MANGANESE DEFICIENCY
Manganese is involved in photosynthesis and chlorophyll production. It helps activate enzymes involved in the distribution of growth regulators within the plant.
Identification
- Symptoms occur first on young leaves
- In early summer, leaves start to pale, and shortly afterward small yellow spots appear in the interveinal tissue while veins stay green resulting in “islands” of yellow areas rather than a continuous discolouration of the leaf
- Leaves maintain a normal size and shape
- If the deficiency is prolonged, the entire leaf yellows and will drop prematurely
- With severe prolonged deficiency, growth of shoots, leaves, berries and maturation of clusters are delayed
Often Confused With
Paraquat injury – herbicide applied in vineyard and dead weeds below vines; localized spots on lower leaves
Magnesium deficiency - yellowing pattern starts at leaf margin; occurs first on basal leaves
Zinc deficiency – small, deformed leaves, poor fruit set
Boron deficiency – small cupped leaves, poor fruit set and bulges in internodes
Scouting Notes
Manganese deficiency may appear early in the season under excessive moisture conditions and later disappear. It is more common when the soil pH is high. Symptoms may be obscured by lime induced chlorosis (Iron deficiency). Symptoms are more severe in spring than later in the summer, especially during cold wet weather.
Management Notes
High applications of magnesium or phosphorous can induce manganese deficiency symptoms on soils that originally contained low levels of magnesium so avoid excess nutrient applications. Foliar sprays may be used but deficiency should be confirmed with tissue analyses before use.
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