Spraying of vineyards with pesticides against grapevine diseases and pests is an inevitable part of vineyard management. With the term “pesticide” we have in mind all chemicals used to control economic pests (i.e. weeds, fungi, arthropods, and nematodes), basically, we are talking here about plant protection products (PPP). The application of pesticides on agriculture fields has been a major concern of environmental pollution. Namely, when pesticides are sprayed in the vineyard, some of the small drops drift to surrounding areas with air currents. And not only that spray drift has negative effects on environment and health, but it’s also a waste of money. Pesticides for chemical control in the vineyard cost a lot of money, and therefore any waste can have a significant economic impact. Also, the portion of pesticides that misses the target, and fall on the ground instead on the vine canopy, pollute the soil, and destroy soil biodiversity. This is why it’s extremely important to apply pesticides precisely and only when needed.
Pesticide spray practices affect on the performance and sustainability of spray applications.
In order to help you optimize spraying in the vineyards – in sense of performance and sustainability of spray applications, we have put together a list of top 5 tips. Note that all of the tips are actually overlapping, and are equally important for a good protection against pests.
1. Spray on-time
Pin-pointing the right timing for spraying is crucial for spraying optimization and good grapevine protection against disease and pests. For the optimum control, each pesticide application should be timed perfectly, not too early nor too late. On-time spraying ensures good protection of the vines, as well as rational use of pesticides. A lot of winegrowers are still using calendar based spraying in order to protect their vines against disease. Unfortunately, this is not a very good practice, because the climate is changing, and weather doesn’t turn by the calendar. Weather conditions in the vineyard, such as temperature, humidity, and rainfall, affect fungus growth and disease spread. And it often happened that in a “good”, dry season, winegrowers spray way too much, and thus lose money, while in more rainy seasons, miss an optimal time for spraying for a day or two, and end up with infected vines.
In order to avoid this to happen, eVineyard app can help you with determining the optimal spray timing based on in-vineyard climate data and your past activities. Every winegrower should really pay attention to suppress early-season (primary) disease infections, as they cause more serious (secondary) infections later in the season. Similarly, it is important to suppress early pest generation, if possible in the stages when the pests are the most vulnerable. Stage and generations of different vine pests can be quite precisely determined by calculating growing-degree days.
2. Know how to use the equipment
Having good equipment for spraying is crucial for top performance. Of course, good equipment does not necessarily mean good protection. It is important to know the equipment well in order to be able to calibrate it – for example, to adjust the air and water parameters, to get the best possible coverage. A lot of different sprayers are available on the market, so the best thing is to ask your dealer to help you out with settings and understanding the sprayer’s capabilities; and then take time to test your equipment. The fact is that you will need to calibrate your sprayer several times during the growing season as canopy grows. Also, depending on the pest and product used, you will either want to spray the whole canopy or only a part of it, and you need to know how to adjust the sprayer base on specific needs. And that’s why you need to know all the setting options of your sprayer; how to calibrate the nozzles position (angles), airspeed and volume, as well as air direction, in order to ensure the best possible deposition of the spray. Before you start calibrating the sprayer, don’t forget to check the weather in the vineyard.
3. Check the weather
Weather plays an important role in optimizing vineyard spraying. Before each spraying, it is necessary to check the weather situation in the vineyard. First off all check the wind speed as it’s best to spray when wind direction is consistent and wind speeds are between 3 and 15 km/h. At wind speed below the 3 km/h finer droplets can suspend in the air, where they evaporate or drift. While at higher wind speed (wind speed over 15 km/h) high loss of spray from the target area can occur, as droplets drift. Also, check the direction of the wind especially in areas with open water and/or human activity, and based on the label instructions, set up the buffer zones. Apart from wind, also temperature and relative humidity influence on spray efficiency. The dryer the air, the faster spray droplet will evaporate. When there is a high air-temperature and low relative humidity, fine droplets may not be able to reach the target because of the evaporation and spray drift. Therefore spray when temperatures are low (<25° C) and relative humidity is high (>40%). In Australia, Delta T chart is used in order to avoid evaporation of droplets. According to the chart, the best conditions for spraying are when Delta T is between 2 and 8. Often the most optimal conditions for spraying are in the early morning.
4. Know the product, and adjust its quantity
An important element of spray optimization in the vineyard is to choose the right product based on disease and pest susceptibility, and to know the product mode of action. Depending on the product mode of action, as well as the nature of the target pest, you will need to either deposit the pesticide in a specific location, or ensure the maximum possible canopy coverage. For example, the contact insecticide works by immediate physical contact with a pest, while systemic products work in a secondary manner and enter into the plant where it can move up the vines and may require the insect to ingest it. And also based on product mode of action, droplet size should be adjusted. Some pesticides producers specify droplet size on product label, while others don’t. It’s somewhat recommended that for contact insecticides and fungicides finer droplets are better, while coarser for systemic products.
Learn more about pesticides mode of action in our e-book: Protection of the grapevine. Download ebook here.
While on most products label the amount of pesticides used is expressed in kg or l per ha, a much better approach is to adjust the volume of product and volume of water based to the leaf surface area. While the surface of the vineyard remains the same year-round, the size of the canopy changes during the season and so the needed volume of spray and water varies as well. Not adjusting the volume of spray and water throughout the growing season can either lead to poor spray coverage and thus poor insect and disease control, or too much of spray is applied which then residues in the vineyard soil or surrounding area. According to the study made in Spain, adjusting application quantity base on canopy size the volume rate can be reduced, as well as pesticide use can be reduced (by up to 53%) when compared to traditional application values.
Adjust the dose to match the real needs for chemical control of pests and diseases and therefore to reduce the environmental impact of spray applications and cut back farming costs. Maximizing the spray coverage is the key to optimize pesticide spraying.
5. Verify coverage
After the spraying, verify the coverage. A very good way to do it is with water sensitive cards, that you can attach to the canopy prior the spraying in order to know how well did you sprayed upper and lower leaf surface as well as grape clusters. Unfortunately, this method can be quite expensive. If this method is not feasible for you, what you can do is to check the vineyard after a few days to see if there are any signs of disease or pests. And if there are, check and note where they are. If you sprayed on-time, it might be that the pesticide didn’t penetrate the canopy, or that under-leaf penetration was poor. Either way, after every spraying, is good to check the situation and, improve based on findings: re-adjust the nozzles, speed, volume, or anything else. Learn from your mistakes and sooner or later you will master it. Note that no improvements can be done without verifying and evaluating.
Emilio, G. et al. 2014. Advanced Technologies for the Improvement of Spray Application Techniques in Spanish Viticulture: An Overview. Sensors (Basel). 2014 Jan; 14(1): 691–708.
Six Elements of Effective Spraying in Orchards and Vineyards, by Dr. Jason Deveau. © Queen’s Printer for Ontario, 2009.
Landers, A. et al. Technologies for the precision application of pesticides into vineyards. Internet Journal of enology and viticulture, 2017, N.2/1
Vallet, A. et al. (2015). Effect of Nozzle Orientation on Droplet Size and Droplet Velocity from Vineyard Sprays. Journal of Agricultural Science and Technology B. 5. 672-678. 10.17265/2161-6264/2015.10.004.
Featured Image from Marlborough District Council web page