GROUNDCOVER MANAGEMENT

Groundcover management is the manipulation of groundcover in order togain its benefits while avoiding its drawbacks. The term groundcover hereindicates either an intentionally seeded herbaceous species, or a naturalwild growth of grass and broadleaf herbs.

Groundcover benefits include the holding of soil against erosion; providingsoil stability and traction for equipment in wet and spring&shyp;thaw conditions;limiting dust within the orchard; and insulating against deep penetrationof winter cold. Growing a groundcover is a very effective way to supplyorganic matter to the soil. Some researchers have suggested that groundcoveris important as a refuge for overwintering colonies of beneficial mitesin orchards.

Undesirable features of groundcover in orchards are related to (1) certainspecies that are noxious or promote pest problems, e.g., horsenettle (stinging)and alfalfa (promotes plant bugs); (2) competitive or allelopathic suppressionof the growth of very young trees; (3) use of soil moisture when soil moistureis inadequate; (4) aggravation of orchard vole problems; and (5) interceptionof sunlight and sprays by tall weed growth.

Avoidance of potential groundcover problems often involves limited use ofherbicides, timed for specific temporary results. For example, noxious andpestpromoting weeds can usually be controlled by spottreatment with postemergenceherbicides when the weeds are seen. Competitive or allelopathic growth suppressioncan be avoided by excluding weed growth within a 23 foot radius around veryyoung trees. Herbicides, cultivation, and mulching are options. Vigoroustree growth is rarely needed in mature orchards, however, so there groundcovercompetition may serve the grower's purpose. The problem of competition forsoil moisture during droughty times can be avoided by temporarily killingthe groundcover in the summer. There are several postemergence type herbicidesavailable for such use. Irrigation may be another option for some growers.

Orchard voles are discussed in this Part I of this guide under the titleOrchard Voles. Tall groundcover provides food and shelter for thesepests, but total elimination of groundcover is neither desirable nor necessaryfor avoiding vole injury.

The problem of tall weeds interfering with sunlight and spray penetrationcan be approached in several ways: (1) mowing; (2) postemergence herbicideapplied before weeds are tall; (3) residual herbicide used with or withouta postemergence herbicide, and (4) use of a pruning and training systemin which limbs and fruit are kept above weed height.

In many orchards a "weedfreestrip" 46 feet wide, or more, is apermanent condition for the life of the orchard, renewed each year throughthe use of a banded residual herbicide treatment. In some orchards theseweed free strips show evidence of serious soil erosion, with many tree rootsexposed. In others one or more grass or broadleaf herb species is usuallypresent over the treated strip. In still others, mosses have become established,providing excellent soil protection. In those orchards with soil erosion,a lower rate of herbicide, or a change in timing of herbicide applicationmay avoid the problem in the future. Or a change in both rate and timingmay be needed, or it may be necessary to switch to a different herbicideor to a nonherbicide practice. Herbicide timing should be chosen so as toassure that live groundcover, or a matting of killed groundcover will bepresent when soil erosion is likely, especially during the dormant season,and when thunderstorms are likely. Practices that promote extensive mossgrowth have not been identified, but it is evident that some herbicidesinhibit moss establishment and others do not.

Maintaining or increasing soil organic matter (humus) should be an objectiveof orchard groundcover management in New England. Soil organic matteris much more than the dead leaves, stems, and roots produced by the groundcoverand orchard trees. As plant tissues decay, through the activity of soilmicroorganisms (bacteria, actinomycetes, fungi, algae, protozoa, and nematodes)they produce humus, a complex mixture of organic compounds that givestopsoil its characteristically dark brown color. The soil microbes themselvesdie, contributing to the total pool of biomass that forms humus. In sodcoveredsoils, humus typically constitutes the bulk of soil organic matter. Buthumus is not permanent. Its constituents undergo a slow, but continuingprocess of decay. If soil is kept bare, the major food source for soil microorganismsis eliminated, and humus can then be expected to disappear faster than itsis formed.

Humus is a major source of nitrogen, phosphorous, and sulfur. These threeessential elements are abundant in all biological tissue, the source ofhumus. Humus also has a controlling influence on the availability of essentialmicro nutrients, not because its parent biological tissues were high inmicronutrients, but because humus can form "chelates" with copper,zinc, manganese, etc. that are released from soil minerals. Chelated micronutrientsare held against leaching from the soil, and, under the right conditions,are available to plant roots.

Another value of humus derives from its electrostatic attraction for oppositelycharged nutrient elements, protecting them against leaching. This property,called cation exchange capacity, is also exhibited by clay particles. Cationexchange capacity, together with chelation, allow soils to hold nutrientsuntil picked up by plant roots. Soils in which these properties are at alow level, as in soils with little clay or organic content, are naturallylow in agricultural productivity, because they cannot supply as much mineralnutrition as the crops are capable of using. Additional functions of soilorganic matter (humus) include:

€It increases moisture retaining ability of sandy soils. Organic mattercan hold up to 20 times its weight in water.

€It acts as "glue" to hold very small soil mineral particlestogether in units called aggregates. Aggregation permits a loose, open,granular condition that aids penetration by water, air, and roots, and resistserosion.

€It has the ability to absorb many organic pesticides, holding themnear the soil surface, where they are more likely to be degraded by biologicalactivity and sunlight, rather than leach to groundwater.

GROUNDCOVER MANAGEMENT OPTIONS

(1) Permanent sod over 100% of orchard floor.
Mowing several times per year is needed to expose vole populations.
Grazing domestic fowl or meat animals is an option only under certain limitedpesticideprograms.

(2) Permanent sod, with herbicide strips centered on the tree row.
This method requires mowing, but herbicide is used where the mower cannotsafely reach. In young plantings, the herbicide strip may be extended toa 36 foot width, to achieve faster tree growth.

(3) Killed sod.
Groundcover is allowed to grow until it reaches a maximum tolerable height,or until its use of soil moisture is detrimental. Then a postemergence herbicideis applied over the entire orchard floor to kill all growth. Depending onthe degree of shade provided by the killed groundcover and the orchard trees,a second application of post emergence herbicide may or may not be neededlater in the year.

Seeding has not been necessary to re establish groundcover where this methodhas been used by the author in Connecticut. The techniques is well suitedto orchards where the lowest limbs are well above ground.

(4) Cultivation.
There are few, if any, orchard sites in New England where clean cultivationis a suitable option. Without groundcover, sloping sites are subject tosevere soil erosion, especially during thunder showers and periods of soilthawing. Organic matter is broken down more quickly under cultivation thanunder other forms of orchard floor management.

Trashy cultivation, light discing that leaves sufficient chopped groundcoveron the surface to prevent erosion, resembles the killedsod management method,but requires more labor and machinery time, and has no apparent advantageover the killed sod method.

(5) Mulching
A variety of mulching materials have been used over the years in effortsto suppress weed growth and soil moisture loss. Hay and straw used as mulcheswill increase soil organic matter and potassium. A problem common to mostmulches is that they provide shelter for pest voles. Such materials mustnot be left in place for long unless damageavoidance techniques are utilized.

If you use herbicides, you are responsible for their safe and properuse. The label is the law. Be aware of the potential for contamination ofwaterbodies, groundwater, and food. See Pesticide Safety, in PartII of this manual.

TYPES OF HERBICIDES

Herbicides can be separated into two broad categories of use: those appliedto the soil before weeds have emerged (preemergence herbicides) and thoseapplied directly to visible weeds (post emergence herbicides). A few preemergenceherbicides have some activity against emerged weeds (Table 20). Herbicidescan also be categorized as being either residual or nonresidual type. Residualherbicides have a lasting effect on the soil. How long weed growth is preventedby an application of residual herbicide depends on how quickly it is brokendown on the soil by sunlight, microbial activity, or soil chemistry, andwhether the herbicide is volatilized or leached below the upper inch orso of soil. Nonresidual herbicides have little or no effect except on weedsthat are present at the time of application.

Finally, some herbicides are effective only on grasses; some only on broadleafherbs; and others show degrees of activity against both types of vegetation.In Table 20, herbicides labeled for orchard use are categorized as preemergenceor postemergence types, and as to their activity against grass or broadleafherbs or woody species. No herbicide is effective against all species inany of the 3 categories of weeds. Some herbicides are effective on certainweed species outside of the indicated category. For a list of specific weedscontrolled, see product labels.


LEACHING and RUNOFF POTENTIAL

Downward herbicide movement is influenced by characteristics of the soil(texture, compaction, organic content, pH, wetness, temperature). In addition,certain soil microorganisms and living weeds can sometimes metabolize absorbedherbicides, rapidly or gradually altering them to nonphytotoxic forms thatmay have different leaching characteristics. Leaching potential is alsoaffected by certain characteristics of the herbicide, including water solubility,electrostatic properties, vapor pressure, and photodecomposition.

Because numerous complex interactions can occur between herbicides and thesoil environment, it is impossible to accurately generalize leaching behaviorfor a wide range of possible soil situations. In Table 21, a designationof high leaching potential means that under conditions favorable for leaching,this chemical could be expected to move downward beyond the upper 23 inchesof soil.

Downward movement is most likely with chemicals that do not degrade quicklyand do not adsorb strongly to clay or organic matter. The potential fortree damage or groundwater contamination is greatest with such chemicalswhen heavy rain comes soon after application, or where
spills occur. Special attention should be given to the mixing and loadingoperation, as spills can quickly overload detoxifying processes of soiland sunlight. See Protecting Water Quality for more information.

Surface loss of herbicides from treated areas can be avoided by the samemeans used to avoid soil erosion. Sloping ground and absence of groundcoverfavor surface runoff. Living sod or other dense groundcover and organicmulches inhibit runoff. Where problems persist, grass strips and berms canbe used to separate treated areas from sensitive borderlands. Practicesthat prevent concentration of rain water into narrow channels will help.Wheel ruts often become streambeds during heavy rainfall, as do channelsfrom previous rainfalls.

For orchards, runoff prevention should include: 1) practices that minimizebareground on erosion prone soil; 2) avoidance of spills or chemical dumping;3) knowing how to minimize runoff if accidental spill does occur; and 4)plant new orchard so that travel lanes run across the slope. Wheel ruttingacross a slope is less severe, and erosion is less likely, than if travelcrosses the contour lines.


USING THE TABLES

€Use Tables 20 and 22 to determine whether any herbicides are availablefor the particular situation you want to treat.

€If one or more herbicides appear to fit your requirements, consultTable 21 and Notes on Herbicides for more information.

€Before deciding which materials to use, obtain and read the labelsfor those products being considered. Sample labels are available from mostlocal chemical suppliers.


HERBICIDES CAN DAMAGE TREES

To avoid tree injury, know the potential for injury, and follow label instructionscarefully. Injury can be local (affecting only tissue directly hit by spray),or it may be systemic. Systemic injury can produce symptoms some distancefrom the site of contact, due to the ability of some herbicides to translocatewithin the plant. The potential for tree damage should be noted for thefollowing materials:
glyphosate, sulfosate: Are absorbed by foliage, bark and fresh pruningwounds, resulting in systemic injury. €diuron, oxyfluorfen, terbacil:Are absorbed by foliage, resulting in local injury.
€paraquat, glufosinateammonium: Are absorbed by foliage, andbark, resulting in local injury.
€2,4D: Is absorbed by foliage, bark, and roots, resulting insystemic injury.
€dichlobenil, diuron, simazine, terbacil, and 24D can, undersome conditions, be taken up by roots, resulting in injury or other symptoms.Root uptake is most likely in soils containing very little clay or organicmatter. In the case of 2,4D, the chemical is highly watersoluble, so movementto roots is possible where groundcover is insufficient to absorb (trap)the 2,4D.

Other listed herbicides may produce injury to trees if not used at the appropriatelabel rates and timings, taking into account tree age, soil texture, andsoil organic matter.

Herbicides do not have federal residue tolerances for fruit, so direct sprayand drift must be kept off fruit. If accidental spraying occurs, the exposedfruit should be removed.


TIMING HERBICIDE APPLICATIONS

Product labels limit timing of some herbicides to certain months, weedgrowth stage, temperatures, crop growth stage, or days to harvest. Someof this information is summarized in Table 21. Detailed information is includedon the product labels.


RATE OF HERBICIDE

For many preemergence herbicides, the lower recommended rate is the bestchoice for coarse texture orchard soils (sandy loam or loamy sand), providedmoisture conditions are suitable. Some preemergence herbicides are stronglyadsorbed onto soil organic matter and/or clay particles. Therefore, on relativelyhigh organic soils (above 3.5 percent by WalkleyBlack method) and on clayloam soils, the higher label rate may be needed for pre emergence control.Soil texture and organic matter content can be determined by soil testinglaboratories. Several different methods are used to estimate soil organicmatter. For the same soil the different methods can give much differentresults. To properly interpret label recommendations regarding soil organicmatter, ask your soil testing laboratory to indicate its estimate of organicmatter as through it had been done by the WalkleyBlack method.

Surface litter (nondecomposed organic tissues) can bond some herbicides,resulting in failure of the chemical to reach the soil where germinatingseeds can be killed. Herbicides that are so affected will include a labelrecommendation for removal of surface litter, or clean cultivation priorto application of the herbicide.

Rates for postemergence herbicides vary according to weed species and growthstage. Drought conditions that slow weed growth may make weeds more tolerantof postemergence herbicides applied during that time.

Unless product labels suggest addition of surfactants or other adjuvants,their use is not likely to improve herbicide activity. Postemergence herbicidesshould be used with enough water to avoid missing any plants or plant parts,while avoiding runoff.


NEED FOR RAIN OR IRRIGATION

Herbicides that are used for preemergence weed control generally require0.51 inch of rain or irrigation, or shallow cultivation to initiate herbicidalaction. The need for prompt incorpo ration varies. Warm bright days speedsurface breakdown and evaporation of certain herbicides. Some herbicidesmust be incorporated within 24 hours after application, while other materialscan be stable for 34 weeks or more. Specific information is provided onproduct labels if rapid incorporation is necessary.

PERSISTENT WEEDS

Perennial and biennial species that persist where preemergence herbicideshave been used can often be killed by one or more treatments with glyphosate,2,4D, or a combination of these two. Such species include bindweed, brambles,Canada thistle, dandelion, dock evening primrose, goldenrod, horsenettle,plantain, poison ivy, and vetch. Yellow nutsedge can be killed with glyphosate,glufosinate, or paraquat, properly timed. MidJune to midJuly is the besttime for paraquat and glufosinate; while August and September is best forglyphosate. Note that preharvest interval requirements may influence choiceof timing.


TANKMIXES

€ Where no statement concerning tank mixing of two or more herbicidesis given on product labels, mixing is legal, though a test for compatibilitywill be necessary.
€ Do a smallscale jar test as follows: Place one pint of water in aquart jar. Add each pesticide or a premix of pesticide in water, one ata time, and shake well with each addition. Use each product in about thesame proportion to water as it will be in the field mixture. One halfof a measur ing teaspoon of herbicide in a pint of water is ap proximatelyequivalent to one pint or one pound of herbicide in 25 gallons water.Unless labels indicate otherwise, add pesticides in this order: wettablepowders, followed by flowables, emul sifiable concentrates, water solubles,and recom mended adjuvants. However, when compatibility enhancers are used(tankmix adjuvants such as Blendex, BufferX, Compex, Sponto 168D, Uni Mix,Unite) these should be added first to the water. Invert the jar 10times, then inspect the mixture immediately and again after 30 minutes.If a uniform mix cannot be made or if nondispersable oil, sludge, or clumpsof solids form, the mixture is incompatible and should not be used. Minorseparation after 30 minutes (without sludge or clumps) that remixes readilywith 10 jar inversions, is tolerable if spray tank agitation is good.
€ When you tankmix in volume, put 2/3 of the water in the tank first.Then add pesticides one by one, with wettable powders first. Agitate forthorough mixing after each addition, before pouring in the next. Finishfilling the tank with water.
€ Maintain continuous agitation until the tank is empty.

(adapted in part from 1995 Pest Management Recommendations For CommercialTreeFruit Production, A.M. Agnello, W.F. Wilcox, , J. Kovach, and W.C.Stiles, Cornell Cooperative Extension.)

See Table 21 for registered crops, restricted entry intervals, formulations,rates, etc.


dazomet (Basamid Granular) Soil fumigant effective against annualand perennial weed seeds, nematodes, soil fungi and some soil insects. Tobe effective it must be incorporated into the soil after cultivating toseedbed condition. Soil should be moist, and between 54 and 64 degrees F.Immediately after incorporation into the soil, it must be sealed in by rollerpacking, sprinkler irrigation, or tarping. Spring planting can follow latesummer or fall treatment. Dazomet is not recommended for weed control unlessnematodes or soil pathogens are the primary concern.

dichlobenil (Casoron, Norosac) Dichlobenil volatizes rapidly underwarm, moist soil conditions. Apply before the soil temperature exceeds 45oFto minimize such loss. Application of 100 lbs. of 4% granules/A is effectiveon many annual grasses and broadleaf weeds, whereas 150 lbs./A are usuallyrequired for control of most established perennials.

diuron (Direx, Karmex) Effective against germinating annual broadleafweeds and some annual grasses. For best results, it must be used in combinationwith an herbicide that is more effective on grasses. It is not effectiveon established perennial grasses and broadleaf weeds. Rate must be determinedin relation to soil texture and organic matter content.

fluazifopbutyl (Fusilade) Effective for post emergence control ofannual and perennial grasses. Good for control of grasses in newly plantedorchard. Two applications are usually necessary with perennial grasses suchas quackgrass. Spot treatments are suggested unless a severe grass problemexists. Inclusion of a nonionic surfactant enhances uptake by grass leaves.glufosinateammonium(Rely) Nonselective herbicide for postemergence control of a broad rangeof annual and perennial grasses and broadleaf weeds, and certain woody species.It has no residual activity in the soil. Rely will injure or kill all greenvegetation contacted by the spray. If desirable vegetation is contacted,the sprayed portion should be rinsed with water immediately to reduce potentialinjury. The maximum label rate (6 quarts per acre in 20 gallons water) producedserious bark and wood injury on mature apple tree trunks in Connecticutorchard in 1995. The chemical, or its formulated surfactant, penetratedan inch or more into the wood beneath wetted bark, killing both contactedtissues. To avoid such injury, tree trunks should be protected from wettingif the high rate of Rely is applied in a low peracre volume of water. Relyis subject to foaming in the spray tank. Nonionic antifoaming agents aresuggested if needed.

glyphosate (Roundup, Rattler) Nonselective broadspectrum contactherbicide for controlling established annual and perennial grasses and broadleafweeds, plus woody brush, vines and trees. No residual soil activity on mineralsoils. Best timing for application depends on the target weed(s), but isusually after the weeds have developed full foliage or have begun to flower.Can be combined with 2,4D or a nonionic surfactant to increase effectiveness.Less effective on weeds that have been recently cut or are under moisturestress. Do not expose glyphosate to galvanized metal or unlined steel tanksas explosive gas may result.
Glyphosate is absorbed by green tissue and can translocate through the entireplant. However, rapidly growing broadleaf weeds and woody species translocateit almost entirely to aboveground growing points, where it may produce aburnback response rather than complete kill. If applied when top growthhas stopped, glyphosate moves to the root, resulting in wholeplant kill.
May be applied by directed spray or by weed wiper underneath apple, pearor cherry trees. Do not allow contact with foliage or green bark of fruittrees. Rootsuckers or low branches that might be contacted by glyphosateshould be removed at least 10 days before application. Use only wiper applicationfor all stone fruits other than cherry. Peaches and plums are EXTREMELYSENSITIVE to glyphosate, and ANY contact with leaves, small branches, ortrunks of young trees may cause severe damage or tree death.

metham (Vapam) Soil fumigant formulated as a water solution. It iseffective against annual and perennial weed seeds, nematodes, soil fungiand certain insects. It must be incorporated into the soil after cultivatingto seedbed condition, then immediately sealed into the soil by roller packing,irrigation, or tarping. Soil temperature must be between 40 and 90 degreesF. Wait at least 3 weeks before planting a treated site. Metham is not recommendedfor weed control unless nematodes or soil pathogens are the overriding concern.

napropamide (Devrinol) Effective against most annual grasses and manyannual broadleaf weeds. Does not give good control of ragweed and Pennsylvaniasmartweed. Napropamide must be present in the soil before weed seed germination,it does not control established weeds. Can be applied in newly planted orchardsas soon as the soil settles around the roots and no open cracks are present.Combination with a contact herbicide (glyphosate, paraquat) is requiredto help control established weeds and those not effectively controlled bynapropamide.

norflurazon (Solicam) Controls most annual grasses and many annualbroadleaf weeds, and suppresses quackgrass and nutsedge. Must be moved intothe soil by water before weed seed germination. Application rate dependson the type of treefruit, and on soil organic matter and clay content. Doesnot control established perennial weeds.

oryzalin (Surflan) Effective against most annual grasses and some annualbroadleaf weeds. Does not give good control of ragweed and Pennsylvaniasmartweed. Not effective against established grasses and broadleaf weeds.Requires 1/2" rain or irrigation to move into the soil before weedseed germination. Oryzalin can be used in newly planted orchards as soonas the soil settles around the roots and no open cracks are present.

oxyfluorfen (Goal) Primarily effective against seedling broadleafweeds. Has preemergence and postemergence contact activity. Uptake can bethrough leaves, stems, or roots, but very little translocation occurs inthe plant. Does not control grasses or established perennial broadleaf weeds.To avoid possible damage from vapors, oxyfluorfen must be applied whiletrees are dormant, before buds swell.

paraquat (Gramoxone Extra) Nonselective contact herbicide that effectivelykills emerged annual broadleaf weeds and grasses, and topkills and suppressesperennials. Contact with foliage, branches, and green bark on trunks ofyoung trees can result in damage to the trees. Paraquat is more hazardousto workers than the other treefruit herbicides listed, follow safety precautionson label. REI is 48 hours, written worker notification required.

pendimethalin (Prowl) Effective for preemergence control of mostannual grasses and some annual broadleaf weeds. Can be used in newly plantedorchards. Limited to nonbearing trees.

pronamide (Kerb) Effective against winter annual and perennial grasses.Must be applied in late fall (but before soil freezes), and moved into thesoil by water to be effective. Range of activity against broadleaf weedsis limited. Application rate depends on the type of grass being controlledand soil texture.

sethoxydim (Poast) Selective herbicide for controlling establishedannual and perennial grasses. Does not control broadleaf weeds or sedges.Rain within 1 hour of application will decrease effectiveness. A cropoilconcentrate must be used with sethoxydim. Rate of application depends onheight of grasses being treated.

simazine (Princep) Effective against a wide range of annual broadleafweeds and grasses. Does not control established perennials. Must be movedinto the soil before weed seeds germinate, so late fall or very early springapplication is suggested. Activity is reduced in soils with low pH. Weedssuch as pigweeds and lambsquarters have developed resistance to simazinewhere it has been the principal herbicide used. Control of these weeds canbe achieved with diuron, oryzalin, or pendimethalin. Type of tree fruit,tree age, soil texture and organic matter content determine the simazinedosage required for weed control and crop tolerance.

terbacil (Sinbar) Effective in controlling most annual grasses andbroadleaf weeds. Also provides partial control or suppression of perennialssuch as quackgrass, horsenettle, and nutsedge. Residual activity in thesoil is relatively longlived. Application rate and crop tolerance dependson soil texture and organic matter content, as well as the type of treefruitand tree age.

2,4D amine (HiDep, Justice, Weedar 64) - Selective postemergencefoliar herbicide effective against many annual and perennial broadleaf weeds.It is particularly effective in controlling dandelions when applied in latefall. Should not be used from the time crop flower buds begin to expanduntil 4 weeks after bloom. Do not allow spray or drift to contact tree.Combination of 2,4D amine with glyphosate is effective in controlling manydifficult perennial broadleaf weeds. REI is 48 hours.

Herbicide labels indicate rate of application as amount of product peracre; that is, per acre actually treated. Only if you broadcast herbicideover the entire orchard floor will the treated acreage equal the orchardacreage. Follow the instructions below to assure application of the correctherbicide rate.

CALCULATING NOZZLE FLOW RATE

Travel Speed:; For most situations, 22.5 mph is best (176220ft./min.).

Pressure: Use low pressure (2035 psi) to minimize formation of smalldroplets, because small droplets can drift off target.

Spray Volume per Treated Acre: Generally, low rates (2030 gals./acre,or less) are more suitable for postemergence herbicides, where runoff fromweeds would reduce effectiveness. Higher rates, 4050 gals./acre, may providebetter coverage and control when using preemergence herbicides.

Nozzles: Avoid nozzles that produce fine mist. Gen erally, hollowcone nozzles produce the finest drop lets, flat sprays are second, and fullcone nozzles pro duce the coarsest spray.

A single boomless offcenter flat spray nozzle, or a flooding nozzle, maybe suitable for some orchards, but one or more regular flat spray nozzleson a boom may be better where branches are close to the ground.

Use the following formula to determine nozzle flow rate in gal./min., thenconsult a nozzle manufac turers chart to select the proper nozzle.


DEFINITION OF TERMS
1. Gallons per Treated Acre (G/TA) = Amount of herbicide spray youwant to apply per treated acre.
2. Swath (S) = Width of the sprayed area in feet.
3. Travel Speed (TS) = Feet traveled per minute.
4. Nozzle flow rate (gallons per minute)
= (Gallons per Acre x Swath x Travel Speed) divided by 43,560
Nozzle Flow Rate = (G/TA x S x TS) / 43,560

EXAMPLE 1: What nozzle flow rate do you need to apply 25 gallons ofherbicide spray mix per treated acre, using a 3 foot wide swath and a travelspeed of 220 feet per minute (=2.5 miles per hour)?

Nozzle flow rate
= (25 x 3 x 220) divided by 43,560
= (16,500) divided by 43,560
= 0.38 gallons per minute.
If using 2 nozzles, select 2 that will give 0.19 gallon per minute eachat the selected pressure.


CHECKING HERBICIDE SPRAYER OUTPUT

Spray Pattern: Check uniformity of spray pattern, using corrugatedfiberglass roofing panels as a spray ing surface. Spray from the same heightas will be used in the orchard. Compare liquid volume collect ed in eachtrough.

Actual Spray Volume: With proper nozzles in stalled, travela measured distance at the selected speed and pump pressure. Use this formulato deter mine the actual spray volume in gallons per treated acre.

Gallons per Treated Acre = (Gallons sprayed during trial run x 43,560)divided by (Feet traveled during trial run x Swath width in feet).

EXAMPLE 2: You emptied a tank containing exactly 3 gallons in a distanceof 1,200 feet. The treated swath was 3 feet wide. How many gallons of sprayare you applying per treated acre?

Gallons per Treated Acre
= (3 x 43,560) divided by (1,200 x 3)
= (130,680) / (3,600)
= 36.3 gallons

If you want to apply 4 lbs. of herbicide per acre, then in this case youwould add 4 lbs. of herbi cide to each 36 gallons of water in the tank.

Agitation: If herbicides are allowed to settle or sepa rate in thesprayer tank, distribution in the orchard will not be uniform. Provide constantagitation when using wettable powders, or any other insoluble formulation(emulsions, emulsifiable concentrates, dry flowables, liquid flowables,and suspensions). Use defoaming adjuvant when needed to control excessive foam.

1996-1997 New England Apple Pest Management Guide