To optimize the utilization of aircraft for herbicide application.

• To determine the distances that herbicide spray drift travel when applied aerially between 6:00 hours and 9:00 hours.

• To determine at what distance herbicide spray drift concentrations are critical.

1) Does herbicide spray drift within the targeted times of application travel distances beyond the established buffer zones?

2) What are the distances at which drift concentrations become critical?

Null 1

Spray drift within the targeted times of application does not travel distances beyond the established buffer zones.

Alternate 1

Spray drift within the targeted times of application travel distances beyond the established buffer zones.

Null 2

Spray drift concentrations are not critical at all distances reached.

Alternate 2

Spray drift concentrations are critical at all distances reached.

The project was done at Rose Hall Estate, East Canje, Berbice, Albion Estate, Corentyne Berbice and Blairmont Estate, West Bank Berbice Guyana South America, done as from February 2018 to August 2018.

[10].

[10].

No formal experimental design was adopted since treatments were fixed and not randomized.

v Three Blocks (Time—6 am to 7 am, 7 am to 8 am and 8 am to 9 am).

v Three replicates per block that is three aerial applications for each hour.

v Each application four points (East, West, North and South) tested.

v Each point having 17 treatments (Distance-30 meters to 510 meters at equidistant).

v 3 blocks × 3 replicates (applications) = 9 applications.

v 9 application × 4 points = 36 points.

v 36 points × 17 treatments = 612 treatments.

v Each side = 153 treatments for all nine applications.

v Each side for each hour = 51 treatments for e.g. 6 am to 7 am = 3 south × 17 = 51.

1) Experiment was done based on the Estate’s herbicide programme.

2) GuySuCo provided labour, aircraft, sensitive papers, dye and herbicides.

Chemicals

2,4-D amine and Ally

2,4-D amine was tank mixed with Ally-Metsulfuron, Figure 6, at a dilution rate of 4.23 UG gallons of water. 2,4-D was used at an application of rate of 1.5

liter per hectare in combination with Ally at a rate of 0.6 grams per hectare for controlling sedges and broadleaf weeds.

2,4-D is a Phenoxy and susceptible to drift depending on the formulation, ester for example are very volatile and can cause vapour drift that remain in the air as vapour for long periods and travel long distances. Unlike amine formulations for e.g., 2,4-D amine can only cause droplet drift, which is generally limited to relatively short distances of up to a few hundred metres. This distance can vary greatly, depending on the specific circumstances of the application.

Both, 2,4-D and Ally are systemic post emergence herbicides, that are selective to the sugar cane plant.

Levanyl Blau dye, Figure 7, was incorporated with the herbicide mixture at a rate of 0.04% volume-to-volume basis, for e.g. 1000 liters of water 40 liters of dye.

This dye aids in the detection of spray drift that is captured onto the sensitive paper. Spray drift is detected by blue spots caused by the dye which is expressed on the sensitive paper.

Sensitive paper, Figure 8, was stapled onto 17 bamboo poles at equidistant of 30 meters starting at 30 meters away from the target area to 510 meters. This was done east, west, north and south of the target area.

The water and oil sensitive paper is a paper specially designed to be used as markers to detect spray drift. It reacts readily with water and oil once contact is made. It has a dimension of 1 inch × 3 inches (3 square inches) = 19.3548 cm².

Aircraft

The Satloc provides state-of-the-art GPS guidance for aerial applicators. Available with AirTrac™ guidance software, the Satloc allows one to fly and spray precise patterns using constant rate flow control. This reduces fuel, flying time, and application costs. The Satloc Bantam light bar guidance system features a real-time graphic moving map display, it provides visual guidance, and shows key features such as swaths sprayed, field boundaries, skips, overlaps, mark points, waypoints, acres applied, and polygons. The AirTrac software allows one to track acres applied and monitor application rates. The Satloc includes a 7-inch touch screen, CPU with 2 USB drives, 2 GB USB stick, A21 antenna, external light bar and 9” touch screen available.

The AU5000 “Micronair” atomizers in the aircraft have been adjusted to give us between 240 - 250 Microns VMD droplet size on eight of the units Figure 9 and Table 5. In addition, the outer most atomizer units on each wing have been adjusted to give a slightly larger droplet VMD size to reduce the drift effect of the wing tip vortices on the spray pattern of these two units.

In general, Ultra Low Volume formulations will tend to form smaller droplets than water-based low volume formulations at the same rotational speed.

1) Treatment area was marked off with flags.

Flags

Four flags Figure 10 were erected on all four corners of the treatment area (target area) this aids the pilot in identifying the area to be treated, even though the aircraft is equipped with GPS Satloc.

2) Bamboo poles were cut and gathered as shown in Figure 11.

3) Bamboo poles were inserted 30 to 510 meters equidistant on each side, for stapling of sensitive paper, as illustrated in Figure 12 and Figure 13.

On the day of application

1) Sensitive paper was numbered and stapled onto the bamboo poles.

Numbering sensitive paper

• Each paper for all sides were number 1 to 17, so as to identify droplets at each distance, as demonstrated in Figure 14.

Stapling sensitive paper

• One sensitive was stapled on each pole for all side for capturing herbicide spray droplets from drift.

1) Time, Wind speed and direction, temperature and relative humidity were recorded.

2) Live weather and climatic conditions were observed via smart phone (online application “The Weather Channel”).

3) All safety precautions were observed before commencement of application (Figure 15).

4) Aircraft operated from Rose Hall Estate airstrip.

5) Sensitive paper was retrieved 2 hours after application.

Magnifying glasses

The magnifying glasses were used to magnify the smaller droplets to aid in counting as shown in Figure 16.

Syngenta’s droplet counting aid

Syngenta’s droplet counting aid is designed with a 1 cm², 1/2 cm² and a 1/4 cm² square, use to categorize few droplets, many droplets, and great number of droplets.

• Data collected was done by counting the amount of spray droplets (indicated by dots) on each sensitive paper from all sides, using the magnifying glass and the droplet counting aid.

Great number of droplets

• Sensitive paper was divided into 60 equal squares with dimensions of 0.635 cm × 0.508 cm = 0.32258 cm² (60 × 0.3225 = 19.356 cm²) (Figure 17).

• Five squares were counted, from four at each corner of the paper and one in the center.

• The sum of droplets were divided by five to giving a mean.

• The mean was then multiplied by 60 to giving an estimated number of droplets on the particular paper.

Few droplets

• The 1 cm² square from the droplet counting aid was used.

• Data collected for each block (time) were recorded.

Parameters of interest

• Spray drift distances and concentrations outside target area for each side.

• The distance at which drift concentrations are critical.

• Data were formatted for compatibility with Statisti × 10 programme.

• Data were tabulated and represented graphically.

• Treatment means were compared at the 95% Confidence Interval, using ANOVA for RCBD and CRD.

• Block means were compared at 95% confidence interval using ANOVA for CRD.

• Distances of drift concentration were determined as being safe and as being hazardous, using Syngenta’s recommendation (30 - 40 droplet concentration, density per cm²).

• Syngenta recommends that, droplet concentration or droplet density for post emergence herbicides should be 30 to 40 droplets per cm² in the target area that means 30 to 40 droplets per cm² will effectively affect the target organism. Therefore, this droplet density or concentration may equally affect off-target organisms.

• The sensitive is approximately 19 cm², the number of droplets on each sensitive paper for each distance was divided by 19 to determine the number of droplets per cm² for each distance.

• Distances that reached and exceeded 30 droplets per cm², was deemed hazardous. On the other hand, those distances that resulted in less than 30 droplets per cm² was deem as safe and may not be hazardous.

Budget

All the costs, as indicated in Table 6 except for labour, sensitive paper and dye was budgeted for in each of the estate’s herbicide programme. However, all costs were covered by the corporation (GuySuCo 2016).

Limitation

Results obtained from this study will be applicable to conditions prevailing only at Rose Hall, Albion and Blairmont Estate.

Beneficiaries

➢ Guyana Sugar Corporation.

➢ Ministry of Agriculture.

➢ Pesticides and Toxic Chemicals Control Board.

➢ Rice and cash crop farmers.

➢ Residents near Rose Hall Estate.

Results and discussions

RELATIONSHIPS BETWEEN TIME OF DAY AND ENVIRONMENTAL CONDITIONS THAT INFLUENCES HERBICIDE SPRAY DRIFT.

Average wind speed recorded was 9.6 km/h from 6 am to 7 am and increased to an average of 12 km/h from 7 am to 8 am, this average further increased to 15 km/h from 8 am to 9 am, Figure 18.

Correlation (Pearson) indicated a relationship with time and wind speed, which is, between 06:00 and 09:00 hours wind speed increases. This resulted in a positive correlation where time = 1 to wind speed = 0.9282 (r = 0.9282).

Average temperature recorded was 24.5˚C from 6 am to 7 am (Figure 19) and increased to an average of 25.3˚C from 7 am to 8 am, this average further increased to 26˚C from 8 am to 9 am.

Correlation (Pearson) indicated a relationship between time of day and temperature, which is, between 06:00 to 09:00 hours temperature increases. This resulted in a positive correlation where time = 1 to temperature = 0.8290 (r = 0.8290).

Average Relative Humidity (RH), Figure 20 recorded was 84.3% from 6 am to 7 am and decreased to an average of 84% from 7 am to 8 am, this average further decreased to 81.6% from 8 am to 9 am.

Correlation (Pearson) indicated a relationship between time of day and RH, which is, between 06:00 to 09:00 hours RH decreases. This resulted in a negative correlation where time = 1 to RH = −0.7037 (r = −0.7037).

➢ Average wind speed increased by 5.4 km/h from 6 am to 9 am = 56.25%.

➢ Temperature increased by 1.5˚C from 6 am to 9 am = 6.12%.

➢ Relative Humidity decreased by 2.7% from 6 am to 9 am = 3.2% as indicated in Figure 21.

With an average wind speed of 9.6 km/h between 6 am and 7 am, drift reached 480 meters with a mean of 0.6 droplet per sensitive paper (3.0 square inches/19.354 cm²), as shown in Figure 22.

Between 7 am and 8 am with an average windspeed of 12 km/h, drift reached 510 meters with a mean of 0.3 droplet per paper. This indicated a decrease of drift concentrations from the 6 am to 7 am hour. However, when compared drift at 480 meters in this hour with 480 meters in the previous hour, there was an increased in drift concentration, with a mean of 2.3 droplets per paper.

From 8 am to 9 am drift also reached 510 meters with a mean of 6 droplets per paper. This indicated an increase of drift concentration from the previous two hours. However, when compared at 480 meters with the previous two hours, drift concentration resulted in a mean of 93 droplets per paper.

This is an indication that, between 06:00 and 09:00 hours drift travels farther and concentrations increases as per distance.

Wind direction was predominantly North North East (NNE) to South South West (SSW) and to a lesser extent East North East (ENE) to West South West (WSW), Figure 23, for all nine applications. A NNE wind direction resulted in a more southerly-drift while ENE resulted in a more westerly-drift. However, for the Eastern and Northern direction drift was insignificant as indicated in Figure 24.

The eastern side recorded a mean drift concentration of 2 droplets per sensitive paper at 30 meters, Figure 25, and reached a total distance of 120 meters with a mean drift concentration of 0.11 droplet per paper, as indicated in Figure 26.

For the northern side, mean drift concentrations at 30 meters were 1.5 droplets per paper and travelled 90 meters at a mean drift concentration of 0.22 droplets per paper, Figure 27.

Drift concentrations were highly insignificant for both the Eastern and the Northern sides. Mean droplets per sensitive paper did not exceed 2 at 30 meters and was less than 1 at 120 meters. This all is seen from the results of Figure 28.

Drift travelled Westerly, 480 meters with a concentration of 1.2 droplets per sensitive paper, the highest concentration was recorded at 30 meters with a mean of 2693.3 droplets per sensitive paper, Figure 29. The critical point was p value.

Drift concentrations at 240 meters recorded a mean of 535.5 droplets per sensitive paper (19.354 cm²), thus resulted in 28.2 droplets per cm². This, may less likely to cause an effect on off-target organisms since it below Syngenta’s

recommendation of 30 to 40 droplets per cm². On the other hand, at 210 meters mean concentration was 685.67 droplets per sensitive paper, which resulted in 36 droplets per cm². This however, according to Syngenta’s recommendation will cause an effect in the target area, thus most likely to do the same in off-target area.

Therefore based on these results distances from 240 meters to 510 meters on the western side can be considered as a safe zone where drift may not be hazardous, whereas from 210 meters to 30 meters can be considered as an unsafe zone where drift can be hazardous, Figure 30.

Drift reached a distance of 510 meters with a mean concentration of 2 droplets per sensitive paper (19.354 cm²), Figure 31 and recorded the highest concentration at 30 and 60 meters with a mean of <10,000 droplets per paper at each distance.

At 420 meters drift concentration was 254 droplets, which is approximately 13 droplets per cm² on the sensitive paper. According to Syngenta’s recommendations, this can be considered as the point where drift is less likely to cause negative effects, hence 420 meters to 510 meters and farther southerly, away from the target area can be considered as a safe zone, taking into account the weather and environmental conditions that prevailed.

30 meters to 390 meters away from the target area can be deemed hazardous. This zone, drift concentration exceeds 30 droplets per cm² on the sensitive paper, which according to Syngenta is recommended to cause an effect on the target organism, hence can potentially cause negative effects on off-target organisms.

Because drift travelled farther southerly with higher concentration than other sides. Distances of critical drift concentrations were determined using the southern direction. Thus, southerly drift concentrations were further evaluated.

There are 11 groups (A, B, C, D, DE, EF, FG, GH, HI, IJ, and J), Figure 32, in which the means are significantly different from each another. However, from

420 meters to 510 meters, treatment means of drift concentrations are not significantly different.

CRD was used to compare block means, Figure 33, statistically there is no significant difference between block 1, 2 and 3. Even though Block 1 (6 am to 7 am), block 2 (7 am to 8 am) and block 3 (8 am to 9 am) recorded different drift concentration means.

However, block 2 has drift concentrations 111% of block 1 and block 3 is 154% of block 1.

Although these blocks are not significantly different statistically, the increased concentrations between 06:00 and 09:00 hours are more likely to cause negative effects to off target organism at varying distances.

➢ 6 am to 7 am—A mean drift concentration of 200 droplets per sensitive paper (19.354 cm²) recorded at 360 meters from 3 applications, averaging 10.5 droplets per cm².

➢ 7 am to 8 am—460 droplets per paper at 390 meters, averaging 24.2 droplets per cm².

➢ 8 am to 9 am—297 droplets per paper at 450 meters, averaging 15.6 droplets per cm².

According to Syngenta’s recommedations, all of the above, Figure 34 drift concentrations can be considered as safe, since there are below 30 - 40 droplets per cm². However, buffer zone cannot be instituted at 360 meters as indicated in the 6 am to 7 am hour as safe. This is because at 360 meters in the 7 am to 8 am hour drift concentration amounted to 900 droplets, averaging 47.4 droplets per cm² and for the 8 am to 9 am hour concentration amounted to 2000 droplets, averaging 105.26 droplets per cm².

Averages of 47.4 droplets and 81 exceeded the recommended number of droplets (30 - 40 per cm²).

Even at 420 meters where the 6 am to 7 am and 7 am to 8 am hours recorded safe concentration, buffer zones cannot be instituted at this distance, this is because a mean of 720 droplets per sensitive paper averaging 38 droplets per cm² was seen at the 8 am to 9 am hour.

Therefore, at 450 meters where the 6 am to 7 am, 7 am to 8 am and 8 am to 9 am hours recorded mean concentrations of 3.66, 16.66 and 297 droplets per sensitive paper respectively can be considered as the safe point, where the highest concentration averages 15.6 droplets per cm², which according to Syngenta’s recommendations is less likely to affect off-target organisms

Hence, distances between 450 meters and 510 meters can be considered as a safe and effective buffer zone, which will determine the distances of buffer zones for all four sides of the target area.