Figure 3 (A-E) reveals that, except for 2003, all females 

 captured by traps were already sexually mature and/or 

 had been mated by the end of the petal-fall period. 

 These findings will be discussed in the next article of 

 Fruit Notes . 



Conclusions 



\n this study we focused on the relative importance 

 of weather factors and tree phenology on the timing of 

 PC immigration into an apple orchard as determined 

 by trap captures. Because odor-baited traps were 

 deployed along the periphery of the orchard block and 

 inspected on a daily basis for the entire period of PC 

 immigration, we believe this study examined timing 

 and extent of PC immigration from overwintering sites 

 (which primarily are woods) more accurately than 

 previous studies that have relied on branch-tapping. 



Based on our combined data, we propose the 

 occurrence of a pre- and a post-petal-fall period of PC 

 immigration, each of which is influenced to a different 

 extent by temperatures prevailing in spring. The relative 

 influence of temperature on patterns of PC immigration 

 was very strong during the pre-petal-fall period of 

 immigration, whereas immigration taking place during 

 the post-petal-fall period depended to a lesser extent 

 on temperature. In almost all cases, captures by panel 

 traps were more strongly influenced by air temperature 

 than captures by pyramid traps. 



Historically, the timing of PC immigration was 

 related to either soil and air temperatures or to host- 

 plant phenology, but the relative influence of these two 

 environmental factors had not been quantified in detail 

 before. Here, we determined that the onset of 

 immigration was better explained by accumulation of 

 DD (base 43°C) than by tree phenology. This finding 

 means that examination of the stages of bud 

 development in spring is a poor tool for forecasting 

 onset of PC immigration. 



Our trap-capture patterns obtained over a five-year 

 period allow us to characterize PC immigration as 

 follows. First, stretches of hot weather occurring 

 during the pre-petal-fall period (as in our 2000 season) 

 are conducive to concentrated PC emergence and 

 immigration. Under these conditions, most adults may 

 be present within orchards before the end of the pre- 

 petal-fall period and thus a petal-fall spray covering 

 the entire orchard block is recommended and should 

 yield excellent control of the majority of the population. 

 Second, during the post-petal-fall period, PC 

 immigiation continues but with a lesser influence of 

 weather, unless cool temperatures (such as in our 2002 

 season) have prevailed during the pre-petal-fall period, 

 which would lead to an extended period of PC 

 emergence and immigration. 



We recommend that, depending on the type of 

 weather (primarily temperature) prevalent during the 

 pre-petal-fall period of PC immigration, the first spray 



Fruit Notes, Volume 69, Fall, 2004 



