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Topics In Subtropics

A quarterly newsletter prepared by Cooperative Extension tree crop Farm Advisors in California.

Issues Articles
Topics in Subtropics Spring 2024
  • Effectiveness of Asian citrus psyllid management in huanglongbing treatment zones in residential Southern California
  • Managed honeybees in a wet year
  • Threats to citrus orchards in California by synergistic effects of dry root rot and phytophthora root and crown rot
  • Microbial Safety in Avocado Farms
  • How Much Fruit is Up there?
  • Tiny Troublemakers: How Geminiviruses are affecting California's Crops
  • Citrus Leprosis Disease – Staying alert on potential threat to California’s citrus industry
Winter Issue - 2024
  •  Pocket Gopher Management
  •  Phytophthora Diseases of California Citrus
  •  Airblast Sprayers
  •  Temperature Inversion Data Helps Guide Frost Responses
  •  Bodil Cass – New Subtropical Fruit IPM Specialist
Topics in Subtropics Fall 2023


  • Pocket Gopher Management
  • Phytophthora Diseases of California Citrus
  • Airblast Sprayers
  • Temperature Inversion Data Helps Guide
    Frost Responses
  • Bodil Cass – New Subtropical Fruit IPM
Topics in Subtropics Summer 2023

Topics in this issue: 

  • Avocado Production in the World: Observations of production and consumption growth 

  • USDA-APHIS Approves New Fuller Rose Beetle Mitigation – a Voluntary Option to Reduce Pesticide Applications
  • DON’Ts – Suggestions for Citrus and Avocado Growers and Others

  •  California Efforts to Control Citrus HLB 

  • Dr. Hamutahl Cohen was appointed as an Entomology Advisor with UC Cooperative Extension in Ventura County

Topics in Subtropics - Spring 2023
Topics in Subtropics - Winter 2023

Topics in this issue:

  • Introducing Fetemeh Khodadi, Assistant Professor of Extension and Plant Pathologist
  • Agave Mites: A Tiny Menace
  • New pest in young avocado orchards
  • Planting Avocados
  • One, one hundred, one thousand
  • UCR Citrus Day, March 2, 2023
Topics in Subtropics - Winter 2022

In this issue:

  • Mandarin Rind Breakdown
  • Breaking the Avocado Alternate Bearing Cycle
  • A Great Friend and Farmer has passed
  • Calculating the Value of Lemon Tree Loss
Topics in Subtropics Spring 2021
  • Progress in Developing Mechanical Harvesting for California Black Ripe ‘Manzanillo’ Table Olives 
  • Developing a Nitrogen Fertilizer Plan for Olive Orchards 
  • Should I Pay for Avocado Pollination Services? 
  • Collaboration is Key to Saving Kern County Citrus

  • Are Finger Limes Just Another Fad?

Topics in Subtropics - Winter 2021

Topics in this issue:

Avocado Establishment Costs

Soil Analysis

Healthy Roots, Healthy Trees

Avocado Weed Control

Salt Leaching

Topics in Subtropics Fall 2020

In this issue:

  • In memoriam: George Goodall
  • Promoting best practices for safe, economical and environmentally sound pesticide application with minimum environmental risks
  • South American Palm Weevil: Update
  • Lemon Establishment and Production Costs and Profitability Analysis in Ventura County, 2020
  • Brief update on ACP/HLB in California with emphasis on the San Joaquin Valley
Volume 22, Spring 2020
    • An Automated Delivery System for Therapeutic Materials to Treat HLB Infected Citrus
    • On-Farm Research
    • Citrus Dry Root Rot
    • Dr. Beth Grafton-Cardwell to Retire

      What are the UC Experts Talking About?
    Memorial to Dr. Travis Bean
Topics in Subtropics Spring 2019
  • Introducing Your New Information Source for CDFA grants, Kern and Ventura Counties 
  • Spotlight on SWEEP in Citrus 

  • Low Pressure Guide to Low-Flow Irrigation Scheduling 
  • The So-Called “Leaf Fleck” Virus Diseases of Citrus 
  • Replanting Trees in Mature Citrus Groves 
  • What About Planting Lemons in Kern County?
Volume 17, Fall 2018
  • California Citrus Network: an online forum to facilitate communication and information exchange regarding California citrus

  • High Density Planting for Avocado Production: A Chilean Perspective

  • Avocado Brainstorming 2018

  • Meet our new subtropical crops specialist at UC Riverside

  • Fall Citrus Meeting Reminder
Vol 17, Summer 2018


• Native Pollinators of California Avocado as Affected by Introduced Pollinator Gardens

• Which Way World Avocados?

• Evaluating Cost Effectiveness of High Density Planting of Avocados: Experiment on Water and Pruning

• Herbicide injury in avocados

Topics in Subtropics Spring 2018

Topics in this issue:

  • A Taste of Coffee
  • Colletotrichum Shoot Dieback: A New Disease of Citrus in California
  • Successfully Irrigating Potted Trees
  • An Update on Huanglongbing disease of Citrus in California
Volume 15, Fall 2017


  • Ah, Rats!
  • So you want to install soil moisture meters?
  • Notes on applying Gibberellic Acid (GA) to Navels in the Southern San Joaquin Valley of California
  • Fall leaf tissue sampling
  • FREE! Citrus: UC IPM Pest Management Guidelines


June 2017
June 2016
Spring Issue Vol.14 Issue 1

Avocado Cultivars, Botanical Races and Genetic Footprints

Drought Induced Problems in Our Orchards

Winter 2015 Vol. 13 Issue 4

Blossom End Rot of Citrus

Using Organic Herbicides in Production Fields and Non-Crop Areas

Pocket Gopher and Ground Squirrel Control: Management Options for Citrus and Avocado Groves

What is that in My Grove, Horseweed or Hairy Fleabane?

Upcoming Programs and Schedules

Fall 2015 Vol. 13 Issue 3

Predicting Water Demand Along the Coast Versus in the Valley

Avocado Farm Families Still Healing, More Than a Decade Later: What Lessons Have We Learned About Fire Readiness and Prevention?

Olive oil chemistry – Let’s talk about quality

Summer 2015 Vol. 13 Issue 2

In this issue:

Did a Newly Introduced Fukumoto Navel Budline from Spain Perform Better than the California Budline in the San Joaquin Valley?

What values should olive growers use for estimating crop nitrogen removal at harvest?

Spring 2015 Vol. 13 Issue 1

In this Issue:

Polyphagous shot hole borer (PSHB) update for avocado growers
Weed Management in Citrus
UC Davis Olive Center:  Sensory Evaluation of Olive Oil Certificate Courses
Water Terminology
Olive Quick Decline in Italy is associated with unique strain of Xylella fastidiosa



Pesticide Worker Safety Training

Pesticide Worker Safety Training Registration


Vol. 12, No. 2, Spring 2014

In this Issue:

  • Vole Damage to Citrus
  • Time to Go Fishing!
  • 'Meyer' Lemon and C-35 Citrange Rootstock
  • Are Hops a Serious Option for a Crop in San Diego County?
Volume 11, No. 4

In This Issue:

  • Rehabilitating Frost Damaged Citrus and Avocado
  • Advances in mitigation of alternate bearing of olive: vegetative growth response to plant growth regulators

  • Fertigation - Measuring Uniformity

  • Olive Fly Update
Vol. 11 No. 3, September/October 2013

In this Issue:

  • Olive Tree Phenology
  • Training and Pruning of Cherimoya
  • High Density Avocado Installation: Use a quick cost study to make a decision
  • Volatile Organic Compound (VOC) Emissions from Pesticides
Spring 2013 - Volume 11 No. 2

In this Issue:

  • Cultural Practices to Reduce Pest and Disease in Avocado and Citrus
  • Polyphagous Shot Hole Borer in California
  • Electronic "sniffer" for Detecting HLB
  • Important Information Sources Related to Fire Management and Protection
  • Bee kill in Oregon - A reminder of pesticide use
Volume 11, No. 1

In This Issue:

  • Costs of Orchard Establishment and Production Summary for Avocados in California
  • Huanglongbing Conference, Florida
  • Going Out of Business in the Citrus Business - Doing it the Right Way
  • The Avocado: Botany, Production and Uses, 2nd Edition
  • Winter Irrigation
  • Update from Israel on the Polyphagous Shot Hole Borer and Fusarium symboint
Volume 10, No. 3
  • Asian Citrus Psyllid Quarantines
  • Decline of Oranges and Mandarins
  • Mitigation of Alternate Bearing in Olive
  • Alternate Bearing in Mandarin
Volume 10 No. 2
  • Simazine Degradation in CA Citrus Orchards
  • Lime-induced Iron Chlorosis
  • Avocado Trunk Cankers
  • Asphyxiation
  • Tree Wraps
  • Stem and Leaf Blight
Vol. 10 No. 1 January-March 2012

In this Issue:

*Quarantine for Huanglongbing

  Declared in Hacienda Heights

  Section of Los Angeles County

 *An Outline of Management Options for HLB in Florida

*Avocado Farming with High Priced Water

*Soil Moisture Sensors

Winter 2011 - Volume 9 No. 2

In this Issue:

Vertebrate Damage

Chemical Thinning of Olives

Tips on Producing the Earliest Early Citrus in the San Joaquin Valley

Herbicide Registration Chart

Resource and Market Information for Enterprise Selection

March thru June 2011

In this Issue:

Organic Herbicides: Do They Work?

Snake Oil: Horticultural Myths and Legends

Success Story before there is a problem

July - September 2010 Vol. 8 No. 3
May 2010 Topics in Subtropics
December -March 2010 Topics in Subtropics
October - December 2009 Volume 7, No. 4
July-September 2009 Volume 7, No. 3
April - June 2009 Volume 7, No. 2
Spring 2009 Volume 7, No 1
Fall 2008 Volume 6, No. 4
January-March 2008 Volume 6, No 1
October - December 2007 Volume 5, No. 4
April - June 2007
January-March 2007
October - December 2006
July - September 2006
April-June 2006
July-Aug-Sept 2005
April-May-June 2005
Jan-Feb-March 2005
Oct-Nov-Dec 2004
July-Aug-Sept 2004
April-May-June 2004
Jan-Feb-Mar 2004
April-May-June 2003