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Grower Notes and Pest News

Asian Citrus Psyllid threat to Santa Barbara County

In light of spotting a couple of Asian citrus psyllids (ACP) in Ventura County about a month ago, it is important to be aware of this exotic and invasive pest and its damage potential.

Asian citrus psyllid, Diaphorina citri Kuwayama in its characteristic posture
(Photo by Michael Rogers, UC)

ACP, Diaphorina citri Kuwayama (Homoptera: Psyllidae) looks like a miniature cicada.  Psyllids are similar to aphids except that they have longer antennae and strong jumping legs hence the name jumping plantlice.

Origin and distribution:
Although native to Asia, ACP has worldwide distribution in tropical and subtropical regions.  After its first discovery in Florida in 1998, it has now spread to Texas and California as well as neighboring Bahamas, Cuba, Jamaica, Mexico, Puerto Rico and other areas.  With its recent detection in La Conchita and Santa Paula areas, the entire Ventura County along with southern Santa Barbara and western Riverside Counties are now considered as quarantined areas.

Damage: ACP is a phloem feeding insect that consumes copious amounts of phloem sap and secrets large quantities of honey dew resulting in sooty mold growth.  Nymphs feed exclusively on young leaves and shoots.  Feeding damage includes cessation of terminal growth and malformation of developing parts.  Mature plants can withstand feeding damage to some extent, but it is severe in nursery stock and developing young trees.  Additionally, ACP transmits an endocellular, phloem-limited bacterium, Liberobacter asiaticum that causes citrus greening or huanglongbing (HLB) or yellow dragon disease.  It is also called citrus Likubin or dieback or leaf mottle in different Asian countries.  Native to China, citrus greening was first detected in Florida in 2005 and is a more serious threat than the feeding damage. This disease is transmitted when ACP feeds on a healthy plant after feeding on a diseased plant.  Disease stays latent for sometime before symptoms appear in an infected plant.  Typical symptoms include mottling and yellowing of leaves.  As the disease progresses, small and narrow leaves, short stems, stunted growth, poor flowering and dieback can also be seen.  Infected fruit is small, hard, lopsided with dark seeds and bitter juice.


Burnt tip of feather flush due to ACP feeding damage (Photo by Michael Rogers, UC)


Yellowing of leaves due to citrus greening disease (Photo by Susan Halbert, FDACS/DPI)


Lopsided fruit with dark seeds due to citrus greening disease (Photo by Michael Rogesrs)


Host range:
Citrus and closely related species like orange jasmine are susceptible both to ACP and citrus greening.  CitropsisCitrus and Murraya are preferred genera in the Rutaceae family.

Biology:
Adults are 3-4 mm long insects with mottled brown wings and have a characteristic angular posture.  Eggs are almond-shaped, bright yellow to orange and are deposited on developing shoots or feather flush.  Adults lay up to several hundred eggs that hatch in about 4 to 10 days.  Nymphs are 0.25 to 1.7 mm long and are yellowish orange.  There are five nymphal instars which take about 13 to 39 days to mature into adults.  Nymphs produce waxy tubules from their posterior end that help divert the honeydew away from their body.  Eggs develop into adults in 14 to 49 days depending on temperature.  Average longevity of adult female varies between 29 and 88 days at different temperatures.  Optimum temperature for development is 25-28oC (77-82oF) and life cycle can be completed in 29 days at 28oC (82oF).


Nymphs with developing wing pads and white wax tubules (Photo by Michael Rogers, UC)

Management: Due to its extensive distribution in Florida it is not expected to be eradicated in that state, but eradication is possible in its new home, California.  Chemical control is possible with neonicotinoids like imidacloprid and dinotefuran, pyrethroids like bifenthrin, deltamethrin and fenpropathrin, the organophosphate, chlorpyrifos, the carbamate, carbaryl, and the ketoenol, spirotetramat.  Biological control is possible with several generalist predators like spiders, lacewings, syrphids, minute pirate bugs, coccinellids (lady beetles) and several parasitoids.  Harmonia axyridis andOlla v-nigrum are abundant and effective coccinellid predators and imported hymenopteran, Tamarixia radiate is a well established parasitoid in Florida. Microbial control is possible with entomopathogenic fungi likeBeuveria bassianaMetarhizium anisopliaeHirsutella thompsonii and Isariaspp. which were found pathogenic to ACP.  Several formulations of these fungi are commercially available.

Additional information: More information about ACP, HLB, tracking, control and quarantine areas can be found athttp://www.aphis.usda.gov/plant_health/plant_pest_info/citrus_greening/
index.shtml
and http://www.cdfa.ca.gov/phpps/acp/.

What to do:Southern Santa Barbara Co is currently under quarantine.  If you have citrus or related host plants, periodically examine the newly developing leaves for ACP feeding damage, waxy substance, honey dew and sooty mold. You can also look for leaf mottling, a symptom of citrus greening.  If you find ACP in a new area, please secure the specimen, note the location, and send or bring in the specimen.  You can reach me at 805-788-2321 or skdara@ucdavis.edu.

http://ucanr.edu/articlefeedback

References:

Grafton-Cardwell, E. E., K. E. Godfrey, M. E. Rogers. C.C. Childers and P. A. Stansly.  2006.  Asian citrus psyllid.  UC ANR publication, 8205.

Halbert, S. E. and C. A. Nunez.  2004.  Distribution of the Asian citrus psyllid, Diaphorina citri Kuwayama (Rhynchota: Psyllidae) in the Caribbean basin.  Florida Entomol. 87: 401-402.

Liu, Y. H. and J. H. Tsai.  2000.  Effects of temperature on biology and life table parameters of the Asian citrus psyllid, Diaphorina citri Kuwayama (Homoptera: Psyllidae).  Annals of Appl. Biol. 137: 201-216.

Michaud, J. P. 2004.  Natural mortality of Asian citrus psyllid (Homoptera: Psyllidae) in central Florida.  Biological Control 29: 260-269.

Padulla, L.F.L. and S. B. Alves.  2009.  Suscetibilidade de ninfas de Diaphorina citri a fungos entomoatogênicos.  Arquivos do Instituto Biológico (São Paulo) 76: 297-302.

Posted on Wednesday, February 2, 2011 at 11:43 AM

Asian Citrus Psyllid threat to Santa Barbara County

I have moved the Asian citrus psyllid article to http://ucanr.org/blogs/pestnews/.  I have created this blog to address issues that are not related to strawberries and vegetables.

Posted on Tuesday, January 25, 2011 at 9:56 AM

Bagrada bug: An exotic pest in southern California

An exotic bug is found invading parts of southern California and Arizona.  It is referred to as painted bug in some literature and is similar to the harlequin bug, Murgantia histrionic in appearance.  But it is called Bagrada bug, Bagrada hilaris (Burmeister) and belongs to the stink bug family Pentatomidae of the order Hemiptera.

Origin and distribution: It is native to Africa and is reported to infest and/or cause crop damage in parts of Asia and Europe.  It is an exotic pest in the US.  It was first reported in Los Angeles in June, 2008 and started causing damage to broccoli, cabbage, cauliflower, kale, radish, rutabaga, collards and other crops by the next year.  It is now seen in Orange, Imeperial and Riverside Counties of California and all over Yuma Co in Arizona.

Host range: Feeds mainly on crucifers like cole crops, but can infest a variety of other hosts including solanaceous plants like potato, malvaceous plants like okra and cotton, leguminoseous plants like legumes, cucurbits like cantaloupes and watermelons, and graminaceous plants like wheat, corn and millets.

Biology: Adults are 5-7 mm long and 3-4 mm wide.  They are black with orange and white markings. Females are larger than males and lay an average of 95 barrel shaped whitish eggs in clusters on foliage or in the soil.  Eggs turn orange as they mature in 3-6 days.  Nymphs resemble ladybugs due to their dark head and thorax and reddish or orange abdomen with white or black markings.  They go through five instars before adults emerge in 5-8 weeks depending on the temperature.  They have multiple generations in a year.

Damage: Bagrada bugs have piercing and sucking mouthparts and feed on the plant juices.  Depending on the crop and plant part they infest, damage can vary from stippling with necrotic spots, stunted growth, loss of apical dominance and formation of multiple heads to death.


Stippling of young cauliflower leaves (Courtesy: Eric Natwick, UCCE)

Multiple heads in broccoli (Courtesy: John Palumbo, Univ. of Arizona)

Management: Reports indicate that Bagrada bug can be controlled with pyrethroids, organophosphates like chlorpyrifos and malathion and neonicotinoids like imidacloprid in conventional fields using different treatment methods.  Neem products have also showed some effectiveness in a study conducted abroad.  Biological and microbial control options are being evaluated by some researchers.

What to do: It has not been reported in vegetable growing California Central Coast or areas other than those mentioned above.  Since they are already found on several cole crops in the neighboring counties, those in Ventura, Santa Barbara, San Luis Obispo Counties or surrounding areas should keep an eye out for this bug.  It is important to be aware of this new pest and report its occurrence.  If you find it in a new area, please call (805-788-2321) or email (skdara@ucdavis.edu) me.

http://ucanr.edu/articlefeedback

References

Ahuja, B., R. K. Kalyan., U. R. Ahuja, S. K. Singh, M. M. Sundria and A. Dhandapani.  2008.  Integrated management strategy for painted bug, Bagrada hilaris (Burm.) inflicting injury at seedling stage of  mustard (Brassica juncea) in arid western Rajasthan.  Pesticide Res. J. 20: 48-51.

Halbert, S. E. and J. E. Eger. 2010.  Bagrada bug (Bagrada hilaris) (Hemiptera: Pentatomidae) an exotic pest of cruciferae established in the Western USA.  Florida Dept of Agriculture and Consumer Services, DACS-P-01750.

Posted on Thursday, January 13, 2011 at 9:44 AM

Maggots and fungus gnat larvae in strawberry fields

I have gathered some more information after my first blog and here is an update on the maggot issue we are seeing in Santa Maria and parts of Oxnard.

Santa Barbara Co entomologist, Brian Cabrera and UC Davis entomologist, Frank Zalom both recovered larvae of the dark-winged fungus gnat (Family: Sciaridae) from the strawberry plants they received.  These larvae primarily feed on fungus and decaying plant material, but they can also feed on plant roots.  They are also known to mechanically vectoring plant pathogenic fungi.


Dark-winged fungus gnat larva from strawberry plants (Courtesy: Brian Cabrera)

A PCA had reported finding seedcorn maggot-like larvae in the strawberry fields near Oxnard.  A few growers had also mentioned similar findings in Santa Maria.  I too found similar maggots in fields I checked later on.  So, we have two species infesting the strawberry plants at this time.

Seedcorn maggot flies are attracted to decaying plant material, but their maggots feed on living plant material.  Dark-winged fungus gnats do not appear to be new in the strawberry fields.  Brian Cabrera found them early this year in dead strawberry plant specimens.  The probable reason for seeing more of them now is that there is more dead plant material from the other maggot damage.  Is it possible that we have a primary invader, seedcorn maggot-like one and a secondary invader, the dark-winged fungus gnat larva?  This is just a thought.  High soil moisture from recent rains can also worsen their problem.  Damage from both maggots can also increase vulnerability of plants to pathogens.

Organophosphates will control these maggots, but Frank Zalom mentioned that growth regulators like azadirachtin can also be effective.  Neonicotinoids like imidacloprid are not known to have any effectiveness.

We need to continue close monitoring of this problem and share the information.

http://ucanr.edu/articlefeedback

Posted on Wednesday, December 22, 2010 at 1:12 PM

Maggots in Young Strawberry Fields


Whitish maggots with a tapering body (above) and about 1/4 inch long (below)



Several growers in the Santa Maria area reported maggot infestation in their young strawberry fields.  I have visited some fields and collected some specimens.  These maggots are whitish with a tapering body and approximately ¼ inch long.  They are legless and seemed to have a thick and opaque skin.  These look like seedcorn maggots [Delia platura (Family: Anthomyiidae)], but accurate identification is pending.  UC researchers, CDFA and Ag Commissioner’s office has the specimens and we are working on identifying the pest.



Maggots were found feeding in the root area at the base of the crown.  Seedcorn maggot adults are usually attracted to decaying crop residue and moist soil.  It is a good idea to set up yellow sticky traps in the fields for catching adults to help with the identification.  It appeared that some growers have treated the fields with imidacloprid, diazinon and chlorpyrifos.

Someone at the field mentioned that these are thought to be fungus gnats.  But these are not.  Fungus gnat larvae have a whitish to translucent and elongated body.  They have wormlike appearance and have a conspicuous shiny black head capsule.

Posted on Wednesday, December 15, 2010 at 5:52 PM

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