28 



most any subsequent period. The attack on the young fruit fre- 

 quently causes a portion to be taken out as though bitten by a 

 grasshopper or some other gnawing insect. This causes a large 

 percentage of the young fruit to fall. Fruits after they are about 

 half developed are not usually attacked. When the fruit has 

 reached considerable size before it has been attacked, corky tissues 

 form and a development takes place resembling scab or verrucosis. 



LEMON. 



LEAF-SPOT AND WITHER-TIP. 



Lemon leaves are attacked in the typical way, causing leaf- 

 spot, and from these the disease extends into the twigs, causing 

 the wither-tip. For a discription of the characteristics of this at- 

 tack see page 26. 



LEMON-SPOT. 



The disease causes the most serious damage to the mature fruit. 

 The fungus finds entrance through some slight bruise or abrasion 

 of the skin, or it may be that infection takes place through the 

 uninjured skin under conditions not known at present. Attempts 

 at artificial inoculation through the uninjured skin of the lemon 

 failed uniformly. Even so slight an abrasion as rubbing the fruit 

 together in a packing crate or handling it roughly gives sufficient 

 opening for the fungus to enter. The results of applying spores 

 from pure cultures to the epidermis confirmed this conclusion. 

 When the fungus has once found its way into the epidermis a 

 dark spot is produced. This continues to enlarge until a definite 

 brown spot is made. The development then continues until the 

 entire rind of the lemon is browned. Ordinarily the diseased skin 

 hardens, so that the actual usefulness of the lemon has not been 

 materially impaired by the attack, but since it is not saleable its 

 value has been destroyed. 



The injury from this disease is the greater because of the fact 

 that infection to a large extent occurs during the handling of the 

 fruit, especially during the colouring period, so that the fruit is sent 

 off to market before the disease is visible. The diseased spots 

 continue to enlarge. This of course makes the fruit unsaleable, 

 and it becomes necessary for the merchant to repack, discarding 

 all fruit that shows infection. Spores are rarely produced on such 

 lemons except when the fruit is kept in a moist place, in which 

 case they are produced in great profusion. 



The peculiar way in which lemons have to be handled for market 

 makes them especially liable to attack, The fruit is picked from 

 the tree when still green. The growers allow the lemons to mature 

 sufficiently to develop in them a certain amount of citric acid. 

 When they have attained the proper size (and this must be learned 

 by experience) so that they will shrink in the course of curing 

 to the size demanded by the market, they are picked and placed 

 in a colouring house, or they may be placed in a large heap, which 

 is then covered with hay or similar material to keep out the light 

 and to keep them at a uniform temperature. It therefore happens 



