FUMIGATION OF CITRUS TREES. 73 



tinued over a period of fully two weeks, much of which was ideal 

 fumigation weather. The resultant injury was very severe, being 

 marked chiefly by a dropping of leaves. In many trees the leaves and 

 fruit were also burned. The old leaves on the tree at the time of 

 spraying especially were affected, the number of these shed being 

 sometimes so great as to form a thick blanket underneath the tree, 

 entirely covering the ground. In these very same 'trees the young 

 tender growth at the top of the tree, which had appeared since the 

 spraying and which normally is the first to be injured by the gas 

 treatment, escaped uninjured. 



The trees were healthy and well cared for, which, coupled with the 

 fact that only the sprayed portion of the trees was affected and not 

 the younger and tenderer growth, proves that the cause of the injury 

 was the spraying. It is well known that distillate oil weakens a tree, 

 and possibly the unnatural addition of Bordeaux mixture makes this 

 weakening even more severe. As further proof of this situation, 

 trees in a neighboring orchard similarly sprayed at about the same 

 time were fumigated. Injury resulted. Unsprayed trees under the 

 same conditions and treated with the same dosages at the same time 

 were uninjured. 



These results show that it is unsafe to fumigate trees which have 

 been recently treated with a Bordeaux-distillate emulsion. Although 

 it does not also prove that trees recently sprayed with distillate alone 

 would be injured, it would seem good policy not to attempt such 

 fumigation until proof of its harmlessness has been secured. 



THE APPEARANCE OF FUMIGATED TREES. 



Orange trees containing young growth usually will have the tender 

 tips of this growth burned back with the ordinary fumigation dosage. 

 The wilting of this affected portion is visible the following day, espe- 

 cially if sunshiny. During cloudy weather the effects are not marked 

 until fully a day afterwards. The tender growth in lemons is burned 

 back even more severely than in the orange. Where the new growth 

 in the tops of the tree is very long it may be affected for 6 inches or 

 even a foot. 



Some weakened old leaves might be shed a few days following the 

 treatment. Healthy leaves are seldom shed and seldom burn, unless 

 some abnormal condition is present. Even in such conditions it is 

 the fruit that is first injured. 



The burning back of the tender growth does not injure the tree in 

 any way. With such vigorous plants as citrus trees all indications of 

 injury have disappeared within a few weeks following the treatment. 

 Fumigators and many growers look upon the burning of young growth 

 as an indication that the proper dosage has been given the tree for 

 good results. Of course such assumptions are correct only in part. 



