At the end of 2017, we leave you with the list of the 10 most sold herbicides this year in Agroterra, at the end of the list we have included the two best sellers authorized for Domestic Outdoor Gardening, that is, those users that do not have an ID card. the phytosanitary product can acquire.
Top 10 Weed Killer
The consumption of herbicides in winter cereals occupies an outstanding place within the total use of phytosanitary products in Spain. However, in recent years, drought conditions, low cereal prices, high costs of some herbicides, the development of resistance and the growing social sensitivity towards the use of agrochemicals have led to the search for control systems more integrated, with more rational use of them. Said rationalization involves making a good diagnosis of the situation, by using a series of agronomic practices that hinder the development of the most problematic weed populations and by the use of clear decision criteria based on scientific knowledge.
MAIN SPECIES OF BAD HERBS
Before carrying out any type of herbicide treatment, it is imperative to carry out a diagnosis as accurate as possible of the situation. For this, it is necessary to know the main weed species present in each of the plots to be treated. It is not a question of taking a floristic inventory or of accurately determining the present densities, but of identifying the most important risks that the crop will have to face during its development.
In the event that the herbicides to be used are pre-emergency, this estimate will have to be made based on the problems detected in the previous years, with the consequent inaccuracies that this implies. In that sense, it is very convenient to have some information about the history of the field, that is, what crops were sown, what cultural practices and herbicides were used, what kind of weed problems were developed. This information will help us to predict the type and severity of the problem that will have to be faced in the next campaign. Given that weed infestations are not usually uniformly distributed throughout the field, it will also be convenient to know the location of the stands that may present the greatest problems, either because they are particularly aggressive species or because they are very high densities. In the event that the previous crop is another cereal, this location may be made at the time of harvest (from the combine’s cabin) and may be collected in the form of a map of the infestations of the plot using some of the technological tools available (mobile mapping equipment with GPS, harvest monitor)
In the case of using post-emergence herbicides (the most common case), it is desirable to make a tour of the plots as soon as the cereal is already established to evaluate the main weeds that invade each plot. This evaluation should be done as soon as possible (as soon as weed populations can be easily recognized by the naked eye) in order to plan and carry out early treatments, which are the most recommendable for their greater effectiveness. However, the high side of most of the plots and the usual spatial heterogeneity of the infestations impede the evaluation of “kicking the field”. The availability of ATV vehicles and mobile mapping equipment with GPS receivers can greatly facilitate this task. The identification of different species in this early stage is not always easy, especially in the case of grasses. For this work it is necessary to resort to seedling identification guides and, above all, a lot of field experience is necessary. Today, there are computer programs to help identify weeds that can be very useful in this regard (eg SIMCEnet).
Although the main infesting species can be quite different from one region to another, from one farm to another and even between different plots of the same farm, we can speak of a few species that are quite widespread throughout the Spanish geography and represent a serious threat for its competitiveness with the crop, for the difficulty of its control and for the rapid expansion of its populations. Among them, we can mention four annual kinds of grass.
APPEARANCE OF RESISTANCES
The emergence of resistance as a result of malpractice is becoming more frequent. The continuous application of the same product (or of products belonging to the same chemical family or to families with the same mode of action) over a certain period of time leads, sooner or later, to the appearance of biotypes resistant to that product This phenomenon has been observed in our country on numerous occasions. Perhaps the best-known cases are those related to the appearance of resistant populations of Lolium rigidumin the Catalan cereals. Originally, more than 17 years ago, this resistance was observed in grain fields that had been continuously treated with diclofop-methyl. Subsequently, numerous types of resistance have been found in this species. The presence of Papaver rhoeas biotypes resistant to tribenuron methyl and/or 2,4-D was initially detected in winter cereals in Catalonia, although later this type of resistance was also found in cereal crops in Navarre and other northern areas from Spain. In the case of Avena sterilis and A. fat, although not currently considered a serious problem, resistant populations have been located incipiently in cereal fields in which this weed shows the difficulty of control with the specific agencies (diclofop-methyl, tralkoxydim, clodinafop, fenoxaprop).
Although the cases of resistance seem to be increasing, checking and confirming the existence of resistance in a plot or in a specific area is not easy. The Committee for the Prevention of Resistance to Herbicides (CPRH) has published several guidelines that detail the procedure to be followed to confirm a case of resistance. In the last case, and if the suspicions seem to be well founded, it will be necessary to contact the Plant Health Services of the corresponding Autonomous Community or a research center or university in the area to confirm the case.
The methods of prevention and control advocated by the CPRH for handling these situations are the following:
- Use of crop rotations, using spring crops to eliminate resistant biotypes before planting or use alternative herbicides not applicable in cereal crops.
- Use of fallow and mechanical control practices during the campaign.
- Avoid the movement of seeds with resistance from one field to another, carefully cleaning the tillage and harvesting equipment.
- Use of appropriate planting densities to obtain a competitive crop.
- Use of herbicides only when necessary, alternating herbicides belonging to different groups according to their mode of action. To know which group a certain herbicide belongs to, it is necessary to resort to one of the aforementioned guides published by the CPRH.
Do not forget that the best strategy to avoid the emergence of resistance is the prevention and integrated use of as many control methods as possible.