General enquiries on this form should be made to:



General enquiries on this form should be made to:

Defra, Science Directorate, Management Support and Finance Team,

Telephone No. 020 7238 1612

E-mail: petitions@defra..uk | |

|SID 5 |Research Project Final Report |

• λ Note

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| |Project identification |

|1. Defra Project code |PS2117 |

2. Project title

|Potential of simple salts to partially substitute for conventional foliar |

|fungicides on crops |

|3. Contractor |Harper Adams University College |

|organisation(s) |      |

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| |54. Total Defra project costs |£ 41,425 |

(agreed fixed price)

| |5. Project: start date |01 April 2007 |

| | end date |31 March 2008 |

6. It is Defra’s intention to publish this form.

Please confirm your agreement to do so. YES NO

(a) When preparing SID 5s contractors should bear in mind that Defra intends that they be made public. They should be written in a clear and concise manner and represent a full account of the research project which someone not closely associated with the project can follow.

Defra recognises that in a small minority of cases there may be information, such as intellectual property or commercially confidential data, used in or generated by the research project, which should not be disclosed. In these cases, such information should be detailed in a separate annex (not to be published) so that the SID 5 can be placed in the public domain. Where it is impossible to complete the Final Report without including references to any sensitive or confidential data, the information should be included and section (b) completed. NB: only in exceptional circumstances will Defra expect contractors to give a "No" answer.

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(b) If you have answered NO, please explain why the Final report should not be released into public domain

| |

| |Executive Summary |

7. The executive summary must not exceed 2 sides in total of A4 and should be understandable to the intelligent non-scientist. It should cover the main objectives, methods and findings of the research, together with any other significant events and options for new work.

| |

|Overall Aim: |

| |

|The scoping study aimed to explore the potential of reducing the environmental and food chain burden of chemical fungicides by exploiting |

|research which has shown that the severity of certain fungal pathogens, of both protected and field crops, can be reduced from applications of |

|inorganic salts. |

| |

|Background-Literature Review: |

| |

|The first of three objectives was to conduct a literature search on the topic of fungal disease control by inorganic salts by performing |

|keyword searches on bibliographic databases, such as Web of Science and Google Scholar. A systematic survey of the available scientific |

|literature on a global scale revealed 34 inorganic salts involved in the suppression of 49 fungal diseases across 35 plant species. Proven |

|antifungal activity occurs in each of five groups of inorganic salts: 1) bicarbonates (e.g. NaHCO3), 2) phosphates (e.g. KH2PO4), 3) silicates |

|(e.g. K2SiO3), 4) phosphites (e.g. KH2PO3) and 5) chlorides (e.g. KCl). Only one group, the phosphites, appeared to be target-specific |

|(Phytophthora spp. and downy mildews); the other groups were found to possess a broad spectrum of antifungal activity, mainly against foliar |

|and soilborne fungi, but even against postharvest fungi. Many contradictory reports were found with regard to the mode of action of inorganic |

|salts as antifungal substances. Collection and comparison of data from the most relevant, robust and advanced studies, indicated that the most |

|likely mechanisms involved are: 1) pH elevation and dehydration of fungal spores (HCO3-salts), 2) induction of systemic acquired resistance |

|(PO4-salts), 3) strengthening of cell walls on leaf surfaces resulting from the accumulation of flavonoid phytoalexins (SiO3-salts), 4) strong |

|and rapid stimulation of plant defence mechanisms and direct inhibition of fungal sporulation (PO3-salts) and 5) osmotic regulation (Cl-salts).|

|Powdery mildews of cucurbits (mainly cucumber), grapes, wheat and fruit trees were the most studied diseases (accounted for almost one-third of|

|all crop/pathogen/salt combinations) and most effectively and consistently managed by: 1) foliar applications of inorganic salts or 2) |

|hydroponic nutrient solutions amended with SiO3-salts (cucurbits). The existing evidence for these salts indicates that they are in general |

|less efficacious than conventional fungicides and could not, on their own, replace them. It appears that little work has been published on tank|

|mixtures of salts with fungicides. However, experiments on mangos and grapes have revealed that tank mixtures of phosphates or silicates with |

|half- or full-rate fungicides, respectively, enabled a 50% reduction in the number of fungicide applications needed to control powdery mildew. |

|This suggests that such an integrated approach should be investigated further. The use of alternate programmes (i.e. salts and fungicides |

|applied in rotation) in the management of foliar fungal diseases, for which more publications were found relative to tank mixtures, also |

|enabled a reduction in the frequency of fungicide applications required for effective control. These findings translate to both cost and |

|environmental benefits and merit further investigations in the UK. |

| |

|Commercial Use: |

| |

|The second objective was to conduct a review of the current commercial use of inorganic salts as alternatives to fungicides or as components of|

|integrated disease management strategies. The starting point was Internet searches of those inorganic salt-based products identified from the |

|literature survey as having potential for fungal disease control. Direct contact with companies selling such products for this purpose was also|

|established. Further to general technical information found on products’ labels, particular attention was given to the following: 1) |

|Identification of criteria and current registration status for inorganic salts used in fungal disease control in the UK and the USA, 2) |

|Evidence for compatibility with organic crop production systems, 3) Fungal pathogen-crop combinations where cost benefit and efficacy have |

|justified commercial application), 4) Evidence of combined use of products containing inorganic salts with conventional fungicides, 5) |

|Comparative efficacy with fungicides and 6) Market size. The key findings of these investigations are as follows: 1) 25 commercial |

|salt-containing products are registered in the USA by the Environmental Protection Agency (EPA) as “biopesticides” with approved uses for |

|fungal disease control (14 phosphites, 7 bicarbonates, 4 phosphates), 2) Four inorganic salts (CuSO4, KHCO3, NaHCO3 and K2SiO3) will have been |

|approved by the National Organic Program (NOP) of the US Department of Agriculture (USDA) by the end of 2008 for use in organic farming, |

|specifically for fungal disease control, 3) Potassium bicarbonate has been granted a Commodity Substance Approval in the UK by the Pesticide |

|Safety Directorate (PSD) and can be used on all crops (outdoor and protected) as a horticultural fungicide, 4) No commercial products approved |

|for use in fungal disease control were found for chloride salts. 5) The market for phosphites has developed since 2001 in the USA and is now in|

|the region of $4-5 million. |

| |

|Implications for future research: |

| |

|The third objective was to identify the scope for further research in the UK. The main target for further research has been identified as |

|powdery mildew (Sphaerotheca fuliginea) in cucurbits because: 1) there is good evidence for control (maximum efficacy 41-99%) by foliar sprays |

|of several inorganic salts from at least 20 peer-reviewed publications, 2) the industry finds it difficult to control, 3) there are very few |

|approved fungicides (e.g. three in pumpkin, all off-label) and there is evidence for resistance to one (bupirimate), 4) potassium bicarbonate |

|has a UK Commodity Substance Approval for this disease. |

| |Project Report to Defra |

8. As a guide this report should be no longer than 20 sides of A4. This report is to provide Defra with details of the outputs of the research project for internal purposes; to meet the terms of the contract; and to allow Defra to publish details of the outputs to meet Environmental Information Regulation or Freedom of Information obligations. This short report to Defra does not preclude contractors from also seeking to publish a full, formal scientific report/paper in an appropriate scientific or other journal/publication. Indeed, Defra actively encourages such publications as part of the contract terms. The report to Defra should include:

λ the scientific objectives as set out in the contract;

λ the extent to which the objectives set out in the contract have been met;

λ details of methods used and the results obtained, including statistical analysis (if appropriate);

λ a discussion of the results and their reliability;

λ the main implications of the findings;

λ possible future work; and

λ any action resulting from the research (e.g. IP, Knowledge Transfer).

Statement of objectives

The scientific objectives of this project were:

1. To review the scientific literature on fungal disease control with inorganic salts for both protected and field crops on a global basis.

2. To review the current commercial use of salts for fungal disease control for both protected and field crops on a global basis.

3. To assess the scope for potential use of simple salts on fungal pathogens of major conventional and organic crops in the UK, alone or in combination with conventional fungicides, leading to a recommendation of crops, target pathogens, salts and conventional fungicides (where appropriate) warranting further research and development in collaboration with industry through LINK.

The above objectives were fully met. The work was conducted by Dr. Thomas Deliopoulos under the direction of Dr. PS Kettlewell and Dr. MC Hare. The action resulting from this research is described at the end of this report.

1. Objective 1 – Review of scientific literature

Status: fully achieved

Research over the last few decades for alternative substances with fungicidal properties has revealed that a potentially useful component of integrated disease management (IDM) programmes against foliar fungal pathogens can be spray applications of inorganic salts, such as chlorides (Mann et al., 2004), phosphates (Mitchell and Walters, 2004) and bicarbonates (Fallik et al., 1997).

Although the component ions in salts can be either inorganic or organic, salts of the latter type, such as benzoates and acetates, are not discussed here as they are synthetic compounds with very little evidence for fungitoxic activity in comparison with inorganic salts and therefore were out of the scope of this review. Information on phytotoxicity from the use of inorganic salts is provided only in a small proportion of published articles and therefore when such data were available full details are given.

The review covers inorganic salts tested worldwide for their effects on fungal disease control, including salts of heavy metals/metalloids; exceptions are: (I) heavy metals or metalloids that occur often as environmental pollutants, that is Cd, Pb, Zn, Ni, Sb and Bi (Rengel, 2003) and (II) heavy metals prohibited to be placed on the market and used as plant protection products under the EU Council Directive 79/117/EEC (e.g. mercuric salts) (Anon., 1979).

The present study was designed with the aim of assessing the potential for reducing the environmental and food chain burden of conventional crop fungicides by exploiting the findings of the research described above. It also aimed to explore the possibility of using inorganic salts: 1) against fungal pathogens for which there is evidence for resistance to synthetic fungicides and 2) on crop/pathogen combinations for which there are few active substances available. To achieve these targets, the available scientific literature on fungal disease control with simple inorganic salts for both protected and field crops was reviewed on a global basis.

Information on the use of inorganic salts in fungal disease management was collected primarily from peer-reviewed papers. Relevant research reports and publications from governmental agencies and levy bodies, such as EPA (Environmental Protection Agency), the European Commission, HDC (Horticultural Development Council) and PSD (Pesticide Safety Directorate) were also included. Initial citation searches were taken from PhD literature surveys previously undertaken at Harper Adams University College (Cook, 1997; Mann, 1999). The majority of original papers, however, were identified from web-search based tools (mainly Web of Science but also Google Scholar) and obtained through the University College library electronic and hard copy journal subscriptions. When full-text papers were unavailable on-site, they were supplied by the British Library. All collected references were categorised into five main groups (see section 4.1) plus an extra group of miscellaneous relevant literature, using Endnote software version 9. Particular emphasis was given to recent papers, published in the course of the last 10 years, due to the tremendous advances in molecular biology and other scientific methods, which have aided in understanding the mode of action of several inorganic salts.

Numerous inorganic salts have been evaluated worldwide for their efficacy against fungal pathogens and the majority of published reports describe reductions in disease severity. The most common method of application involves foliar sprays with or without an adjuvant (e.g. oils, sucrose etc.). Some inorganic salts are applied through hydroponic nutrient solutions (root-applied, silicates only), while others are applied to the soil surface or as seed treatments. Their effectiveness has been investigated under a broad range of conditions, including, most commonly, glasshouse and field experiments, but also in vitro and controlled environments. The range of crops on which inorganic salts have been trialled for their suitability to suppress fungal diseases is also wide and includes both field and protected crops. The number of potential target fungal pathogens is also large covering diseases of the foliage, stem, ear, fruit/tubers (pre- and post-harvest), seed and the root. Emphasis is given to plant diseases affecting aerial plant parts, typically managed by foliar applications of conventional fungicides. Soilborne fungal diseases against which salts have shown proven efficacy are also discussed, but to a lesser extent. Powdery mildews are the diseases which control with inorganic salts has been investigated the most (more than 50 citations).

These inorganic salts are of low mammalian toxicity and most are widely used as food ingredients (Lindsay, 1985) or fertilisers (Simpson, 1986; Fixen, 1993). The evidence for disease control by these salts indicated that they were mostly less efficacious than conventional fungicides and could not replace them. Nevertheless, if used in mixture with fungicides or as a supplementary measure to an existing fungicide programme, inorganic salts could enable the quantity of conventional active substances or the number of fungicide applications to be reduced, therefore providing a more sustainable method for fungal disease control. It can be concluded that spray applications of inorganic salts can be a very useful component in the integrated management of foliar fungal diseases, particularly powdery mildews, and could lead to environmental and financial benefits. The main body of the Literature Review is presented in Section 4, after the report on Objective 3.

2. Objective 2 – Review of commercial use

Status: fully achieved

The starting point for collecting information on the current commercial use of inorganic salts in crop protection was Internet searches. A database of inorganic salt-based products exhibiting antifungal activity and of corresponding companies found in research papers from the literature survey (Objective 1) was initially created. Names of products and companies were then used as search terms in order to find their websites and obtain some technical (e.g. application rates and methods, spectrum of uses) and other information (e.g. effects on humans and the environment). Additional products not present in peer-reviewed journals were identified online and added to our database; sources were farming magazines, university/research stations trials results, gardener handbooks, technical bulletins and reports/newsletters from levy bodies. This was achieved by performing searches using relevant terms, such as biopesticides, natural/food-grade/environmentally friendly substances or using the names of particular salts (e.g. potassium bicarbonate) or their group (e.g. bicarbonates) or more specifically using the names of particular crop/pathogen/salt combinations. Data availability varied with company; some would provide online the product’s MSDS and label, while others would describe the basic properties of their product in the form of “material fact sheet”, “advantages of product”, “press release” or “technical information”. In addition to gathering general technical information for commercial products containing inorganic salts, attention was given to their registration status (Table 1), as this relates to the conditions under which these products can be sold and used.

Direct contact with companies selling such products was also established by a variety of methods including email, telephone or personal communication at agricultural events and conferences, e.g. in the ‘Potato 2007’ BPC Event, Harrogate and the International Plant Protection Congress 2007, Glasgow. The aim was to obtain some extra information on the current commercial use of inorganic salts mainly not available online. A questionnaire was also prepared and emailed or submitted via online forms to ten companies requesting information on the following topics: 1) Field/glasshouse trials results, 2) Range of crop-pathogen combinations where efficacy and cost benefit have justified commercial application, 3) Application methods and rates, 4) Evidence of combined use of name of product with fungicides, 5) Comparative efficacy with fungicides and 6) An indication of quantities sold. Although most companies responded, only five provided us with some data. The rest could not supply the information requested due to the proprietary nature of the data from a technical and business perspective but some advised us to look up brochures available on their website for technical information. One company, Nufarm Americas, Inc., provided information on the comparative efficacy of their product with synthetic fungicides.

By far the best response was received from PQ Corporation (Dr. Judy Thompson), a US company that has formulated three K2SiO3-based products; Sil-MATRIX™, AgSil® and KASIL® 6. In addition to answering as many of our queries as possible, the company provided us with 13 attached documents on the beneficial effects of K2SiO3 on crop protection, including revised petition to the National Organic Program (NOP) of the US Department of Agriculture (USDA), publications on the use of silicates against fungal pathogens but also against species of insects and nematodes. As informed by the company, the petition mentioned above for aqueous K2SiO3 has been approved by the National Organic Standards Board (NOSB) and it will be allowed for organic growing by the end of 2008. PQ Corporation also informed us that in the USA, to make any claim of plant disease control (whether or not it is a direct effect on the pathogen), the material must be registered with the EPA as a pesticide. Sil-MATRIX™ () is an EPA-registered pesticide and consequently the company can make the pesticide claims. This is the only K2SiO3 product sold for crop protection uses in the USA. Information on application rates is available on the EPA label. It is registered for control of the following diseases: 1. powdery mildew – grapes, cucurbits, ornamentals, 2. Botrytis – blueberry, 3. root diseases such as Pythium, Fusarium crown and root rot – cucurbits, peppers, 4. turf diseases including dollar spot, gray leaf spot, brown patch and powdery mildew. The product is also approved for insecticide and miticide uses.

Nufarm Americas, Inc., provided data on the use of Phostrol®. The main active substances in Phostrol® (53.6%) are mono- and dibasic salts of phosphorous acid. The product is labelled as fungicide with EPA and is included in the list of biopesticides. Target fungi include various Phytophthora and Pythium spp. and it can be used on many food and non-food crops, including turf, ornamentals and trees. The company has conducted two trials to compare the efficacy of Phostrol® and Alliete® in the control of Phytophthora palmivora, causal agent of brown rot. There were significant decreases (ranging from 35-90%) in disease incidence for both Phostrol- and Aliette-treated fruit 45 and 90 days after treatment, compared with the untreated. In both trials and observation dates, fruit treated with Phostrol had lower incidence of brown rot than Aliette, but the difference was significant only in one trial at the 90-day time period (c. 90% lower disease incidence in the former than the latter). The company also sent us results from research trials on the efficacy of Phostrol® (as foliar spray or postharvest treatment) against potato late blight and pink rot, in comparison with various synthetic fungicides (Ag Clor 310, Oxidate, Ranman 400, Ridomil Gold 4EC). Data showed that: a) Phostrol® was consistently more effective than the competitive treatments against both diseases and b) late blight control was optimised with three foliar applications of Phostrol® at 14 l ha-1. The US market for phosphites was non-existent in 2001 and is worth about $4-5 million today. Currently, the biggest markets in the USA are citrus, potatoes, leafy vegetables and grapes (Scott Reichl, Nufarm Americas, personal communication).

Mr Gary Schmunk, marketing manager of Helena Chemical Company informed us that Eco-Mate Armicarb “O”, which contains 85% KHCO3 active substance, is a registered product approved for use in organic crop production by the USDA NOP. It is approved for use on 89 plant species for the control of 20 foliar fungal diseases including several spots, blights and powdery mildews.

In the USA, any substance to be used in organic production has to be certified by the NOP. Petitions are prepared by companies and submitted for consideration to the NOSB in collaboration with a panel of technical advisory reviewers. Each of three reviewers uses scientific data to evaluate the proposed substance against seven criteria: 1. Potential for detrimental interactions with other materials used, 2. Toxicity, mode of action, breakdown products, persistence in the environment, 3. Probability of environmental contamination, 4. Effects on human health, 5. Effects on biological and chemical interactions in the agro-ecosystem, 6. Availability of alternatives and 7. Compatibility with sustainable agriculture.

The analysis summary includes the reviewers’ recommendation to NOSB on: a) whether the substance should be listed as synthetic or non synthetic in the ‘National List of Allowed and Prohibited Substances’ and b) whether the substance should be allowed or prohibited in organic crop production. The ‘National List of Allowed and Prohibited Substances’ is a list of exceptions to the general requirement that all naturally-occurring substances are allowed (unless listed as prohibited) and all synthetics are prohibited (unless they are on the list). Such substances may be synthetic, non-synthetic or non-agricultural (non-organic). Three inorganic salts petitioned for use in organic crop production, CuSO4 and KHCO3 (synthetic) and NaHCO3 (non-synthetic), have been specifically approved by NOSB for use in plant disease control without restrictions. Similar approval has been granted for horticultural oils, which are used as surfactants in foliar applications of inorganic salts. Other inorganic salts that have been approved by NOSB for use in organic crop production (allowed for specific uses or prohibited with exceptions) include: NaSiO3 (synthetic) – allowed only as floating agent in postharvest handling, CaCl2 (non-synthetic) – prohibited unless used as foliar spray to treat physiological disorders associated with calcium uptake, KCl (non-synthetic) – prohibited unless it derives from mined sources and is applied in a manner that minimises chloride accumulation in soil. A revised petition has been recently submitted to NOSB by PQ Corporation (Dr. Judy Thompson, personal communication) for aqueous K2SiO3 to be allowed for use in organic crop production. Further information on the current status of inorganic salts with respect to their use in organic agriculture in the USA (with NOSB recommendations) is available at .

Several inorganic salts were found to be included in the EPA website list of biopesticides (Table 2). Biopesticides are defined by the EPA as “naturally occurring substances that control pests” and classified in three main groups: a) biochemical pesticides (includes the inorganic salts), b) microbial pesticides and c) plant-incorporated protectants (). In Europe, biopesticides are regulated under Council Directive 91/414/EEC and are divided into four groups: a) biochemicals (includes inorganic salts), b) semiochemicals, c) microorganisms and viruses, d) macroorganisms. According to this Directive, before an active substance, including inorganic salts, can be approved for plant disease control, it has to be thoroughly evaluated in relation to six specialised areas: a) physical chemical properties, b) methods of analysis, c) mammalian toxicology and worker exposure, d) residues, e) ecotoxicology and f) efficacy (). Similarly, in the USA, the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) requires that EPA carries out extensive evaluation of the proposed substance to assure that there will be no unreasonable risks of harm to human health and the environment from its use ().

According to the EPA, the use of KHCO3 and NaHCO3 as fungicides was not expected to have any adverse effects on humans and the environment and would possibly offer an alternative to the more toxic conventional fungicides. The two compounds were eventually registered in the USA as pesticide ingredients in 1994 (Greenway, 1999). An additional advantage with respect to the use of these substances in plant disease management is that in 1996, the EPA has ruled that both are exempt from pesticide residues legislation. This development illustrates that the use of these materials is in accordance with food safety regulations and would facilitate the formulation of commercial bicarbonate products for use in horticulture (Kuepper et al., 2001). In the UK in 2005, KHCO3 (99.0% w/w) was granted Commodity Substance Approval and can be used on all crops (protected and outdoor) as a horticultural fungicide. It is currently sold in the UK as AgriKarb (food-grade KHCO3) by Farm-Fos Ltd. The maximum approved concentration for KHCO3 is 20 g l-1 and the maximum total dose is 60 kg ha-1 per annum (outdoor crops) (). Commodity substances are chemicals with various non-pesticidal uses and a limited number of pesticidal uses. If such substances are to be used as pesticides they must be approved under the Control of Pesticides Regulations (COPR) and are granted approval only for use (). Inorganic salt-containing commercial products with approved uses for fungal disease control are presented in Tables 1 and 2. The use sites, target diseases and application methods of the EPA-registered inorganic salt-containing biopesticides are summarised in Table 3.

Table 1. Fungal disease control-approved products containing inorganic salts and their registration status

|Product Name / Salt active substance |Company Name |Registration |

| | |Status*1 |

| A. Bicarbonates | | |

|Armicarb 100-F (KHCO3) |Church & Dwight Co., Inc. (NJ, USA) |BIO |

|Armicarb Potassium Bicarbonate, FCC (KHCO3) |Church & Dwight Co., Inc. (NJ, USA) |BIO |

|Armicarb Sodium Bicarbonate, FCC (NaHCO3) |Church & Dwight Co., Inc. (NJ, USA) |BIO |

|Armicarb Potassium Bicarbonate, TFF (KHCO3) |Church & Dwight Co., Inc. (NJ, USA) |BIO |

|GreenCure (KHCO3) |H & I Agritech, Inc. (NY, USA) |BIO |

|Kaligreen® (KHCO3) |Toagosei Co, Ltd (Tokyo, Japan) |BIO |

|Bi-Carb Old Fashioned Fungicide® (KHCO3) |Lawn and Garden Products, Inc. (CA, USA) |BIO |

|Eco-Mate Armicarb "O" (KHCO3) |Helena Chemical Company (TN, USA) |NOP |

|Omex K-50 (KHCO3) |Omex Agriculture Ltd (Lincoln, UK) |PHP |

|AgriKarb (KHCO3) |Farm-Fos Ltd (Hereford, UK) |CSA |

| B. Phosphates | | |

|Lexx-A-Phos fungicide (K2HPO4) |Foliar Nutrients, Inc. (GA, USA) |BIO |

|Vital (KH2PO4) |Luxembourg-Pamol, Inc. (TN, USA) |BIO |

|Ekspunge (KH2PO4) |Lidochem, Inc. (NJ, USA) |BIO |

|Nutrol LC (KH2PO4) |Lidochem, Inc. (NJ, USA) |BIO |

| C. Silicates | | |

|Sil-MATRIX™ (K2SiO3) |PQ Corporation (PA, USA) |NOP*2 |

| D. Phosphites | | |

|14 products (H3PO3 and its K, Na, NH4 salts) |see Table 2 |BIO |

|Exel LG systemic fungicide (KH2PO3, K2HPO3) |Organic Laboratories, Inc. (FL, USA) |SYS |

*1 BIO; Biopesticide = Environmental Protection Agency (EPA)-registered/USA (pesticides/biopesticides), CSA; Commodity Substance Approval = Pesticide Safety Directorate (PSD)-approved/UK

(), NOP; National Organic Program (NOP), = approved by the US Department of Agriculture (USDA) for organic crop production (ams.nop), PHP; Plant Health Promoter, contains 50% KHCO3, SYS; Systemic fungicide (images/logos/110_MSDS%20Exe%20LGl.doc) *2; effective from end of 2008 (Dr. Judy Thompson, PQ Corporation, personal communication)

3. Objective 3 – Scope for further research in the UK

Status: fully achieved

In order to fulfil this objective, three stages of work were involved. The first stage was to use the information from Objective 1 which identified salts with efficacy against fungal diseases. The literature review revealed that several salts belonging to different groups were effective against a particular disease. For example, 16 different salts have shown efficacy against powdery mildew in cucurbits, while grape powdery mildew or wheat leaf rust were found to be suppressed from applications of five and four inorganic salts, respectively. The second stage was to identify intractable disease problems relevant to the UK, based on the following main criteria: 1) limited number of approved fungicides, 2) pathogen resistance to synthetic fungicides, 3) problems with synthetic fungicide residues. The third stage was to examine the weight of published evidence (Objective 1) and commercial evidence (Objective 2) for control by salts of the intractable diseases identified in the second stage. The output of these three stages was a shortlist of candidate crop-pathogen-salt combinations for further research in the UK (Table 4).

Table 2. Commercial products containing phosphorous acid and its potassium, sodium and ammonium salts; registered in the USA by the Environmental Protection Agency (EPA) as biopesticides for fungal disease control

|Product Name |Company Name (State) |Approved for use on lettuce vs. downy mildew (Bremia |

| | |lactucae) |

|Agri-Fos Systemic Fungicide |Liquid Fertiliser Pty. Ltd (trading as |Yes |

| |agrichem) (IL) | |

|Arborfos |J. J. Mauget Co. (CA) |No |

|Fosphite Fungicide |JH Biotech, Inc. (CA) |Yes |

|Fungi-Phite |Plant Protectants, LLC (CA) |Yes |

|Phos Pro Fungicide |Grow More, Inc. (CA) |Yes |

|Phospho-Jet |Arborjet (MD) |No |

|Phosphorous Acid Technical |Nufarm Americas, Inc. (IL) |No |

|Phostrol Agricultural Fungicide |Nufarm Americas, Inc. (IL) |Yes |

|Plant Synergists Phosphorous Acid Technical |L & L Formulators, LLC (WA) |No |

|Prophyt |Luxembourg-Pamol, Inc. (TN) |Yes |

|Resist |Actagro, LLC (CA) |Yes |

|Riverdale Magellan |Nufarm Americas, Inc. (IL) |No |

|Vital-Sign |Luxembourg-Pamol, Inc. (TN) |No |

|Whippet Fungicide |Arbor Systems, LLC (NE) |No |

Table 3. Use sites, target diseases and application methods of inorganic salt-containing biopesticides registered in the USA by the Environmental Protection Agency (EPA) with approved uses for fungal disease control

|Inorganic salt (No. of products) |Use sites |Target diseases |Application method |

|Potassium and sodium bicarbonate (7) |Wide range of fungal diseases |All food commodities, turf, flowers |Diluted with water and sprayed on |

| |(including powdery and downy |and ornamentals. |foliage using ground equipment. |

| |mildew) | | |

|Dipotassium phosphate (1) |Broad spectrum: powdery mildew, |Woody ornamentals, turfgrass, |Leaf spray or soil drench at a rate |

| |leaf spot, root rot, downy mildew,|non-bearing fruit and nut trees and |of 1-2% v/v. |

| |etc. |grapes. | |

|Potassium dihydrogen phosphate (3) |Powdery mildew |Apples, grapes, cucumbers, melons, |As needed (not specified). |

| | |summer and winter squash, |Applications should be repeated at |

| | |watermelons, mangos, peaches, |7-14- day intervals, depending on |

| | |nectarines, plums, cherries, peppers,|infestation intensity. |

| | |tomatoes and roses. | |

|Phosphorous acid and its ammonium, sodium|Phytophthora and Pythium spp. |Many food and non-food crops, |Before disease onset, then at 2-3 |

|and potassium salts (14) | |including turf, ornamentals and |week intervals. As foliar spray, |

| | |trees. |sprinkler irrigation systems, direct |

| | | |addition to soil, root dipping |

| | | |transplant. |

Table 4. Main target fungal diseases for practical research with inorganic salts in the UK

|Disease/ | Fungicides (BCPC, 2008) |Intractable Disease Problems |Salts (weight of |

|crop/fungus | | |evidence) |

| |On-label a.s. |Off-label a.s. | | |

| | | | | |

|Powdery mildew / cucurbits / |1. bupirimate (pro+out) |1. azoxystrobin (pro+out) |1. Resistance to bupirimate &|KHCO3, K2HPO4, |

|Sphaerotheca fuliginea, |2. imazalil (pro) |2. bupirimate (pro) |imazalil (Alford, 2000) |KH2PO4, K2SiO3, MnCl2 |

|Erysiphe cichoracearum |3. copper ammonium |3. Fenarimol (pro+out) |2. Mildew tolerant cultivars:|etc. |

| |carbonate (out) |4. myclobutanil (pro+out) |chlorosis under low light, |(numerous publications|

| | |5. sulphur (pro) |lower yields compared with |and commercial |

| | | |susceptibles (Alford, 2000) |products, 1 Commodity |

| | | | |Substance Approval: |

| | | | |KHCO3) |

|Downy mildew / lettuce / |1. mancozeb (pro+out) |1. dimethomorph+mancozeb (out) |1. Can devastate crops in |K2HPO3, KH2PO3 (few |

|Bremia lactucae |2. propamocarb HCl |2. fosetyl-Al (pro+out) |prolonged wet & cool |publications on other |

| |(pro+out) | |conditions (RHS, 2008) |crops, e.g. grape, |

| |3. fosetyl-Al (pro) | |2. 14% samples of protected |pumpkin, Speiser et |

| |4. thiram (pro) | |lettuce residues > MRLs (PSD,|al., 2000; Cushman et |

| | | |2003) |al., 2007; numerous |

| | | |3. Insensitive isolates to |commercial products, |

| | | |fosetyl-Al reported in CA, |especially phosphites,|

| | | |USA (Brown et al., 2004) |Table 2; 1 US patent: |

| | | | |6,911,415 B1) |

pro = protected only; out = outdoor only; pro+out = protected and outdoor

Powdery mildew (Sphaerotheca fuliginea Schlecht. ex Fr. and Erysiphe cichoracearum DC. ex Merat) in cucurbits was identified as the main target for further practical research with inorganic salts in the UK. The survey identified 16 salts (silicates, bicarbonates and phosphates) with potential to suppress powdery mildew in cucurbits (percentage reduction in disease severity compared with untreated controls was 41-99%, calculated from the best treatment of each of 20 peer-reviewed studies; examples shown in Table 5). Powdery mildew fungi have a high potential for fungicide resistance development (e.g. bupirimate and azoxystrobin). In bicarbonates, the multiple mechanisms found to be involved in disease suppression (pH elevation on leaf surface, potassium ion imbalance, dehydration of fungal spores) suggest a lower risk of resistance development relative to synthetic fungicides. Phosphates and silicates appear to have more specific modes of action; induction of systemic acquired resistance and accumulation of flavonoid phytoalexins on infected leaves, respectively. Application of salts is primarily by foliar sprays of 0.5-1% (5-10 g l-1) solution, plus an oil or surfactant adjuvant, beginning before the onset of the disease or at first sign of symptoms and then at 7- to 10-day intervals until harvest. Symptoms of slight phytotoxicity (e.g. leaf scorch) have been reported when rates were increased to 2%. The evidence for powdery mildew control by these salts indicated that they are either equally effective (e.g. KH2PO4 vs. pyrifenox) or less effective (e.g. KHCO3 vs. myclobutanil) than conventional fungicides. There was no evidence that salt-fungicide tank mixtures enhance the efficacy of the fungicide treatment alone against cucurbit powdery mildew. The high efficacy of inorganic salts in suppressing cucurbit powdery mildew (Table 5) coupled with recent advances in the formulation of bicarbonate, phosphate and silicate salts (Table 1) may enable a reduction in the number of fungicide applications needed. The challenge remains to identify the rates of fungicides required for optimum control in combination with inorganic salts (applied separately).

Downy mildew (Bremia lactucae) in lettuce has been identified as an additional target for further research because few fungicides are approved for this use and published evidence shows insensitivity to approved products and residue problems. The survey found evidence of suppression of downy mildew by phosphite salts on grapes. Successful strategies for using inorganic salts on these two targets have the potential to be extended to a wide range of other species.

Based on the above criteria, major UK crop diseases for which there is a large number of fungicide active substances available were not identified as an immediate target for future research. This was despite the fact that the scoping study revealed evidence for efficacy with foliar applications of inorganic salts, in both scientific papers and commercial products brochures. Three such diseases in the UK are wheat powdery mildew and septoria leaf blotch and potato late blight, for which there are 37, 66 and 20 registered fungicides available (BCPC, 2008). For other diseases, such as greymould in strawberries (Botrytis cinerea), there seems to be no benefit from introducing inorganic salts in spraying control programmes, because there was no convincing evidence in the literature for efficacy by salts and there are several fungicides available.

Table 5. Published evidence of significant suppression of powdery mildews in cucurbits (Sphaerotheca fuliginea Schlecht. ex Fr. or Erysiphe cichoracearum DC. ex Merat) following applications of inorganic salts

|Ino|Adjuvant |

|rga| |

|nic| |

|sal| |

|t | |

|*1 | |

9. This section should be used to record links (hypertext links where possible) or references to other

published material generated by, or relating to this project.

| |

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