October, '21] weldon: thrips injuring peach 425 



from thrips. While this injury does not render the peaches valueless, 

 many of them are culls that must be canned as very low grade fruit, 

 while none of them can be packed in the higher grades. 



Life History 



While it was not possible to make careful enough life history studies of 

 the pest to enable one to conclude definitely as to where it spends the 

 winter season, etc., it was found that as soon as the peaches began to 

 bloom in the spring adult thrips imm.ediately got into the blossom 

 where egg laying took place and where feeding was done by both 

 adults and larvae. 



Throughout the tim.e of blooming of the peaches and, later until the 

 time when the husk shed from the Httle peach the injury continued. 

 Practically no injur\^ was done after the shedding of the husk. The very 

 uneven blooming season during 1920 made it difficult to get any results 

 whatsoever with a contact spray. Various things were tried but with no 

 success as will be indicated later. The blooming period lasted approx- 

 imately two to three months, according to the variety and all this time as 

 the trees were coming into bloom, thrips were going into the blossoms. 



After the peaches had attained considerable size m.any thrips were 

 found in the tender growth at the tips of the twigs. In fact, throughout 

 the entire summer season some of them could be found in such places 

 but none on the fruit for any length of time after the shedding of the 

 husk. The injun,- therefore, by this species, was found to be done while 

 the trees were in bloom and afterwards up to the time of the shedding of 

 the husks. 



Demonstrations 



A series of demonstrations were planned during the season of 1920 

 which were designed to give the growers an idea as to how the pest 

 might be controlled. It had been claimed by those who had worked 

 on the pest in Placer County that a thorough spraying while the peaches 

 were in bloom, or a Httle later, with Nicotine vSulfatc Distillate Emul- 

 sion mixture which is so successfully used in pear thrips control, 

 would bring results. After one or two demonstrations had been con- 

 ducted it was determ.ined that so sm.all a percentage of the thrips was 

 being killed that the spraying was not paying for itself. Careful ob- 

 servations of the insect in treated blossoms led to the belief that not 

 over fifty percent were killed by a single application of the Nicotine 

 Sulfate Distillate Emulsion mixture. It must not be understood from 

 this that the mixture did not kill for it was found that where it was 



