OLIVE 



OLIVE 



2337 



tree. Heavy winter and spring irrigations followed by 

 thorough summer cultivation are usually sufficient, 

 though a supplementary watering just before blossom- 

 ing time (March to May) and one when the fruit 

 is almost of full size are useful in many soils and 



locations. 



Diseases and insects. 



The only serious disease 

 which attacks the olive in 

 California is the "olive- 

 knot." This disease is 

 characterized by numer- 

 ous knots or tumors on 

 the leaves, twigs, branches 

 and trunk, varying in size 

 from J/8 inch to 1 or 

 occasionally 2 inches (Figs. 

 2573, 2574). When badly 

 attacked, the tree is much 

 weakened and, in extreme 

 cases, killed or rendered 

 unprofitable. The disease 

 is infectious and caused by 

 specific bacteria (Bacte- 

 rium savastanoi). Though 

 found in several widely 

 scattered districts, few 

 orchards have been seri- 

 ously injured and it seems 

 probable that its spread 

 can be controlled by 

 quarantine. It is most 

 harmful to young trees 

 and in rich moist soils 

 of the warmer districts. 

 Eradication by means 

 similar to those used for 

 pear blight seems possible. 

 A fungous disease of the 

 leaves (Cycloconium olea- 

 ginurti) occurs, but is not 

 important. Rarely, sus- 

 ceptible varieties are 

 slightly weakened by an 

 unusually heavy attack. Fungous decays of roots and 

 stem have been noted, but do little damage as a rule. 

 Old olive trees in Europe often bear satisfactory crops 

 even after a great part of the interior of the trunk has 

 decayed (Fig. 2575). 



The black scale (Saissetia olese) is very injurious to the 

 olive in the moister regions of the coast ranges, in some 

 parts being so prevalent as to prevent the profitable 

 growing of the tree. In the dry summer air of the 

 interior the scale is absent or not injurious. The 

 noxious olive-fly and olive-moth of Europe do not exist 

 in California. 



Harvesting. 



The stage of maturity at which the olives are har- 

 vested depends upon the use that is to be made of them. 

 For green pickles, they should be gathered as soon as 

 or just before they have reached full size and before 

 they show the slightest change of color. Only at this 

 stage is it possible to preserve the clear yellowish green 

 which the consumer demands and which insures the 

 best price. In ripe pickles, the consumer demands a 

 deep uniform shade as nearly black as possible. Differ- 

 ent varieties of olives vary considerably in the amount 

 of coloring matter they contain, but in all varieties it 

 develops its full intensity only at full maturity. As the 

 olives on a tree do not all ripen together, it is customary 

 to wait until nearly all have developed a good black 

 color. If gathered too soon, many will bleach to yellow 

 or red in the pickling process; if left too long many will 

 become too soft. Both these difficulties can be over- 



148 



2574. Tuberculosis of olive. 



come to a large extent by modifications in the methods 

 of pickling. 



When used for oil-making, the quality and quantity 

 of the oil will vary according to the degrees of ripeness of 

 the fruit, when gathered. The maximum quantity is 

 obtained by harvesting the olives when they are com- 

 pletely mature and soft. There is an increase in the 

 percentage of oil afterward, due to a partial drying of 

 the fruit, but no increase in the total quantity of oil. 

 The finest and most highly prized oil is made from 

 olives gathered just before they begin to soften. 



In gathering olives for any purpose, they must be 

 picked from the tree by hand and all bruising of the 

 fruit avoided. Cloth bags or lined buckets hung over 

 the shoulders of the pickers are used. Knocking the 

 olives off the trees with rods and gathering from the 

 ground is never practised for pickling olives; nor is it 

 advisable for oil olives, as the mechanical injuries to 

 the fruit promote rotting and molding which much 

 depreciate the quality of the oil. Beating the trees 

 also destroys much of the best fruit wood and tends to 

 promote the spread of the olive-knot disease. Where oil 

 olives can be marketed immediately, they may be 

 gathered by means of special rakes with wooden 

 teeth. 



Pickling olives. 



When pickles are made, the olives should be cleaned 

 and sized as soon as possible after gathering. The sizing 

 is done by mechanical graders which sort the olives 

 into three or more sizes. The larger sizes are each 

 pickled separately and the smallest used for oil. The 

 grader should be such that the fruit is bruised as little 

 as possible. The cleaning is accomplished by a blower 

 which removes leaves and similar light materials and 

 by running the olives into water which removes the 

 dust. 



The pickling process consists in removing the bitter- 

 ness by means of soda or potash lye and water, then 

 hardening and preserving the olives with a solution of 

 common salt. 



The nature of the lye treatment will depend on the 

 variety, size and degree of ripeness of the fruit. For 

 this reason, each variety and grade should be treated 

 separately. The effect of the lye is partially to destroy 

 the bitterness and to make the skin more pervious to 

 the pickling solutions. Some varieties of olives are 

 extremely bitter or thick-skinned and require two or 

 three tunes as much lye as other varieties. If too little 

 lye is used, the extraction of the bitterness will be very 

 slow and often incomplete; if too much is used, the 

 olives will become soft, the flavor will be injured and 

 the nutritive value impaired by saponification of some 

 of the oil. 



2575. Ancient olive tree in orchard in south of France. 



