Fungicides are phytosanitary products used to control pathogenic fungi in crops, however it is important that the application is done well, in order to have good disease control and avoid product waste.
One of the biggest problems in the application of fungicides is related to the solubility of the active ingredients, especially when it comes to multisite fungicides, which are those capable of inhibiting more than one process in the fungal cells.
These products have low solubility in water and one of the main products used that fall into this classification is mancozeb, used mainly to control Asian soybean rust. The solubility (ppm) in water at 20 ºC of mancozeb is only 6.2 (Degaro, 2017), that is, it is a product that can be considered insoluble. Therefore, some care is needed to avoid clogging of filters and nozzles (tips), heating of the pump seal or rupture of any pump structure, as all product particles must be solubilized in water so that these problems do not occur. occur.
How to make the application of Mancozeb successful?
O mancozebe é vendido como um produto sólido, nas formulações WG (grânulos dispersíveis) e WP (pó molhável).
Abaixo elencamos estratégias utilizadas para uma boa aplicação do produto, sem haver formação de grumos que provocam entupimento:
One of the strategies used to prevent the formation of lumps is the use of surfactant adjuvants, which will break the surface tension of the water, allowing greater wetting of the mancozeb particles.
No entanto, segundo o engenheiro agrônomo Marcelo G. Madalosso, professor e pesquisador na Universidade Regional Integrada, é muito importante que se misture o adjuvante à água (com aproximadamente metade do tanque) antes do mancozebe, e que a mistura de mancozebe à água + adjuvante deve ser feita de forma lenta, a fim de que a água possa “molhar” bem todas as partículas de mancozebe. Se o fungicida for colocado muito rapidamente, a água não irá penetrar em todas as partículas do mancozebe.
One of the secrets to good homogenization of mancozeb particles is good agitation, which must be constant from the moment water enters the tank until the end of product application.
In addition to mancozeb, a range of products are generally used alongside the tank, therefore, it is recommended to carry out a pre-mix test to check the physical compatibility of these products, in addition to following the manufacturers' recommendations.
Ex: In a transparent and inert container (preferably glass, or even PET), add 1L of water and add the same proportion of products to be mixed to the tank, in the same mixing order that you will add to the tank. Shake the solution well and observe to check that there has been no decantation of the products, formation of precipitates, formation of lumps, heating or phase separation. In case of any sign of physical incompatibility. If these problems occur immediately, it is recommended to change the mixture and apply separately those products that cause the problem. Decantation of mancozeb for between 5 and 10 minutes can be expected, as it is difficult to dilute, a factor that reinforces the need for continuous stirring of the syrup.
For more information about mixtures, leia o nosso post sobre incompatibilidade de misturas.
As indicated in the product leaflets, it is ideal to pre-mix mancozeb when filling the tank, adding the recommended amount of the product to a separate container with water to obtain pre-dilution, and then adding it to the product. spray tank gradually, diluting with the rest of the solution. In most cases, when formulated in WP (Wettable Powder), dilution in the pre-mix in a ratio of 1-2 (product-water) is recommended.
One of the ways to reduce the surface tension of water is to increase its temperature, as this promotes the loosening of hydrogen bonds between water molecules, reducing surface tension. According to Hansen (2007), heating water helps in the solubilization of poorly soluble solutes, such as mancozeb.
However, care must be taken here not to use very high temperatures, as these may impair the effectiveness of the product (slows absorption). According to Boff, et al. 2019, the temperature of the syrup must not exceed 40 ºC. Therefore, using water that is extracted directly from a well tends to have lower solubility compared to water that has been stored in a tank exposed to the sun, making it easier to dissolve mancozeb.
After completing the applications, it is recommended to thoroughly clean the spray tank and spray lines with a specific product for tank cleaning, as often, days later, using the sprayer with other products, it is possible to notice the presence of precipitates of mancozeb that were stuck to the tank structure, detaching and causing problems with clogging of filters and tips. Talk to your supplier about the most suitable product and the correct cleaning procedure.
In general, the detergent is mixed with clean water next to the tank, the agitation is kept on for a while, then the product is left to rest in the tank for a few hours and finally it is removed through the ends of the bars. . It is important to remove this water with detergent through the cleaning points of the branches and not through the nozzles, as this water with product will carry with it a lot of residue that will come off the tank.
SaveFarm® Technology in Fungicide Management
Our system provides advantages not only in the application of herbicides, but also in all operations throughout the year, for example in the use of fungicides such as mancozeb, in which the PWM valves make it possible to maintain constant spray pressure, guaranteeing independent spray droplet uniformity. speed of work and better distribution of the product in the plants.
COSTA, L.L.; POLANCZYK, R.A. Technology for applying phytosanitary mixtures. Funep, Jaboticabal, SP. 2019;
HANSEN, C. M. Hansen solubility parameter – a user’s handbook. 2. ed. Boca Raton: CRC Press, 2007.
BOFF, J.S. Water temperatures and the preparation of mancozeb. PERSPECTIVE, Erechim. v. 43, n.163, p. 99-106, September/2019