THE CAMPHOR THRIPS. 2$ 



to be practically as many adults and larvae present as on the un- 

 sprayed checks and no dead insects were found. On June 21, which 

 was a bright, warm day, several adult thrips were found in the space 

 of a very few minutes. They continued to feed on the young shoots 

 and the spray apparently did them little or no harm. It was very 

 obvious that this spray, without the lime-sulphur solution, was 

 not satisfactory. It was much less effective than when the lime- 

 sulphur solution was added. 



Several experiments were also conducted to determine the effect 

 of the lime-sulphur, tobacco, and soap combination spray Upon 

 the camphor thrips eggs. On August 23 twenty-three eggs which 

 had been deposited August 22 and 23 were dipped in some of the 

 solution which had been used for spraying the camphor trees. On 

 August 27 no eggs had hatched. Two days later the eggs still had 

 not hatched, but appeared to be in perfect condition. The checks 

 at this time were hatching. On August 30 all the treated eggs were 

 broken and found to be dried out or to contain a partly developed 

 embryo. All of the eggs were dead. Again on August 31 a limb 

 containing camphor thrips eggs of various ages was dipped in the 

 same solution. Some of these eggs were hatching on the day they 

 were treated. September 1 two eggs hatched and each of the larvae 

 was found dead near the eggshell from which it had emerged. On 

 September 2 no eggs hatched. From September 3 to 5 a few eggs 

 hatched and the larvae were found crawling on the limbs. Of the 

 eggs present on August 31 only a small percentage hatched. The 

 dipping tests certainly indicate that practically all eggs which are 

 wet by the spray will fail to hatch. The check eggs all hatched in 

 the normal time. Where the main object is to kill the eggs, it 

 would be advisable to make the solution somewhat stronger than 

 that used in these tests. 



Several experiments were conducted in dusting infested camphor 

 trees with lead arsenate, calcium arsenate, flour of sulphur, flowers 

 of sulphur, dry lime-sulphur, and Bordeaux powder. These dusts 

 were used both separately and in various combinations with each 

 other and with lime, but in all cases positive killing effects were 

 lacking. Dusts containing nicotine sulphate were not available at 

 the time. 



PRUNING. 



Under the system of pruning as practiced on semicommercial 



f)lantations, in which the growth was cut back without regard to the 

 ocation of the nodes, or the trees were dehorned at a height of from 

 4 to 6 feet (PL IV, B ; PL VI, A) , the pruning not only was injurious to 

 the trees but stimulated their growth so that they were not resistant 

 to cold. This method also seemed to produce an unlimited food 

 supply for camphor thrips, and following such pruning they appeared 

 in countless numbers. It was obvious that a different system of 

 pruning must be adopted which would avoid not only the direct injury 

 to the camphor trees but also the- secondary damage caused by the 

 thrips. 



The method consists of cutting off the trees at the level of the 



f round. This eliminates the dying back of the cut ends due to 

 ranch pruning, avoids the injury which might follow low tempera- 

 tures, and destroys the food supply and breeding places of the cam- 



