WO1993003613A1

WO1993003613A1 - Broad-spectrum biocompatible fungicides

Info

Publication number: WO1993003613A1
Application number: PCT/US1991/007825
Authority: WO
Inventors: Lawrence Kirschner; R. Kenneth Horst
Original assignee: Church & Dwight Company, Inc.
Priority date: 1991-08-19
Filing date: 1991-10-22
Publication date: 1993-03-04
Also published as: AU8869391A

Abstract

Biocompatible broad-spectrum fungicidal compositions are provided which include a bicarbonate in combination with a horticultural oil. The bicarbonate concentration is in a range of about 0.0125 to 0.5 % (w/v). The horticultural oil is in a concentration in the range of about 0.5 to 1.0 % (v/v).

Description

BROAD - SPECTRUM BIOCOMPATIBLE FUNGICIDES

Field of the Invention The invention relates to fungicidal compositions which employ one or more bicarbonates in combination with a horti- cultural oil and methods of using same.

Background of the Invention Fungus infections account for significant losses in crop and plant production. A number of fungicides are available in the marketplace to combat this problem. However, none is completely satisfactory, especially from the environmental standpoint.

For example, fungicides may have a very limited spectrum of activity, i.e., they may only be active against certain species of fungus and/or on certain types of plants. Other fungicides, such as the bisdithiocarbamates, are known to have a broad spectrum of activity against many types of fungus infections. However, due to the high toxicity of these latter fungicides, they are gradually being regulated out of common usage. Indeed, the potential environmental damage caused by conventional fungicides is a major disadvan¬ tage in their continued use.

It has been reported that sodium bicarbonate has fungi¬ cidal properties. See e.g.. Punja et al. "Effects of Inorgan¬ ic Salts, Carbonate-bicarbonate Anions ... On Sclerotial Germ- ination of Sclerotium rolfsii.¹¹. Phytopathology Vol. 72, pp. 634-639 (1982) . Additionally, it has been reported that combining sodium bicarbonate with an emulsifier (glycerine fatty acid ester) or with a surfactant improves adhesion of sodium bicarbonate to plant leaves, avoids crystallization thereof and obtains uniform distribution on the surface of the leaves to improve antifungal results over the use of aqueous solutions of sodium bicarbonate alone. See Journal of Pesti¬ cide Science, Vol 6, pp. 145-153 and pp. 201-209 (1981) . A disadvantage of using sodium bicarbonate with or without an e ulsifier/surfactant is that it is washed off the plant leaves by rainfall or supplemental watering. Therefore, such fungicidal compositions suffer the disadvantage that they require repeated application to maintain a desired level of effectiveness.

In general, sodium bicarbonate is known to be effective against various fungi at a concentration of 2,000 ppm (2% (w/v)). For example, U.S. Patent No. 4,599,233 discloses that sodium bicarbonate in combination with an emulsifying agent is 98-100% effective against cucumber powdery mildew (Sphaero- theca fulginea) at a concentration of 2,900 ppm. Efficacy dropped off slightly at 1,000 ppm and was markedly reduced at 500 ppm. Sodium bicarbonate was even less effective at the lowest dose tested, 250 ppm. The effectiveness also varied depending on the choice of e ulsifier and concentration thereof. In all cases, however, a sodium bicarbonate concen¬ tration of at least about 1,000 to 2,000 ppm was required to achieve effective fungicidal activity.

Summary of the Invention

It has now been found that a bicarbonate, particularly sodium bicarbonate, potassium bicarbonate and/or ammonium bicarbonate when combined with a horticultural oil in aqueous solution or suspension provides a broad spectrum biocompatible antifungal composition which is extremely effective at significantly lower bicarbonate concentrations than previously reported.

The inventive compositions include the bicarbonate in the range of about 0.0125 to 0.05% (w/v), more preferably about 0.0125%, in combination with the horticultural oil in an amount of about 0.05 to 1.0% (v/v) in aqueous solu¬ tion/suspension. Preferably the bicarbonate is sodium bicar¬ bonate, potassium bicarbonate or ammonium bicarbonate, most preferably sodium bicarbonate. Preferably a spreader-sticker type horticultural oil is used, such as Triton B, Rohm and Haas Co., Philadelphia, PA or Sun Spray^® Ultra Fine™ Oil, Safer^® Incorporated, Newton, MA. In accordance with the invention, the above-described antifungal compositions are applied to fungus infected plants weekly during the production season or as needed.

Accordingly, it is an object of the present invention to provide a broad spectrum biocompatible antifungal composition. Other objects of the invention will be apparent from the following drawings and detailed description of the invention.

Description of the Drawings

Figure 1 shows the average disease severity rating of powdery mildew on five combined rose cultivars Bridal Pink, Lavande, Prive, Royalty, and Sonia treated with NaHCO- and oil, alone and in combination. Lines on each bar represent standard deviations at each date.

Figure 2 shows the average disease severity rating of powdery mildew on untreated rose cultivars Bridal Pink, Gold Rush, Lavande, Prive, Royalty, Samantha, and Sonia. Lines on each bar represent standard deviations at each date. Figure 3 shows the average disease severity rating of powdery mildew on individual rose cultivars Bridal Pink, Lavande, Prive, Royalty, Samantha, and Sonia. Lines on each bar represent standard deviations at each date.

Figure 4 shows the average disease severity rating of powdery mildew on rose cultivar Prive treated with NaHCO- plus oil, and propiconazole. Lines on each bar represent standard deviations at each date.

Figure 5 shows individual leaves of cultivar Samantha (A) NaHC0₃ plus oil treated leaf which demonstrates protective properties on powdery mildew; (B) untreated leaf of cultivar Samantha with severe powdery mildew; (C) NaHC0₃ plus oil treated leaf (infected prior to treatment) which demonstrates the eradicative properties on powdery mildew.

Figure 6 shows the average disease severity rating of blackspot on rose cultivars Mr. Lincoln and Pascale treated with combinations of NaHCO- plus Tween 20, Tween 20 plus oil, and NaHCO- plus Tween 20 plus oil, and Tween 20 alone.

Detailed Description of the Preferred Embodiments The fungicidal compositions of the invention are active against a broad spectrum of fungi, including but not limited to Powdery mildew, particularly of roses (Sphaerotheca pannosa var rosae) cucurbits (Sphaerotheca fuligena) and potatoes (Erysiphe cichoracearum) ; Downy mildew, particularly of roses (Peronospora sparsa) ; blackspot, particularly of roses (Diplo- carpon rosae) ; Fusarium stem rot, particularly of carnation (Fusarium graminearum) ; Rust of Carnation (Uro vces dianthi) ; Alternaria blight of carnation (Alternaria dianthi) and of other crops; and Colletotrichum, especially of cucurbits (Colletotrichum lagenarium) . Preferably the bicarbonate concentration is below 1,000 ppm (0.1% w/v) . More preferably the bicarbonate concentration is in the range of about 125-500 ppm, most preferably about 125 ppm and lower (i.e., about 0.0125% w/v). Surprisingly it has been found that effective fungicidal activity, not heretofore attainable at concentrations below 1,000-2,000 ppm can be achieved in accordance with the invention by combining the bicarbonate with a horticultural oil in an aqueous solu¬ tion. Even more surprisingly, it has been found that fungi¬ cidal activity is not significantly diminished, if at all, at the lower concentration.

The ability to exhibit effective fungicidal activity at bicarbonate concentrations below 1,000 ppm enables the use of the inventive fungicidal compositions on plants, most notably roses, as to which bicarbonate concentrations of 1,000 ppm and higher have been found by the inventors to be phytotoxic. Therefore, the herein described fungicidal compositions, in addition to having a broad spectrum of fungicidal activity, may also be used on a wide range of plants without fear of phytotoxicity that might otherwise occur at the much higher bicarbonate concentrations heretofore disclosed in the art. The bicarbonate is preferably an alkali metal bicarbon¬ ate, such as sodium or potassium bicarbonate or may be ammo¬ nium bicarbonate. The fungicidal compositions may employ a single bicarbonate or may employ combinations thereof. The horticultural oil is preferably a spreader - sticker oil, most preferably Sun Spray^® ϋtra-Fine™ Oil. Combinations of horti¬ cultural oils may also be employed, if desired.

An especially preferred composition is an aqueous solu¬ tion of sodium bicarbonate (0.0125% w/v) and Sun Spray^® Ultra-Fine™ Oil (1.0% v/v) .

EXAMPLE 1

FUNGICIDAL ACTIVITY ON ROSES MATERIALS AND METHODS:

Powdery Mildew - Seven cultivars of rose were used in powdery mildew experiments: Bridal Pink, Gold Rush, Lavande, Prive, Samantha, Sonia, and Royalty. All plants received the same fertilizer treatment following Cornell Recommendations for Commercial Floriculture Crops. They were grown under glass and in a soil based medium amended with perlite and peat moss. A randomized split block design was used within each of four greenhouse concrete benches, 19.8 m by 1 m, and plants were spaced 30 cm on center. Each cultivar block contained 12 plants and there were 2 blocks of each cultivar within each bench. An individual bench received one of the following 4 treatments: water; 0.05% (w/v) aqueous solution of sodium bicarbonate (NaHC0₃) ; 1.0% (v/v) Sun Spray^® Ultra-Fine™ Oil and 0.05% NaHC0₃ plus 1% Sun Spray^® Ultra-Fine™ Oil. Sprays were applied weekly during a two month interval. Disease evaluations were made at approximately 14 day intervals beginning one week before treatment.

Another experiment was designed for the same greenhouse on two additional benches containing the cultivar Prive to compare 0.05% NaHCO- plus 1.0% oil, 5 fl. oz. Banner 14.3% EC (propiconazole)/379 1 water, and water spray for their effectiveness in powdery mildew control during the same time period of the previously described experiment. Each treatment was applied weekly to two randomized blocks containing 57 plants per block. The disease rating system was as follows:

Each plant was rated on a scale of 0 to 5 where 0 = no mildew lesions, 1 = 1-25% total leaves per bush with lesions, 2 = 26-50% with lesions, 3 = 51-75%,4 = 76-90%, and 5 = >90%. Data were collected from 1,014 plants and the means and standard deviations were calculated for each treatment and cultivar. Analyses were done by the general linear procedure of Statistical Analytical Service, Cary, NC. Disease severity data were analyzed with a two-way analysis of variance (ANOVA) to identify main treatment effects and interactions. Planned orthogonal contrasts were also evaluated. Data were trans¬ formed into rating scale values as described by Little and Hills. Little, T.M. and Hills, F.J. 1978. Agricultural experimentation: design and analysis. Wiley, N.Y. These transformed rating scales were used to adjust treatment means and to ensure homogeneity of variance.

Blackspot - Cultivars Mr. Lincoln and Pascale were used in blackspot experiments. Eighty-one plants of each cultivar were planted in separate ground beds. Treatments were: no spray; 0.05% NaHC0₃ plus 1.0%-Sun Spray^® Ultra-Fine™ Oil; 0.05% NaHC0₃ plus 1.0% Sun Spray^® Ultra-Fine™ Oil plus 0.6 ml Tween 20/3.8 liters water; 1.0% Sun Spray^®m Ultra-Fine™" Oil; and 0.6 ml Tween 20/3.8 liters water. Treatments were arranged in randomized blocks within each cultivar with 2 blocks of each treatment and 1 block with no treatment. Each block contained 9 plants spaced 30 cm on center. The disease rating was the same as that used to evaluate powdery mildew.

RESULTS

Powdery mildew - The first disease evaluations were made

6 days prior to treatment. It was obvious from data presented in Fig. 1 that infection was established among plants prior to initial spray applications. Prior-to-treatment disease rating also provided a baseline for subsequent comparisons. There were no statistically significant differences among cultivars and treatments in disease readings taken initially except cultivar Gold Rush, which was totally resistant to S. pannosa var. rosae infections throughout the experiment (Fig. 2) . The establishment of powdery mildew among roses included in this planting was anticipated since the existing environmental conditions in the greenhouse were especially conducive to powdery mildew epidemics, i.e., night/day temperatures and relative humidities were 16/27 °C and 90-99%/40-70%, respec¬ tively. Disease ratings in highly susceptible cultivar Samantha, reached 5 within three weeks and remained at that level for the duration of the experiment. Highly significant (p<0.0001) differences in treatment effects on disease severity were confirmed by ANOVA computations (Table 1) .

TABLE 1

Analysis of variance and planned orthogonal contrast analysis of NaHC0₃ and oil treatment effects, and treatment and cultivar interactions in severity of powdery mildew on rose cultivars Bridal Pink, Gold Rush, Lavande, Prive,

Royalty, Samantha, and Sonia.

^a Analysis of variance using type III sum of squares of the SAS general linear procedure. ^b Contrasts calculated using SAS general linear models proce¬ dure.

Furthermore, disease severity among cultivars was significantly different. Planned orthogonal contrast computa¬ tions to determine contrast differences revealed very signifi¬ cant reduction in disease severity of NaHC0₃ compared with NaHC0₃ plus oil(P=0.0002) and NaHCO- plus oil compared with oil alone (P=0.0002). Because cultivars Samantha and Gold Rush represent the extremes in sensitivity to powdery mildew infec¬ tions (Fig. 2) and because the standard deviations for the 2 cultivars skewed the evaluation of treatments in controlling the disease, mean differences and their standard deviations were evaluated on the five cultivars representing moderate to severe susceptibility to powdery mildew (Fig. 1) . The combination of NaHC0₃ plus oil significantly reduced powdery- mildew incidence on all disease reading dates and the amount of powdery mildew continued a linear reduction profile to the completion of the experiment.

Oil alone significantly reduced infection on three out of the four reading dates; however, some variation was noted. For individual cultivars, NaHC0₃ and oil, alone and in combination, were effective in reducing infection from S__. pannosa var. rosae. and this reduction was evident even on the highly susceptible cultivar Samantha (Fig. 3) . Furthermore, NaHCO- plus oil was eradicative as shown in Fig. 1 and by the disappearance of powdery mildew lesions from infected foliage as shown in Fig. 5. Moreover, NaHC0₃ plus oil significantly reduced S. pannosa var. rosae infections on cultivar Prive on all reading dates in the experiment designed to compare its effectiveness with propiconazole (Fig. 4) . Although propicon- azole somewhat reduced disease severity, significant reduction as shown by mean standard deviation was not found until the final readout date.

Blackspot - Inoculum of D. rosae for this experiment was provided by severe blackspot incidence in roses previously planted in the ground beds. Frequent rains provided the mois¬ ture required for natural infections. Applications of NaHCO- plus Tween 20 resulted in a reduction in disease severity for blackspot. Data presented in Fig. 6 showed that NaHC0₃ plus Tween 20 and NaHC0₃ plus Tween 20 plus oil reduced the inci¬ dence of blackspot more than Tween 20 alone or Tween 20 plus oil. "Mr. Lincoln" was more susceptible to D. rosae than "Pascale." Some problem was encountered with spray run off from rose foliage due to frequent rainfall.

From the foregoing, it is evident that NaHC0₃ and horticultural oil are effective biocompatible fungicides for control of powdery mildew and blackspot on rose. Although their effectiveness is quite good when applied singly, it is improved in combination. Their usefulness would be amplified if they were incorporated into production control programs in lieu of those fungicides that possess mammalian and environ¬ mental toxicity.

The application rates of NaHC0₃ and oil discussed herein are critically important since phytotoxicity to rose with rates >1.0% of both NaHC0₃ and oil were observed. An impor¬ tant feature to recognize in frequency of treatment is that rose foliar tissues become more resistant to S. pannosa var. rosae infections as tissues age. Since flowers are continu- ously cut in cut rose production, young unsprayed foliar tissues are continuously available for infection.

EXAMPLE 2 Bicarbonate inhibition of phytopathogenic fungi in vitro. The growth of Fusarium graminearum was assayed in vitro over a range (0.05 to 2.0% w/v) of concentrations of three bicar¬ bonate salts-sodium, potassium and ammonium. Inhibition of fungal growth on agar supplemented with NaHCΘ₃ and KHC0₃ was evident at 0.4, 1.6 and 2.0%, while NH₄C0₃ was lethal to the fungi at these same concentrations. Inhibition of F. graminearum on NaHCO- and KHCO- appeared to result in a departure from the sporodochial growth form to a pinnotal form, compared with control plates. The possibil¬ ity of a pinnotal mutant, or compact conidial form, could be a mechanism utilized by the fungus to bypass inhibition by the bicarbonates. Conversely, interference with typical F. gram- inearum conidial formation appears to be a mechanism of in vitro bicarbonate inhibition. Nevertheless, the exact mecha¬ nism of action of the inventive compositions is not yet fully understood. Field observations have confirmed the fungicidal activity of the instant compositions at sodium bicarbonate concentra¬ tions as low as 0.0125% (w/v) in combination with 1.0% (v/v) oil in aqueous solution. The above-described compositions may be advantageously employed as biocompatible broad-spectrum fungicides. The discovery that bicarbonates, in combination with a horticultural oil, may be used at much lower bicarbon¬ ate concentrations than were heretofore believed to be fungicidal, enables the use of bicarbonate based biocompatible fungicides on a variety of plant species, e.g. roses, as to which the higher bicarbonate concentrations heretofore believed necessary would be phytotoxic.

Claims

We claim:

1. A biocompatible fungicide composition, comprising: a. a bicarbonate in the range of about 0.0125 to 0.05 percent w/v; and b. a horticultural oil in the range of about 9.5 to 1.0 percent v/v.

2. The composition of claim 1, wherein the bicarbonate is selected from the group consisting of sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate.

3. The composition of claim 2, wherein the bicarbonate is sodium bicarbonate.

4. The composition of claim 3, wherein the sodium bicarbonate concentration is about 0.0125 percent w/v.

5. The composition of claim 2, wherein the bicarbonate is potassium bicarbonate.

6. The composition of claim 5, wherein the potassium bicar¬ bonate concentration is about 0.0125 percent w/v.

7. The composition of claim 2, wherein the bicarbonate is ammonium bicarbonate.

8. The composition of claim 7, wherein the ammonium bicarbon¬ ate concentration is about 0.0125 percent w/v.

9. A method of inhibiting fungus growth on plant tissue, comprising applying to the plant tissue a fungicidal composi¬ tion comprising an aqueous solution of a bicarbonate in combination with a horticultural oil, wherein the bicarbonate is in a concentration within the range of about 0.0125 to 0.05 percent w/v and the horticultural oil is in a concentration within the range of about 0.5 to 1.0 percent w/v.

10. The method of claim 9, wherein the bicarbonate concen¬ tration is about 0.0125 percent w/v.

11. The method of claim 10, wherein the bicarbonate is selected from the group consisting of sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate, and combina¬ tions thereof.

12. The method of claim 11, wherein the bicarbonate is sodium bicarbonate.

13. The method of claim 9, wherein the plant is a rose cultivar.

14. The method of claim 13, wherein the rose cultivar is selected from the group consisting of Bridal Pink, Lavande, Pride, Samantha, Sonia, Royalty, Mr. Lincoln and Pascale.