.  (Photo by Larry L. Strand)


It's cherry growing season and a good time to begin looking for spotted wing drosophila (SWD), Drosophila suzukii.  SWD is a small fruit fly that attacks soft-flesh fruit such as cherry, blueberry, raspberry, and blackberry.  It first appeared in 2010, and its damage to fruit and increased management costs led to significant economic losses to cherry growers throughout California and the Pacific Northwest. 

Unlike other fruit flies that infest rotted fruit, SWD attacks undamaged fruit.  As cherry fruit begins to develop and starts to change color from light green to straw, SWD lays its eggs just under the skin of fruit, creating a small scar or a “sting.”  One to three larvae may develop inside each cherry, feeding on the fruit and causing it to become brown and soft.  Many times SWD flies are not noticed until fruit is mature, and by that time management is not very effective.  


Small hole or 'sting' created by SWD on a ripe cherry.  (Photo by Larry L. Strand)

Prevention is the key, and one way to prevent damage is to monitor for the pest when it first becomes active.  SWD can be monitored with several types of traps partly filled with apple cider vinegar to lure the pest.  Monitor traps weekly through the end of harvest, and be sure to confirm the presence of SWD, as other Drosophila spp. may be present in trap catches.  SWD males have a single dark spot on the tip of its wing and females have a large ovipositor.  See the UC IPM Pest Management Guidelines for identification help and a dichotomous key

The Haviland trap, named after UCCE advisor David Haviland (Photo by D. Haviland)

Spotted wing drosophila is still a relatively new pest, and management information continues to change.  UCCE Entomology Advisor David Haviland and other researchers have been working to provide what help they can.  Haviland has designed a bucket trap called the “Haviland trap” and is working with others to field-test experimental lures for SWD.  He's also studying a possible biological control agent.  Research has led to new grower guidelines so that early season cherries can be produced and sold internationally.  Check out the 2014 Recommendations for Sweet Cherry (PDF).

For management in backyard cherries or other urban areas, see the SWD Pest Note.

For more information about UC IPM's recent work, see the 2013 Annual Report.

Posted on Friday, April 18, 2014 at 10:25 AM

Asian citrus psyllid found in San Luis Obispo County


Adult and nymphal stages of the Asian citrus psyllid, Diaphorina citri (Photo by Michael Rogers, UC)

An Asian citrus psyllid (ACP) was found on a trap in southern Arroyo Grande last week (identification was made by CDFA on 26 March, 2014). This is the first discovery of this invasive pest in San Luis Obispo County.   After its first detection in California in August, 2008, ACP was found in January, 2011 in Ventura County, 7 November, 2012 in Santa Maria, and March, 2014 in San Luis Obispo County.

CDFA will be working with Ag Commissioner in establishing a quarantine area and other actions to handle the situation.

ACP is an invasive pest that transmits a devastating bacterial disease, huanglongbing (HLB) or citrus greening or yellow dragon disease threatening the California citrus industry.  It is estimated that each year California spends more than $3 billion to handle exotic and invasive pest, disease, and weed problems.  Exotic and invasive organisms are native to other areas or countries which are inadvertently brought to California and cause a major concern. 

HLB infection was found in a tree in Hacienda Heights a couple of years ago, where more than 20 infected twigs brought from another country were grafted to a backyard citrus tree.  This was detected by CDFA and the tree was immediately destroyed.  It is important for general public to be aware of the risk and refrain from bringing in plant material without a quarantine permit.

Below is a short animated video made by Ellen Schofield and David Andow of the University of Minnesota that explains how invasive species become a problem in an introduced area.

Management options for growers and homeowners can be seen at http://ucanr.edu/sites/ACP/.

USDA ARS researchers in Fort Pierce, FL found out that exposing potted citrus plants for at least 48 hours to 104-107 oF reduced or eliminated HLB infection.  Additional details of this study can be read at http://www.ars.usda.gov/is/pr/2013/130805.htm.

My previous blog (http://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=4165) about this pest gives an overview of the pest biology and control.

Current distribution of ACP, HLB, and the parasitic wasps of ACP in California can be seen at http://ucanr.edu/sites/ACP/Distribution_of_ACP_in_California/.

Growers and homeowners with questions about ACP or HLB can contact local UCCE or Ag Commissioner offices.  Citrus growers in Santa Barbara or San Luis Obispo Counties can also contact Cressida Silvers, ACP/HLB Grower Liaison of Citrus Pest and Disease Prevention Program at cressidasb@gmail.com or 805-284-3310 for additional information.

Posted on Thursday, April 3, 2014 at 12:01 PM

Weeping fig thrips, Gynaikothrips uzeli found in California


Adult weeping fig thrips, larva, and eggs.  (Photo by Gevork Arakelian, Senior Biologist, Los Angeles County)

Another exotic pest has recently found its way to California.  Los Angeles County entomologist, Gevork Arakelian, identified the thrips in infested weeping fig samples sent by CE Advisor in Los Angeles, Donald Hodel in January, 2014, as weeping fig thrips.  These infestations were discovered by Linda Ohara of El Camino College in Torrence, California.  In the second week of April, 2014 Santa Barbara County entomologist, Brian Cabrera received Ficus microcarpa L. leaf samples infested with thrips from Hope Ranch, which CDFA later identified as weeping fig thrips and Cuban laurel thrips.

Weeping fig thrips, Gynaikothrips uzeli Zimmerman belongs to the largest family of Phlaeothripidae in the order Thysanoptera.  It is a dark colored thrips with a stout body.  It is very similar to Cuban laurel thrips, G. ficorum (Marchal) except for a minor morphological characteristic - the length of the pronotal posteroangular pair of setae.  The length of the posteroangular setae is short for Cuban laurle thrips, while it is long for weeping fig thrips.  Weeping fig thrips primarily infests weeping fig, F. benjamina L. (Moraceae) and Cuban laurel thrips primarily infests F. microcarpa, which is known as Indian laurel, Chinese banyan, or curtain fig. 

Origin and distribution:  Weeping fig thrips is native to southeastern Asia and has been found in other countries such as Belize and Trinidad and Tobago.  In the United States, it was first reported in 2003 in Florida on weeping fig which is a popular ornamental plant.  In the next three years, weeping fig thrips was reported in Hawaii, Louisiana, Mississippi, Tennessee, and Texas.

Damage: Weeping fig thrips can feed on other hosts, but requires F. benjamina for successful completion of its life cycle.  Weeping fig thrips galls appear as leaf folds in contrast to the galls made by Cuban laurel thrips, which are leaf rolls.  Feeding damage appears as reddish spots on galls and severe damage leads to defoliation or stunted growth.


Leaf gall by weeping fig thrips.  Reddish spots result from feeding damage.  

(Photo by Steven Arthurs, University of Florida)

Biology: Adults are 2.5-3.0 mm long with brownish-black body and whitish fringed wings.  Females are larger compared to males.  As gall formation is necessary for the development of immatures, adult feeding causes the young leaves to fold along the midvein due to hypertrophy of parenchyma forming a permanent gall.  Adults deposit whitish eggs inside the gall.  Larvae are translucent with dark terminal abdominal segments when they newly emerge.  They turn yellowish-tan as they mature within 15 days.  Larvae have red eyes and feed in groups inside the gall.  Galls can be inhabited by inquilines such as other members of Phlaeothripidae, mealybugs, scales, whiteflies, or various species of natural enemies.

Inside the gall is a colony of weeping fig thrips.  Whitish eggs, translucent newly emerged larae, yellowish older larvae, and dark-bodied adults can be see in a galled leaf.  (Photo by Steven Arthurs, University of Florida)

Mature weeping fig thrips larva.  (Photo by Gevork Arakelian,Senior Biologist, Los Angeles County)

Control: Multiple species of natural enemies are associated with weeping fig thrips.  They include ants, eulophid wasps (Thripastichus gentilei, T. gentilei), lacewing larvae (Chrysoperla sp.), minute pirate bug (Montandoniola moraguesi), predatory mites, and various species of spiders.  Studies indicate that chemical control with insecticides such as acetamiprid, bifenthrin, clothianidin, cyfluthrin, dinotefuran, imidacloprid, and thiamethoxam can be effective.  Kaolin clay was also found to be effective in reducing galls.

Predatory anthocorid bug (Montandoniola confusa) attacking an adult weeping fig thrips.  (Photo by Steven Arthurs, University of Florida)

References

Arakelian, G.  2014.  Weeping ficus thrips (Gynaikothrips uzeli).  Pest sheet.  County of Los Angeles Department of Agricultural Commissioner/Weights and Measures.

Arthurs, S., J. Chen, M. Dogramaci, A. D. Ali, and C. Mannion.  2011.  Evaluation of Montandoniola confusa Streito and Matocq sp. nov. and Orius insidiosus Say (Heteroptera: Anthocoridae), for control of Gynaikothrips uzeli Zimmerman (Thysanoptera: Phlaeothripidae) on Ficus benjamina.  Biol. Control 57: 202-207.

Borbon, C. M. and J. P. Agostini.  2011. Gynaikothrips uzeli (Zimmermann) and Androthrips ramachandrai Karny (Thysanoptera, Phlaeothripidae), first records for Argentina.  Rev. FCA UNCUYO 43: 253:260.

Cambero-Campos, J., R. Valenzuela-Garcia, C. Carvajal-Cazola, C. Rios-Velasco, and O. Garcia-Martinez.  2010.  New records for Mexico: Gynaikothrips uzeli, Androthrips ramachandrai (Thysanoptera: Phlaeothripidae) and Montandoniola confuse (Hemiptera: Anthocoridae).  Florida Entomol. 93: 470-472.

Held, D. W. and D. Boyd.  2008.  Evaluation of sticky traps and insecticides to prevent gall induction by Gynaikothrips uzeli Zimmerman (Thysanoptera: Phlaeothripidae) on Ficus benjamina.  Pest Management Sci. 64: 133-140.

Held, D. W., D. Boyd, T. Lockley, and G. B. Edwards.  2005.  Gynaikothrips uzeli (Thysanoptera: Phlaeothripidae) in the southeastern United States: distribution and review of biology.  Florida Entomol. 88: 538-540.

Held, D. W., Wheeler, C., Boyd, D. W., Jr. 2009. Kaolin particle film prevents galling by Gynaikothrips uzeli.  O nline. Plant Health Progress doi:10.1094/PHP-2009-0407-02-RS.

Mound, L. A., C.-L. Wang, and S. Okajima.  1995.  Observations in Taiwan on the identity of the Cuban laurel thrips (Thysanoptera, Phlaeothripidae).  J.  New York Entomol. Soc.  103: 185-190.

Posted on Monday, March 24, 2014 at 11:53 AM

Downy mildew of clobbers impatiens


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/

Posted on Friday, January 31, 2014 at 12:17 PM

Current distribution of Bagrada bug in California


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

Posted on Thursday, January 16, 2014 at 10:54 AM

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