Equipment

The Affect of Drop Size on Control with Postemergence Herbicides

A basic understanding of droplet size effects on postemergence herbicides is important when selecting techniques for foliar application. The relationship between droplet size and the resulting coverage on the target is complex, resulting in several common misconceptions regarding droplet size and foliar application. For example, it is generally believed that applying small droplets at high spray pressures will provide increased control with low volumes of spray solution. Research data, as well as a study of particle dynamics, does not substantiate this theory. It is true that atomizing a known amount of spray solution into smaller droplets will increase the coverage possible, but you must also consider evaporation, drift potential, canopy penetration, and deposition characteristics.

Table 1 shows some characteristics of various size droplets. Decreasing the droplet size from 200 to 20 microns will increase coverage 10 fold, but a 20 micron water droplet will travel less than 1 inch before it completely evaporates in less than 1 second. Droplets less than 100 microns in size obtain a horizontal trajectory in a very short time and evaporate very rapidly. The pesticides in these droplets become very small aerosols, most of which will not fall out until picked up in falling rain. Droplets over 150 microns in size resist evaporation much more than smaller droplets due to their larger surface area. From these and other research results, we can conclude that there is a rapid decrease in the drift potential of droplets as their diameter is increased to about 150 microns in diameter.

Table 1. Spray droplet size and its effect on coverage 
and drift.
---------------------------------------------------------------
		       1 gal/A application   Evaporating Water*
		     ----------------------  ------------------
				 Coverage
				Relative to  Lifetime  Lifetime
Droplet	   Type of    Droplets  1000 Micron	of	 Fall
Diameter   Droplet    per in2	   Drops      Droplet	 Dist
---------------------------------------------------------------
(microns)		(no.)		       (sec)	 (in)	
    5	   Dry fog   9,220,000	    200	         .04	     <1
   10		     1,150,000	    100	         .2	     <1
   20	   Wet fog     144,000	     50	         .7	     <1
   50		         9,220	     20	        4	      3
  100	 Misty rain	 1,150	     10	       16	     96
  150		           342	      7	       36	    480
  200	 Light rain	   144	      5	       65	   1512
  500		             9	      2	      400 	 >15000
 1000	 Heavy rain	     1	      1	    1,620   	>>15000
---------------------------------------------------------------
*Air temperature of 86øF and 50% relative humidity.

Several factors determine if a spray particle will be deposited and captured by the natural surfaces of a particular weed. These include: 1) the size and content of the droplets; 2) the size, shape and density of the target; 3) the wind speed and other meterological conditions; and 4) the nature of the deposition surface. In general, the deposition efficiency of droplets on a weed surface increases with droplet size and wind speed, and decreases as the size of the target increases. Very small droplets (less than 50 microns) are collected efficiently by insects or by needles on coniferous plants, but tend to remain in the airstream and be carried around stems and leaves of weeds. Medium size droplets that are applied when there is some air velocity will deposit more efficiently on stems and narrow vertical leaves such as grasses while large droplets will deposit most efficiently on large flat surfaces such as broadleaved weeds. In reality, a range of droplet sizes is required to effectively deposit on the variety of week sizes, shapes, and orientations that occur in actual field conditions.

The actual droplet size range for effective control of weeks from postemergence herbicides depends on the specific herbicide being applied, the kind and size of the target weed, and the weather conditions. There have been conflicting reports regarding the ideal spray volume, pressure, and nozzle type to obtain the most consistent weed control. Most of the conflict is due to the large variation in the parameters mentioned previously during the actual application.

Considerable research has been done to evaluate the biological performance of several postemergence herbicides when applied with a variety of nozzle types. A general summary statement can be made that experimental results to date suggest that any nozzle type that produces a droplet size spectrum in the range of 100 to 400 microns does not greatly influence biological performance over a range of conditions unless application volumes are extremely high or very low. Exceptions to this exist for specific herbicides.

(Submitted by Vern Hofman, Agricultural and Biosystems Engineer)

Safety

Annual Report on Pesticide Illnesses Released

SACRAMENTO -- There were 1,332 illnesses in 1994 that had a potential or confirmed link to pesticide use, Cal/EPA's Department of Pesticide Regulation reported today.

All reported pesticide illnesses in the state are investigated, and DPR prepares an annual report on the results. (DPR scientists are still evaluating the 1995 illness reports.)

Of the 1,332 illnesses in 1994, 448 involved agricultural use of pesticides. The remaining 884 occurred in non-agricultural settings.

(The term *pesticide* is an umbrella term for substances that kill or control pests. Therefore, pesticides include insecticides, herbicides, rodenticides, disinfectants, and sanitizers.)

Illnesses among agricultural field workers declined in the late 1980s, and this trend continues. From 1982 to 1988, the average number of field worker illnesses was 280 a year. From 1989 through 1994, the annual average was 149. (In 1994, there were 109 field worker illnesses.)

The decline followed regulatory action by DPR against three pesticides which had accounted for a disproportionate share of field worker illnesses. The insecticide phosalone was taken off the U.S. market by its manufacturer after DPR sharply limited its use in California. Also in the late 1980s, after a series of field worker illnesses caused by exposure to methomyl and propargite, DPR mandated longer waiting periods between pesticide application and when workers could reenter treated fields.

The 1,332 illnesses that occurred in 1994 included 514 cases of eye or skin irritation. The other 818 involved symptoms of systemic illnesses. ("Systemic" symptoms include respiratory problems caused by inhaling vapors, and symptoms such as headache or nausea that strike a part of the body not directly exposed to the pesticide.) Overexposure to pesticides caused three deaths. They included two elderly men who swallowed fatal doses of pesticides and one man who broke into his apartment while the building was being fumigated.

Most of the cases reported -- 1,211 of the 1,332 -- occurred while people were at work. California law requires that doctors report all illnesses that they suspect of being caused by pesticide exposure, whether work-related or not. However, because most physician reports come through the workers' compensation system, most reported illnesses are occupational. As a result, pesticide illnesses outside the workplace are probably under-reported. Nonetheless, the variety of cases reported alerts DPR to pesticide problems and it is unlikely that significant hazards escape detection.

Under state law, county agricultural commissioners are the local enforcement agents for pesticide laws and regulations. They investigate all pesticide-related illnesses or injuries reported in their counties, whether they occur in agricultural or non-agricultural settings. DPR specialists analyze the results of the illness investigations to decide if pesticide exposure caused the illnesses.

The U.S. General Accounting Office called the DPR illness surveillance program the nation's *most effective and well-established monitoring system.* No other state has a similar reporting and investigative program. It helps DPR evaluate the effectiveness of its pesticide and worker safety programs. DPR uses the information gathered in the illness investigations to determine if it should make changes in how a pesticide is used to provide greater protection from overexposure.

DPR is working with the State Department of Industrial Relations and Cal/EPA's Office of Environmental Health Hazard Assessment to improve illness reporting by physicians and to train physicians on how to better recognize pesticide illnesses.

For a copy of the 55-page report, or the separate 10-page overview, contact DPR's Worker Health and Safety Branch, 1020 N Street, Room 200, Sacramento 95814, phone (916) 445-4222. The report and overview can also be downloaded from the publications section of DPR's Internet Web page (www.cdpr.ca.gov).

(December 12, 1996 Press Release, Department of Pesticide Regulation, California EPA)

Training

January 21, 1997
Doublewood Inn -- Fargo (in conjunction with the NCTGA Conference)

Ag-Pest, Right-of-Way, Seed Treatment, Aerial and Research & Demonstration

January 22 & 23
Westward Ho -- Grand Forks
Initial Certification Only(must attend both days)

February 3 & 4
Civic Center -- Bismarck
Initial Certification Only(must attend both days)

February 10 & 11
Holiday Inn -- Minot
Initial Certification Only(must attend both days)

February 21
Satellite at many locations
Recertification Only

March 3 & 4
Radisson Hotel -- Bismarck
(with NDAAA Meeting)
Recertification Only(must attend both days)

March 14
Satellite at many locations
Recertification Only

March 24 & 25
Doublewood Inn -- Fargo
Initial Certification Only(must attend both days)

Fumigation

February 25
Doublewood -- Fargo
Initial & Recertification Training

February 26
Holiday Inn -- Bismarck
Initial & Recertification Training

February 27
International Inn -- Minot
Initial & Recertification Training

Satellite Locations for February 21 Meeting

County . . . Location
Barnes . . . Valley City High School
Benson . . . Maddock Public School
Bottineau . . . Bottineau Public School
Bowman . . . Bowman Public School
Burke . . . Burke Central Public School
Burleigh . . . Doublewood Inn
Cass . . . Doublewood Inn
Dunn . . . Killdeer Public School
Foster . . . Carrington Research Center
Grand Forks . . . Holiday Inn
Hettinger . . . Mott Public School
Kidder . . . Tuttle Public School
LaMoure . . . LaMoure Public School
McKenzie . . . Watford City High School
Pembina . . . Drayton Public School
Ransom . . . Lisbon Public School
Richland . . . Hankinson High School
Rolette . . . Rolla High School
Sargent . . . Sargent Central Public School
Stutsman . . . James Valley Area Vocational Tech Center
Towner . . . Bisbee High School
Ward . . . Holiday Inn
Williams . . . Airport International Inn

Satellite Locations for March 14 Meeting

County . . . Location
Bottineau . . . Bottineau Public School
Cass . . . Doublewood Inn
Cavalier . . . Langdon High School
Divide . . . Divide County High School
Foster . . . Carrington Research Center
Grand Forks . . . Holiday Inn
LaMoure . . . LaMoure Public School
McHenry . . . Towner Public School
McKenzie . . . Watford City High School
McLean . . . Washburn Public School
Mercer . . . Hazen High School
Morton . . . Fort Lincoln Elementary Public School
Mountrail . . . Stanley High School
Nelson . . . Lakota High School
Pierce . . . Rugby High School
Renville . . . Mohall Public School
Richland . . . Hankinson High School
Stutsman . . . James Valley Vocational Tech Center
Walsh . . . Park River High School
Ward . . . Holiday Inn
Wells . . . Harvey High School

Advanced Crop AdvisorWorkshop

This is an advanced workshop for individuals that desire the latest information on agriculture fertility, crop management and information technology. This program is designed for crop consultants, agronomists, ag dealers, extension agents and industry representatives.

Registration

The number of workshop participants will be limited to 150 persons. Preregistration (including fee payment) is required and workshop enrollment will be filled on a first-come first-serve basis.

Workshop fee is $125 per person if received with completed preregistration form by February 7. After this date, the workshop fee is $150. The fee covers the cost of refreshment breaks, noon meals and reference materials. A full refund of the preregistration fee will be provided if requested prior to the workshop.

Lodging

Reservations for lodging may be made directly with motels in the Fargo/Moorhead area. A limited block of rooms have been reserved until February 5 at a reduced rate at the Kelly Inn, 3800 Main Ave., Fargo. Phone: 701-282-2143. All workshop participants should make their own lodging arrangements.

Campus Parking

NDSU campus parking passes will be available for workshop participants. Car pooling is strongly encouraged when travelling to campus to reduce competition for limited parking spaces.

AGENDA

Tuesday, February 18

Morning -
 8:00  Registration and Refreshments
       Memorial Union - Dakota Ballroom
 9:00  General Session - Introduction
 9:30  Concurrent Sessions*
11:30  Lunch

Afternoon -
12:30  Concurrent Sessions*
 2:30  Refreshment Break
 3:00  Concurrent Sessions*
 5:30  Social
 6:30  Kelly Inn - O'Malley & Oleary Rooms


Wednesday, February 19

Morning -
 7:00  Continental Breakfast
 7:30  Program Highlights
 8:00  Concurrent Sessions*
10:00  Refreshment Break
10:30  Concurrent Sessions*

Afternoon -
12:30  General Session - Lunch
       "Ag Communications in a Rapidly Changing World"
       Mike Herger, Farm Director, 
       Red River Farm Network, Grand Forks


Participants will attend all three sessions on February 18 
and two of the three sessions offered on February 19

CEU credits for the Certified Crop Advisor Program have 
been requested in the following areas:
    2SW    2PM    6CP    2SP

Concurrent Sessions

February 18

Using Weather Data in Agriculture
Discussions will focus on the use of current weather data available through NDAWN and Ag Winds. Computer access to the data bases will be available throughout the Workshop.
John Enz, Leon Osborne

Wheat Growth and Management
Wheat growth and development will be examined from germination through maturity. Weather conditions effect on each critical growth state will be interrelated with management decisions that help determine final grain yield and quality.
Terry Gregoire

Advances in Sprayer Technology and Field Comparisons
Discussions will focus on characteristics of many different sprayers including air assist, high pressure, electrostatic, and other ground sprayers, plus aerial applications, and chemigation. Speakers will discuss results of field trails designed to test spray coverages on crop foliage.
Vern Hofman, Gary Secor

February 19

Soils Issues --

Salinity Development and Management
Jimmie Richardson

Iron Chlorosis in Soybean
Dave Franzen

Genetically-Engineered Crops
The implications of managing weeds and insects by growing genetically-engineered crops will be discussed.
Ken Ostlie, Richard Zollinger,
Kevin Thorsness, Paul Isakson

Precision Farming --

Remote Imaging Applications for Agriculture
Rodney Faleide

Precision Farming; Soil Sampling, Yield Monitor
Interpretation and a Broader Vision
Rick Vanden Heuve

Preregistration Form
Advance Crop Advisers Workshop

(Please print or type)

Name(s)______________________________________________________

Organization_________________________________________________

Address______________________________________________________
	
City______________________________  State______  Zip_________
	
Phone (________)_________________________

Fee: $125 per person if received by Feb 7, 1997 ($150 after 2/7/96)

Payable to: Advanced Crop Advisers Workshop

Return form and fee to:	Advanced Crop Advisers Workshop
			c/o Greg Endres
			Research Extension Center
			Box 219
			Carrington, ND 58421
			701/652-2951    (fax) 701/652-23055