A new biorational fungicide formulation of potassium bicarbonate

A new bio-rational fungicide formulation of potassium bicarbonate for horticultural crops, vines and ornamentals Dr Jean-Pierre Laffranque and Dr Steve W. Shires INTRODUCTION APPLE SCAB (Venturia inaequalis) • Two field trials in Belgium in 2002 and two in Austria in 2004 • Standard reference product: Captan at 1000 g a. i. /ha and Kresoximmethyl at 100 g a. i. /ha • A total of 10 or 11 sprays were applied at 7 to 12 days intervals. • Potassium bicarbonate is a naturally occurring inorganic salt found in soil, water, sediments, plant and animal tissues. • Registered by both CODEX and the EU as a food additive, classified as GRAS (Generally Recognised As Safe) in the USA. • Indistinguishable from natural potassium and bicarbonate, therefore exempt from residue tolerances (MRLs) in USA. • Mode of action related to osmotic and p. H effects on fungal hyphae and spores, non site specific, therefore resistance is extremely unlikely. • Research to find a formulation that gives optimum spreading and penetration carried out by Cornell University and Church & Dwight Co. Ltd • Soluble powder formulation containing 85% potassium bicarbonate, is now registered and commercialised in the USA, and is being developed in Europe under the brand name of Armicarb 85 SP®. RESULTS • High crop selectivity • High scab infestation • Potassium bicarbonate activity similar to standards (Fig. 3). VINE POWDERY MILDEW (Uncinula necator) • Reference products: Captan and Kresoxim-methyl • Untreated check incidence: Fruits: 100% Leaves: 100% • 13 field trials were conducted in Austria (2), France (5), Spain (1) and Switzerland (5) in 2003 and 2004. STRAWBERRY POWDERY MILDEW (Sphaerotheca macularis) Apples • 10 trials were conducted in France (7), Belgium (2), Spain (1) • Strawberries were grown under plastic. • Application rates for potassium bicarbonate were between 2125 to 4250 g/ha. • Two to eight sprays at one week intervals • Potassium Bicarbonate application rate: 4250 g a. i. /ha in Austria and Switzerland; 5100 g a. i. /ha in France and Spain § 3 to 10 applications at 8 to 14 day intervals § Comparison with standard reference products: Sulphur at 10 kg a. i. /ha; Spiroxamine at 250 g a. i. /ha; Penconazol at 25 g a. i. /ha Grapes infected with powdery mildew RESULTS on Vine Powdery Mildew • Crop selectivity was generally good, although moderate phytotoxicity observed in two trials that had been sprayed twice within two days • Potassium bicarbonate at 4250 and 5100 g a. i. /ha provided good control of powdery mildew (Figs. 1 and 2) • Overall efficacy was numerically but not statistically slightly lower than the standard products RESULTS • Crop selectivity was excellent in all trials • Potassium bicarbonate gave good control in all French trials where natural substrate was used • In Spain potassium bicarbonate was superior to the standard sulphur and in Belgium it was superior to myclobutanil but inferior to kresoxim-methyl (Fig. 4) Untreated check incidence: Leaves: 72% • French trials confirmed that potassium bicarbonate performs best when applied preventatively CONCLUSIONS • The recently developed 85 SP formulation of potassium bicarbonate provides commercially acceptable control of some key diseases. Efficacy trial on Cucumbers Powdery mildew (Erysiphe cichoracarum) • In vines, potassium bicarbonate applied at 4250 to 5100 g a. i. /ha gave similar or only slightly reduced control of powdery mildew compared with the standards. • In apples, 3825 to 4250 g a. i. /ha of potassium bicarbonate gave similar control of scab on fruits but slightly inferior on leaves compared with the standards. ab a a a • In strawberries, 2125 to 4250 g a. i. /ha provided high powdery mildew protection ab a a a • Potassium bicarbonate is a naturally occurring inorganic salt and the concentrations used in agriculture are unlikely to have any adverse effects on man or the environment. • Exemption from residue tolerances have been granted in the USA and a similar request has been made to the European authorities. • Reference products: Penconazol or Spiroxamine • Untreated check severity (pest pressure): Bunches: 33% Leaves: 51% Untreated check severity (pest pressure): Bunches: 51% Leaves: 27% • Other trials ongoing in Europe are demonstrating interesting efficacy against powdery mildew in vegetables (e. g. cucurbits) and Botrytis in vines. Untreated check Formulated potassium bicarbonate at 3 kg/ha