- Author: Ben Faber
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.
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/h3>/h3>/h3>/h3>
- Author: Cheryl Reynolds
New Pesticide Resistance Online Course with Continuing Education Units
Author: Cheryl Reynolds, UC Statewide IPM Program
An online course highlighting how pesticide resistance develops among pests is now available on the UC IPM Web site. Created primarily for pest control advisors and other licensed pesticide applicators, this course describes the mechanisms of resistance in pathogens, insects, and weeds and discusses ways to manage resistance within the different disciplines.
The online course is divided into three narrated presentations followed by a final test for each section. This course has been approved for 2 continuing education units in the “Other” category from the Department of Pesticide Regulation.
This course is based on a series of workshops held in Davis, Fresno, and at the Kearney Agricultural Research and Extension Center during the spring of 2014 presented by Dr. Doug Gubler (Dept. of Plant Pathology, UC Davis.), Dr. Larry Godfrey (Dept. of Entomology and Nematology, UC Davis), Dr. Beth Grafton-Cardwell (Lindcove Research and Extension Center and UC Riverside), and Dr. Kassim All-Khatib (UC Statewide IPM Program).
Check out the new course at http://www.ipm.ucanr.edu/training/pesticide_resistance.html.
- Author: Jodi Azulai, UC Statewide IPM Program
Imagine a pesticide sprayer smart enough to hit trees and turn off between them. What would that mean for your wallet? What would it mean for the rivers and streams near your orchard? View On Target, a video that shows how smart sprayer technology is helping farmers manage orchard pests with clever results:
- Substantially reduced pesticide use and cost
- Less pesticide movement to rivers and streams
- Full tree coverage
- Same efficacy as conventional sprayers
- Ease of use
- Valuable application data
Walt Bentley, retired UC IPM Advisor, narrates this video showing a smart sprayer in action.
Smart sprayer technology is based on the use of high frequency sound waves. An onboard computer directs sound waves toward trees. When sound waves are returned, a target is detected and the computer triggers nozzles to spray. When sound waves are not returned, a gap is identified, prompting the program to turn off nozzles.
Find the video on the UC IPM Mitigation Pesticide Hazards page at http://www.ipm.ucdavis.edu/mitigation/index.html. Scroll down to the second bullet under “Before application.” Remember this page the next time you plan a pesticide application. It will help you consider practices that minimize environmental and efficacy problems.
- Author: Tunyalee Martin, UC Statewide IPM Program, Davis, CA
(This article summarizes California Department of Pesticide Regulation’s online VOC information.)
It’s that time of year again when hot weather fuels the creation of ground-level ozone, also called smog. High levels of ozone can harm people and crops. Ozone is caused by mixing volatile organic compounds (VOCs), nitrogen oxide, and sunshine. Some pesticides emit VOCs that contribute to ozone formation.
Between May 1 and October 31 when smog is likely to form, using pesticides that release VOCs may be restricted in the five nonattainment areas (NAAs) where ozone levels do not meet federal or state air quality standards:
- Sacramento Metro NAA: all of Sacramento and Yolo counties; parts of El Dorado, Placer, Solano, and Sutter
- San Joaquin Valley NAA: all of Fresno, Kings, Madera, Merced, San Joaquin, Stanislaus, and Tulare counties; parts of Kern
- Southeast Desert NAA: parts of Los Angeles, Riverside, and San Bernardino counties
- South Coast NAA: all of Orange County; parts of Los Angeles, Riverside, and San Bernardino
- Ventura NAA: all of Ventura County
In NAAs, regulations affect field soil fumigation with:
- methyl bromide
- metam sodium
- metam potassium
- sodium tetrathiocarbonate
Regulations may require reduced application rates, specific injection depths, soil compaction requirements, and a tarpaulin repair response plan. Fumigants used in greenhouses and for certain nursery fumigations, potting soil, individual tree and vine replantings, or harvested commodities are not affected.
In the San Joaquin NAA, where 65% of the VOC emissions are from nonfumigant pesticides, regulations begin November 1, 2013 for high-VOC pesticide formulations of:
Pesticides that contain solvents typically release high rates of VOCs. Solid formulations release the least amount. Starting in 2014 a PCA recommendation is required for use during May 1 to October 31. If the VOC emissions level is exceeded, applications for high-VOC formulations may be prohibited.
Whether in a NAA or not, simple steps can minimize the release of VOCs into the air.
- Use other pest management tactics.
- Choose low-emission pesticides or formulations.
- Avoid emulsifiable concentrate (EC) formulations and fumigants.
- Use DPR’s VOC calculators to determine emissions.
- Consider reducing the amount of pesticide applied by spot treating, making fewer applications, or using target-sensing equipment.
- Choose low-emission application methods for fumigants.
- Fumigate and cover with tarpaulins.
- Fumigate and cover with several post-fumigation water treatments.
- Apply through drip irrigation.
- If possible, apply pesticides before May or after October.
- Follow laws and regulations, especially in NAAs where additional regulations may be in effect.
When choosing a pesticide using the UC Pest Management Guidelines, click on the Air Quality button at the top of each treatment table.
- Citrus: http://www.ipm.ucdavis.edu/PMG/selectnewpest.citrus.html
- Avocado: http://www.ipm.ucdavis.edu/PMG/selectnewpest.avocado.html
It will take you to the Department of Pesticide Regulation’s VOC calculators to determine emissions from fumigant and nonfumigant pesticides.
- VOC emissions from pesticides: http://cdpr.ca.gov/docs/emon/vocs/vocproj/vocmenu.htm
- Nonattainment area maps: http://cdpr.ca.gov/docs/emon/vocs/vocproj/em_region.htm
- Reducing VOC emissions from field fumigants: http://cdpr.ca.gov/docs/emon/vocs/vocproj/reg_fumigant.htm
- Reducing VOC emissions from nonfumigant pesticide products: http://cdpr.ca.gov/docs/emon/vocs/vocproj/reduce_nonfumigant.htm
- Get on the VOC email list to be alerted about changing situations (go to cdpr.ca.gov and click on “Join E-lists” at the bottom left-hand corner)
- Posted By: Jeannette E. Warnert
- Written by: Franz Niederholzer, UC Farm Advisor, Sutter/Yuba Counties and Rhonda Smith, UC Farm Advisor, Sonoma Co.
Agricultural spray adjuvants are materials added to the spray tank when loading the sprayer. They include products classified as activator adjuvants and marketed as wetters/spreaders, stickers, humectants, and/or penetrators. Activator adjuvants are marketed to improve the performance of pesticides and foliar fertilizers.
Activator adjuvants can have a place in tree (and vine) crop sprays, but matching the material to the job can be tricky. A bad match can lead to minor or major losses to the grower. Minor losses can result from excess spreading and pesticide runoff from the target plant. Phytotoxicity can cause major damage.
This article describes ingredients and functions of activator adjuvants commonly sprayed on tree and vine crops. Suggestions regarding activator adjuvant selection are offered. Growers must make their own activator adjuvant use decisions based on experience, particular needs, and risk tolerance.
Do I need to add an activator adjuvant?
Read and follow the specific instructions on the label. If the pesticide or foliar fertilizer label indicates the product should be used with certain types or brand of adjuvant(s), that’s what you need to use.
Do I want to add an activator adjuvant?
If the label includes phrases such as "use of an adjuvant may improve results" or “complete coverage is needed for best results” then you may want to look into selecting and using an appropriate activator adjuvant. Before proceeding with use of an activator adjuvant, first look at your existing spray program. Are you already doing the best spray job you can? Good spray coverage begins with proper sprayer calibration and set up. Is your sprayer calibration dialed in for different stages of canopy development?
Optimum sprayer set up – gallons of spray per acre, ground speed, fan output, and nozzle selection/arrangement-- changes from dormant to bloom to early growing season to preharvest sprays. Adjusting your sprayer to best match orchard and vineyard conditions at each general stage in canopy development is the foundation of an effective, efficient spray program. An activator adjuvant will not make up forexcessive tractor speed, poor nozzle arrangement and/or worn nozzles. Your money is best spent first dialing in your sprayer(s) for the whole season, before considering an extra material in the tank (that is not required on the label). If you have your sprayer(s) dialed in for each orchard and stage of growth, now is the time to say “OK, I want to think about a little extra boost to my spray job”.
Which activator adjuvant properties do I want?
First, know the properties of the pesticide you will use. Does it work on the plant surface or inside the plant? This is a key point in selecting adjuvants. Here is a quick review of the main classifications and characteristics of activator adjuvants as they currently appear in the field. Note: Certain products can provide more than one adjuvant property – that can be beneficial in the field. For example, non-ionic surfactants can work as surfactants and penetrators, depending on use rate.
Wetters/spreaders: These materials contain surfactants that decrease the contact angle and increase the spreading of the spray droplet on the target. High rates of wetters/spreaders may also increase penetration of pesticide into the target tissue (leaves or fruit), potentially causing phytotoxicity. Excessive spreading of pesticide spray solution and runoff from the target may result when using a new or higher rate of spreader -- especially when using silicon “super-spreaders”. Test new combinations of spreader material(s) and spray volume before regular use. Spray volume per acre or adjuvant use rate will probably have to be reduced if a labeled rate of adjuvant provides excessive spreading.
To check for excessive spreading, place alength of black plastic sheeting under several trees or vines in a row. Secure the plastic with spikes, wire staples, and/or weights. Spray the new adjuvant and pesticide combination using your current sprayer set up. Reenter the field right after spraying, wearing appropriate PPE, and evaluate coverage. If material is pooling at the lower portion of leaves and/or fruit, excessive spreading is occurring. Check to see if pooling is occurring only in a certain area(s) of the canopy or throughout the canopy. If more spray solution is landing on the black plastic tarp under the trees/vines than between them, then runoff is occurring. [Some ground deposit should be expected from standard airblast sprayer use.]
Compare the results of your adjuvant test with a similar application of your current pesticide/adjuvant combination on another portion of the row. If there is no pooling or runoff with the new adjuvant in the tank, you can use the adjuvant with confidence. A lack of pooling or run off with the new adjuvant also might mean that your old sprayer setup and tank mix didn’t deliver adequate coverage. If the test with the new adjuvant showed pooling on leaves and/or runoff on the ground, you have several choices.
- You can reduce spray volume per acre by replacing some or all nozzles with smaller nozzle sizes on the sprayer in an effort to reduce overspreading. If you saw overspreading on some portions of the canopy, but not others, reduce nozzle size only on the part of the spray boom that targets the over-sprayed part of the canopy. Recheck spray coverage if nozzling changes were made.
- Reduce the adjuvant rate and recheck coverage/spreading.
- You can just go back to your established program without the new adjuvant. What’s the “best” course of action? That depends on your farming operation.Reducing spray volume per acre means more ground covered per full spray tank – a potential time and cost savings. If spraying is done during the heat of the day in hot, dry climate, spray water evaporation is a major issue and it may be best to keep the higher spray volume and reduce the spreader rate or eliminate it entirely. Checking coverage and overspreading allows you to make the best decision possible; avoid damage and, hopefully, save money. All farming operations are different. Make the choice that best fits your farm.
Stickers: These adjuvants can increase the retention time of the pesticide on the leaf and reduce rain wash off. They may limit movement of systemic pesticides into the plant, and are probably most beneficial when used with protectant materials (cover sprays). Do you overhead irrigate? Is there rain on the horizon? If you answer yes to either one of these questions, you may benefit from using a sticker.
Humectants: Under low humidity conditions humectants can help reduce spray droplet evaporation before and after deposition on the plant. This is especially valuable when small droplets and/or materials that must be absorbed into the plant (systemic pesticides, PGRs, nutrients, etc.) are used in the summer under high temperature and low relative humidity conditions.
Penetrators: Frequently used with herbicides, these products include oils (petroleum, vegetable, or modified vegetable oils) and non-ionic surfactants used at higher rates. In crop sprays, penetrators can be used to increase absorption of systemic pesticides (for example, oil with Agri-Mek) as well as translaminar materials. Penetrator adjuvants should be used with caution oravoided entirely with surface active pesticides such as cover sprays or else phyto may result. Finally, some penetrators can increase the rain-fastness of some pesticides.
Which adjuvant material should I select?
Use a product intended for crop spraying. Many activator adjuvants were developed and intended for use with herbicides. Products that are advertised for use with plant growth regulators should have a higher chance of crop safety compared with those that don't. This is still no guarantee of a phyto-free application. Ask for help from your PCA or the adjuvant manufacturer’s sales rep. How much do they know about the particular activator adjuvant in the spray mix you are planning? Can they show you the kind of information on a single product similar to what you can find at: http://www.ast-us.com? (This website is intended as an example, not an endorsement of the web pages it contains including specific adjuvants.)
Will the adjuvant I selected work in the spray I’m planning?
If you choose to use an adjuvant that is not specifically listed on the pesticide or foliar fertilizer label, jar test the planned spray solution first. Use the same spray water source. Include all leaf feeds, other adjuvants, and pesticide(s) that you plan to put in the spray tank. Do this before tank mixing these materials. A lot of time and money rides on effective pesticide application. Do your homework before the spray tank is filled and you will be well on your way to solid results.