NZ202344A - Fungicidal compositions and use in dressing seeds or treating crops:two active ingredients - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £02344 202344 Priority Date(s): Complete Specification Filed: .^7//.*.??£ Class: . fiQ./Mj/QQ:, Publication Date: .... P.^P,j?®?, P.O. Journal, No: .$3%' NEW ZEALAND PATENTS ACT, 1953 x IWe* IMPERIAL CliEfllCAL INDUSTRIES PLC of Imperial Chemical House, Millbank, London, SW1P 3J7, England, a British Company hereby declare the invention for which ^ / we pray that a patent may be granted to me/us, and the method by which it is to be performed, XX to be particularly described in and by the following statement:- 1 (followed oy page la) 202344 K- FTTNOTPTflAT. rOMPflSTTTOMB This invention relates to compositions for combating plant fungi. More particularly the invention relates to mixtures of fungicidal substances containing a pyrimidine derivative such as the fungicides ethirimol, dimethirimol 5 and bupirimate and at least one other anti-fungal substance having a different mode of anti-fungal effect.

The hydroxypyrimidine fungicides, ethirimol, dimethirimol and bupirimate are used commercially to control powdery mildews on a variety of crops, including 10 cereals, cucurbits and apples. These fungicides have been shown to have a mode of action based upon the inhibition of the enzyme adenosine deaminase.

It is known that plant fungi, especially races (strains, types) thereof, can develop resistance to, that 15 is become insensitive to, anti-fungal chemicals thereby reducing the efficacy of a particular chemical. Insensitivity to the hydroxypyrimidine fungicides dimethirimol (by cucurbit powdery mildew) and ethirimol (by barley powdery mildew) has been reported* There are also believed to be in existence certain plant fungal pathogens which, axe resistant to fungicides of the type which combat them by inhibiting their ability to biosynthesise certain 25 steroids essential to their metabolism, for example ergosterol. These fungicides, more specifically either block the incorporation of acetate into ergosterol, an essential metabolic pathway of the fungus. Thereby disrupting the synthesis and function of cell membranes by 30 the fungus. Plant pathogens of the latter type include, in particular, races etc., of powdery mildew diseases such as Erysiphe graminis which infect'cereal plants, for example crops of barley and wheat, and mildews which infect non-cereal crops such as vines and apples, such latter diseases 2 being for example, Uncinula necator, Podosphaera . leucotricha and Sphaerotheca fuliginea or other diseases such as Venturia inacguatis on apples or Cercospora leaf spots on peanuts, banana and sugar beet. The triazole 5 fungicides (e.g. triadimefon, triadimenol, etaconazole, propiconazole, fluotrimazole, bitertanol and diclobutrazol) are used extensively in agriculture to control a range of fungal diseases of cereals, vines, apples and other crops, 10- along with several imidazole fungicides (e.g. imazalil, prochloraz and fenaponil) and certain tricyclic pyrimidine fungicides (e.g. nuarimol and fenarimol) have been shown to have a mode of action based on the inhibition of the 14 alpha demethylase enzyme complex of sterol biosynthesis in 15 fungi. However, resistance (Insensitivity) to triadimefon and triadimenol in barley powdery mildew populations has been reported. Cross-resistance between members of these groups of fungicides 20 has been demonstrated. Surprisingly, however, no examples of cross-resistance between an adenosine deaminase inhibitor and a 14 alpha demethylase inhibitor have so far been __ demonstrated.

Thus it.has now been found that certain mixtures of, or combinations of, fungicides are not only less prone than the individual components thereof to suffer from reduction in their efficacy due to resistant (insensitive) species of plant pathogens infecting crops upon which they are sprayed 30 (or the seed pre-treated with them), but in addition often display synergism, that is to say the combined antifungal effect of the mixture is greater than that which would have been expected if the fungicidal components were active separately. Such mixtures are ones in which a pyrimidine 35 fungicide is combined with one or more fungicides having a different mode of action against the fungal pathogens being combated. 3 According to the present invention there is provided an anti—fungal composition comprising a synergistic mixture of a pyrimidine fungicide and at least one further fungicide having a sterol biosynthesis blocking mode of action in its antifungal effect.

By "a pyrimidine fungicide" is intended single ring compounds such as ethirimol, dimethirimol and bupirimate. The term is not intended to embrace bicyclic and tricyclic compounds in which a central carbon atom bears a . pyrimidine ring and one or more other aryl or heterocyclic rings.

The fungicide ethirimol is the subject of New Zealand) Patent Specification No 148027 and it has the chemical structure CH OH N \ The fungicide dimethirimol is also the subject of New Zealand Patent Specification No 148027 and it has the cnemical structure:- CH3 °H ?P2M4 4 The fungicide bupirimate is the subject of New Zealand Patent Specification No 1682621 and it has the chemical structure:- In a further aspect the invention provides an antifungal composition comprising a pyrimidine fungicide which is ethirimol, dimethirimol or bupirimate and at least one further anti-fungal substance which is an inhibitor of the ability of the fungus to biosynthesise sterols. Examples of such compounds, and the class to which they belong, are as follows:- CLASS AND TRADE NAMES OP FUNGICIDAL PRODUCTS COMMON NAME CONTAINING THE FUNGICIDE OF FUNGICIDE Imidazoles Imazalil Fungaflor, Mist-O-Matic Murbenine H Prochloraz Plus, Mist-O-Matic. Muridal Seed Treatment Sportak Fenaponil •i ^2 7-saw; CY r^j 202344 Piperazines Triforine Pyridines Buthiobate 5 EL 241 Piperidines Fenpropidin Pyrimidines Fenarimol 10 Nuarimol Triarimol Triazoles Bitertanol 15 Diclobutrazol Fluotrimazole Propiconazole Triadimefon Triadimenol Etaconazole PP969 Saprol, Triforine LST, Nimrod T Parnon Rubigan Triminol, Mist-O-Matic Murox Seed Treatment Baycor, Sibutol Vigil, Vigil K, Vigil T Persulon Tilt 250 EC, Tilt mbc 45WP, Radar Bayleton, Bayleton 5, Bayleton BM, Bayleton CF Baytan Vanguard, Sonax 2023 Morpholines Dodemorph Fenpropimorph Tridemorph BASF F238 Corbel, Mistral Calixin, Bardew, Beacon, Cosmic The chemical structures of the foregoing chemical substances are set out below:- 20234 4 " 7 ~ IMIDAIOLES CI I2 ^5 CI C" * £ 6 ImiiHI PIPERAZINES f«n.ponU prochlorar <pto CHO f f —rn triforin* ^ W f 3 CC13 pyridines ob c4«9-s-f-s- <*r£}-ctc"3>3 ci^O~rO~ci 6 6 buth5obate EL-241 • P2PXPIDIWES O* (a,3> 3 f enpropiiin pypiMiDiuss I f enaria>ol traariinol TRIA20LES /~W CI CH—CHOH—C (CH,)., I 33 Cl D X .0 ci / H<-CH —CHOH—C (CH-) A o bi ter^anol CF.

CH<3 Cj fluotrimazole propiconazole CGA 64250 R=n-C3H7 etaconazole CGA 64251 K-C2H5 di clobutrazol ci- — CH—C—C(CH3)3 c1_^/\_0_ch—CHOH—C(CH3)3 & CS triadimefon triadimenol OH I Ti tL-C4H9— CH—CH—CH2—- C 1"C4H9 u .4^3 PP969 KORPHOLINES cb3 . T03 CH, CH. <So<5 eroorph f enpr opimorph """4' trideroorph It is to be noted that all of the foregoing classes, with the exception of the morpholines and piperidines, are ones which interfere with fungal metabolism by blocking the 14 alpha demethylase complex in the biosynthesis of 5 ergosterol thus disrupting the synthesis and function of the cell membranes of the fungus. The morpholines inhibit the piperidinesA? to A ' isomerisation during the conversion of fecosterol to episterol.

In a further aspect, therefore, the present invention 10 provides a fungicidal composition comprising ethirimol, dimethirimol or bupirimate and at least one further antifungal substance as defined above.

In a preferred aspect the invention provides an antifungal composition for treating cereal seed which 15 comprises ethirimol and at least one fungicidal substance selected from the foregoing substances defined above.

The invention also provides a process for treating seed which comprises dressing seed with a composition according to the invention.

In another aspect seed may be dressed first with ethirimol and then with a fungicide which inhibits sterol biosynthesis in plant fungi. Batches of seed treated with one, or both, such fungicidal substance types may be mixed with untreated seed, e.g. tumbled therewith, so as to '25 produce a batch of treated seed.

The invention further provides, in yet another aspect, a process for combating plant fungi which comprises applying to a plant, to seed of a plant, or to the locus of a plant or seed, an anti-fungal composition 30 as defined in any of the preceding paragraphs.

In a still further aspect the invention provides a process of combating plant fungi which comprises alternately treating, e.g. spraying crops with ethirimol, dimethirimol or bupirimate and with a fungicide which 3 5 inhibits sterol biosynthesis in plant fungi. 2023 4 The amounts of fungicidal substance used in the invention compositions can readily be determined by simple experimentation, but in general, in view of the ability of the invention compositions to better combat resistant 5 (insensitive) races etc., of plant fungi and the synergism displayed, it is not necessary to use the full rates of chemical normally applied.

By way of illustration only there are described various experiments which have been carried out to 10 investigate the interaction between triadimefon (as an example of a fungicide which inhibits 14 alpha demethylase activity) and ethirimol (as an example of a hydroxypyrimidine fungicide which inhibits the enzyme adenosine deaminase) in controlling barley powdery mildew 15 (as an example of a powdery mildew) isolates resistant to one or other groups of fungicides.

EXAMPLE 1 Materials and Methods 1) Plant Sowing : Approximately 10 seeds/pot of Golden 20 Promise spring barley were sown into John Innes compost number one in minipots. 1.1. Growth Conditions : Day temperature 21"C, Relative Humidity 60%, Night temperature 17°C, Relative Humidity 95%, 16 hour daylength.

The plants were watered by an automatic watering system. 2) Test method for spraying the plants : Plants were sprayed at 6 days old; the chemicals were made up in 0.03% Tween 20; and the plants were sprayed to give an even coverage on both leaf surfaces, using a hand held De Vilbiss spray gun at 15 psi (pounds per square inch).

After spraying the plants were transferred to a second growth chamber for 24 hours to allow plants to dry. 2.1. Growth conditions in this room were : Day temperatue 24°C, Relative Humidity 60%, Night temperature 17°C, 5 Relative Humidity 95%, 16 hour daylength. The plants were watered by an automatic watering system. 3) Method for preparing the repli dishes ; Plants were removed from the Growth Room and cut into 2 cm lengths from just below the tip of the prophyll. Only uniform plants 10 were chosen. Only one leaf piece was taken from each prophyll.

The cut leaf pieces were then placed into a slit in the agar in the repli dish. The dishes contained 45 ml of 10% tap water agar. The top rate of chemical first proceeded by 15 lower rates. For each chemical rate there were 5 replicate leaf pieces.

When changing from one rate of chemical to a lower rate the scissors and forceps were wiped with a swab soaked in Methanol to avoid contamination. Particular attention was 20 paid to ensure that the leaf pieces did not touch the lid nor overlap one another in the dish. The former would cause condensation to run down the leaf pieces and could wash off some spores, the latter would lead to uneven inoculation and hence misleading results. 4) Inoculation Method : Infected leaf pieces were cut from stock plants in propagating tubes and placed in petri dishes on moist foam squares 48 hours prior to inoculation, The infected leaf pieces were kept in a 19°C constant temperature room with a 16 hour day length.

Repli dishes were inoculated using a settling tower, the tower was placed over the opened repli dish and sporulating leaf pieces held in forceps were placed in the nose of the tower. An air line set at 3/41b per square inch pressure 5 was used to blow the spores off the leaf pieces and into the settling tower.

The repli dishes remained inside the tower for 2 minutes after which the tower was removed and the lid replaced on the repli dish. The tower, forceps and air line were 10 swabbed with Methanol to decontaminate them.

Once all of the repli dishes were inoculated they were placed in a 19°C constant temperature room with a 16 hour daylength, where they remained until assessment 6 days later. 5) Assessment : The percentage sporulating disease on the leaf pieces was assessed and the results statistically analysed.

RESULTS In the first experiment a number of isolates of barley 20 powdery mildew were obtained which represented varying degrees of sensitivity to ethirimol and triadimefon. These were tested as indicated earlier with the following results.

Relative Sensitivites of Various Isolates+ of Barley Powdery Mildew % control (based on % leaf cover) Chemical Rates ppm ai 1 2 Isolates 3 4 6 Ethirimol 0.5 100 100 100 100 100 99 0.1 99 100 97 100 59 0 0.05 87 97 39 0 Triadimefon 0.5 100 100 100 100 100 100 0.1 51 100 100 100 0.05 100 0 0 99 100 + Origin of isolates i i—■ Isolate No.

Year of Isolation Barley Variety from which isolated Crop treated in the field with (a> 1 1 1973 - - 2 19 78 Wing Triforine Seed Trt 3 1981 Golden Promise Triadimefon Spray KJ O 4 1981 Golden Promise Triadimefon Spray 1973 Julia Ethirimol Seed Trt NJ 6 1980 Wing Ethirimol Seed Trt OJ £02 3 4 Isolates of barley powdery mildew which were sensitive to ethirimol (isolates 1, 3 and 4) were relatively insensitive to triadimefon, whereas isolates 5 and 6 which were sensitive to triadimefon were relatively insensitive to 5 ethirimol. Isolate 2, which originally came from a triforine seed treated crop was sensitive to both fungicides. These data, obtained from a limited number of barley powdery mildew isolates, suggests a negative correlation between the isolates in their resistance to either ethirimol or 10 triadimefon.

Isolate 1 was chosen for further work as an example of a triadimefon insensitive (but ethirmol sensitive) isolate and isolate 5 as an example of an ethirimol insensitive (triazole sensitive) isolate for further experimentation.

EXAMPLE 2 In a further experiment triadimefon and ethirimol were examined for their ability to potentiate each others activity against isolate 5, both alone and in various ratios, over the rate range 0.01 to 0.5 ppm (ppm = parts 20 per million).

Results ethirimol insensitive isolate (Tables 1 and 2) With isolate 5 (an ethirimol insensitive isolate) ethirimol showed no activity over the rate range tested. Which is perhaps surprising in that it showed some activity at 0.1 25 and 0.5 ppm in the first test which characterised these isolates. However, variation between tests is not uncommon in such experiments due to slight differences in the conditions in which plants are grown etc. The results within the experiment were, however, consistent.

Z0234 Results Triadimefon alone, Ethirimol alone, and three mixture ratios of triadimefon and ethirimol were tested for their activity against an isolate of Erysiphe graminis f. sp. hordei (Isolate 5). Table 1 shows the activity for each fungicide or mixture, expressed in terms of percentage disease control compared to untreated controls, at a range of total active ingredient rates.

I o TABLE 1. Activities of various proportions of Triadimefon : Ethirimol Total ppm a.i.

Rate Mixture Triadimefon : ethirimol 0.01 0.02 0.03 0.04 0.05 0.10 0.50 % Disease control 50 : 50 97.00 95.00 98. 75 99. 75 98. 75 99. 75 100 : 75 68. 75 47.50 93.50 93.00 99.25 99. 75 100 75 j ; 25 - 70.00 83. 75 88.25 88.50 92. 75 100 0 i : 100 0 0 0 0 0 0 0 100 : : 0 52.50 72.50 65.00 90.00 96. 75 90.00 100 20X144 TABLE 2 LC50's and Co-toxicity coefficients of Triadimefon: ethirimol Mixtures A fit of parallel logit-logarithm dose response curves gives the estimates of LC50's* for each mixture as shown in 5 Table 2. Also shown are the co-toxicity coefficients which indicate synergism for the 50% — and 25% triadimefon mixtures (being far in excess of 100), but probably not for the 75% triadimefon mixture. The co-toxicity coefficients were calculated using a conservative 10 estimate of 0.50 for the LC50 of ethirimol.

* LC50 = concentration of chemical resulting in a 50% reduction in disease relative to the controls.

Mixture Co-toxicity Triadimefon : Ethirimol LC50 Co-efficient 50 : 50 0.00159 1330 : 75 0.00861 471 75 : 25 0.01147 125 0 : 100 0.5 100 : 0 0.01080 This part of the invention therefore clearly demonstrates synergy between triadimefon and ethirimol in controlling an isolate of barley powdery mildew which is relatively insentive to ethirimol.

HGHA/jw/SPEC286 ^27JUNBB5 ^ M. t vviiihm * .e Fnv-fJ*-' 202344

Claims (2)

WHAT WE CLAIM IS:

1. An anti-fungal composition comprising a synergistic mixture of a pyrimidine fungicide as hereinbefore defined and at least one further fungicide having a sterol biosynthesis blocking mode of action in its anti-fungal effect.

2. An anti-fungal composition according to claim 1 wherein the pyrimidine derivative has the chemical structure: or n—C4H9 CH-\- OH II N .N N H" C2H5 , n-C4H9 CH \ OH Nv.^N /N\ CH CH- J 1 o 202.344 - 19 - An anti-fungal composition as claimed in claim 1 or claim 2 wherein the further fungicide is a triazole, imidazole, piperazine, pyridine, piperidine, pyrimidine or morpholine compound. An anti-fungal composition as claimed in any of the preceding claims wherein the further fungicide is one or more of the specific fungicides hereinbefore set forth. A process of treating seed which comprises subjecting the seed to a dressing treatment with an anti-fungal composition as defined in any of the preceding claims. A process of dressing seed which comprises dressing seed separately with ethirimol and separately with a fungicide which inhibits sterol biosynthesis. A process for combating plant fungi which comprises applying to a plant, to seed of a plant, or to the locus of a plant or seed, an anti-fungal composition as defined in any of claims 1 to 4. A process of combating plant fungi which comprises alternately treating crops with —-—— ethirimol, dimethirimol or bupirimate and with a fungicide which inhibits sterol biosynthesis in plant fungi. DATED THIS c2^^DAY CF A . J . PA R K & SON PER °Y CLQjQ;S4^--I AGENTS FOR THE APPLICANTS fV.r S/l' ; <r o . L 7/ /