Development of a Simple Method to Evaluate the Deposition of Pesticide Droplets

DEVELOPMENT OF A SIMPLE METHOD TO EVALUATE THE DEPOSITION OF PESTICIDE DROPLETS

A report to the Viticultural Consortium

Dr Andrew Landers

Cornell University 2nd January 2002 DEVELOPMENT OF A SIMPLE METHOD TO EVALUATE THE DEPOSITION OF PESTICIDE DROPLETS

OBJECTIVES

1. To improve the standard of crop spraying and the understanding of safer pesticide application

2. To develop a simple, readily adopted method of identifying spray deposits

3. To evaluate the effectiveness of such a deposition test in the vineyard

4. To assist farmers and growers in their selection of appropriate technology to reduce pesticide use and minimise environmental pollution via correct targeting of sprays.

BACKGROUND

How do growers assess how effective a crop sprayer is at depositing the spray into the target? The leaves of a grape canopy tend to shingle and sometimes prevent droplet penetration into the centre of the canopy. How can growers compare the effectiveness of novel direct deposition sprayers against traditional airblast designs? How much hits the target and how much drifts – deposition techniques can detect drift.

When water is used in extension meetings, only a few growers go into the rows to see good or bad deposition. Water is difficult to see on the green leaf surfaces.

Water sensitive cards certainly help, they show where water droplets have hit the upper or lower leaf surfaces, how close the water deposits are to the grape cluster. The problem occurs when needing to replicate the position of the cards to compare different spraying machines.

Deposition systems were developed which: a) shows deposition within the canopy b) allows repeatability for comparing different sprayers and c) allows a degree of portability

Trials were conducted using:

1. Water and tracers A number of food safe dyes are available in the market place, some require Ultra-violet (black-light) to detect droplets but growers often have to wait until dark to see the droplets. A number of commercially available tracers were tested for their effectiveness in daylight. Table 1 shows the results, it can be clearly seen that Saturn yellow at 30% solution performed best in daylight on all leaf colours of the traditional tracers. When the same product was diluted to 5% it became more difficult to see it, unless a daylight UV lamp was used. Saturn Yellow maybe obtained from 1-800 4DAYGLO TABLE 1 FIELD TESTS OF DIFFERENT TRACERS ON DIFFERENT COLOURED GRAPE LEAVES

Tracer Dark leaves Mid range Light Leaves

Blaze Orange Bright and visible without UV, the lamp does Slightly harder to see Bright, better visibility compared to the dark and 30% brighten some deposits mid range leaves 8/10 7/10 9/10 Saturn Yellow Very bright with good contrast against back Very bright with good contrast against back Very bright still no UV needed but maybe not as 30% ground, don’t require UV light ground, don’t require UV light bright as on darker leaves. 9-10/10 9-10/10 9/10 Saturn Yellow Can Only see large drops without light UV Can see deposits with lamp when shaded Deposits progressively more difficult to see as 5% brightens but shading is necessary 4/10 without light 8/10 with UV leaves lighten 5/10 without light 8/10 with UV 2/10 without light 7/10 with UV Furness Yellow Cant see without UV, deposits are also only Still poor, need shade and UV Require lamp and shade visible with some from of shading 2/10 2/10 2/10 Surround No UV required, stark contrast between the No UV required, stark contrast between the No UV required, good contrast between the white white deposit and leaf white deposit and leaf deposit and leaf 9-10/10 9-10/10 9/10 Surround, an organic insecticide, based upon Kaolin clay, was also tested and found to be highly visible and less expensive than Saturn yellow. Surround: 25lbs in 50 gallons – requires good agitation, make sure it is premixed before going into the spray tank!!

Surround maybe obtained from: www.engelhard.com

3. Ultra-violet lamps Ultra violet lamps are useful in a darkened room to show individual leaves removed from the canopy. UV tracers, as described in the table above, can be used and the lamp shows quite clearly the droplets. A new lamp, developed in Sweden and claimed to work in daylight was evaluated. The Labino lamp was certainly rugged and with its battery pack is ideal for field use although it is frightfully expensive. Unfortunately it doesn’t work well in bright sunshine and needs shade for it to work moderately well, like an inexpensive UV black light it works perfectly well in a darkened room.

Labino maybe viewed at: http://www.labino.com/

4. Water sensitive cards and strips These cards and strips are available in 3” x 1”, 3” x 2” and 20” x 1” lengths. They can easily be attached to leaves with paper clips or staples as long as the canopy is dry and the user wears rubber gloves. They are used extensively by the Spray Team at Cornell where a removable record of deposition is required for further analysis. They are quite expensive, around $35.00 for a pack of 50 cards, 3” x 1”. They maybe obtained from: Spraying Systems Co. PO Box 397 Dillsburg, PA 17019 717 432 7222 http://www.teejet.com/

Water sensitive strips can also be used to show drift deposition, they can be attached with staples to long wooden poles, 1” x 3” x 14’, in adjacent rows to the target row and demonstrate where water droplets are directed from an airblast sprayer.

Alternatives to water sensitive papers are: a) Chromocote paper cut into 2” x 1” strips attached to the leaves. A pink foam dye from Precision Labs, 847 498 0800, placed into water in the sprayer tank is sufficient to give bright pink droplets onto the cards. b) Plain glossy business cards or file cards maybe used in conjunction with a readily available kitchen food dye. 5. Droplet scan An objective assessment method, using a desktop scanner can be used to assess droplets obtained from water sensitive paper. The system, developed by WRK of Arkansas will provide the user with information regarding the %area covered, droplet size, number of droplets etc. It is used for research purposes at Cornell and is still to be evaluated in a field/barn situation. It is extremely expensive.

6. Air direction indicators It is important to know the direction the air is blowing from an airblast sprayer. Where the air goes, the droplets will follow. A simple demonstration device was developed to show air movement. Cotton ribbons, 12” long were attached to a 12” grid of mono- filament line. The whole assembly is fitted to a frame, 4’ x 14’ made of 3” diameter plastic pipe and can be assembled in a vineyard onto a wooden base. Ribbon units may be situated side by side to see the distance the wind blows, as in plate 1. Any adjustments made to deflectors for example maybe clearly seen.

7. A standard, portable penetrometer A frame was built which mimics a standard canopy, it ensures uniformity of target when comparing different crop sprayers. One of the problems with comparing sprayers in action is the canopy varies so much along the row and within the vineyard. The standard penetrometer allows direct comparisons to be made against a standard. The frame can be placed at the end of a row, the sprayer passes and the individual frames panels drawn out to show the audience. Water sensitive paper attached to the frame panels indicates penetration, see Plates 2 & 3, Figure 2.

Acknowledgements

I would like to acknowledge the technical help of Doug Caveney, Jean Benjamin and Mike Helms in constructing the Ribbon air flow frame and the penetrometer. Funding for this project was provided by the Viticultural consortium, Lake Erie Regional Grape Program, Grape production research fund, New York wine growers, and the Wine and Grape foundation

Plate 2 Penetrometer showing 4 panels of 4” plastic pipe

Plate 3 showing panel 2 opened to show penetration

1 Tractor and sprayer