18 BULLETIN 71, HAWAII EXPERIMENT STATION 



496) give a comprehensive discussion of verrucosis. It is known 

 to have been present in Japan from ancient times and in recent 

 years has spread to many other parts of the world (23, p. 33). 

 Verrucosis attacks the young leaves, twigs, and fruits of lemons, 

 sour oranges, grapefruits, some mandarins, and certain other 

 varieties of citrus. The outstanding characteristic of the disease 

 is the formation of irregular, slightly raised corky lesions called 

 "warts." These lesions are pinkish-colored at first, but darken 

 with age, and the tops are covered with scab. The disease is 

 most evident in moist weather. Its virulence varies from year 

 to year, depending on climatic conditions, and nature of growth 

 at the time of infection. 



Control — Verrucosis can be controlled in Hawaii by thor- 

 oughly spraying the trees with Bordeaux mixture in late winter 

 or early spring and when the fruit is forming. Bordeaux mix- 

 ture is made of copper sulphate (bluestone), unslaked lime, and 

 water in definite proportions. The 3-3-50 formula is generally 

 considered to be of standard strength for controlling citrus dis- 

 eases. To make convenient stock solutions, dissolve copper sul- 

 phate at the rate of 1 pound in each gallon of water in a wooden 

 container. This is easily done by suspending the copper sulphate 

 for about 12 hours in a sack in the top of the water. Slake the 

 lime separately in a little water, then add more water to form 

 a lime solution consisting of 1 pound of lime to each gallon of 

 water. These two solutions may be stored separately for sev- 

 eral months if they are covered tightly to prevent evaporation. 

 For a 3-3-50 mixture, place 3 gallons of each solution in a wooden 

 container and add 50 gallons of water while the agitator is run- 

 ning. The mixture should then be strained into the spraying 

 tank and frequently agitated to prevent the settling of the pre- 

 cipitate formed by chemical union of the lime and the -copper. 

 Bordeaux mixture may be made destructive to insect pests fol- 

 lowing its use by the addition of 1 part of spraying oil at the 

 time the mixture is poured into the spraying tank. This would 

 give a formula of 3-3-50-1. 



HARVESTING 



The citrus crop should be handled with considerable care. 

 Carelessness in this respect causes severe losses often after fine 

 crops have been grown. The season of maturity of citrus fruits 

 in Hawaii varies somewhat in different localities, but the main 

 crop matures from midsummer to December. However, citrus 

 of one kind or another may be found ripening in some locality 

 during almost any month. Each fruit should be cut, not pulled, 

 from the tree. The clippers should have, preferably, cup-shaped 

 blades with rounded points (fig. 2, B, k) . The stem should be 

 cut close to the calyx or "button," which should be left on the 

 fruit. The clipped fruit should be put into a cloth picking sack 

 carried over the shoulder of the picker (fig. 2, B, j) . Several 

 types of picking sacks are in use. The improved type is adjust- 

 able in capacity, holding from 20 to 50 fruits, and opens at the 

 bottom to keep the fruit from bruising when it is emptied into 

 the field container. 



