Production

How Cold Temperatures Can Help Olive Production

Very low temperatures and snow can have positive effects on olive trees by reducing the olive fruit fly population, containing fungal diseases and aerating the soil.

Jan. 26, 2017
By Ylenia Granitto

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Over the past month, olive oil pro­duc­tion areas such as Italy, Greece and Croa­tia were affected by excep­tion­ally low tem­per­a­tures and snow at low alti­tudes. Apu­lian olive groves at sea level have been whitened by snow­drifts for days.

An undoubted advan­tage of low tem­per­a­tures and snow is the reduc­tion of the olive fruit fly pop­u­la­tion.- Nicolan­gelo Mar­si­cani

Italy reg­is­tered unusu­ally severe win­ters in 1929, 1956 and 1985 that caused dam­age to the olive sec­tor and agri­cul­ture gen­er­ally. The cold can affect the wood of olive tree if the min­i­mum tem­per­a­ture drops below ‑7°C (19.4°F) for 8 – 10 days, and cause irrepara­ble harm to the canopy and trunk if they fall below ‑10/-12°C (14/10.4°F) in a few hours.

In broad terms, it is prefer­able to choose native vari­eties for their abil­ity to adapt to soil and weather con­di­tions in their region of ori­gin, and a few days under the snow can have pos­i­tive effects on the devel­op­ment of an olive tree and its pro­duc­tion. It is not with­out rea­son that an old rural Ital­ian proverb says in rhyme, Sotto la piog­gia, fame; sotto la neve, pane, which means Under water, famine; under snow, bread.”

This win­ter was gen­er­ally very cold with wide­spread frosts and snow­falls in large areas of the coun­try,” said Nicolan­gelo Mar­si­cani, an expe­ri­enced olive grower from Cam­pa­nia which man­ages 6,000 olive trees in Sicilì di Morigerati, located in the National Park of Cilento, Vallo di Diano and Alburni.

The cold is crit­i­cal to allow a period of veg­e­ta­tive rest and pos­i­tively impact the devel­op­ment of the olive tree. Along­side fewer day­light hours and less time for pho­to­syn­the­sis, the period of dor­mancy due to low tem­per­a­tures pro­motes flow­er­ing.” In fact, last win­ter in Italy tem­per­a­tures did not decrease enough in sev­eral areas, and this was blamed for a drop in pro­duc­tion.

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An undoubted advan­tage of low tem­per­a­tures and snow is the reduc­tion of the olive fruit fly pop­u­la­tion,” Mar­si­cani observed. In late fall and win­ter, most of the last gen­er­a­tion’s lar­vae leave the olive and pupate in the soil; their vital­ity is under­mined at around 0°C (32°F) and a high mor­tal­ity rate can be reg­is­tered if tem­per­a­tures drop below ‑5/-6°C (23/21,2°F) for some days, espe­cially for those lying in the top lay­ers.

A fur­ther ben­e­fit given by cold weather is the con­tain­ment of fungi. Dis­eases such as Pea­cock spot, which is caused by the Spi­lo­caea oleaginea, are often over­looked,” our farmer con­sid­ered. How­ever, when dam­aged leaves fall, the decreased pho­to­syn­thetic sur­face will affect devel­op­ment and pro­duc­tion. The cold is a good ally in pre­vent­ing the spread of this kind of dis­ease.”

More­over, the expan­sion of water upon freez­ing (by approx­i­mately 9 per­cent) causes micro­c­racks which aer­ate the soil just like it was tilled. If frost lasts for sev­eral days and the process of thaw­ing is slow, this will pro­vide a good water reserve, with­out runoff of organic sub­stance.

In any case, we must be care­ful that too much snow does not over­bur­den the sec­ondary branches since frac­tures can facil­i­tate the pen­e­tra­tion of Pseudomonas savas­tanoi in more sus­cep­ti­ble vari­eties,” Mar­si­cani con­cluded.

As soon as tem­per­a­tures go back to nor­mal and the ground and the olive trees are dry, we can return to the olive grove and start again with the appro­pri­ate agri­cul­tural prac­tices like prun­ing.


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