​The right time to apply the fungicide

The moment the fourth or fifth leaf appears, the decision begins for the farmer who planted his soybeans. What to do? Do you apply the fungicide or not? What do you need to observe? Does the climate influence this decision? Do I need to check if there is inoculum before applying?

There are many issues that influence farmer productivity when managing disease and pest resistance. For them to be answered correctly, it is necessary to understand how the physiology of the plant and also the disease works. Without the necessary knowledge, the wrong decision could affect the entire production. Even using the fungicide, but in this case late, you will probably have ineffective control and will have to combat an outbreak of rust or spots.

It is very important that it is clear how the process works. With four or five leaves, soybean infection by spots, for example, has already occurred. Rust, as it has a slightly slower progression, is happening. Whether it rains or not has more to do with how long the disease takes, which is faster during the rainy season. However, soybean inoculation is happening, as on a large or small scale, wind and rain have already helped in this process.

The doubt about this physiology arises, as it is only at the moment of full flowering, in some regions of Brazil even later, that the symptoms begin to be seen by farmers. But when the signs appear, resistance control management becomes increasingly difficult to contain. It is always easier to treat at the beginning, rather than when the infection has already reached alarming proportions.

For these reasons, the fungicide must be applied at the time when the disease is taking hold in the plant, even if there are no clear symptoms that a disease exists. It is much better to be safe than sorry.

It is necessary to expand the spectrum of action of the fungicide. From the emergence of the fifth leaf is the moment when the plant has very good physiological activity, with an initial level of infection. This is when the performance of the technological solution reaches its maximum power. If the producer waits to act later, when we already have a very high level of infection, the response to the product will certainly drop.

So, with soybeans reaching growth of four or five leaves and flowering, it is the exact time to make the first application, regardless of any external factor, whether related to the climate or whether the infection actually exists. There's no way to wait and see.

This 20-day window, between the beginning and flowering, is the time when the farmer needs to make the first application, be close to his crop and hold the evolution of the inoculum, because if he lets it grow, he creates inoculum, and there is growth of the leaf area, the fungicide will no longer reach the bottom when applied and it will certainly have difficulty controlling rust, for example.

But just having the right time to start applying the fungicide is not the only solution to have production with pest and disease resistance control carried out in the ideal way. You need to follow the normal schedule. With an interval of 15 to 18 days, the producer must make the second application. Then, decreasing the interval period a little, the third and so on. Only in this way will you be able to keep the infection at a low level, under your control. If you still have doubts, it is essential to consult an agronomist to guide you in your production.