Spring and early summer
Copper: Where a deficiency occurs in young non-bearing trees apply an un-neutralised (no lime added) spray of copper sulphate at 50g/100L with addition of an approved wetting agent. Apply to runoff. A supplementary surface dressing may also be considered (see surface dressings following).
Zinc: Zinc sulphate can be applied to the foliage of non-bearing trees only at the rate of 150g/100L (+ wetting agent). Fruit russeting can result from application to bearing trees. Zinc sulphate can be applied as a defoliant spray in autumn at the rate of 2kg/100L.
Zinc and magnesium: For young non-bearing trees, apply zinc sulphate (150g/100L) plus a spray grade formulation of manganese sulphate (250g/100L) together with a wetting agent. Fruit russeting can result from application to bearing trees.
Magnesium: Apply magnesium sulphate (Epsom salts) at 1kg/100L plus a wetting agent, when symptoms are identified. A late summer spray is recommended where leaf magnesium deficiency symptoms have developed, or if leaf analysis has shown a serious deficiency. Complete spraying before leaf fall.
Sprays during dormancy are supplementary to spring and summer sprays where leaf analysis has shown one or more elements to be deficient. Spray in fine weather, concentrating on the upper two-thirds of the tree to saturate the bark. Spray before, or two weeks after, a winter oil application. Single nutrient sprays listed below can be mixed. Note that high concentrations of copper sulphate can damage some spray pump components.
Copper: Apply copper sulphate at 500g/100L.
Zinc: Apply zinc sulphate at 2–5kg/100L. Spray immediately after pruning.
Manganese: Apply the spray grade formulation of manganese sulphate at 4kg/100L.
Zinc and manganese: Apply zinc sulphate (2.5kg/100L) and spray grade formulation of manganese sulphate (2.5kg/100L) together with a wetting agent.
Nutrients in fungicides
Sulphates are not the only formulations containing trace elements. Many of the commonly applied fungicides also contain high concentrations of trace elements as part of their formulations. Examples are:
Copper: Copper oxychloride® (approx 59% copper) and Kocide® (approx 65% copper)
Manganese: Mancozeb® (16% manganese)
Zinc: Ziram® (20% zinc). Metiram® (16% zinc) and Mancozeb® (2% zinc).
While most fungicides are formulated to remain on the leaf surface, it is recognised that some of the trace element fraction may eventually be taken up by the plant through leaf stomatal openings. This could contribute to overcoming a low trace element status in the tree, but these products should not be used as the sole source of trace elements to correct a known deficiency.
New products using different formulations (often chelates) are continually entering the market and should be assessed for their nutrient content and purpose before being applied in the orchard.