Pomona College Journal of Economic Botany 53 



their twigs and branches. A citrus tree affected with wither-tip will begin 

 to lose its inside leaves. The outer leaves then turn yellow and fall, leaving 

 many bare and discolored branches. The fruit also drops, with or without 

 spotting. 



HOW TO PRUNE 



The important thing in pruning is to cut out enough Of the wood, in order 

 to get rid, not only of the bare branches, but also of all the branches that 

 show even a slight sign of the disease. In severe cases of wither-tip, there 

 are seen, in addition to bare branches, many limbs on which the yellowish 

 leaves are about to fall. Close examination will show that the disease is 

 slowly making its way back and poisoning these limbs. This poisoning may 

 start from an infection at the tip, or from an infection on a side branch lower 

 down, from which the poisonous effect has spread to the main limb. Some- 

 times only one side of a tree, or only one branch, is severely affected ; while 

 the remaining part of the tree is uninjured. Whatever may be the conditions, 

 it is important to get rid of these poisoned limbs. All limbs that show the 

 beginnings of the disease must be taken out. Drastic measures must be em- 

 ployed, and many bearing limbs may have to be sacrificed. To prune only 

 half-heartedly may make matters worse, rather than better. When pruning, 

 care should be taken to make smooth cuts, usually at the base of a branch or 

 limb, so as not to leave any projecting stubs, in which infection is almost 

 sure to start again. After pruning, paint the larger cut surfaces with 

 carbolineum or pine tar. 



The grove should be given unusual care after a severe pruning of this 

 kind. It should be fertilized, so as to bring about a vigorous healthy growth, 

 and to render the trees resistant to further attacks of the fungus. 



WHEN TO PRUNE. 



Winter pruning for wither-tip should be done between the middle of De- 

 cember and the middle of January. It is important not to delay the work 

 beyond this date. Do not prune while the new growth is putting out, for 

 this is almost sure to result in injury rather than benefit. Begin the work 

 at once, and do not consider the looks of the trees, but take out everything 

 that shows the presence of the disease. 



The beneficial results already obtained on hundreds of acres of groves treated 

 in this way, under the direction of Experiment Station workers, have proved 

 the effectiveness of this treatment." 



To this we may add the advice given by Prof. Rolfs, in Bull. No. 52, 1904, 

 page 18 : 



"In a small orchard, or in the case of an isolated tree, especially in a 

 young orchard, much good can be done by cutting out the diseased twigs 

 and picking off the diseased leaves. Where this is practiced with thoroughness 

 the disease can be reduced to a point where it does only a small amount of 

 damage, or it may be eradicated ; but pruning and picking must be done 

 at frequent intervals and very thoroughly. This would probably be an 

 effective method of keeping the fungus under control in the case of small 

 orange and pomelo orchards. 



