O'Neal, Henry

Valco, Thomas D.

English

OAKTrust Digital Repository (Texas A&M Univ)

L-2293Texas Agricultural Extension ServiceTexas CitrusOrchard SprayingThomas D. Valco and Henry O'Neal*Air carrier sprayers are used in citrus orchardsto discharge a high velocity of air for propellingand distributing pesticides throughout the trees.These sprayers, sometimes called air-blast sprayersor mist blowers, produce air speeds ranging from80 to 150 miles per hour (mph) and air volumes of5,000 to 60,000 cubic feet per minute (dm). Theair stream breaks up liquid into droplets by air-shear or centrifugal energy and distributes dropletsto all leaf, bark and fruit surfaces for effective pestcontrol. Good pesticide distribution requires lowground speeds with small droplets or large volumesof pesticide.The required volume of spray material per acrewill vary with the sprayer type used and the targetpest. Effective pest control has been obtained withfrom 5 gallons per acre to 500 gallons per acre. Alow-volume application in small droplet size readilyadheres to tree parts with virtually no drip orrunoff. This generally occurs with high volumesprays. By decreasing application rate, applicationcosts may be lowered through improved sprayerfield capacity, achieved by reducing filling andmixing time. 'Pesticide label rates should still beused with low-volume application rates.Selecting a SprayerDifferent air carrier sprayers operate on differentprinciples to form spray droplets and propel theminto the trees. The volume of solution applied peracre dictates the type of sprayer needed. Spraycoverage is a result of the air horsepower, arelationship between air velocity, capacity, outletarea and fan pressure-not just air velocity orcapacity alone.A sprayer is a combination of many designfeatures, and it cannot be stated that one machine*Extension agricultural engineers, The Texas A&M UniversitySystem.is better than another because one feature isdifferent. The proof of the sprayer's overall worthcomes from how well it controls pests in a cropand not from a higher outlet velocity, a biggercapacity, a mechanical agitator or some othersingle factor. The most expensive sprayer a growercan buy is one that is not designed for the job.Some of the low-volume sprayers on the marketare much less expensive than most medium- tohigh-volume machines. Some growers who cannotjustify the expenditure necessary for a largermachine may find low-volume sprayers to be themost satisfactory machine.Nozzles and Nozzle ArrangementThe orifice size of the nozzle and nozzleoperating pressure determine the rate of dischargefor any given nozzle type. To determine operatingpressure at the nozzle, place a pressure gage in thedischarge manifold or replace a nozzle with apressure gauge. Check the pressure on both sidesof the sprayer and set it to conform with the manu-facturer's specifications. As the nozzle orifice wears,the spray rate increases. This causes most growersto apply more spray then intended. Once a nozzleoutput exceeds 10 percent of its designed rate, itshould be replaced.To determine nozzle arrangement on thesprayer, determine the gallons-per-minute dis-charge for each nozzle. This rate may be found inthe nozzle manufacturer's catalog. Arrange thenozzles to apply 70 percent of the spray to the tophalf of the tree and 30 percent to the bottom half(Figure 1). Use larger nozzle sizes rather thanmore nozzles to obtain the additional output inthe upper zone. Larger nozzles produce largerdroplets, which are desirable for tree tops.Spray distribution in the orchard should then bechecked with water and dye. The addition ofTexas Agricultural Extension Service. Zerle L. Carpenter, Director. The Texas A&M University System. College Station, Texas~---------------------------hydrated lime to the spray water leaves a traceableresidue to help determine coverage. (Mix approxi-mately 10 pounds of hydrated lime per 100 gallonsof water. Do not allow material to settle in tank;maintain constant agitation.) Check to see thatspray material reaches the tops of the trees but isnot excessive. Then examine the lower tree skirtsand inside the tree canopy for coverage. If coverageis not as desired, rearrange the nozzles and nozzleorifice sizes to get the desired coverage.Sprayer CalibrationProper maintenance and calibration are criticalfor achieving good pest control. Air carrier sprayersare equipped with centrifugal pumps, piston pumpsor roller pumps. Occasionally check engine speedand pump drive belts for slippage because thesetwo factors affect pump operating pressure. Checkpump pressure at the discharge manifold ratherthan at the pump. Clogged strainers, air leaks intopump suction line, worn pump impellers andfaulty pressure regulators also affect pump operat-Ing pressure.Other factors which can cause variation in therate of application are: (1) number of nozzles onthe manifold, (2) ground speed and (3) nozzleorifice size. All of these factors must be consideredto calibrate a sprayer. Sprayers should be calibratedprior to initial use and periodically during theseason.Step 1: Determine sprayer ground speed.Load the sprayer tank with water and make atest run to find a ground speed at which desiredcoverage is obtained and record the gear andthrottle setting.Then make a test run at the desired groundspeed and count the number of trees passed in 1minute. Determine the ground speed in miles perhour (mph) with this formula: gpm = 5.14.06.08.012.020.05.0 4.57.0 6.510.0 9.015.0 13.024.5 22.088495495100 x 1 x 25gpa x mph x d495990gpm =gpm =Tree spacing(feet)10 12.5 15 18 20 22(Number of trees passed per minute)9.0 7.0 6.013.0 10.5 9.018.0 14.0 12.026.5 21.0 17.044.0 35.0 29.5tree spacing (ft) x trees passed/minute1.01.52.03.05.0Speed oftractor(mph)gpm =mph =15 x 6mph =88gpm =Example: Orchard requires a 100-gallons-per-acreapplication rate with tree rows spaced 25 feetapart. Ground speed is 1 mph for a two-sideddelivery sprayer.two-side deliverygpa x mph x dgpm =sprayer discharge rate in gallons per minutegpa =application rate in gallons per acremph =sprayer speed in I~iles per hourd = tree spacing between rows in feetTable 1 may be used to determine sprayer speedbased on tree spacing. Select the column whichrepresents the tree spacing in your orchard andthe speed you desire to travel. From that you canget the number of trees to pass in 1 minute.Table 1: Tractor speed based on tree spacing.Step 2: Determine the desired sprayer dischargerate with these formulas:one-side deliverygpa x mph x dExample: If trees are on IS-foot spacings and sixtrees are passed in 1 minute,HRecommended proportioning of sprayFigure 1.material.,I,III,------~Step 3: Determine the actual sprayer dischargerate.The discharge rate in gallons per minute for aspecific nozzle and pressure may be obtained fromthe nozzle manufacturer's catalog. To verify sprayeroutput, make a. trial run with the sprayer inoperation.a. Fill the tank with water to a known level.b. Set gear and throttle setting for desired groundspeed.c. Select the pressure setting recommended bysprayer manufacturer.d. Spray for a measured interval of time.e. Refill the tank to the known level, measuringthe number of gallons of water required.f. Determine the actual discharge rate with thisformula:spray discharged in gallonsgpm = time interval in minutesExample: 15 gallons sprayed in 3 minutes.minimize problems and prolong the useful life ofthe pump and sprayer:• Put clean chemicals, solutions and water in thesprayer. Small amounts of silt or sand particlesrapidly wear pumps and parts of the sprayersystem.• Use chemicals that the sprayer and pump weredesigned to use. For example, liquid fertilizersare corrosive to copper, bronze, ordinary steeland galvanized surfaces. If the pump is made ofthese materials, it can be ruined by just oneapplication of liquid fertilizer. Use stainlesssteel pumps for fertilizer application.• Before using a new sprayer, clean the screensand nozzles of all metal chips and other foreignmaterial.• Flush the spray system with clean water aftereach day of spraying.• Inspect screens and nozzle tips after each day ofspraying. Clean by soaking and using a softbrush such as a toothbrush. Tips and screensmay be damaged if cleaned with metal objectssuch as a knife or wire.spray discharged in gallonsgpm = time interval in minutesgpm = 5153• Clean the sprayer thoroughly after each use orwhen chemicals are changed. Many chemicalscause metal corrosion and a chemical residuesometimes will react with succeeding chemicals,causing a loss of effectivness.Compare the desired spray discharge with theactual discharge from the sprayer. If the actualoutput is greater than desired, increase sprayerground speed or reduce nozzle sizes or do both.(Caution: Because the volume of air discharged isan integral part of the coverage, increasing groundspeed beyond 2 miles per hour can cause poorspray distribution.) When the output is less thandesired, reduce tractor speed, select larger nozzlesor do both.Sprayer MaintenanceThe owner's manual supplied by the manu-facturer is the best source of information onroutine sprayer maintenance. Maintenance of theengine is the same as for any engine. Lubricate,check filters and service cooling systems daily.More pumps are ruined by improper main-tenance than are worn out. Pump wear anddeterioration occur with ordinary use but these areaccelerated by misuse. These suggestions will helpSafetyPesticides are potentially dangerous when notused properly. Sprayer operators should be thor-oughly familiar with both chemicals and equipmentbefore spraying. Read the pesticide label for allsafety instructions. Wear protective clothing andequipment such as goggles, respirator, gloves, hat,boots, long sleeved-shirt and long trousers duringmixing and application of pesticides. Do notsmoke or eat while handling chemicals.Always store and dispose of chemicals andcontainers properly. Triple rinse empty containersand dispose of them in accordance with the pesti-cide label instructions.Make sure that sprayer operators and chemicalhandlers have the telephone numbers of poisoncontrol centers and physicians and that they knowwhich chemical is being applied. Know the signsand symptoms of pesticide poisoning and what todo if it occurs.{§--------------Equipment and machinery also can be dangerous.Some important safety practices in machineoperation include:• Stop the engine, disconnect the power sourceand wait for all machine movement to stopbefore serVICIng, adjusting or cleaning equip-ment.• Make sure all persons are clear of machinerybefore starting the engine, engaging power oroperating a machine.• Keep all guards in place when machines are inoperation.• When operating a tractor with a sprayer, watchfor dangers and obstacles, especially at rowends, on roads and around trees.• When possible, avoid operating the sprayernear ditches, embankments and holes.• Allow no riders on equipment.References1. Hidalgo County DemonJtration Handbook,1982, "Citrus Spray Volume Demonstration,"Texas Agricultural Extension Service.2. CitruJ Grower.r Guide to Air Spraying, FloridaCooperative Extension Service, Circular 351.Educational programs conducted by the 1exas Agricultural Extension Service serve people of all ages regardless of socioeconomiclevel, race, color, sex, religion, handicap or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics, Acts of Congress of May 8, 1914, asamended, and June 30, 1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter, Director, TexasAgricultural Extension Service, The Texas A&M University System.1.5M-9-88, New HORT 2-2, ENG 5-1

Texas Citrus:  Orchard Spraying.

https://oaktrust.library.tamu.edu/bitstream/1969.1/174953/4/2293/Leaf2293.pdf

Texas Citrus: Orchard Spraying.

Abstract

Similar works

Full text

Available Versions

OAKTrust Digital Repository (Texas A&M Univ)