Subtropical Fruit Crops Research & Education
University of California
Subtropical Fruit Crops Research & Education

Posts Tagged: spray

Learning How to Spray Trees Better

Dr. Peter Ako Larbi is a Cooperative Extension Specialist in agricultural engineering with UC ANR. As part of his research and extension program, his focus is on developing and promoting best practices for safe, economical, and environmentally sound pesticide application with reduced environmental risks. He is based at the Kearney Agricultural Research and Extension Center in Parlier. 

Prior to joining ANR, Dr. Larbi had been an Assistant Professor of Agricultural Systems Technology in the College of Agriculture at Arkansas State University since 2014. He developed an integrated teaching and research program related to agricultural systems technology; developed and managed research in precision agriculture, agricultural machinery systems, remote sensing and sensor technology; and provided service to the university, college, local community and general scientific community. He held a joint appointment in the Division of Agriculture at University of Arkansas.

From 2012 to 2014, Dr. Larbi was a postdoctoral research associate at the Center for Precision and Automated Agricultural Systems at Washington State University. From 2011 to 2012, he was a postdoctoral researcher at the University of Florida Citrus Research and Education Center.

Larbi earned a Ph.D. in agricultural and biological engineering from University of Florida and a M.Sc. and a B.Sc. in agricultural engineering from Kwame Nkrumah University of Science and Technology in Kumasi, Ghana.

Dr. Larbi invites you to kindly take the following needs assessment survey to help him assess outreach, education, and training needs in pesticide spray application to better plan and implement a program that serves the people of California well:

Please contact him at if you need further information. Thank you very much for your assistance.

citrus spray blast
citrus spray blast

Posted on Friday, February 15, 2019 at 7:04 AM
Tags: citrus (311), pesticides (23), spray (6)

Spray Safe Training



MARCH 20, 2018




I.            Registration (7:30–8:30 a.m.)

II.            Opening Session (8:30–8:55 a.m.)

1.      Welcoming Remarks and Introductions — Brian Benchwick, Chairman, Ventura County Spray Safe Planning Committee

2.      Ventura County Spray Safe Overview — John Krist, Chief Executive Officer, Farm Bureau of Ventura County

3.      The Importance and Value of Compliance — Eric Lauritzen, Policy Advisor, California Department of Pesticide Regulation 

III.            Morning Speakers (8:55–10:10 a.m.)

  1. How Water Quality Regulations Address Pesticide Use and Safety— Jenny Newman, TMDL Unit Chief, Los Angeles Regional Water Quality Control Board
  2. Understanding the Pesticide Registration Process — Debbie Stubbs, Regulatory Product Manager, Syngenta Crop Protection
  3. Protecting Schools Near Farms — Colleen Robertson, Principal, Somis School


IV.            Station Training Sessions(10:15 – 11:50 a.m.) Attendees will be divided into four groups, which will rotate through the stations, with 20 minutes per station and 5 minutes of move time per rotation.

1.      Improving Water Quality Through Pesticide BMPs — Nancy Broschart, Farm Bureau

2.      Drift Avoidance and Safety — Kevin Miskel, Aspen Helicopters; Danny Pereira, Rio Farms

3.      Spray Rig Calibration — Marianna Castiaux, California Strawberry Commission

4.      Field Inspection and Worker Safety Compliance — County Agricultural Commissioner


V.            Buffet Lunch (11:50 a.m. – 12:45 p.m.) — Marshall's Bodacious BBQ


VI.            Closing Session (12:45 – 1:30 p.m.)

1.      Speaker Introductions — Brian Benchwick

2.      Statewide Regulatory Perspectives and Issues — Brian Leahy, Director, California Department of Pesticide Regulation

3.      Closing Remarks — William Terry, Vegetable Grower, Terry Farms


Attendance is free, but advance registration is

required. Fax (805) 987-3874 or email


spray safe
spray safe

Posted on Saturday, March 10, 2018 at 12:51 PM
Tags: IPM (15), pesticticides (1), spray (6), training (7), worker safety (4)

Continuing Eduction Credit in Spray Technology

This is a course that was developed for vineyards but it works for any crop.


Continuing Education Credits

Online Courses are now available for obtaining continuing education (CE) credits approved by the Department of Pesticide Regulations (DPR).

Effective Vineyard Spraying & Drift Management

This one-hour online course is self guided, and can be viewed from your desktop computer, laptop or tablet. You must turn up your volume to hear the presentations. There will be a quiz at the end of the one hour course. Participants must score a 70% or greater on the quiz. To obtain your verification of attendance via email, you must register at the link below and provide payment of $20 for 1.0 hours of DPR CE credits in the "other" category.  If you are not interested in obtaining CE credits, you may simply view the presentation for free, and skip the quiz. We hope you find it informative and educational either way.

Pay for 1.0 hour of CE credit HERE.

View the online course HERE.


Posted on Tuesday, April 7, 2015 at 6:35 AM
Tags: drift (3), pesticides (23), spray (6)

Surface inversions cause spray drift

On typical days, the air near the ground is warmer than the air above it. This is because the atmosphere is heated from below as solar radiation warms the Earth's surface. A surface inversion occurs when the atmosphere at the earth's surface is colder than the layer above it. There are four common causes of surface inversions, some of which can occur at the same time. Remember - inversions flow like water:

Advection of cool air:

A slab of cool air slides into and under a warmer air mass. This "drainage inversion" can occur when there are sea breezes, cold fronts or when cool air drains downhill into warmer air.

Advection of warm air:

Warm air flows over cool surfaces and lower layers cool more rapidly than those above.


Shading from trees as well as from rolling terrain can cause an inversion to set in earlier and stay later.

Radiation cooling:

Around sunset, the ground cools rapidly by radiating heat upwards into space. The air in contact with the ground cools by conduction, causing the lowest layer of air to be cooler than higher layers. Air within this "radiation inversion" tends to remains in place.

Radiation inversions create problems for spray operators because they can cause pesticide spray to:

  • stay concentrated for long periods over the target,
  • move with the cool air for many miles when the breeze picks up,
  • drain down slopes and concentrate in low-lying regions,
  • drift unpredictably as the inversion dissipates during the morning

Radiation inversions happen every day and should always be expected to begin 3-4 hours before sunset, reach their apex just before sunrise and then dissipate no longer than an hour or so after sunrise… unless one or more of the following conditions occur:

  • There is continuous overcast, low and heavy cloud.
  • There is continuous rain.
  • Wind speed remains above 7 m/h for the whole period between sunset and sunrise - although even this isn't always true.

Field air temperatures are often very different from local or regional forecasts, so the most reliable method of detecting inversion conditions is to measure temperatures at, and several meters above, the ground. Spray operators can recognize a surface inversion when:

  • there is a big difference between the daytime and night time temperatures,
  • evening and night time wind speeds are considerably less than during the day,
  • sounds seem to carry further,
  • odors seem more intense,
  • daytime cumulus clouds tend to collapse toward evening,
  • overnight cloud cover is 25% or less,
  • mist, fog, dew and frost occur
  • smoke or dust hangs in the air and/or moves laterally in a sheet.

If you suspect there's an inversion, then don't spray. Often, it's right on the label.


Farm Advisor Mark Battany measuring inversions


Posted on Thursday, March 19, 2015 at 1:49 PM
Tags: drift (3), inversion (2), pesticides (23), spray (6), weather (8)

Spray Adjuvants: what’s in a name?

If you can’t speak the language, you can’t follow the conversation.  Talk about adjuvants used in agriculture can be filled with unfamiliar terms like activator, non-ionic surfactant, penetrant, humectants, and buffers.  To help growers who want follow a sales pitch or discussion on adjuvants, the following article lists and describes common adjuvant categories by function.  This is the first of a series to help growers better understand adjuvants and their effective use.

There are two types of adjuvants – spray adjuvants and formulation adjuvants.  Spray adjuvants are packaged separate from pesticides.  Formulation adjuvants are mixed with the pesticide active ingredient during packaging and formulation.  This article is concerned specifically with spray adjuvants. 

Spray adjuvants are pesticides according to California Department of Pesticide Regulation (CDPR).  They must be registered.  Spray adjuvants are defined by CDPR as “a product solid in a separate package and intended to be used with another pesticide to aid the application or enhance the activity of the pesticide.”  Growers must report spray adjuvant use in their monthly pesticide use reports. 

There are two general categories of spray adjuvants: 1) activator adjuvants and 2) utility adjuvants.  Activator adjuvants directly enhance pesticide performance once the spray hits the plant target.  They include wetter-spreaders, stickers, penetrants, and humectants.  Utility adjuvants help make the spray application process go better.  This group includes defoamers, drift control agents, deposition aides, water conditioners, acidifiers, buffers, and colorants.  A single adjuvant product can be both an activator and a utility adjuvant.  For example, a product that contains a spreader/penetrant plus a buffer/acidifier is both an activator and utility adjuvant.

There are several categories based on product function within the general groups of activator and utility adjuvants.  Many adjuvants fit into multiple categories, as a particular set of ingredients may provide spreading and penetrating properties to a single packaged product. 

Wetter-Spreaders:  contains surface-active ingredients – surfactants -- that reduce the contact angle of the spray droplet on the target (see Figure 1.).  This allows the spray solution to contact more of the target surface.  Spreading is essentially an extension of the wetting process.  A spreader adjuvant allows the spray droplet to spread over a larger area of the target compared to a droplet with no spreader. 

Most pesticides are mixed with water and sprayed.  Wetter-spreaders behave differently in your spray tank based on their electrical charge in water.  Surfactants –the active ingredients in wetter-spreader adjuvant -- are further categorized as non-ionic, cationic, anionic, or amphoteric surfactants.  Why is this important to a grower?  When choosing an adjuvant to use with a water soluble ionic herbicide, you don’t want an adjuvant “tying up” your pesticide and reducing pest control.  For example, when mixed in the spray tank, a cationic spreader may bind to an anionic herbicide, possibly reducing the pesticide activity. If you use an adjuvant, make sure it matches the pesticide label adjuvant recommendation.   

Wetter-spreaders are surface active because they contain surfactant molecules that have a fat/wax loving (lipophilic) end and a water loving (hydrophilic) end.  Common ingredients include fatty amines, glucosides, alkyphols, alkylamine ethoxylates, polyethylene oxides, and organosilicones.

Stickers: contains non-evaporating ingredients that resist dislodging of the spray deposit from the target surface.  Common sticker ingredients include synthetic latex, low volatile oils, pinene polymer, water-soluble polymers, and resins.  The less water soluble the ingredients the lower the “wash off” potential of the pesticide deposit. 

Humectants: contains ingredients that reduce spray droplet evaporation before and after it reaches the

target.  Humectant materials include glycerin, various glycols, petroleum oils, vegetable oils, and urea.   

Penetrators:  contain ingredients that help the chemical enter the target plant once the spray is deposited.  Petroleum oils, vegetable oils, or modified vegetable oils are common penetrator ingredients.

Compatibility Agents:  commonly used to keep a homogeneous solution in a spray tank that contains multiple ingredients, usually including liquid fertilizer.

Defoamers: eliminate or suppress foam in the spray tank. 

Drift Control Agent:  used to reduce the percentage of spray droplets below a certain diameter in an application.  Small droplets are considered “driftable fines”.  The smaller the droplet, the farther it will move with wind.  Droplets with a diameter less than 150 mm are frequently characterized as “driftable”.  Drift control agent commonly include polyacrylamides and polysaccharides.  

Deposition agent: do not change spray droplet size, but improve the amount of pesticide deposited on the target – indirectly reducing drift -- or improve the uniformity of spray deposits. 

Water Conditioner: eliminates or reduces the interaction of ions in the spray solution with the pesticide.  For example, glyphosate efficacy can be reduced when hard water is used in the spray tank.  A range of materials including chelating agents, citric acids, and fertilizer salts such as ammonium sulfate and ammonium nitrate are used as water conditioners to improve glyphosate activity when the spray water source contains hard water.

Acidifier:  usually a dilute strong acid solution used to reduce spray water pH.  An acidifier will commonly not maintain – that is, buffer – the spray solution at a certain desired pH range.  Addition of an alkaline pesticide or fertilizer will increase the spray solution pH that was initially lowered by an acidifier.  

Buffer:  a product that will resist change in the spray solution pH.   Buffers will limit the change in solution pH when an acid or base are added to the tank.  A buffer/acidifier will reduce spray water pH AND hold the pH in a certain range.  How long the pH is held in a certain range when other pesticides or fertilizers are added differs between products.  The correct rate of buffer depends on the water source and materials in the tank.  Commonly used buffers are buffer/acidifiers using ingredients such as phosphates or organic acids.  

Colorants:  alters the color of the spray solution so that previous spray passes are visible to the applicator. 

So, there’s the general “line up” of adjuvant materials.  Once you know the players and their roles in the spray tank, you can begin to select the right material for the job. 


Posted on Thursday, April 4, 2013 at 11:25 AM
  • Author: Franz Niederholzer
Tags: adjuvants (1), spray (6)

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