DISEASE
 
   NAME
     Magnesium Deficiency
     Nutrient Deficiency

Description
Magnesium becomes unavailable in very acid soils or is insoluble in alkaline soils.

Symptoms
As this element is highly mobile throughout the plant and older leaves show symptoms first with interveinal chlorosis, or bronze-yellow discolouration along the margins towards the apex. This discoloration can be seen on the lower leaves forming arcs towards the base of the leaf forming a ‘V’ shape at the apex. The apex is the first to die followed by the base. 
It is normally first seen on young leaves but in some cases the leaf reverts to green on maturity. The over all effect on the plant is a lack of vigour and poor quality fruit.

		   Gardenia augusta

Favoured Conditions
It occurs in infertile acid soils and may be more prevalent where regular cropping of the same species is carried out.
Insufficient Magnesium in the soil may result from adjusting the pH with lime rather than dolomite. The deficiency may also result for excessive potassium applications or high sodium levels in irrigation water and is more pronounced in adverse climatic conditions such as, very wet or dry and cold weather.

	
Affected Plants
Deficiency is found in many plants but is more frequently seen in Citrus and Gardenia species.

Non-chemical Control
Organically chicken manure can be added to reduce alkalinity in sandy soils. Add lime to extremely acid soils to increase the pH making magnesium more available.

Chemical Control
Magnesium sulphate can be sprayed on effected plants at a rate of 1g per 1 litre. Spraying should be carried out during spring to avoid marking the developing fruit. 
Note 
More information in the pest and disease glossary.