Evaluating new nozzles and their placement for improving spray coverage and effectivness of fungicides on beets

Andrew Landers, Pesticide Application Technology Specialist,

Dept. of Entomlogy, Cornell University, NYSAES, Geneva, NY14456

George Abawi, Professor, Dept. of Plant Pathology, Cornell University, NYSAES, Geneva NY14456

The goals of this project were to evaluate available sprayer nozzles that will target and maximize spray coverage for improving the efficacy of Quadris in controlling pocket rot (Rhizoctonia solani) and leaf spot diseases of beets. The effectiveness of different nozzles and different mounting positions on the boom (one on top of the row vs. two nozzles at 45 degree angle/row) were evaluated for pocket rot control in the experimental plot at Geneva.

New drift reducing nozzles improve coverage by delivering more spray to the appropriate target and also by reducing drift. It is important to evaluate spray coverage by looking at both the level of disease control as well as using targets such as water sensitive paper because disease control is the ultimate measure of coverage and includes measurements on the entire canopy.

Cone nozzles on a boom sprayer provide poor distribution patterns compared to flat fan nozzles. Dropleg nozzles certainly get the spray down into the canopy but are in danger of being damaged or even broken as they operate so close to the ground.

Two nozzles with good potential to improve coverage were selected for this trial:

1. Twin-jet flat fan nozzles use forward and rearward pointing flat fans, this in effect gives two applications, one as the sprayer travels towards the target and one application as the sprayer moves away. To ensure the application rate remains constant (and comparable with flat fan/cone nozzles), the quantity of spray from the forward fan is 50% of output and a similar % from the rear. The net effect is smaller droplets for a given output. Smaller droplets stick to leaves, therefore the potential for better deposition maybe acceptable.

2. Air induction, air inclusion or venturi nozzles are flat fan nozzles where an internal venturi creates negative pressure inside the nozzle body. Air is drawn into the nozzle through two holes in the nozzle side, mixing with the spray liquid. The emitted spray contains large (450 micron) droplets filled with air bubbles (similar to a candy malt ball) and virtually no fine, drift-prone droplets. Normally these droplets would be large enough to bounce off their target. However, because of the air they explode on impact and spread over the leaf as the air absorbs the impact load. Coverage is similar to conventional, finer sprays when used as a fan nozzle in herbicide application, it will be interesting to see if they cover the leaf well enough for disease control. The major advantage of air induction nozzles is reduced drift, very important when working near water courses thus providing the grower with a minimum buffer zone.

The nozzles were fitted to a standard boom and to a dropleg system. The twin-jet nozzles were also pointed inwards at 45degrees towards the plants thus giving a three angle direction towards the target: forwards and backwards at 45 degrees and, by using a two inch long angled pipe, inwards at 45 degrees.

Procedures:

Research trials were conducted at the vegetable research farm of the NYSAES, Geneva.

Physical effectiveness:

Spray coverage was evaluated using 2 x 20inch water sensitive papers placed between the rows, either side of the target row to monitor deposition. 1 vertical water sensitive strip was placed next in the row adjacent to the target row to detect drift

Standard Boom

Trial 1Red04flat fan2 mph40 psi40 gpa

Trial 2Red04Air Induction 2 mph40 psi40 gpa

Trial 3Red04Twin Jet 2 mph40 psi40 gpa

Modified Boom

Trial 4Yellow02Twin jets, angled holder on boom40 psi40 gpa

Trial 5Yellow 02Droplegs + Twin jets40 psi40 gpa

Trial 6 Yellow02Droplegs + Flat fan40 psi40 gpa

Results

The data obtained on the deposition and drift on the WS paper clearly showed that Trials 4 & 5 gave the best overall physical deposition with an acceptable, low level of drift.

horizontal sections are left+right of the target row
Trial / % coverage on left of target row / % coverage on right of target row / % coverage on vertical water sensitive paper
1 / 100% / 45% / 1%
2 / 80% / 40% / 0.50%
3 / 100% / 75% / 5%
4 / uniform throughout 95% / uniform throughout 95% / 0.50%
5 / 95% / 90% / 1%
6 / 25% / 20% / 1%

Quadris at 9.6 fl oz/A at 2-week interval was highly effective in reducing pocket rot, Cercospora leaf spot and powdery mildew diseases occurred on beets in this trial (Table 1). Surprisingly, all the nozzle types, nozzle positions and spray volume treatments were about equally effective in reducing the severity of beet diseases. The latter might be the result of the high efficacy of the fungicide treatment used and/or the frequent over-head irrigations that were applied (6 inches in 10 applications during July - October) to promote diseases development in the plot area. Under normal weather conditions or using a lower rate of Quadris, considerable differences in diseases suppression might be observed among the various nozzle types and positions as well as the spray volumes included in the present investigation.

Table 1. Yield and diseases of table beets after Quadris sprays of different nozzle type, arrangement and gallonage. NYSAES Research Farm, 2002.
Beets / 10 ft. row / % Pocket Rot / Foliar Ratings 9/25
Nozzle / Position / GPA / Number / Wt.(lbs) / Number / Wt.(lbs) / Cercospora / P. Mildew
flat fan / 20 / 128 / 14.5 / 2 / 2.2 / 2.8 / 2.8
flat fan / 30 / 149 / 17.7 / 4 / 4.7 / 2.0 / 3.0
flat fan / 40 / 139 / 15.8 / 2 / 2.1 / 2.5 / 2.8
air induction / 20 / 138 / 15.5 / 3 / 3.7 / 2.8 / 3.3
air induction / 30 / 139 / 15.9 / 2 / 4.1 / 2.0 / 2.3
air induction / 40 / 134 / 15.3 / 6 / 6.2 / 2.3 / 2.8
twin jet / 20 / 139 / 16.2 / 3 / 5.0 / 3.3 / 3.3
twin jet / 30 / 123 / 16.3 / 5 / 10.0 / 2.5 / 2.3
twin jet / 40 / 132 / 17.4 / 2 / 3.5 / 2.0 / 2.8
*twin jet / angled holder / 30 / 147 / 16.8 / 4 / 9.1 / 2.3 / 2.8
twin jet / angled holder / 40 / 121 / 16.6 / 3 / 4.7 / 3.3 / 3.0
twin jet / drop leg, angled / 40 / 141 / 16.8 / 4 / 6.7 / 2.0 / 2.0
flat fan / drop leg, angled / 40 / 139 / 15.9 / 4 / 6.5 / 2.3 / 2.3
unsprayed check / 128 / 13.5 / 15 / 15.3 / 5.8 / 6.5
lsd (p=0.05) / nsd / 3.69 / 6.1 / 8.92 / 0.71 / 0.88
*this spray at 30 psi. All others at 40 psi.
sprays on 21 Aug and 4 Sep with CO2 backpack sprayer.