Analysis of the assortment of chemical plant protection products for rapeseed in Belarus

A. A. Zaprudsky 1, D. F. Privalov 1, Yu. K. Shashko 2

Introduction. In the Republic of Belarus, rapeseed (winter and spring forms) is the leading oilseed crop. Over the last 10 years, the cultivation area for this crop in our country has fluctuated within 300–320 thousand hectares, with a gross harvest of oilseeds of 700–950 thousand tons, primarily due to winter rapeseed. At the same time, to stabilize production volumes, implementing protection measures against pests, diseases, and weed plants plays a key role in the crop cultivation technology.

Annual monitoring of the phytosanitary situation indicates that the following occur in crops: field pansy, cornflower, common chickweed, scentless mayweed, field pennycress, shepherd's purse, common lambsquarters, white campion, couch grass, cleavers, and other weed species. Among pests, the greatest damage to the crop is caused by the cabbage seed weevil, cabbage stem weevil, rapeseed blossom beetle, seed weevil, pod midge, cabbage sawfly, diamondback moth, etc.

Phytopathological analysis of rapeseed seed indicates a high infection rate with the following disease pathogens during the growing season: Alternaria blight, phoma stem canker, Cylindrosporium leaf spot, Fusarium wilt, and downy mildew. The dominant diseases during the rapeseed growing season are Alternaria blight, Sclerotinia rot, grey mold, etc.

Taking into account the high harmfulness of phytophages, phytopathogens, and weed plants in the rapeseed agrocenosis, the chemical method of control is the most effective from an economic perspective. At the same time, the presence of a large list of plant protection products used in the rapeseed agrocenosis and having official registration necessitates an analysis of their assortment, taking into account their chemical class and mode of action.

Materials and methods of research. Trade names of plant protection products registered for use on rapeseed, their formulation types, active ingredients, and application rates were taken from the official registers of plant protection products and fertilizers for the period from 1995 to 2023. The concept of the "life period" of an active ingredient refers to the period from its inclusion in the Pesticide Properties DataBase to its mention in the register of the corresponding publication year. The year of registration in the PPDB was taken from the website; the name of the active ingredient class was taken from the website. Recommended prices for plant protection products for 2023 were taken from specialized industry resources. A unique active ingredient is defined as one that is part of at least one preparation, whether single-component or multi-component. Accordingly, non-unique ones can be part of several preparations.

Results and discussion. The analysis showed that the following types of products are registered for the protection of rapeseed: seed treatments, fungicides, insecticides, herbicides (including glyphosates), growth regulators (since 2008), and desiccants (as a separate group in 1995 and since 2017).

Since 2000, there has been a steady increase in the number of preparations registered for rapeseed. The number of herbicides (excluding glyphosates, 77 unique preparations were registered in 2023), fungicides (61 preparations), and insecticides (58 preparations) grew particularly rapidly. The number of herbicides with active ingredients from the glyphosate class stabilized since 2008 and was represented by 23–31 items.

Figure 1 – Dynamics of registered plant protection products (by type) used on rapeseed

If we analyze the number of active ingredients in registered rapeseed preparations for pre-sowing treatment of seed (seed treatments), fungicides, insecticides, and herbicides, the result is not as impressive: there is an increase in number, but it has been significantly smaller since 2014. In 2023, 24 unique active ingredients were registered for all types of plant protection products (23 for herbicides + glyphosate).

Figure 2 – Dynamics of unique active ingredients in plant protection products registered for rapeseed in

From 1995 to 2023, the number of unique active ingredients increased almost 4-fold from 29 to 96. In the case of fungicides, their number increased 25-fold. This is due to the fact that as a result of a sharp increase in development costs, the rate of synthesis of new active ingredients has dropped sharply. After the expiration of patent protection, any manufacturer can use active ingredients from different manufacturers in their preparations. In addition, the situation regarding the resistance of harmful organisms to single-component pesticides has become very acute. All this has led to the fact that it is easier and more effective for manufacturing firms not to develop new active ingredients, but to follow the path of recombining existing substances. This has led to the rapid development of generic manufacturing companies and a significant expansion of the product assortment, which, in turn, has led to increased complexity in the work of final agronomists in plant protection. On the other hand, an experienced specialist can select a preparation that contains substances with a spectrum of action that is optimally suited to the range of harmful objects present in a specific field. Moreover, potential preparations will differ in price, which will allow for minimizing the expenses of the agricultural enterprise.

Evidence of the slowing pace of creating new active ingredients is the increase in the usage period of existing active ingredients. If we consider all active ingredients, including glyphosates, their average usage period in 1995 was 20.9 years, while for insecticides it was 13.8 (which is an extremely short period, considering the long duration of registration studies in various countries). However, by 2023, the average usage period of active ingredients had reached 37.9 years, i.e., almost doubled. Table 1 – Dynamics of the usage period of active ingredients in plant protection products registered for rapeseed in the Republic of Belarus

Average usage period of active ingredients, years Year herbicides glyphosates average (excluding glyphosates) average (excluding glyphosates) seed treatment fungicides insecticides (with glyphosates) 1995 28.8 19.0 13.8 21.7 21.0 20.8 20.9 1998 31.8 16.3 18.0 19.4 24.0 21.4 21.9 2000 36.8 15.5 19.5 19.4 26.0 22.8 23.4 2005 34.4 20.7 24.3 21.5 31.0 25.2 26.4 2008 31.3 18.8 27.5 25.9 34.0 25.9 27.5 2011 32.2 23.4 24.5 25.9 37.0 26.5 28.6 2014 29.3 25.3 28.9 28.3 40.0 28.0 30.4 2017 30.5 25.9 31.5 31.7 43.0 29.9 32.5 2020 33.5 28.0 32.7 35.4 46.0 32.4 35.1 2023 36.6 30.4 35.9 37.4 49.0 35.1 37.9

It is worth mentioning separately that in Belarus, there are still 14 active ingredients older than 45 years in use as of 2023. The "oldest" active ingredient is thiram, which was registered as a fungicidal seed treatment in 1941. One of the most common herbicides will celebrate its 50th anniversary in 2024! The "youngest" active ingredient among seed treatments is cyantraniliprole, which was registered in the PPDB in 2008 (usage period 15 years); among fungicides – isopyrazam and fluopyram (15 years); among insecticides – chlorantraniliprole (16 years); and among herbicides – aminopyralid (18 years). Table 2 – Active ingredients older than 45 years used in plant protection products registered for rapeseed in the Republic of Belarus (data as of 2023) Active ingredient Year of registration in PPDB Usage period, years Thiram 1945 78 Dimethoate 1957 66 Picloram 1963 60 Thiabendazole 1963 60 Chlorpyrifos 1965 58 Carboxin 1969 54 Napropamide 1970 53 Glyphosate 1974 49 Carbendazim 1974 49 Metamitron 1975 48 Metolachlor 1976 47 Triadimefon 1976 47 Dimethachlor 1977 46 Clopyralid 1977 46

Despite the large assortment of plant protection products registered for rapeseed in the Republic of Belarus, the Ministry of Agriculture and Food does not recommend prices for the entire range. This may be explained by the fact that some products may be absent from the market for various reasons.

The average recommended price for fungicides, insecticides, and seed treatments (as a derivative of the first two groups) was approximately the same, in the range of 45.3–48.6 USD per 1 L (kg). Herbicides cost on average 77.0 USD, and glyphosates 15.5 USD per 1 L (kg), under prepayment conditions. The difference in price is apparently due to the level of complexity of the chemical synthesis of different classes of active ingredients.

Table 3 – Recommended prices for plant protection products registered for rapeseed in the Republic of Belarus in 2023

Plant protection products Number of products registered in the registry, units Number of products with recommended prices from the Ministry of Agriculture and Food, units % Average price, USD per 1 L (kg)* Seed treatments 26 17 65.4 45.7 Fungicides 61 50 82.0 45.3 Insecticides 58 43 74.1 48.6 Herbicides** 77 57 74.0 77.0 Glyphosates 29 15 51.7 15.5 Total 251 182 72.5 * – prices are provided based on prepayment conditions; ** – excluding glyphosates.

The characteristics of fungicide active ingredients registered for rapeseed in 2023 are presented in Table 4. In total, 61 products containing 114 non-unique active ingredients were registered for rapeseed during this period.

This indicates that the majority of products are multi-component. Most fungicides contain 2 or 3 active ingredients. However, the number of unique substances is limited; consequently, the same substance is included in the composition of different fungicides. For example, tebuconazole is part of 25 products, and azoxystrobin is in 15.

In general, two classes prevail among fungicide active ingredients: the "older" class – triazoles, accounting for 69.3% of the product composition (average usage period 35.2 years), and the "younger" class – strobilurins, accounting for 18.4% (average usage period 23.4 years). In addition, carboxamides, morpholines, and other classes are found much less frequently. The "youngest" are isopyrazam from the carboxamide class and fluopyram from the benzamide class – both registered in the PPDB in 2008.

The large number of components in fungicides is largely due to the need to expand the spectrum of action of the products, as well as to combat the development of resistance in harmful objects. It is known that active ingredients from the strobilurin class are inhibitors of cytochrome b1 in the mitochondria of phytopathogens, thereby blocking the energy production process. This is a very narrow stage of biosynthesis, controlled by 1 gene, so mutations, even point mutations, can help the fungus bypass this blockade, which leads to a very rapid emergence of resistance. In this regard, strobilurins are not used in their pure form. They must be combined in fungicide compositions with substances that inhibit other biosynthetic pathways in the pathogen's cells (most often triazoles); in this case, the risk of resistance development is significantly reduced.

Table 4 – Characteristics of fungicide active ingredients registered for rapeseed, 2023

Active ingredient Class Year of registration in PPDB Usage period, years Number of products, units* % of total quantity Difenoconazole 1989 34 9 Metconazole 1994 29 3 Paclobutrazol 1986 37 1 Propiconazole 1980 43 10 Prothioconazole 2002 21 10 Tebuconazole Triazoles 1988 35 25 Triadimefon 1976 47 1 Flutriafol 1981 42 9 Cyproconazole 1989 34 8 Epoxiconazole 1993 30 3

35.2 79 69.3 Azoxystrobin 1992 31 15 Dimoxystrobin 2003 20 1 Picoxystrobin Strobilurins 2001 22 1 Pyraclostrobin 2000 23 3 Fluoxastrobin 2002 21 1

23.4 21 18.4 Boscalid 2002 21 4

Carboxamides Isopyrazam 2008 15 1

5 4.4 Spiroxamine 1

Morpholines Fenpropimorph 1983 40 1

2 1.8 Others 9 6.1 Total 114 * – here and below, this refers to the total number of mentions of the inclusion of a unique active ingredient in various preparations.

The use of triazoles, especially mono-preparations, can be no less of a problem. Thus, in 2023, 25 out of 68 fungicides for rapeseed contained the active ingredient tebuconazole; in addition, it is part of 3 seed treatments. 4 fungicides (Bukat 500, SC, Kolosal, EC, Orius 250, EW, Titanium 250, EW) and 1 seed treatment, Tebu 60, ME, contain only tebuconazole. All this contributes to the emergence of resistance and requires mandatory compliance with all elements of the resistance management system (RMS), which includes:

Correct selection of fungicides and their rational use (combining preparations with single-site and multi-site active ingredients);

Application of fungicides with different mechanisms of action so that if resistance to one of them develops, the pathogen falls under the control of a partner preparation with a different mechanism of action, as well as periodic rotation of preparations with different mechanisms of action;

Strict adherence to regulations on the total dose and number of treatments according to the instructions on the method of application of the preparation, as well as recommended application rates.

Great importance is attached to the choice of resistant cultivars, crop rotation (the predecessor should not contribute to the accumulation of infection), and agricultural practices adequate for the crop cultivation area in order to avoid insufficient or excessive irrigation and/or fertilizer application, since both can stimulate disease development.

These elements of the RMS will also extend to other harmful objects.

Characteristics of active ingredients of insecticides registered for rapeseed. Among the active ingredients of insecticides for rapeseed, representatives of the organophosphate class (16%) are still present with an average duration of use of 52 years.

Nevertheless, pyrethroids (40.7%), which appeared after organophosphates, and even "younger" neonicotinoids (33.3%) prevail. The newest substances are the pyrethroid gamma-cyhalothrin (2003 registration in PPDB) and the neonicotinoid clothianidin (2002).

In total, 58 insecticides are registered for rapeseed in Belarus, containing 81 non-unique active ingredients. Of the 58 preparations, the majority are single-component, and there are also 18 two-component and 3 three-component ones. As with fungicides, multi-component preparations contain substances with different mechanisms of action. The widespread use of pyrethroids has led to the emergence of many insect populations with various levels of resistance throughout the world. The two main mechanisms of resistance to pyrethroids are increased detoxification due to P450 monooxygenases and mutations in the voltage-gated sodium channel gene. As a result, pyrethroids are more often used with other substances.

Characteristics of active ingredients of seed treatments registered for rapeseed. Seed treatments can be of fungicidal, insecticidal, and combined types. The list of registered preparations includes 11 fungicidal, 11 insecticidal, and 4 combined types of seed treatments. Among the active ingredients of the fungicidal type, triazoles prevail at 14.4%, and among the insecticidal ones, neonicotinoids at 28.8%.

Table 5 – Characteristics of active ingredients of insecticides registered for rapeseed, 2023.

Year of Year of Quan- % of Active ingredient registration in PPDB use, years tity total quantity

Class Alpha-cypermethrin 1985 38 6 Beta-cypermethrin 1989 34 1 Bifenthrin 1984 39 4 Gamma-cyhalothrin 2003 20 1 Deltamethrin 1984 39 5

Pyrethroids Zeta-cypermethrin 1984 39 2 Lambda-cyhalothrin 1985 38 8 Tau-fluvalinate 1985 38 1 Cypermethrin 1977 46 4 Esfenvalerate 1987 36 1

36.7 33 40.7 Acetamiprid 1995 28 12 Imidacloprid 1991 32 4

Neonicotinoids Clothianidin 2002 21 3 Thiacloprid 1999 24 7 Thiamethoxam 1997 26 1

26.2 27 33.3 Dimethoate 1957 66 5 Malathion OPs* 1991 32 2 Chlorpyrifos 1965 58 6

52.0 13 16.0 Others 8 9.9 Total 81 * – organophosphorus compounds.

Also, imidazoles (8.8%), dithiocarbonate, strobilurins, and benzimidazoles (6.7% each) were used as fungicides. It seems that manufacturing companies treat the development of seed treatments as a residual concern compared to other types of preparations. As noted above, seed treatments are not even separated into a specific group for which FAO statistics are collected, which indicates a small volume of their production. In Belarus, the active ingredients in registered seed treatments for rapeseed have always been relatively "old." Thus, if the average duration of use of insecticides in 1995 was 13.8 years, fungicides 19.0 years, herbicides 21.7 years, then seed treatments were 28.3 years old. Seed treatments were the "oldest" type of pesticides until 2014. Manufacturers explain this fact by the fact that it is not very profitable for them to invest in the development and production of new seed treatments since their volume of application is insignificant. With an average application rate of seed treatments per 1 ton of rapeseed seeds in 2023 of 6.2 L and a seeding rate of 4 kg/ha, the average consumption of the preparation would be 0.00248 L/ha (about 10 tons for the entire rapeseed sowing area in Belarus). Table 6 – Characteristics of active ingredients of seed treatments registered for rapeseed, 2023.

Year of Quan- % of Active ingredient use tity

Class of compound in PPDB quantity years

PPDB units quantity years

Fungicidal active ingredients Difenoconazole 1989 34 1 Ipconazole 1994 29 2 Tebuconazole 1988 35 3

Triazoles Triticonazole 1988 35 2 Flutriafol 1981 42 2 Cyproconazole 1989 34 1

34.8 11 24.4 Imazalil 1977 46 2

Imidazoles Prochloraz 1980 43 2

44.5 4 8.8 Thiram Dithiocarbamates 1945 78 3 6.7 Azoxystrobin 1992 29 1

Strobilurins Fluoxastrobin 2002 21 2

42.7 3 6.7 Carbendazim 1974 49 1

Benzimidazoles Thiabendazole 1963 60 2

54.5 3 6.7 Others 5 11.0

Insecticidal active ingredients Acetamiprid 1995 28 1 Imidacloprid 1991 32 9

Neonicotinoids Clothianidin 2002 21 2 Thiamethoxam 1997 25 1

26.5 13 28.8 Others 3 6.6 Total 45

Characteristics of herbicide active ingredients registered for rapeseed. If glyphosate is moved into a separate category, then only two active ingredients predominate among the registered herbicides for rapeseed: pyridinecarboxamide clopyralid (included in 19 products) and metazachlor (18 products). Table 7 – Characteristics of herbicide active ingredients registered for rapeseed, 2023.

Term Co- % of

Year of regis- use Active total

Class tration in PPDB years ingredient quantity

Glyphosate Organophosphorus 1974 49 29 22.7 Dimetachlor 1977 46 2 Dimethenamid-P Amides, 1999 24 2 Metazachlor Chloroacetanilides 1982 41 18 Metolachlor (chloroacetamides) 1976 47 1 Propisochlor 3

PyridinecarboxClopyralid 1977 46 19 14.8 amides Propaquizafop 1991 32 1 Fenoxaprop-P-ethyl 1990 33 1

AryloxyphenoxyQuizalofop-P-tefuryl propionates 1989 34 1 Quizalofop-ethyl 1989 34 7

39.5 10 7.8 Aminopyralid 2005 18 3

Aminopyridines Picloram 1963 60 7

39 10 7.8 Clethodim 1987 36 5

Cyclohexanediones Cycloxydim 1989 34 1

35 6 4.7 Imazamox Imidazolinones 2001 22 6 4.7 Quinmerac Quinolines 1993 30 6 4.7 Others 16 12.5 Total 128

Analysis of herbicide nomenclature and phytosanitary situation

Moreover, clopyralid is represented in 8 herbicides as the sole active ingredient:

• Agron, AS
• Bris, WDG
• Clorit, AS
• Lontrel Grand, WDG
• Lontagro, AS
• Lornet, AS
• Hacker, WGR

Metazachlor is also represented in eight products:

These facts, as well as the significant volumes of glyphosate application, contribute to the emergence of populations of weeds resistant to herbicides.

An analysis of the phytosanitary situation in rapeseed crops (winter and spring forms) indicates the need to carry out protective measures against a complex of harmful organisms. A key role here is played by the high-quality application of registered plant protection products.

Resistance management of harmful organisms

At the current stage of the chemical industry's development, the pace of developing new active ingredients for all types of plant protection products has decreased sharply. Manufacturers, when creating new pesticides, generally follow the path of recombining existing active ingredients.

To reduce the risks of resistance of harmful organisms to the most common classes of active ingredients (triazoles, strobilurins, pyrethroids, neonicotinoids, amides, pyridinecarboxamides, etc.), all elements of the management system for resistance must be strictly observed.