The more the better?
The determination of appropriate application rate for crop protection products is part of professional practice in farming. A range of factors need to be considered in making such judgements and these may include: pest pressure, weather, whether or not other product/s are being tank- mixed, resistance threats etc. Additionally, if adjuvants are being added, these may increase the efficiency of a product, even at lower application rates. But growers should seek manufacturer guidance on this. The fine tuning of application rate, may reduce the costs of crop protection.
Every now and then, media and environmental protection organisations report of uncontrolled application of crop protection products in farming. Manufacturers give out recommendations for the application rate of each product. These recommendations originate from tests and practical trials and are to guarantee the optimal efficacy against pests. Each product also has a maximum application rate which can be applied but not exceeded. Each farmer has to document the products applied and their application rate.
Within the annual surveys of the Kleffmann Group in different crops, the question about the application rate of the different products is also integrated. When evaluating the data it is obvious that many farmers try to stay below the, manufacturers recommended, application rates. In Germany, the Kleffmann Group has registered in total 68,244 entries of crop protection products in cereal, rape and maize, fungicides, selective herbicides and insecticides in 2015. In 28% of these cases, the farmers used the application rate recommended by the manufacturer. In 60% of the mentioned products, however, the farmers stated to have decreased the application rate and in only 10% of cases a higher dosage was used. But in all cases the farmers did not exceed the maximum application rate. Higher application rates are being used if the application has to take place in unfavourable weather conditions. In case of a very high pest pressure or impending resistance the application rate can also be slightly increased.
These numbers, however, clearly have to be distinguished by segments. In case of fungicides, the recommended amount was used by 16%, while 80% of indications stated a decreased application rate. Only in 3% of mentioned products, the farmers increased the application rate (Figure 1). If the application rates were lower, they were reduced by 43% on average. In case of higher application rates it was only 26% more on average. In case of selective herbicides, the amount of products that were applied with the recommended application rate is with 23% slightly higher. Here, in 62% of cases the application rate was reduced and in 13% of cases the dosage was increased (Figure 2). It is a different picture when looking at the insecticides. Within this segment, in 77% of the named products the recommended amount was used or was even slightly reduced (Figure 3). Especially the segment of insecticides is often being criticised in public.
Also, when comparing individual countries, bigger differences can be seen. Especially in Denmark it can be noted that the farmers considerably reduce the application rates. Where rates were cut, the application rate was reduced by more than 60% on average. This is also due to tighter restrictions for the application of crop protection products. Moreover, the products are very expensive and certain substances are being taxed additionally. Due to the tax itself, the product price is ten times higher in some cases. The farmer tries to compensate for these increasing costs by reducing the application rates. However, the steady application of only very low doses leads to the eventual emergence of resistance. Additionally, the tax on products is differentiated according to indicators of relative health and environmental impacts of the different pesticides. That is why the farmer focuses on the pesticides with the least negative load on the environment and health, which are less taxed and therefore cheaper. This also leads to fewer changes in substances and consequently the emergence of resistance.
An opposite picture can be noted in Great Britain. It is quite obvious here that many farmers use a higher application rate in every product group than recommended. This is the case for 36% of mentioned products within the fungicides, within the selective herbicides it is already 58% and within the insecticides it is 80% of products where a higher application rate was mentioned. The key drivers for this are increased occurrence of resistance in all sectors, where growers are faced with resistant grass and broadleaf weeds, aphids and fungal pathogens. Resistance strategies are adopted to limit the impact of these factors and regain control where possible. Combined with this is seasonally variant weather conditions where spraying opportunities may be limited and efficacy reduced.
It can be concluded that the application rate depends on different circumstances such as the weather conditions and the usage of the tank mix. But also political provisions, such as in Denmark, can have an influence.
The studies of the Kleffmann Group show that the farmers try to restrict their crop protection to the level necessary, such as the good professional practice asks for it. The assumption that the dosage is too high in general can therefore not be approved.
In order to produce safe groceries, possibilities for crop protection are inalienable. Only the availability of different substances which can be used interchangeably, resistance can be avoided effectively. Thereby, the application rates can be reduced because there is no need for the farmer to fight against resistance by applying higher application rates.