“There is diquat, which is the most used, as well as glufosinate, and also some Protox inhibitors…”
Alfredo Junior Paiola Albrecht and Leandro Paiola Albrecht, professors at the Federal University of Paraná, Palotina Sector, Department of Agricultural Sciences and supervisors of the Supra Pesquisa group.
Leandro Paiola Albrecht (left) and Alfredo Junior Paiola Albrecht (right), professors at UFPR
AgriBrasilis – What are the options for pre-harvest desiccation in soybean farms?
Alfredo and Leandro Albrecht – There is diquat, which is the most used, as well as glufosinate, and also some Protox inhibitors, such as carfentrazone, flumioxazin and saflufenacil, which can be used in a mixture with diquat or mainly with glufosinate, in order to improve and/or accelerate desiccation.
There is also available a ready-made mixture of diquat with amicarbazone focused on pre-harvest desiccation. Recently, this year, a registration of florpyrauxifen-benzyl was approved, which is a new type of product to be used for pre-harvest desiccation of soybeans.
AgriBrasilis – What is the cost-benefit of glufosinate and diquat desiccants?
Alfredo and Leandro Albrecht – Pre-harvest desiccation is mainly used to standardize the soybean crop for harvesting, but it can also bring forward the harvest by a few days (which is very interesting for bringing forward the sowing of second-crop corn or cotton), and it can even help control some weeds.
It is complex to measure the cost-benefit, but if the desiccation is done at the correct stage and in the correct way, there are benefits that outweigh the costs invested in the operation, not only in the case of diquat and glufosinate, but for other products and mixtures that can be used.
With the ban on paraquat, diquat was its main substitute (due to some characteristics similar to paraquat and also due to its price). The second product that most replaced paraquat was glufosinate, which was already used for pre-harvest desiccation of other crops. It is worth noting that today we have other products with great potential that can be used for this purpose.
AgriBrasilis – What is the observed effectiveness of florpyrauxifen-benzyl and how does it compare to other products?
Alfredo and Leandro Albrecht – It is difficult to address a complex subject like this in a few words. In short, we can say that this new herbicide is a good option for pre-harvest soybean desiccation, with high efficiency and great potential for use in the coming years. In fact, we recently had an article published in a great scientific journal (Florpyrauxifen-Benzyl: A New Chemical Group for Use in Preharvest Soybean Desiccation) and we wrote papers presented at a conference on this topic, expanding the subject through in-depth research.
Florpyrauxifen-benzyl is a modern product focused on more modern soybean cultivars, which typically have indeterminate growth. It has a slower effect than diquat, due to the characteristics of the molecules, closer to the speed of glufosinate, but it can be applied earlier in the soybean crop, without loss of productivity. For example: for diquat, we recommend the application at the R7.3 stage of soybean; for florpyrauxifen-benzyl, it is recommended at R7.1.
AgriBrasilis – How are experiments that evaluate the efficiency and selectivity of herbicides carried out?
Alfredo and Leandro Albrecht – These experiments are normally carried out in the field or in a greenhouse, using the main crops farmed in Brazil and focusing on the main and most complex weeds present in our production system.
Through visual assessments, based on scientific scales, we measure the percentage of weed control and whether the commercial crop has suffered any injury or damage due to phytotoxicity. This can now also be assessed using computer image analysis.
Weed mass measurements and measurements of the commercial crop are also carried out, in addition to height, development, etc. In the case of the crop of interest, it is also recommended to evaluate its production components. All of this is done so that at the end of a research project we can have an efficient herbicide to control weeds without causing damage to the crops or the environment. This can be done for pre- and post-emergent herbicides and our team has published hundreds of papers in this area, during our 18 years of applied research seeking solutions for agriculture.
AgriBrasilis – What is “weed interference” and how is it calculated?
Alfredo and Leandro Albrecht – Weed interference is the damage that weeds can cause to the cultivated plants. Weeds can reduce the quantity and quality of the harvested products and this needs to be measured in order to understand how and when we should carry out the best possible control of such weeds.
Basically, we calculate the damage that the densities (quantity) of weeds can cause in a crop and/or the damage that the coexistence periods of these weeds can cause in the crop. Recently, we have had several studies demonstrating, for example, that one plant of buva per m2 can result in losses of 14% of soybeans, and one plant of goosegrass per m2 can result in up to 21% loss of productivity in soybeans.
AgriBrasilis – Why was there such a rapid increase of Bidens spp. weed species in soybean farms in the States of Paraná and Mato Grosso do Sul?
Alfredo and Leandro Albrecht – Such increases are not normally caused by a single factor. In the case of Bidens spp. in Paraná and Mato Grosso do Sul, the main factor was the increase in cases of resistance to herbicides.
For many years, Bidens spp. has been resistant to several ALS-inhibiting herbicides, and, more recently, there has been a sharp increase in resistance to atrazine (the main herbicide used in corn); even more recently, resistance to glyphosate has occurred.
This makes control more difficult and increases dispersion, which can occur mainly due to machines and counterfeit seeds. In addition, Paraná and Mato Grosso do Sul are on the border with Paraguay, where Bidens spp. is one of the main and most complex weeds.
AgriBrasilis – Does the use of herbicides reduce the microbial quality of soils?
Alfredo and Leandro Albrecht – In our recent research, we have not found any harmful effects from the pre-emergent and post-emergent herbicides that we normally use on our crops. However, this is an extremely important topic, which must be continually studied, due to its relevance to the sustainability of our production system.
Suggested materials to delve deeper into these and other topics:
In this link below you can find most of our recent publications:
https://drive.google.com/drive/mobile/folders/1HNQVvX5N1RS1E1dNI1i7fdB7spMA4Dn0?usp=sharing
We also have our YouTube channel:
https://www.youtube.com/c/ProfessoresAlfredoLeandroAlbrecht
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