Table 1. Comparative effects of Margosan-0 (neem extract) and 

 Imidan on plum curculio and apple maggot. 



Injured fruit {%) 



Apple maggot 

 larval tunnels 



Treatment 



Plum curculio 

 stings 



On tree 



In drops 



Margosan-0 

 Imidan 

 Untreated check 



62 a* 

 16 b 



63 a 



14 b 

 13 b 

 38 a 



42 b 

 30b 

 76 a 



'Means in each column followed by a different letter are signifi- 

 cantly different at odds of 19:1. 



acre to 120 mature, semi-dwarf Liberty and 

 Jonafree trees on May 22 (petal fall), May 26, May 

 29, and June 2. As a control treatment, Imidan at 1.5 

 pounds per 100 gallons was applied on May 22 and 

 May 29 to 120 other Liberty and Jonafree trees. Yet, 

 another 120 trees of these varieties remained 

 unsprayed as checks. Sampling consisted of exam- 

 ining20 fruit per tree on four replicates of eight trees 

 each per treatment on June 8. 



Against apple maggot, a treatment of Margosan- 

 O at one gallon per 100 gtdlons was applied with a 

 mist blower at 300 gallon of water per acre to 60 

 mature, semi-dwarf Prima and Burgundy trees on 

 July 1, July 8, July 15, and July 22. As a control 

 treatment, Imidan at 1.5 pounds per 100 gallons was 

 applied on July 1 and July 15 to 60 other Prima and 

 Burgundy trees. Yet, another 60 trees of these 

 varieties remained unsprayed as checks. Sampling 

 consisted of examining 10 on-tree and 10 dropped 

 fruit per tree on six replicates of two trees each per 

 treatment on August 19. Fruit were held at room 

 temperature for one week (drops) or four weeks (on- 

 tree fruit) before examining for larval trails in the 

 fruit flesh. 



Results 



As shown in Table 1, use of Margosan-O failed to 

 provide any detectable reduction in firuit injury by 

 plum curculio compared with untreated check fruit, 

 even though it was applied every three to four days 

 from petal fall to within six days of sampling. Imidan 

 applied every seven days provided reasonable 



curculio control in the face of the very high popula- 

 tion of curculios. 



As shown in Table 1, use of Margosan-0 resulted 

 in a significant decrease in percent fruit infested 

 with apple maggot larval trails. In fact, it was little 

 different from Imidan in this regard. Neither pro- 

 duced a high level of maggot control, possibly be- 

 cause there was a four-week gap between the last 

 treatment and removal of fruit in sampUng for 

 maggot injury. 



Conclusion 



We conclude that neem plant extract formulated 

 and sold as Margosan-0 offers little or no promise for 

 controlling plum curculio but does offer substantial 

 promise for controlling apple maggot. We do not 

 know if its effects on apple maggot were through 

 reduction of fly egglaying punctures in fruit or 

 through prevention of growth of larvae hatching 

 from eggs. Either way, we can anticipate that 

 application of Margosan-0 against apple maggot 

 might need to be twice as frequent as application of 

 Imidan to provide equivalent levels of control. We 

 hope in the near future to be able to evaluate 

 Margosan-0 against leafminer larvae and leafhop- 

 per nymphs. Quite possibly, Margosan-0 might 

 soon be registered for agricultural use. 



Acknowledgements 



This work was supported by a grant from the 

 W.R. Grace Company, to whom we are grateful. 



Fruit Notes, Spring, 1993 



19 



