cultural Research Center were partitioned into 

 seven blocks of six trees each. On July 22, two 

 trees in each block received a single mixed 

 fungicide application (2 lbs. Captan 50WP/100 

 gal. + 3 oz. Benomyl 50 DF/100 gal.), two trees 

 received a normal fungicide application (2 lbs. 

 Captan 50WP/100 gal.), and the remaining two 

 trees were not treated with fungicide. On Au- 

 gust 1, one of the two trees for each fungicide 

 treatment within each block was summer 

 pruned. Because of natural soil variation across 

 the field, trees in a portion of the blocks were 

 vigorous, with dense foliar canopies, while trees 

 within the remaining blocks were only moder- 

 ately vigorous, with fairly open canopies. 



The results are shown in Table 1. The vigor 

 of the trees had a significant impact on the level 

 of sooty blotch and flyspeck. The more vigorous, 

 dense trees had more blemished fruit than the 

 open trees. For the moderately vigorous trees 

 with a relatively open canopy, additional sum- 

 mer pruning had no effect on sooty blotch and 

 flyspeck; however, if the canopy was dense, 

 summer pruning significantly reduced the total 

 disease incidence. Applying a single fungicide 

 treatment to dense trees or using summer prun- 



ing decreased flyspeck by approximately the 

 same amount. No treatment significantly re- 

 duced sooty blotch in dense trees, but either 

 pruning or fungicide reduced the disease in open 

 trees. 



Using a fungicide significantly reduced the 

 combined levels of sooty blotch and flyspeck; 

 however, there was no difference between the 

 two fungicide treatments. The combination of 

 fungicide and summer pruning generally was 

 better than either treatment alone in the trees 

 with dense canopies, but did not significantly 

 aid control in those trees with open canopies. 



While some treatments significantly re- 

 duced disease, no treatment gave adequate com- 

 mercial control of flyspeck (less than 0.1%); 

 however, the application of fungicide was not 

 close enough to protect against a major rain 

 which occurred in mid-August. The time be- 

 tween the application of the fungicides and the 

 rain was 24 days, more than the three weeks 

 recommended for benomyl plus captan or the 

 two weeks recommended for captan alone. Next 

 season, we plan to time fungicide sprays accord- 

 ing to accumulated wetting hours, a technique 

 which has proven successful in North Carolina. 



*«X» vl> *JL» vt> 

 »j» «Y» *J* *x* 



Fruit Notes, Winter, 1992 



17 



