ox 



a 



B 



a 



O 



2.5 



0.5 







1 



Notrt 



Apogee 



Provado 



Ap + Prov 



Figure 2. Potato leatTiopper damage (0-5 scale, with being no injury and 5 being severe injury) on 15- 

 year-old Mclntosh/M.7 trees as affected by Apogee and Provado. 



untreated leaf area where shoot growth is inhibited. 

 For Apogee alone, it is possible that visual or chemical 

 cues used by the insects are muted by the treatment, or 

 it could be that the leafhoppers begin feeding but find 

 the treated plant unpalatable. Behavioral studies of 

 potato leafhoppers exposed to Apogee-treated and 

 nontreated foliage separately and in choice situations 

 will be conducted to try to elucidate the nature of the 

 response. 



Regardless of the reason, however, the fact that 

 injury appears to be reduced by the inhibition of 

 gibberellin synthesis is of significance for growers 

 needing to control this insect. Specifically, where 

 Apogee has been used and leafhopper numbers are not 

 exceptionally high, there may be no need for an 

 insecticide directed at the leafhoppers. In cases where 

 a severe fire blight outbreak is in progress and 

 leafhopper numbers are high, an insecticide may still 

 be warranted, and should hopefully have greater 

 efficacy in combination with the Apogee. 



More work needs to be done to understand the 

 nature of the effects of gibberellin synthesis inhibition 

 on leafhoppers and on to understand the relationship 

 between potato leafhoppers and fire blight. In addition. 



it would be enlightening to repeat the experiment under 

 higher populations of potato leafhopper and see 

 whether or not the effects continues to hold true, or 

 are muted or enhanced under such conditions. 



References 



Byers, R.E., Yoder, K.S., and Smith, A.H. Jr. 1 997. The 

 effect of BAS-125W on apple tree growth, fruit quality 

 and fire blight suppression . HortScience 32:557. 



Hildebrand, M., Dickler, E., and Geider, K. 2000. 

 Occurrence of Erwinia amylovora on insects in a fire 

 blight orchard. Phytopathology 148:251-256. 



Koehler, GW. ed. 2000. 2000-2001 New England Apple 

 Pest Management Guide. 



Maredia, K.M., Whalon, M.E., Gage, S.H., and Kaeb, 

 M.J. 1998. Observations of first occurrence and 

 severity of potato leafhopper Empoasca fabae (Harris), 

 (Homoptera:Cicadellidae) in the North Central and 

 Eastern United States. Great Lakes Entomologist 

 31:73-84. 



Paulson, G.S. and Hull, L.A. 1999. Influence of Apogee 



Fruit Notes, Volume 67, Winter, 2002 



11 



