Date 27 August 1992

Title of Project Analysis of Spraying Systems for the Greenhouse

Institution where work is being conducted University of California - Davis

Amount of Endowment Grant $ 12,000
Covering Period 1/1/92 to 12/31/92

Anticipated Date of Project Completion/Final Report January 1993

Individual(s) Conducting Project:

(List Project Leader First)

Ken Giles - Title Associate Professor

Telephone Number 916-752-0687

Mike Parrella - Title Chair and Professor

Spray Application for the Greenhouse

Ken Giles and Mike Parrella

University of California-Davis

Progress Report to the American Floral Endowment, 8/27/92

A. Project Objectives:

The objectives of the project are to determine pesticide deposition and dissipation characteristics of air-atomization,electrostatic spraying equipment and to compare the characteristics to those of conventional,

“wet” sprayers. The goal is to improve pest control efficacy and reduce the amount of pesticide used and

the accompanying human hazard in greenhouses.

B. Summary of Work Since Project’s Inception, andC. Results to Date:

Greenhouse trials of conventional, “wet” spray and electrostatic (ESS, Inc.) applications have beenconducted at Oki Nursery in Sacramento, CA. Permethrin (formulated as PounceTM 3.2 EC) was applied

to florist chrysanthemums grown at 4 plants per 6 inch pot. Using both application techniques, Pounce

was applied at a rate of 40 oz/acre in application volumes of 5 gal/acre for the electrostatic system and

250 gal/acre for the conventional system. To study the effects of different weather conditions,

applications were made in winter and summer tests. Pesticide deposition and residue on the

chrysanthemum foliage was measured at 1, 3, 7 and 14 days after application. Pesticide deposition was

also measured on the bench tops, aisle ways and underneath benches. Preliminary results from the

testing were discussed in the March 1, 1992 project report.

Follow-up analysis has investigated the durability or dislodgeability of spray deposition on the plantfoliage. The ease of which pesticide residue can be removed from the plant surfaces may be closely

related to the exposure of re-entry workers to applied pesticide. This is a great concern since our

previous work has shown that electrostatic spraying can result in 2-4 times more deposit of pesticide on

plant leaves. With cooperation from the Worker Health & Safety Division of the California Department

of Pesticide Regulation, a procedure has been developed to “brush” leaf samples and remove pesticide

residue by dry, mechanical means. A wet, detergent, wash method is typically used to remove pesticide

from leaves for analysis and estimation of worker hazard. This is believed that the dry, brushing method

may be a more accurate way to estimate cultural worker exposure.

Figure 1 (over) shows the relative amounts of pesticide that was removed from the chrysanthemumleaves which had been treated with conventional, wet spraying and electrostatic, reduced-volume

spraying. While the wash technique showed the typical 3-4 fold increase in electrostatic deposition, the

dry, brushing method showed much less difference between application techniques. These results may

indicate that application techniques that increase spray deposition may not necessarily increase potential

worker exposure.

D. Future Plans Covered by the Endowment Grant:

Future plans are to continue field studies of reduced-volume application of pesticides, particularly biorationalmaterials. Worker safety has become a primary concern with regard to reduced-volume spray

application. Studies are being designed which directly address worker exposure to pesticides from

conventional and reduced-volume spraying.

E. Anticipated Benefits for Floral Industry:

The anticipated benefits to the floral industry are reduction in application rates of pesticide required forefficacious pest control. Information regarding worker exposure, residue dissipation and reduction in

greenhouse contamination (pesticide on non-target areas) may assist in regulatory decisions regarding the

equipment.

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