on five shoots per tree ( 1 shoots per tree for the first 

 two sample sessions) at 10-day intervals beginning at 

 petal fall to assess the effectiveness of the Apogee 

 treatment. Potato leafhopper injury was evaluated with 

 a spectrophotometer early in the season, but this method 

 became cumbersome and was eventually supplemented 

 with a visual rating scale of injury, with being no 

 visible injury and 5 being severe injury. Because of 

 the high mobility of potato leafhopper adults, which 

 were the predominant life stage, we did not succeed in 

 getting a reliable count of leafhopper numbers per 

 shoot, hi future studies a field-adapted vacuum cleaner 

 device may be used for this purpose. 



Results & Discussion 



Shoot length measurements showed that Apogee 

 had a highly significant effect on shoot growth (Figure 

 1), both in the presence and absence of potato 

 leafhoppers. Potato leafhoppers arrived later than usual 



in New England and did not reach high numbers in 

 any location, leading to a fairly low damage level in 

 the control. Using the visual rating scale assessment 

 of leafhopper injury, Apogee and Provado, individually, 

 had a highly significant effect on reducing leafliopper 

 injury (Figure 2). Where both materials were used 

 together, leafhopper injury was singificantly lower than 

 where either material was used alone. On the last 

 assessment date, August 15, 200 1 , the average level of 

 feeding injury where Apogee was used alone was 0.83, 

 where Provado was used alone was 0.78, and where 

 both were used together was 0.3 1 . Untreated control 

 trees showed an injury level of2. 13 for this date. Thus, 

 there appears to be a substantial benefit to potato 

 leafhopper control using Apogee either alone or in 

 combination with insecticide. 



The mechanism by which gibberellin inhibition 

 affects leafhopper feeding is not known and will be 

 investigated further. The enhanced effect of Apogee 

 plus insecticide may be due to the reduction in new. 



10 



Fruit Notes, Volume 67, Winter, 2002 



