EFFECTS OF FREEZES ON CITRUS IN CALIFORNIA 279 



Pruning. It has been the practice of many lemon growers to 

 prune in the fall of the year. Groves were found where trees that 

 had been pruned at this time were much more seriously injured than 

 unpruned trees which were under otherwise similar conditions. The 

 most severe damage was to those trees that had started a vigorous 

 growth as a result of the pruning. In one grove of young trees, which 

 had been stimulated into growth by pruning, the bark of the trunks 

 and limbs was badly split. Some adjacent trees of the same age and 

 similarly located, which had not been pruned, were injured but little. 

 The pruning was done the last of September, so that in this case there 

 had been a three months ' interval between the pruning and the freeze. 



Where the cutting had been done so late that no new growth had 

 started there was, as a rule, no noticeable difference in resistance be- 

 tween the pruned trees and those which had not been pruned. In 

 one young grove, however, a very marked difference was to be seen 

 between some trees which were unpruned and some adjacent rows 

 where the pruning had been discontinued the night before the freeze. 

 The grove consisted of four-year-old Eureka lemon trees and the cut- 

 ting had been moderate. There was a very marked difference in 

 condition between the section which had been pruned and that which 

 had not been pruned. This difference was not so decided immedi- 

 ately after the freeze as it was when the trees began to grow. At 

 this time the unpruned trees showed much more vigor than the other 

 trees. The pruning of the grove was finished in the spring and all 

 of the trees had been made the same size, so that there was no differ- 

 ence in that respect. Any one in walking through the grove could 

 easily tell to a row where the pruning had been done before the freeze. 



A few instances of late pruning were found which resulted -in a 

 greater loss of fruit than in trees not pruned. This, of course, is to 

 be expected, for the abundant top growth affords considerable pro- 

 tection to the fruit. 



Unhealthy Trees. Sickly trees were invariably more severly in- 

 jured than vigorous, healthy trees. This was very noticeable in the 

 case of trees suffering from such diseases as gummosis and scaly bark. 

 Trees that had been badly infested with insect pests were damaged 

 more than trees which were in good health and free from pests. 

 Branches that had been attacked with red spider were completely 

 killed in many trees which suffered only partial defoliation of the 

 other branches. 



Sometimes healthy trees had been given some treatment before the 

 freeze that weakened them and augmented the frost damage. For 

 example, young trees which had been scored along the trunks on one 



