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We survey CFOs throughout the COVID-19 crisis to learn how multiple dimensions of corporate flexibility affect their short- and long-term business plans. We find that i) workplace flexibility, namely the ability for employees to work remotely, plays a central role in modulating firms’ employment plans during the health crisis; ii) investment flexibility allows firms to increase or decrease capital spending based on their business prospects in the crisis, with effects shaped by workplace flexibility; and iii) financial flexibility contributes to stronger employment and investment, with effects shaped by the firm’s cost structure. While the role of workplace flexibility is new to the COVID crisis, CFOs expect lasting effects on employment and investment as low workplace flexibility firms adopt automation to replace labor.

This article reviews approaches to analytical pesticide deposition modeling for aerial, ground boom, and orchard airblast sprayer applications, and describes modeling approaches including the Lagrangian model commonly used for aerial spraying, which tracks the mean position and standard deviation of spray material released into the ambient environment. This review also describes the approaches used in mechanistic ground sprayer modeling, including near-nozzle effects and spray sheet obstruction of the ambient flow. The random-walk approach for ground spraying and the significant computational fluid dynamics (CFD) problem associated with modeling orchard airblast spraying are also described. These mechanistic approaches predict the spray deposition downwind from an application area for any set of initial conditions, and can recover results consistent with field datasets. Incorporation of spray deposition modeling into a Geographic Information System (GIS) platform is also discussed.

The biological target is becoming increasingly more important in pesticide spray evaluation and to research directed toward improving the safety and effectiveness of pesticides. Various techniques have been used to study the nature of drops which impact and deposit on tree foliage. A few basic techniques are summarized in this paper. Additionally, results are presented on the assessment of drops directly on foliage of slash pine (Pinus elliottii Engelm.) and Ocala sand pine (Pinus clausa [Chapm. ex Engelm.] Vasey ex Sarg. var. clausa). This was one of several techniques used to assess spray coverage from an aerial spray on a project conducted by the United States Department of Agriculture, Forest Service, in cooperation with the Florida Forest Service. Testing was conducted at the Withlacoochee State Seed Orchard, Florida, during February 1980. Results show a greater deposit of spray drops in the upper tree crown than in the lower crown. This was true for both pine species; however, fewer drops per linear length of needle were found on the Ocala sand pine when compared to the slash pine. Zusammenfassung Zur Tropfchenverteilung auf Kiefernnadeln bei aviochemischen Bekampfungsmasnahmen Im Hinblick auf die immer wichtiger werdenden biologischen Aspekte sowie die Erzielung noch groerer Sicherheit und Wirksamkeit bei der Ausbringung pestizider Spruhmittel wird ein Literaturuberblick uber verschiedene Spruhtechniken und ihre Ergebnisse gegeben. Zusatzlich werden die Erfahrungen aus eigenen Versuchen, die in den USA an Pinus elliottii und P. clausa im Februar 1960 durchgefuhrt wurden, mitgeteilt. Es ergab sich bei beiden Kiefernarten eine grosere Ablagemenge an Tropfchen in der oberen Kronenregion, jedoch waren die Nadeln von Pinus clausa pro Langeneinheit mit einer groseren Zahl Tropfchen belegt als jene von P. elliottii.

A deterministic Eulerian model of aerial pesticide application is introduced. Various assumptions allow the model to include transport of aerosol droplets with a continuous size distribution, vapour production, on-target deposition, off-target drift, and to consider interactions with plant canopies. The model allows optimization of mechanical parameters such as nozzle type, site constraints such as canopy and pest densities, and application approaches such as aircraft type. Simplifying assumptions are introduced which significantly reduce computational complexity, yet allow important dynamical parameters to be included in the optimization or simulation. An optimization example is demonstrated; such optimization would not be possible with the larger pesticide application models currently being used.

The near-wake portion of the USDA Forest Service aerial application prediction model FSCBG is applied to a sensitivity study of the length of the spray boom relative to the length of the aircraft wingspan or helicopter rotor diameter. Building on extensive previous work, this study examines the predictions by the near-wake Lagrangian trajectory model of swath width, mean deposition within the spray block, and drift fraction downwind of the edge of the field. Ten aircraft and four BCPC droplet size distributions are used to simulate a typical agricultural application scenario. Findings from this study demonstrate the effects of varying boom length on downwind drift, the reduction of downwind drift with larger droplets, and the inherent ability of certain aircraft type to reduce downwind drift more easily than others. Model results indicate that a broad range of boom length (between 60 and 100% of aircraft wingspan or helicopter rotor diameter) recovers approximately the same levels of downwind drift, decreasing levels of mean deposition within the spray block, and increasing swath width between flight lines. The suggestion that boom length should be less than 75% of wingspan or rotor diameter is perhaps based more on the anticipated position of the rolled-up vortices than on solid experimental evidence.

Drift of the pesticide Bacillus thuringiensis Berliner var. kurstaki (Bt) was measured downwind from a gypsy moth (Lymantria dispar L.) treatment block in mountain terrain. The study was conducted in conjunction with a project to eradicate the moth along the Wasatch mountain range of Utah. Objectives of the study were to quantitate drift, to evaluate drift sampling methods, and to compare FSCBG (Forest Service Cramer-Barry-Grim) computer model predictions to field measurements of Bt based on colony-forming units. The treatment block was sprayed by helicopter three times, within a 12-d period during June 1991, which provided a study of three replicates. During each spray, downslope drainage winds carried the spray over an array of samplers that extended 3,150 m downwind. The FSCBG dispersion model, exercised after the treatments, used meteorological inputs measured during the treatments to predict spray deposition and airborne dosage of Bt. Results of the study demonstrated a correlation among dosage, deposition and total flux samplers; a potential of Bt drift of at least 3,150 m; and FSCBG model predictions that generally followed the field recovery data.

The development of the aerial spray dispersion model FSCBG (Forest Service, Cramer, Barry and Grim) by the USDA Forest Service and the U.S. Army is reviewed. FSCBG predicts the behavior of spray material released through nozzles into the wake of a spray aircraft (helicopter or fixed-wing), traveling through idealized atmospheric effects, penetrating a canopy and depositing on the ground. FSCBG contains simplified models for the complex flow structure behind aircraft and the mechanisms that affect the fate of aerially released material: downwind drift, evaporation, canopy penetration, and ground and canopy deposition. Model development efforts encompass the areas of spray behavior, aircraft wake effects, meteorological influences, canopy interaction, and deposition. These efforts are supplemented by model validation with field tests. The ability of the model to quantify off-target spray drift is particularly important.

Aerial applications of esfenvalerate in a Douglas-fir seed orchard in the Oakridge Ranger District of the Willamette National Forest are used to evaluate the effectiveness of insecticide treatments to control seed and cone insects of Douglas fir. Data from Kromekote spray deposition cards are compared with canopy penetration and deposition predictions from FSCBG, a Forest Service computer model that predicts the behavior of pesticide sprays released from aircraft. Predictions of canopy penetration and ground deposition am within an average of 7.8% of the overall field dataset. These results demonstrate the usefulness of the simulation model for selecting spray application parameters and describing the environmental distribution of pesticides.

Soil and leaf populations ofBacillus thuringiensis(Bt) were monitored following aerial application of commercial Bt formulations at the rate of 72 billion international units per acre per year during a 5-year period. Data from soil sample spore counts suggested that Bt spores persisted in Wasatch forest soils for up to 2 years but they did not proliferate. Bt isolates were recovered from leaf samples 12 months post application from sprayed, previously sprayed and from nonsprayed areas. The frequency and diversity of Bt isolates recovered from leaves was independent of sample area spray history. In accordance with U.S. Forest Service criteria, aerial application of Bt during a 5-year period resulted in the eradication of gypsy moth (Lymantria dispar,L) from the Wasatch Front region of the Wasatch Mountain Range, Utah.

A series of aerial applications were made with a helicopter and a biplane to evaluate the feasibility of using aircraft to apply 5 gallons per acre of a water-base spray to southern pine seed orchards. Application parameters were established by a mathematical model which predicts spray coverage. Data obtained on spray deposition at the canopy top and in the tree crown provide a basis for using aircraft to apply pesticides to seed orchards. More spray deposits were found in the upper tree crown than in the lower tree crown. The helicopter achieved higher quantities of deposit in the crown than the biplane. On a percentage basis, however, spray observed at each of the 3 crown levels was comparable in both aircraft. A greater number of spray drops was observed on the slash pine (Pinus elliottii Engelm.) needles than on the Ocala sand pine (Pinus clausa var. clausa (Chapm. Ex Engelm.) Vasey ex Sarg.), suggesting that higher application rates may be required to achieve comparable coverage in densely foliated pines. Under conditions similar to these trials, i.e. aircraft tank mix, drop size, foliage, meteorology, release height, and swath width, one should expect comparable results when treating southern pine seed orchards.

INSECTICIDE drops were counted and sized on coniferous foliage following application of Bacillus thuringiensis, carbaryl, and trichlorphon insecticides to forested areas in Montana, for control of western spruce budworm, Choristoneura occidentalis Free. Majority (86 to 94 percent) of drops observed on con-iferous foliage was < 61 pan in diameter. These an-alytical data are important in any fundamental eval-uation of the actual mechanism of transport and de-position of pesticide spray droplets in a forest environment.

OVER the last 4 years the USDA Forest Service and the DOD Atmospheric Sciences Laboratory have continued the development of the AGDISP (AGricultural DISPersal) computer code that predicts the deposition of material released from helicopters or fixed-wing aircraft. The features of the code are reviewed and the predictive capability of the code is assessed by comparison with recent test data. Code applications and limitations are also discussed.

Dugway Proving Ground conducted 10 trials of the DC-7B aircraft aerial spray system during October 1974. Two spray formulations were disseminated and evaluated using three flow rates. Spray droplets were sampled vertically on towers and horizontally on ground surfaces. This report presents data on deposition and impaction sampling, droplet spectra, spray mass deposit, swath width, and mathematical modeling of the spray behavior. (Author)