Orchard Sprayer Research Articles

ATMOSPHERIC STABILITY EFFECTS ON PESTICIDE DRIFT FROM AN IRRIGATED ORCHARD

Spray transects through an 11-m-tall pecan orchard with an air-blast orchard sprayer were replicated 10times over a wide range of atmospheric stability conditions. Drift was measured by collecting tracer (malathion) usingground plates (f), high volume air samplers (hv), and string (s) collectors distributed downwind in the adjacent field outto a maximum distance of 18 canopy heights (198 m). Atmospheric conditions were measured above the orchard canopywith fast-response, three-dimensional wind, temperature, and humidity sensors. Atmospheric stability, characterized bythe surface layer stability parameter ( ), was the primary factor affecting drift amounts measured on and above theadjacent field. On average, the total amount of drift caught by the samplers in very stable conditions was 5.9, 3.6, and 2.1times the amount of drift in unstable conditions for the plates, the hvs, and the strings, respectively. The transition fromone condition to the other took place over a very small stability range where the air was dynamically stable (0.0 < <0.3). In this range, very small changes in atmospheric conditions resulted in very large changes in the atmospheresaerosol transport characteristics. The effect of stability on the amount of drift collected in the adjacent field is describedby a symmetric hyperbolic tangent function over the entire range of stability encountered.

Comparison of spray operator exposure during orchard spraying with hand-held equipment fitted with standard and air injector nozzles

A field study using a patch method to assess operator exposure showed that compared to standard cone nozzles, spraying with air injection nozzles reduced exposure. The results indicate that this nozzle type deserves consideration as an efficient and economic contribution to safe application of plant protection products.

Rind distortion of lemon caused by Botrytis cinerea Pers

The infection process by Botrytis cinerea Pers. on lemon fruits (Citrus Union (L.) Burm.), and development of rind distortion are described. Infections occur on juvenile fruitlets soon after petal fall from hyphae growing over the surface of the fruit from adjacent colonised flower debris. The hyphae form compact infection cushions at their tips. There is a collapse of epidermal cells and several layers of underlying cells in the vicinity of the infection cushion, leading to the formation of small necrotic pits on the surface of the fruit. As the fruitlets grow, there is generalised hyperplasia in a zone up to 20 cell layers deep in the region of the necrotic pits, leading to conspicuous outgrowths on the fruit surface. The initial wound becomes stretched, flattened, and corky as the fruit enlarges. A cambial layer is located below the area of damaged tissue, fluorescence in the vicinity of the cork cambium indicates the presence of suberin in the cambium. There was no evidence of suberin or lignin deposition in the region of the original necrotic pit. The necrotic pits are characteristic of a non‐pathogenic reaction between the fungus and the host, with fungal hyphae failing to become established in the necrotic tissues of the pit. The hyperplasia leading to the rind distortions is considered to be a generalised reaction to the initial wound and is commonly observed in lemon following other types of injury to the rind. The principal sources of inoculum in orchards are Botrytis‐colonised floral debris caught up in flower clusters or adhering directly to the fruit surface. The etiology of the disorder helps explain why control by conventional fungicides is seldom successful. Not only are there physical limitations to providing a protective cover on very small fruit, but also the extended period over which flowering occurs in lemon imposes limits on the number of applications able to be economically applied. In the absence of effective control systems, growers are advised to modify husbandry practices such as lowering the density of shelter belts, opening lemon canopies to assist drying out of the flowers, and use of air blast orchard sprayers to physically remove floral debris from the vicinity of young fruit.

Cholinesterase inhibition in tree swallows (Tachycineta bicolor) and eastern bluebirds (Sialia sialis) exposed to organophosphorus insecticides in apple orchards in Ontario, Canada

Apple orchards occupy approximately 12,565 ha of land in Ontario, Canada, and are treated with the greatest number and applications of pesticides among all agricultural crops within the province. The potential for exposure to wildlife from frequent organophosphorus (OP) spray applications is therefore considerable. This study investigated the impact of agricultural spray ap- plications of azinphos-methyl, diazinon, phosalone, and phosmet in apple orchards on the cholinesterase (ChE) activity of wild birds nesting in orchards. These four OP pesticides ranked among the most widely used insecticides used on all fruit crops in Ontario in 1988. Tree swallows ( Tachycineta bicolor) and eastern bluebirds (Sialia sialis) were chosen as monitor species because they commonly breed and forage within apple orchards, utilize different feeding strategies, and are readily attracted to nest boxes. Brain and plasma ChE activities were determined for nestling bluebirds and swallows, and plasma ChE was measured in adult swallows for comparison with nestling data. In adult tree swallows, mean plasma ChE levels were significantly inhibited 41% compared to controls 12 h after a second application of azinphos-methyl. Mean plasma ChE activity in another group of adult tree swallows dropped by 21 and 19% following a multiple phosmet application. In nestlings, brain ChE activities obtained postspray often fell below predicted activities calculated from control siblings. This trend was especially apparent in the younger nestlings, less than 6 d old. However, for bluebirds the rates of increase of brain ChE with age in nestlings from treated sites was significantly lower than in nestlings from control sites. Brain ChE activity of two nestlings found dead following a phosalone application gave no indication that insecticide exposure was responsible. No other dead or moribund birds were discovered during the course of the study. Sequential plasma sampling of siblings, before and after OP application, was beneficial in reducing the required number of nests sampled by one half, but plasma ChE was less reliable overall than brain ChE in indicating exposure. Results of depressed ChE levels in tree swallows and eastern bluebirds inhabiting apple orchards are consistent with avian species in other orchard monitoring studies. No indication was found that OP exposure due to agricultural spraying in apple orchards adversely affected the survival of the birds we monitored.

SPRAY VOLUME RATE ERRORS IN INTERMITTENT OPERATION OF HYDRAULIC NOZZLES

Two air-carrier orchard sprayers, using centrifugal and diaphragm pumps, were operated at six nozzle selections commonly used to obtain low, medium, or high volume rates in Florida citrus applications. Nozzle pressure and flow rate were measured for the one- and two-sided operations. The difference in the pressure or flow rate was related to the application rate error. For all nozzle selections, closure of the nozzles on one side of the sprayer increased the operating pressure and the flow rate on the other (open) side. The sprayer with a diaphragm pump was much more sensitive to the flow restriction than the sprayer with a centrifugal pump. For the latter, the pressure difference peaked at about mid pressure range and decreased with further increase in pressure or flow rate. However, with the positive displacement pump, the difference generally decreased as operating pressure increased. Overall, the pressure error of the one-sided versus two-sided spraying was less than 20% for the centrifugal pump but exceeded 200% for the diaphragm pump system. The volume rate errors at 470, 2350, and 4700 L/ha nominal rates were 1.0, 3.5, and 3.5% (centrifugal) and 6.0, 7.5, and 47.0% (diaphragm), respectively.

Stochastic modelling of turbulent spray dispersion in the near-field of orchard sprayers

Abstract A Lagrangian approach is adopted to study the turbulent dispersion of spray droplets in the near-field of air-assisted orchard sprayers. In order to compute the mean and turbulent properties of the air flow generated by the moving sprayer, the generalised mass and momentum conservation equations, coupled with a k – e turbulence model, are solved numerically using finite volume methodology. These equations utilise a spatial-averaged porous medium model to take into account the effect of interactions between the air flow and crop. Airborne spray flux distributions have been calculated from ensemble-averaged particle trajectories predicted by two random-walk models (i.e. with and without temporal correlation). The results show that both stochastic models give reasonable agreement with measured drift profiles.

Codling Moth Control in Pears, 1997

Abstract The study was conducted on mature ‘Bartletty’ pear trees in a commercial orchard near Fairfield, CA. Eight treatments were replicated four times in a RCB design. Each replicate consisted of an individual tree. Treatments were applied with a handheld orchard sprayer operating at 200 psi and delivering 200 gpa of finished spray (2.87 gal/tree). Application timings were based on degree days (DD). DD were calculated with a 25 Mar biofix for the first generation and 1 Jun for the second generation using a single sine horizontal cutoff model with a: lower threshold of 50°F and an upper threshold of 88°F and with air temperature data from the IMPACT weather station in Cordelia. Target DD application timings (with actual DD timings and dates in parentheses) were: Knack and Comply with or without Volck oil at 100 DD (137 DD-8 Apr) followed by Azinphos-M at 650 DD (678 DD-16 May) from 1st biofix and 250 DD (311 DD-17 Jun) from 2nd biofix; Comply with Volck oil at 100 DD (137 DD-8 Apr) and 500 DD (521 DD-8 May) from 1st biofix followed by Azinphos-M at 250 DD (311 DD-17 Jun) from 2nd biofix; Danitol, Brigade, and Azinphos-M (industry standard) at 250 (294 DD-21 Apr) and 650 DD (678 DD-16 May) from 1st biofix and 250 DD (311 DD-17 Jun) from 2nd biofix. Control of the first CM generation was evaluated on 4 Jun by inspecting 50 fruit from the bottom of the tree canopy and 50 fruit from the top of the tree canopy/replicate. Control of the second CM generation was evaluated at commercial harvest on 21 Jul by inspecting a maximum of 125 fruit from the bottom of the tree canopy and 125 fruit from the top of the tree canopy per replicate. Control of motile TSSM, ERM, and PP nymphs was evaluated weekly from 4 Jun through 21 Jul by sampling 10 exterior and 10 interior leaves/replicate. The leaves were brushed and the motile TSSM, ERM, and PP nymphs were counted under magnification (20X).

Drift from orchard spraying

Research from 1989 to 1996 into drift from air blast orchard spraying, principally in kiwifruit blocks with live shelter, is reviewed. A mass balance study showed 96% of applied vinclozolin could be accounted for with 75% on the target crop, 19% on the ground or shelter and about 2% leaving the block as drift. Summarising results from 21 trials gave trends for both deposited and aerial drift outside the shelter to decrease exponentially with distance (distance for 50% decline, d0.5, ca. 26 m). Chlorpyrifos, pirimiphos-methyl and particularly diazinon gave elevated drift levels that persisted after spraying ceased. This was attributed to volatilisation from the crop. Typical drift levels for a range of pesticides were 0.5-5mg/m 3 in air samples and 20-200 mg/m2 in deposits 50 m downwind of shelter. Air measurements in urban areas 0.5-1 km from orchards detected low levels of chlorpyrifos and diazinon (5-40 ng/m 3). Drift levels were not strongly influenced by formulation, water rate (5002150 litres/ha) or wind speed (0.5-5 m/sec). Risks to human health from drift outside sprayed blocks were assessed as minimal.

Reducing spray volumes and dosages on conventional airblast orchard sprayers using low volume nozzle systems

Summary.Low volume, fine-droplet hollow cone (HC) Delavan nozzles were fitted to a conventional airblast machine in an attempt to reduce both the volume of spray and the dosage of chemical to thin apples. Red ‘Delicious’ trees at the Grove Research Station in southern Tasmania were thinned with ethephon at full bloom and the post-bloom thinner 6-benzyladenine at 20 days after full bloom. An unthinned control was compared with a treatment hand-thinned at 20 days after full bloom and chemically thinned treatments. The chemical sprays were applied with an airblast sprayer at high volume using conventional nozzles or Delavan HC nozzles at 50, 100, 200, 400 or 800 L/ha at 50, 75 or 100% of the dosage used at high volume. Most chemical treatments had some effect on the parameters measured when compared with the unthinned control while some were as effective as the hand-thinned treatment. The most consistent treatments were at 200 L/ha at the 75 and 100% dosages. Higher or lower volumes tended to be less effective, however, this could have been caused by either spray drift or evaporation of the smaller droplets used at these volumes. Although reducing the dosage to 75% did not reduce thinning effects, reduction of dosage to 50% resulted in significantly less thinning. These results offer a breakthrough for many orchardists to convert to low volume spray application very economically using the Delavan HC nozzles which produce a better droplet size than traditional high volume hydraulic nozzles. It also offers possibilities to significantly lower chemical usage by reducing dosage of chemical applied per hectare. Even more important is the reduction of wastage and pollution.

Twospotted Spider Mite Control with Cm-006,1996

Abstract The study was conducted in a commercial walnut orchard near Visalia, CA on 3-year old trees. Six treatments were replicated six times in a RCB design. Each replicate consisted of an individual tree. There was a buffer row in each direction from the experimental trees. Treatments were applied on 10 Jul with a hand-held orchard sprayer operating at 200 psi and delivering 37.5 gpa of finished spray (0.5 ga/tree). TSM were sampled weekly from 10 Jul (pre-treatment sample) through 7 Aug by collecting five leaflets per replicate. The leaflets were brushed and TSM were counted under magnification (20 X).

Control of Pecan Weevil in Pecans, 1995

Abstract Three insecticides were evaluated for control of pecan weevil (PW) on ‘Western’ cultivar of pecans. Trials were conducted at the Pecan Research Station located near Sparks, OK (Lincoln Co.) and were arranged in a RCB design with three single-tree replications. Timing of application was based on monitoring PW emergence from the soil using Tedder’s traps. Insecticides were applied when a threshold of 0.4 weevils/trap/day was captured. Based on this threshold, two applications were made, the first on 11 Sep and the second on 27 Sep. Treatments were applied using a PTO driven, air blast orchard sprayer calibrated to deliver 97 gpa. All chemical treatments were applied with a surfactant, Latron B-1956, at 0.5 pt/100 gal. PW populations did not reach threshold levels after the second application. Damage was evaluated at harvest (November) using random samples of 40 nuts/tree before cleaning. Each nut was cracked by hand and examined for presence of weevils. Percentage infestations were calculated for each tree, then data were analyzed using ANOVA with mean separation by DMRT.

Codling Moth Control in Pears, 1996

Abstract The study was conducted on mature ‘Bartlett’ pear trees in a commercial orchard near Fairfield, Calif. Eighteen treatments were replicated 4 times in a RCB design. Each replicate consisted of an individual tree. Treatments were applied with a hand-held orchard sprayer operating at 200 psi and delivering 200 gpa of finished spray (2.87 gal/tree). Application timings were based on degree days (DD). DD were calculated with a 31 Mar biofix for the first generation and 17 Jun for the second generation using a single sine horizontal cutoff model with a lower threshold of 50°F and upper threshold of 88°F. Air temperatures were taken from the IMPACT weather station in Cordelia. Target degree-day timings and “actual timing-date” in parentheses were: V-71639 and CGA-59205 at 100 (104-10 Apr) and 500 DD (523-14 May) from 1st biofix; CM-001 at 200 (216-25 Apr) and 600 DD (699-28 May) from 1st biofix and 200 DD (280-1 Jul) from 2nd biofix; CM002/X, Brigade and Azinphos-M (grower standard) at 250 (288-29 Apr) and 650 DD (699-28 May) from 1st biofix and 250 DD (280-1 Jul) from 2nd biofix. Due to rain on 15 through 18 May and again on 21 May and high winds through 25 May, the 600 DD and 650 DD applications were postponed until 28 May (699 DD). In addition, V-71639 and CGA-59205, which were applied on 14 May, were retreated on 28 May. Control of the first CM generation was evaluated on 6 Jun by inspecting 50 fruit from the bottom of the tree canopy and 50 fruit from the top of the three canopy per replicate. Control of the second CM generation was evaluated at commercial harvest on 22 Jul by inspecting a maximum of 125 fruit from the bottom of the tree canopy and 125 fruit from the top of the tree canopy per replicate. Control of motile TSM, ERM and PP nymphs was evaluated weekly from 18 Jun through 16 Jul by sampling 10 exterior and 10 interior leaves/replicate. The leaves were brushed and the motile TSM, ERM and PP nymphs were counted under magnification (20X).

Cell wall metabolism in gibberellin-treated persimmon fruits

The application of gibberellin [GA3] to persimmon fruits as an orchard spray, at least 2 weeks prior to harvest, has been shown to delay ripening of the fruit on the tree and its rate of softening after harvest. This effect persisted during and after cold storage. The delay in softening has been attributed to the effect of the phytohormone on cell wall metabolism. To examine this hypothesis, cell walls of GA3-treated fruit were compared to those of non-treated fruit. Comparison between fruit was from harvest till the termination of post-storage softening. The study included TEM examinations, assay of certain hydrolase activities and determination of compositional changes occurring in the various cell-wall carbohydrate polymers. Our findings indicate that GA3 either delays or inhibits all of the cell wall changes that were found to accompany fruit softening, including dissolution of the middle lamella, separation of the plasmalemma from the cell-wall, mitigation of the structural coherence and density of the primary cell wall, increases solubilization of pectic polymers, loss of neutral sugars, predominantly arabinose and galactose, and increased activities of exo-polygalacturonase [PG] and endo-1,4-β-glucanase [EGase]. The principal discernible compositional difference between GA3-treated fruit and control fruit at harvest was a higher total carbohydrate content in the cell wall material extracted from GA3-treated fruit, which was due chiefly to an increased amount of cellulose.

Testing of crop protection equipment in use in Europe1

A comparative analysis has been made of the testing of field and orchard sprayers in European countries, and of glasshouse sprayers in The Netherlands. The tests are mostly voluntary. but there is movement towards compulsory testing. The elements of sprayer perforniance and construction which are tested are summarized. The main defects encountered in testing spray equipment in The Netherlands are presented.

Distribution quality of orchard sprayers1

Studies of the variability of initial deposition on leaves from orchard sprayers showed that both minimum and maximum values and the coefficient of variation of the amounts deposited increased in a linear manner with the application rate. The minimum and maximum amounts of deposit are important for biological efficacy, potential development of resistance. determination of the dose rate and effects on beneficial organisms. Measurements of the amounts deposited on leaves at different tree heights showed that the reproducibility of curves is considerably interfered with by random effects. There was not always a connection between these curves and measurements on a lamellate vertical distribution test stand. Measurements of vertical distribution from a fixed position differed considerably from those produced with forward movement.

Results of a European programme to compare methods used to test orchard sprayers1

A research programme was set up by European Institutes to compare the testing methods employed by their laboratories to measure characteristic parameters of air‐assisted orchard sprayers. The parameters studied in this programme were: air flow rate, air velocity and liquid distribution. The study showed differences between the laboratories. which could partly be explained as resulting from the measuring devices or the testing methods. Recommendations are given to avoid major measurement errors.

Codling Moth Control with Insect Growth Regulators, 1995

Abstract The trial was conducted in a commercial walnut orchard near Tracy, Calif. Twelve treatments were replicated four times in a RCB design. Each replicate consisted of an individual tree. Treatments were applied with a hand-held orchard sprayer operating at 300 psi and delivering 400 gpa of finished spray (5.7 gal/tree). Application timings were based on degree days (DD). DD were calculated with a 2 Apr biofix for the first generation and 25 Jun biofix for the second generation using a single sine horizontal cutoff model with a lower threshold of 50°F and an upper threshold of 88°F and with air temperature from the San Joaquin County weather station in Tracy. Target application timings were: Confirm and Neemix-250 DD from 1st and 2nd biofix and 1250 DD from 2nd biofix, Dimilin-300 DD (combined with Lorsban), 900 and 1900 DD from 1st biofix, Comply and Pyriproxyfen-300 DD (combined with Lorsban or Lorsban alone) from 1st biofix, 100 and 1100 DD from 2nd biofix and grower standard-300 DD from 1st biofix, 250 and 1250 DD from 2nd biofix. Control of the overwintering CM generation (first application) was evaluated by inspecting all dropped nuts weekly from 31 May through 7 Jul for CM infestation. In addition, control of the overwintering generation was evaluated by banding each tree with single sided corrugated cardboard on 15 May. The cardboard was removed and inspected for CM larvae or pupae on 7 Jul. Control of the summer generations was evaluated by inspecting 100 nuts/tree at commercial harvest on 18 Sep for CM and NOW infestation.

Timing of Confirm Applications for Codling Moth Control, 1995

Abstract The study was conducted on mature ‘Bartlett’ pear trees in a commercial orchard near Fairfield, Calif. Five treatments were replicated four times in a RCB design. Each replicate consisted of an individual tree. Three Confirm application timings (100, 200 and 300 degree days (DD)) were applied after the beginning of each CM flight and were compared to Guthion at 200 DD and an untreated control. DD were calculated with a 2 Apr biofix for the first generation and 25 Jun biofix for the second generation using a single sine horizontal cutoff model with a lower threshold of 50° F and upper threshold of 88° F and with air temperature from the IMPACT weather station in Cordelia. Treatments were applied with a handgun orchard sprayer operating at 200 psi and delivering 400 gal/acre of finished spray (3.85 gal/tree). Control of the first CM generation was evaluated on 13 Jun by inspecting 50 fruit from the bottom of the tree canopy and 50 fruit from the top of the tree canopy per replicate. Control of the second CM generation was evaluated at commercial harvest on 24 Jul by inspecting 125 fruit from the bottom of the tree canopy and 125 fruit from the top of the tree canopy per replicate.

Aerial Applications of Esfenvalerate to Suppress Contarinia oregonensis (Diptera: Cecidomyiidae) and Megastigmus spermotrophus (Hymenoptera: Torymidae) in Douglas-Fir Seed Orchards

Aerial applications of esfenvalerate significantly reduced populations of a Douglas-fir cone gall midge, Contarinia oregonensis Foote, and a Douglas-fir seed chalcid, Megastigmus spermotrophus Wachtl, in mature Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, seed orchards. Populations of the spruce spider mite, Oligonychus ununguis (Jacobi), increased significantly in treated areas. Our results demonstrated that aerial applications can be made under conditions in the Pacific Northwest and can reduce insect damage levels with between 10 to 20 times less metric insecticide than when high-volume orchard sprayers are used.

Codling Moth Control with Insect Growth Regulators, 1992

Abstract The trial was conducted on ‘Serr’ walnuts in a commercial orchard near Arbuckle, Calif. Five treatments were replicated 4 times in a randomized complete block design. Each replicate consisted of an individual tree. There was a buffer tree in each direction from the experimental trees. Treatments were applied with a hand-held orchard sprayer operating at 300 psi and delivering 400 gal/acre of finished spray (8.3 gal/tree). RH-5992 at 0.125 lb Al/acre was applied on 15 Apr (CM egg deposition) and again on 11 May. RH-5992 at 0.25 lb Al/acre, Imidan and Lorsban (grower standard program) were applied on 27 Apr (5-10% CM egg hatch) for the overwintering generation. In addition, RH-5992 at 0.125 lb Al/acre was applied on 3 Jun (start of oviposition for the first CM generation) and again on 24 Jul, while RH-5992 at 0.25 lb Al/acre, Imidan and Guthion (grower standard program) were applied on 17 Jul (5% to 10% egg hatch of first generation). Control of the overwintering generation was evaluated by counting all CM-infested dropped nuts weekly from 26 May through 24 Jun. Control of the first generation was evaluated by inspecting 100 nuts/tree at commercial harvest on 17 Sep for CM and NOW infestation.