Article 64 of the German Plant Protection Act requires that manufacturers, distributors and importers of plant protection products report to the BVL (Federal Office of Consumer Protection and Food Safety) with their annual domestic sales of such products and the active substances contained in them by amount. The BVL kindly provided the statistics on the sales of copper pesticides in Germany from 2010 to 2014.

Julius Kühn Institute (JKI) has regularly conducted surveys on the use of chemical plant protection products in the main agricultural and horticultural crops in Germany since 2000. They have been continued as “PAPA surveys”, categorized under a different legislative framework since 2011 [7]. PAPA is an acronym for Panel Pesticide Applications. Networks of crop-specific survey farms that gather and report detailed annual data on pesticide use were established under the PAPA program. The selected crops (winter wheat, winter barley, winter rye, corn, potatoes, sugar beet, dessert apples, hops and grapes) are those considered most relevant for the National Action Plan on Sustainable Use of pesticides [8]. Data on the use of copper pesticides can also be gathered from these surveys. It should be noted that the PAPA surveys only collect data from conventional farms; German organic farming associations collect the corresponding data on organic farming. This is a component of the JKI’s copper pesticide reduction strategy paper with specific consideration of organic farming [6].

Since 2001, the Federal Program for Organic Farming and Other Forms of Sustainable Agriculture (BÖLN) has funded research projects aiming to contribute to the reduction of copper used in plant protection. The results and resource needs of these projects are summarized below. These measures were supported by the European CO-FREE Project (Innovative strategies for copper-free, low-input and organic farming systems, 2012-2016; funding budget: 3 million euros), in which eleven European partners collaborated to find alternatives to copper. The results of the CO-FREE project were not included in this analysis because the final reports were not yet available. The individual projects funded by BÖLN were examined prior to our literature search. Relevant projects were filter-searched on the Federal Program website (https://www.bundesprogramm.de/index.php?id=916, Accessed on 14 September 2016). A total of 67 projects involving research on copper reduction were identified using the keyword “copper” to search the list of “Research and Development Projects” under the heading “Crop”. A comparative analysis of these projects was then performed (e.g. aim of the projects, effective ingredients, efficacy, costs).

The estimated amounts [kg ha - 1 ] of copper used in conventional farming in Germany in 2003 are shown in Table 1. The amounts used for conventional farming of potatoes, hops and grapes were significantly lower than those used in organic farming. The copper application rates were less than 1 kg ha - 1 yr - 1 in potato and grape-growing, and approximately 1.7 kg ha - 1 yr - 1 in hop-growing. Conversely, the amounts of copper used for apple-growing were almost equal in organic farming (average of 1.41 kg ha - 1 yr - 1 in 2010 to 2013) and conventional farming (1.4 kg ha - 1 yr - 1 in 2013). However, comparison of the total amounts of copper used in both farming systems (Tables 1 and 2) showed that, when adjusted for differences in the sizes of application areas, only 24% (26.5 metric ton, t) of the total amount of copper was used in organic farming compared to 76% (84.8 t) in conventional farming.

Table 3 lists only those crops in which copper pesticides were used in integrated pest management. They were not used in any arable crops except potato. Table 3 clearly demonstrates how copper oxychloride (trade name: Funguran), which was initially the most prevalent active ingredient, was replaced by copper hydroxide (trade names: Cuprozin Liquid, Cuprozin Progress, Funguran Progress, and Kocide OPTI) over the analyzed time period. The applied quantities of copper oxychloride decreased from 163.7 t in 2011 to 1.8 t in 2014 (Table 4). The reverse was observed for copper hydroxide. The application rate of this active substance increased approximately three-fold, from 45.6 t (2011) to 132.6 t (2014). Use of the other two copper- containing active ingredients (copper sulfate and copper octanoate) was marginal. Because basic copper sulfate (trade name: Cuproxat) is only allowed in grape- growing and does not play a significant role, at least in conventional agriculture, it was not included in the table. Copper octanoate (trade name: Cueva) is allowed in potatoes, apples, grapes and ornamental plants, but is only used in viticulture in conventional farming.

In organic farming, the application of copper-containing pesticides is based on forecast model predictions and not always on the total cultivated area (except in hop- growing). This comprises over 90% of the total organic farming area. Table 5 shows the amounts of copper used in organic viticulture in recent years. The differences in copper application rates between the different growing regions are sometimes substantial. This can be attributed to regional differences in climatic conditions and weather profiles between the different growing regions. A regional analysis was performed on part of the collected data (Figure 1). Comparison showed that the lowest amounts of copper are used in the Ahr grape-growing region [9].

The highest amounts of copper were used in organic hop-growing due to the high amount of foliage per unit area. Application rates in hops exceeded 3 kg ha - 1 yr - 1 in four out of six years (Table 6). The small scale of organic cultivation of this crop (max.85 ha in 2015) should be noted.

The copper application rates in organic fruit-growing on the other hand, were less than 2 kg ha - 1 yr - 1 . A general decrease in the amount of copper used in apples, peaches, pears and stone fruit occurred over the observation period (Table 7).

Regarding potatoes, farms associated with Demeter Association do not use copper in potato and vegetable-growing and sometimes accept the risk of considerable yield losses, alternatively they switch to low-infestation regions to protect critical crops [10]. The copper application rates in organic potato-growing were below 2 kg ha - 1 yr - 1 (Table 8).

In organic vegetable-growing, a substantial percentage of farming area is managed in accordance with the minimum limits of the EU organic farming regulations alone, and the German farming associations have not yet recorded the copper application rates there. The average copper application rates reported in Table 9 are, therefore, based on reports from only two organic farming associations, Bioland and Naturland. Pumpkin was the sole crop in which copper products were used in all four years studied. In cucumber, fennel, leek and ornamentals, copper was used in only one out of 4 years.

Since its establishment in 2001 to 2015, BÖLN has funded a total of 67 projects for research on copper replacement and minimization. The BÖLN Federal Organic Farming Scheme has awarded a total of 10.2 million euros in grants (Table 10).

The number of projects supported varies by crop type, in some cases greatly. Most of the projects carried out involved crops that are highly dependent on the use of copper, e.g., fruit and grapes. Although relatively large amounts of copper pesticide are regularly used in hop-growing, only two projects funded so far involved this crop. Projects that were not unique to a given crop type or which contributed to the minimization of copper indirectly were included in the subcategory “Others”.

The use of copper-containing pesticides in German grapes and hop growing is focused on the last application of the year (in August) in order to control downy mildew of grapes and hops. This application, therefore, has an important key function in terms of the necessary active ingredient rotation and successful resistance management. It should be noted that the copper application rates used for the final treatment in integrated viticulture are substantially higher than those normally used in organic viticulture. To date, no cases of resistance to copper-containing pesticides have been reported- since the first use of copper-containing substances in plant protection about 150 years ago. This underscores the importance of copper pesticides for crop protection as, until now, no other plant protection product has shown such a long duration of effect. In fruit-growing, copper pesticides are mainly used in the winter months (December to March) to control apple canker (Nectria galligena), and in March to control bark scab. The current use of copper-containing pesticides in conventional potato-growing is negligible.

Research funding to promote copper reduction in German agriculture has focused on the following fields of study:

Our status quo analysis clearly showed that German research on copper reduction and replacement is based on close collaboration between research, practice, advisory services and industry, and needs to be continued and further developed.

At present, it is still not possible to completely refrain from using copper pesticides in organic farming. Emerging diseases, such as grape black rot (Guignardia bidwellii), can result in partial to complete yield loss [32]. The combination of copper- containing pesticides with sulfur-based products is currently the only effective way to combat grape black rot in organic viticulture [32]. It should be noted that research funding in Germany is accompanied by other measures that contribute to successful copper minimization. This includes the advancement of Strategy Paper on Copper Reduction in Plant Protection [6] and the annual conferences on the theme of “Copper as a Pesticide”, which are jointly organized by the German Federation of the Organic Food Industry (BÖLW) and the Julius Kühn Institute. These are important contributions to continuously documenting the progress made, and measures needed, to achieve copper reduction.