Subtropical Fruit Crops Research & Education
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Subtropical Fruit Crops Research & Education

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Seguridad de Pesticidas/Pesticide Training

Posted on Tuesday, August 15, 2017 at 3:48 PM

What Hath the Rain Wrought in the Avocado Foothills

 Title: Area Livestock and Natural Resources Advisor
Specialty: Rangeland Ecology and Management, Rangeland Conservation, Grazing Management, Conservation of Biological Diversity, Watershed Protection and Management.
County: San Benito County
Address:
Cooperative Extension San Benito County
3228 Southside Road
Hollister, CA 95023
Phone: 831-637-5346 x14
Email: drorao@ucanr.edu

Do you have yellow starthistle, Italian thistle, Himalaya blackberry, white top, or other common Central Coast rangeland weeds on your ranch? If so, you may be wondering which herbicides are most effective, how much they cost, what is required to purchase and spray a particular herbicide, when to spray, whether the herbicide affects grasses or clovers, and if the herbicide is safe for your livestock and pets. Many Central Coast rangeland landowners have been asking these same questions. So, I compiled this information in two tables. Table 1 shows some of our common rangeland weeds and different herbicide treatment options. Table 2 lists six of the most commonly used rangeland herbicides, and answers questions about cost, when to spray, purchasing requirements, affected plants, and grazing/pet restrictions. All of this information is already available from a variety of sources, but I have put it together in two easy to use reference tables. The tables are self-explanatory for the most part, but the information below may clarify a few things.

Integrated Pest Management (IPM)

IPM is a weed management approach that uses multiple control methods. Control methods could include mechanical control, manual control, grazing, seeding, herbicide, etc. The most effective options will depend on the particular species you are trying to control. This blog post focuses on herbicide because I am often asked about chemical treatment options. However, your weed control efforts will likely be most successful if you use a variety of methods.

Operator ID's, Restricted Materials Permits, & Private Applicator Certificates

Most of the herbicides in Table 2 are general use pesticides, meaning that you only need an operator ID to purchase and use them (Carbonaro, pers. comm.). Operator ID's are free and can be obtained from your County Agricultural Commissioner's office. No test is required. But, you'll need to show a property map in order to get your operator ID.

One herbicide in Table 2, 2, 4-D, is a California state restricted pesticide when applied on rangelands. Before you can purchase or spray California state restricted pesticides, two things are required: a Private or Commercial Applicator Certificate and a restricted materials permit. You can get a Private Applicator Certificate from your County Ag Commissioner's office. This requires taking a free test. The test is based on Pesticide Safety: A Reference Manual for Private Applicators, 2nd Ed., published by the University of California. This book can be purchased from most County Ag Commissioner or UC Cooperative Extension offices or online at: http://anrcatalog.ucanr.edu/Details.aspx?itemNo=3383. Once you have your Private Applicator Certificate you'll be able to obtain a restricted materials permit, again from your County Ag Commissioner's office. Alternatively, you can hire a licensed pest control business to purchase and spray California state restricted pesticides.

Read Labels, Follow Federal, State & Local Regulations, and Report Pesticide Use to Your County Ag Department

Although Table 2 includes information from the herbicide labels, it is not a substitute for reading the entire herbicide label before you spray (Carbonaro, pers. comm.). Always read the label before using any of these herbicides. In California, in addition to following the label, applicators will also need to follow federal, state, and local regulations. And, remember that you should submit a pesticide use report to your County Agricultural Commissioner's office for all pesticides used on rangelands.

For additional information about weeds and how to manage them, check out this website: http://wric.ucdavis.edu. The Invasive Thistles of Bay Area Counties & Herbicides for Controlling Thistles Handout compiled by Guy Kyser, UC Cooperative Extension Specialist in Weed Science at UC Davis is a great resource and is attached at the bottom of this blog post.

References

Carbonaro, D. 2017. Personal communication, 4/16/2017. Carbonaro is a Senior Biologist/Inspector with the San Benito County Agricultural Commissioner's Office.

DiTomaso, J.M. G.B. Kyser et al. 2013.  Weed Control in Natural Areas in the Western United States.  WRIC, UC.

Kyser, G. Unpublished. Invasive Thistles of Bay Area & Herbicides for Controlling Thistles.

 

Table 1. Common Central Coast Rangeland Weeds

PlantSpecies

Herbicides Options Approved for useon CaliforniaRangelands

Rangeland Herbicides Known to beEffective

 

Bullthistle

(Cirsium vulgare)

2, 4-D (Severalnames) Aminopyralid(Milestone) Clopyralid(Transline) Dicamba (Banvel,Clarity)

Triclopyr (Garlon 3A/Garlon 4Ultra)Chlorsulfuron(Telar)

Imazapyr (Arsenal,Polaris)

Milestone, Transline, Capstone (=Milestone + Garlon),Garlon, Roundup (Kyser,unpublished)

 

2,4-D is often used because it is inexpensive. However, itis not as effective as otherherbicides.

Bull thistle weed report:

 http://wric.ucdavis.edu/information/natural%20areas/wr_C/Cirsium_vulgare.pdf

Cocklebur (commonand spiny cocklebur) (Xanthium strumarium) (Xanthium spinosum)

2, 4-D (Severalnames) Aminopyralid(Milestone) Clopyralid(Transline) Dicamba (Banvel,Clarity) Fluroxypyr (VistaXRT)

Triclopyr (Garlon 4 Ultra, RemedyUltra)Glyphosate (Roundup, Accord XRT II,and others)

Imazapyr (Arsenal,Polaris) Sulfosulfuron(Outrider)

Aminopyralid(Milestone) Clopyralid(Transline)

Cocklebur weed report:

 http://wric.ucdavis.edu/information/natural%20areas/wr_X/Xanthium_spinosum-strumarium.pdf

Fiddleneck (Menziesandcoastfiddleneck) (Amsinckiamenziesii)(Amsinckia menziesiivar. intermedia)

Aminopyralid(Milestone)

Glyphosate (Roundup, Accord XRT II,and others)

Chlorsulfuron(Telar)Imazapyr (Arsenal,Polaris) Sulfosulfuron(Outrider)Hexazinone (VelparDF)

Aminopyralid(Milestone) Chlorsulfuron(Telar)

Fiddleneck weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_A/Amsinckia.pdf

 

Foxtail (Mediterraneanand harebarley)

(Hordeum marinumssp.gussonianum) (Hordeum murinumssp.leporinum)

Glyphosate (Roundup, Accord XRT II,and others)

Imazapyr (Arsenal,Polaris) Rimsulfuron(Matrix)

Sulfometuron + chlorsulfuron(LandmarkXP)

Sulfosulfuron(Outrider)Hexazinone (VelparL)

Glyphosate (Roundup, Accord XRT II, and others) iseffective, but is nonselective, so will kill most other plants as well.If glyphosate is to be used, reseed to reduce bare groundand encroachment of other weedspecies.

 

Rimsulfuron (Matrix) will likely control control foxtail,based on limiteddata.

Foxtail weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_H/Hordeum_marinum-murinum.pdf

Frenchbroom

(Genista monspessulana)

Triclopyr (Garlon 3A, Garlon 4Ultra,PathfinderII)

Aminopyralid + triclopyr(Capstone) Triclopyr + 2,4-D(Crossbow)

Glyphosate (Roundup, Accord XRT II,and others)

Imazapyr (Arsenal,Polaris)

Triclopyr (Garlon 3A, Garlon 4 Ultra, PathfinderII)

 

Glyphosate (Roundup, Accord XRT II, and others) iseffective, but resprouts will need to be controlled. Glyphosateis nonselective, so will kill most other plants as well. Ifglyphosate is to be used, reseed to reduce bare groundand encroachment of other weedspecies.

French broom weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_G/Genista.pdf

Goatgrass (jointed and barbgoatgrass) (Aegilops cylindrica) (Aegilops triuncialis)

Glyphosate (Roundup, Accord XRT II,and others)

Sulfometuron + chlorsulfuron(LandmarkXP)

Research is currently being conducted to identify most effective options for goatgrass.

Goatgrass weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_A/Aegilops_cylindrica-triuncialis.pdf

 

Himalayablackberry

(Rubus armeniacus)

Dicamba (Banvel,Clarity) Fluroxypyr (VistaXRT)

Triclopyr (Garlon 3A, Garlon 4Ultra,PathfinderII)

Aminopyralid + triclopyr (Capstone) Glyphosate (Roundup/Accord XRT II,and others)

Hexazinone (VelparL) Tebuthiuron(Spike)

Triclopyr (Garlon 3A, Garlon 4 Ultra, Pathfinder II) canbe effective on smallindividuals.

 

Glyphosate (Roundup/Accord XRT II, and others) canbe effective, but may requireretreatment.

Himalaya blackberry weed report:

http://wric.ucdavis.edu/information/natural%20areas/wr_R/Rubus.pdf

Italian thistle

(Carduus pycnocephalus)

2, 4-D (Severalnames) Aminopyralid(Milestone) Aminopyralid + 2,4-D (ForefrontHL) Aminopyralid + triclopyr(Capstone) Clopyralid(Transline)

Dicamba (Banvel,Clarity) Fluroxypyr (VistaXRT)

Triclopyr (Garlon 3A, Garlon 4Ultra)Triclopyr + 2,4-D(Crossbow)

Glyphosate (Roundup, Accord XRT II,and others)

Chlorsulfuron(Telar)Imazapyr (Arsenal,Polaris) Hexazinone (VelparL)

Aminopyralid (Milestone) is highly effective on thistles.

 

Milestone, Transline, Capstone (=Milestone + Garlon),Garlon, Roundup (Kyser,unpublished)

 

2,4-D is often used because it is inexpensive. However, itis not as effective as otherherbicides.

Italian thistle weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_C/Carduus_acanthoides-nutans-pycnocephalus-tenuiflorus.pdf

 

Medusahead (Taeniatherumcaput

-medusae)

Aminopyralid(Milestone)

Glyphosate (Roundup, Accord XRT II,and others)

Rimsulfuron(Matrix) LandmarkXP

Aminopyralid (Milestone) provided up to 90% controlof medusahead  based on research in the CentralValley.

Medusahead weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_T/Taeniatherum.pdf

Milkthistle

(Silybum marianum)

2, 4-D (Severalnames) Aminopyralid(Milestone) Clopyralid(Transline) Dicamba (Banvel,Clarity) Chlorsulfuron(Telar)Rimsulfuron(Matrix)

Milestone, Transline, Capstone (=Milestone + Garlon),Garlon, Roundup (Kyser,unpublished)

Milk thistle weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_S/Silybum.pdf

Purple starthistle

(Centaurea calcitrapa)

2, 4-D (Severalnames) Aminopyralid(Milestone) Clopyralid(Transline) Dicamba (Banvel,Clarity)

Glyphosate (Roundup, Accord XRT II,and others)

Hexazinone (VelparL)

Milestone, Transline, Capstone (=Milestone + Garlon),Garlon, Roundup (Kyser,unpublished)

Purple starthistleweed report:

http://wric.ucdavis.edu/information/natural%20areas/wr_C/Centaurea_calcitrapa-iberica.pdf

 

Tumbleweed(Russian thistle)

(Salsola tragus)

2, 4-D (SeveralNames) Aminocyclopyrachlor +Aminopyralid(Milestone) Dicamba (Banvel,Clarity)

Triclopyr (Garlon 3A, Garlon 4Ultra)Glyphosate (Roundup, Accord XRT II,and others)

Chlorsulfuron(Telar)Imazapyr (Arsenal,Polaris) Hexazinone (VelparL)

Research is currently being conducted to identify most effective options fortumbleweed.

Tumbleweed weedreport:

http://wric.ucdavis.edu/information/crop/natural%20areas/wr_S/Salsola_paulsenii-tragus.pdf

Whitetop/hell weed

(Cardaria draba)

2, 4-D (Severalnames) Dicamba + 2,4-D

Glyphosate (Roundup, Accord XRT II,and others

Chlorsulfuron(Telar)Imazapyr (Arsenal,Polaris)

Chlorsulfuron (Telar) is one of the best control optionsfor plants in the Cardariagenus.

 

2,4-D is often used because it is inexpensive. However, itis not as effective as otherherbicides.

Whitetop weedreport:

http://wric.ucdavis.edu/information/natural%20areas/wr_C/Cardaria_chalepensis-draba-pubescens.pdf

Yellowstarthistle

(Centaurea solstitialis)

2, 4-D (Severalnames) Aminopyralid(Milestone) Clopyralid(Transline) Dicamba (Banvel,Clarity)

Triclopyr (Garlon 3A, Garlon 4Ultra)Glyphosate (Roundup, Accord XRT II,and others)

Chlorsulfuron(Telar)Imazapyr (Arsenal,Polaris) Hexazinone (VelparL)

Aminopyralid (Milestone) is the best option to controlyellow starthistle.

 

Clopyralid (Transline) is also veryeffective.

 

Glyphosate (Roundup, Accord XRT II, and others) is thebest option in the lateseason.

Yellow starthistleweedreport:

 http://wric.ucdavis.edu/information/natural%20areas/wr_C/Centaurea_solstitialis.pdf

 

Table 2. Commonly Used Rangeland Herbicides, Including When and How to Use Them

Chemical Name/Product Name1

 

 

Price2*

Registered

for useonCalifornia rangelands3

Requirements to Purchase/Spray Herbicide3

 

Preemergent/ Postemergent1

 

 

Best time tospray4

 

 

TargetedPlants4

Triclopyr(Garlon 3A/Garlon 4Ultra,Remedy Ultra,PathfinderII)

$70/gallon

Yes

Operator ID#

Postemergent

Spray after all of theweed seed has germinated,but before the plants getbig.

Kills broadleaves, but not grasses

 

Killsclovers5

Aminopyralid(Milestone)

$300/gallon

Yes

Operator ID#

Preemergentand postemergent

January -March

Kills thistles andlegumes, and some otherbroadleaves, but notgrasses

 

Killsclovers5

Glyphosate (Roundup, Accord XRT II, and others)

$21/gallon

Yes

Operator ID#

Postemergent

Spray after all of theweed seed has germinated,but before the plants getbig.

Kills any greenvegetation. Tree leaves can be sprayed, but it will not be effectiveifsprayed on treetrunks.

 

 

Chemical Name/Product Name1

 

 

Price2*

Registered

for useonCalifornia rangelands3

Requirements to Purchase/Spray Herbicide3

 

Preemergent/ Postemergent1

 

 

Best time tospray4

 

 

TargetedPlants4

Chlorsulfuron (Telar)

$21/ounce

Yes

Operator ID#

Preemergent,

can also be usedas postemergent

Spray around the timeof the first rains, a littlebefore or a little afterthe first rains is fine.Spraybefore seedilngs getbig.

Check label for plants affected. This herbidiceisspecies specific. Although,itis generally safe on grasses1.

 

Killsclovers5

Clopyralid(Transline)

$170/gallon

Yes

Operator ID#

Postemergent

Spray after all of theweed seed has germinated,but before the plants getbig.

Kills thistles and legumes,but notgrasses

 

Killsclovers5

2, 4-D (DMA4IVM,

Weedar 64and manyothers)

2, 4-D Amine-

$13/gallon2, 4-D Ester-

$19/gallon

Yes

Restricted materialspermit and applicator certificate

Postemergent

Spray after all of theweed seed has germinated,but before the plants getbig.

Kills broadleaves, but not grasses

 

Killsclovers5

 

Triclopyr(Garlon 3A/Garlon 4Ultra,Remedy Ultra,PathfinderII)

"Grazing green forage: There are no grazing restrictions for livestock or dairy animals on treated areas...Haying (harvesting ofdried forage): Do not harvest hay for 14 days after application...Slaughter Restrictions: During the season of application, withdrawlivestock from grazing treated grass at least 3 days before slaughter...Livestock Use of Water from Treatment Area: There are no restrictionson livestock consumption of water from the treatmentarea."

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Garlon_3A_Label1i.pdf

Aminopyralid(Milestone)

"Grazing and Haying Restrictions: There are no restrictions on grazing or grass hay harvest following application of Milestone atlabeledrates. Cutting hay too soon after spraying weeds will reduce weed control. Wait 14 days after herbicide application to cut grass haytoallow herbicide to work. Do not transfer grazing animals from areas treated with Milestone to areas where sensitive broadleafcrops occur without first allowing 3 days of grazing on an untreated pasture. Otherwise, urine and manure may contain enoughaminopyralidto cause injury to sensitive broadleaf plants...For applications on rangeland and permanent grass pastures (not harvested for hay)andnon-cropland areas, do not enter or allow worker entry into treated areas until sprays have dried...Grazing Poisonous Plants:Herbicideapplication may increase palatability of certain poisonous plants. Do not graze treated areas until poisonous plants are dry andnolonger palatable to livestock...Hay from grass treated with Milestone within the preceding 18-months can only be used on the farmor ranch where the product is applied unless allowed by supplemental labeling." Check label for specific restrictions on moving hay,or using hay for silage,etc.

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Milestone_Label1h.pdf

Glyphosate (Roundup, Accord XRT II, and others)

"DOMESTIC ANIMALS: This product is considered to be relatively nontoxic to dogs and other domestic animals; however, ingestionof this product or large amounts of freshly sprayed vegetation may result in temporary gastrointestinal irritation (vomiting, diarrhea,colic, etc.). If such symptoms are observed, provide the animal with plenty of fluids to prevent dehydration. Call a veterinarianifsymptoms persistfor morethan24hours...Donotfeedor grazeturfgrass grownfor seedor sodproductionfor 8weeks followingapplication...If application rates total 4.5 pints per acre or less, no waiting period between treatment and feeding or livestockgrazing is required. If the rate is greater than 4.5 pints per acre, remove domestic livestock before application and wait 8 weeksafter application before grazing orharvesting."

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Roundup_Custom_Label2.pdf

 

 

Chlorsulfuron (Telar)

"There are no grazing or hay harvest restrictions for any livestock, including lactating animals, with application rates up to 11/3 ounces/acre of TELAR® XP. No exclosure is required for any animals. Do not apply more than 1 1/3 ounces/acre of TELAR® XP peracreper year. No exclosure is required for anyanimals."

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/DuPont_Telar_XP_Herbicide_Label5a.pdf

 

Clopyralid(Transline)

"Grazing/Haying: There are no restrictions on grazing or hay harvest following application of Transline at labeled rates exceptfor exported grass hay from California, Nevada, Washington and Oregon (see instructions in the Range and Permanent GrassPasturesection)...Do not transfer livestock from treated grazing areas, or from feeding of treated hay, to sensitive broadleaf cropareaswithout first allowing 3 days of grazing on an untreated pasture (or feeding of untreated hay). If livestock are transferred withinless than 3 days of grazing untreated pasture or eating untreated hay, urine and manure may contain enough clopyralid to cause injuryto sensitive broadleaf plants...For applications to fallow cropland, rangeland, pasture, and non-crop areas, do not enter treatedareasuntil sprays have dried. For early entry to treated areas, wear eye protection, chemical-resistant gloves made of anywaterproof material, long-sleeved shirt, long pants, shoes andsocks."

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/Transline1v_Label.pdf

2, 4-D (DMA4IVM,

Weedar 64and manyothers)

"For grazed areas, the maximum use rate is 4.21 pints of DMA 4 IVM (2 lb of acid equivalent) per acre perapplication...Preharvest Interval: Do not apply within 7 days of cutting forage for hay... If grass is to be cut for hay, Agricultural Use Requirements for the Worker Protection Standard areapplicable."

Herbicide Label:https://s3-us-west-1.amazonaws.com/www.agrian.com/pdfs/DMA_4_IVM_Label1d.pdf

 Tables 1 $ 2 from Devii Rao, drorao@ucanr.edu

Posted on Monday, August 14, 2017 at 6:13 AM
  • Author: Devii Rao
Tags: avocado (176), fire (9), foothills (1), weed control (6), wild lands (2), wildfire (1), wildlands (1)

Avocado Pest Resource from the Past

 

What a great find and it was there all along, just like a used book store can be a gold mine at times.

 http://www.avocadosource.com/papers/research_articles/ebelingwalter1959b.pdf

 

 

This is the section of Subtropical Fruit Pests by Walter Ebeling that covers avocado pests in not only California, but what was and is known to exist in other avocado growing regions around the US and the world.  It was reproduced at the Hoshi Foundation's Avocadosource website.  At this point it only contains the chapters pertaining to avocado. Other chapters in the full text cover citrus, grape, walnut, almond pecan, olive, fig, date and other "Minor Subtropical Fruits".  The beauty of the book is not only historical, but that it is still current (although the DDT recommendations are out of date) for many pests.  It also chronicles pests that have appeared in the past, disappeared and then reappeared.  An example is Avocado Bud Mite - here, gone, here and seemingly gone again, probably to reappear sometime in the future.  This is no replacement for the UC-IPM website, http://ipm.ucanr.edu/PMG/crops-agriculture.html , but it is a good look at how the pest has been managed in the past and is done so currently. 

I thought I had the only copy of this book in Ventura County, but you could too.  There are some listed on ABE Books for cheap.

This pestiferous book was compiled by Walter Ebeling at UC Riverside/Los Angeles.  He was of some note, considered the Father of Urban Entomology.  As you can see from the descriptions of avocado pests, he was a good all round entomologist, as well. Urban entomology really forces you to know a lot because of the diversity of arthropods in urban settings. He passed in 2010 and was recognized world-wide for his work.

 

 

IN MEMORIAM

 

WALTER EBELING

 

Professor Emeritus of Entomology

 

UC Riverside

 

November 26, 1907 – December 17, 2010

 

Walter Ebeling, world-renowned entomologist and pioneer in the field of Urban Entomology, died 17 December 2010 in a care facility in Bandon, Oregon at the age of 103. "Professor Ebeling was a legendary research entomologist," said Dr. Michael Rust, Professor of Entomology at the University of California, Riverside, who replaced Dr. Ebeling upon his retirement in 1975. "He had tremendous abilities, tireless energy, and a passion for science. He was an expert in so many fields of entomology including agriculture, physiology, and insect behavior. Dr. Ebeling helped develop Urban Entomology into a respected independent area of research."

Read more of his Memoriam: http://senate.ucr.edu/agenda/120221/IN%20MEMORIAM-Walter%20Ebeling.pdf

 

 

 

 

Posted on Thursday, August 10, 2017 at 2:45 PM
Tags: avocado (176), citrus (194), date (2), Ebeling (1), fig (3), Hofshi (1), UC Publications (1)

Hass or Haas Avocado?

There was just a group of Florida researchers here in California sharing their experiences with ambrosia beetles and a fungal disease in avocado and other members of the laurel family. This is a pest/disease complex similar to that found here caused by a shot hole borer and fusarium.  Avocados grown in Florida are of the West Indian or West Indian cross with Mexican or Guatemalan varieties.  They are usually big, green fruit that tend to be of a lower oil content.  Some marketers promote them as “low cal” or “slimcados” as a result.  Whatever. 

One of the things that struck home during these wonderful talks was the pronunciation of the word Hass. It was “hozzz”.  The “a” was pronounced like the a in hot, not in hat.  It made me think that this is probably how our familiar fruit is probably pronounced in much of the US.  I also hear Californians (and CA growers, too) pronounce this iconic fruit “hozzz”.  The generally accepted pronunciation of this name is “HaaaaSSSSS”. Like in the verb “has” - “He has an avocado”.

The fruit variety was found by a California grower named Rudolph Hass in the 1920's. The name Hass is of German origin. How it has come to be pronounced differently from his name is not clear to me. According to Google Translate, even in German it is pronounced as “has”, though with a somewhat clipped “s” on the end.

And not only has the pronunciation of the name been changed, sometimes the spelling in many produce departments is “Haas”. I once saw it on packaging spelled this way and when I asked the produce manager how that had happened, he told me that they had asked the packer explicitly to spell it that way because that's the way the consumers wanted to see it spelled.

So, the consumer drives the market. Maybe how people say it isn't important, as long as they know what they are buying and enjoy the fruit. At least most Californians seem to know how to say the word Hass.

Can you say Hass?

 

Photo: On the left: Florida (Slimcado) avocado. On the right: Haas avocado or Lamb-Haas. From: The Gardening Cook, http://thegardeningcook.com/slimcado-information/

Posted on Tuesday, August 8, 2017 at 5:34 PM
Tags: avocado (176), Florida (2), guatemalan (1), lauraceae (1), laurel (1), mexican (1), Persea (4), subtropical fruit (4), varieites (1), west indian (2)

University of Florida Researchers Visit California for Laurel Wilt Summit Avocado Seminar Series

During the first week of August, the California Avocado Society, Inc., California Avocado Commission, University of California Cooperative Extension hosted six Laurel wilt researchers from the University of Florida.  The speakers were Randy Ploetz, Jonathan Crane, Bruce Schaffer, Daniel Carrillo, Jeff Wasielewski and Edward Evans. In addition to talking at all three seminar locations, San Luis Obispo, Ventura, and Fallbrook, the researchers were also able to tour the major avocado growing regions.

Laurel wilt is a deadly disease of redbay (Persea borbonia) and other tree species in the Laurel family (Lauraceae), which includes the avocado tree. The disease is caused by a fungus (Raffaelea lauricola) that is introduced into host trees by a nonnative insect, the redbay ambrosia beetle (Xyleborus glabratus). Native to Southeast Asia, the ambrosia beetle has similarities to our current ambrosia pest, Polyphagous shot hole borer and the Kuroshio Borer. That is why this visit from our fellow extension researchers from the University of Florida. However the fungus associated with Laurel Wilt is unlike the disease here in California. Laurel Wilt is a disease that that causes a reaction in the tree to restrict water flow in the tree and the tree collapses rapidly.  The tree dies so fast that it doesn't even have a chance for the leaves to fall of the dead branches.

The beetle has the ability to spread the specific pathogen to other ambrosia beetle vectors which happens when they feed on infected trees. Sanitation is the most effect way to manage this problem. Scouting for wilted branches and their rapid removal has been the key to early intervention and eradication. Dr. Ploetz suggests removing the tree immediately. By the time you see frass and streaks in the wood, the tree is already infected and has been for sometime. As soon as a growers see the wilt in the branches, its time to move quickly. This disease may be mistaken for Verticillium wilt or Phytophthora. It can spread throughout the grove by root grafting.

The generation time for the beetle inside avocado trees takes about 40-50 days depending upon temperatures. Their flight activity is highest in the late afternoon and early evening. Dr. Carrillo mentioned that ambrosia beetles are notoriously difficult to control because they are inside the tree most of their life cycle versus being outside the tree. Contact herbicides will not work, because the insects are primarily inside the tree. One of the first goals to avoid infection, is to keep your trees healthy. A sick tree is more attractive

to beetles. They like dense canopies, non-pruned trees with overlapping leaves and branches. Chipping infected trees is effective in reducing the spread of the disease.  Chips should be as small as possible and spread so that they dry out.  However, beware, the smell of the chipped wood can attract other wood boring insects. The researchers are currently working with different commercial formulations of insecticides that still need more testing. Carrillo strongly suggests that our industry start monitoring for this pest/disease complex.

 

Scouting for laurel wilt in commercial avocado groves

1. Surveying for the symptoms of laurel wilt is a key component of limiting the spread of laurel wilt. Growers and their workers should survey their groves immediately and then weekly or more often if an infestation is detected in an adjacent grove. Pathogen sniffing dogs are currently being used, however there are less than half-dozen trained dogs for this purpose. Symptoms to look for might include:

i. Leaf and young stem wilting.

ii. Leaf color changing from light green to dark green, bluish-green or greenish-brown. Some leaves showing leaf mottling (dark and light green areas) and yellowing.

iii. Dead leaves curled hanging on the tree.

iv. A few stems and limbs with 2 to 4 ft of dieback or whole sections or entire limbs with dieback.

 v. Inspection of the trunk and major limbs may show dried sap (white, crystalline powdery material) that indicates insect boring. In any case, on symptomatic limbs remove the bark down to the sapwood and look for dark streaking. Dark streaks in the sapwood may indicate fungal infection. Normally this sapwood should be white to yellowish with no dark staining or streaking. In addition, small, dark holes in the sapwood further indicate wood boring beetles are present.

2. If the tree shows only a few stems and limbs with 2 to 4 ft of dieback, wait for confirmation of laurel wilt before removing the tree. You can remove the dead part of the limb by cutting several feet below the dead area of the limb; burn or bury the infested limb.

 

Posted on Sunday, August 6, 2017 at 9:29 PM

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