Agri-Mek: A 1996 Field Trial in 

 a Commercial Apple Orchard 



Glenn Morin and Roberta Spitko 



New England Fruit Consultants, Montague, Massachusetts 



The 1996 growing season witnessed the 

 introduction of a new pest-management tool 

 with the federal registration of Agri-Mek 

 (Merck and Co.) for managing both leafminer 

 and mite in apples and pear psylla in pears. 

 Following the withdrawal of Omite from the 

 marketplace in April, most apple producers 

 were pleased to have another option for 

 European red mite (ERM) control. However, 

 Agri-Mek's late-spring registration combined 

 with the absence of experimental work 

 conducted in New England left most field 

 consultants and growers with limited informa- 

 tion on how this product would be utilized best 

 in the rapidly approaching season. 



The active ingredient in Agri-Mek, 

 abamectin, is a naturally derived substance 

 produced by a soil microorganism and is 

 effective at extremely low rates. Agri-Mek is 

 not related to other currently registered 

 materials and therefore should prove useful in 

 managing tolerant pest populations and 

 prolonging the effective life of presently 

 available compounds when used 

 in a rotational program. 

 Abamectin is absorbed into the 

 leaf tissue where it forms a 

 reservoir of active ingredient 

 against foliar feeding pests. As 

 a result, Agri-Mek is currently 

 recommended within six weeks 

 after petal fall and in combina- 

 tion with horticultural oil in 

 order to maximize absorption. 

 Affected individuals essentially 

 are paralyzed, stop feeding, and 

 die within a few days. 



Optimal timing is critical to 

 the cost-effective use of this 

 material. Ideally, one would 



expect a single application to provide season- 

 long suppression of ERM and leafminer 

 populations. The focus of our trial was 

 European red mite, as this pest would likely be 

 the primary target for most Northeast growers 

 considering the use of this material. The two 

 most vulnerable periods for ERM within the 

 recommended application time frame are 1) 

 petal fall, when the majority of overwintering 

 egg hatch has been completed and 2) first- 

 generation egg hatch approximately 3-4 weeks 

 later. ERM populations are fairly synchronous 

 at these two times and are more easily 

 disrupted than when multiple life stages are 

 present. The following study was conducted to 

 determine which of these two application 

 timings would prove more effective in 

 managing ERM populations. 



Procedure 



Treatments were applied to adjacent, non- 

 replicated plots in a commercial apple orchard 



Table 1. Materials, rates and application dates for 

 Agri-Mek trial, 1996. Materials were delivered in 150 

 gal /acre of water. All plots received 3 gal/acre oil on 

 April 24. Check plot was treated July 7 with 18 oz/acre 

 Carzol SP, July 25 with 5 lbs/acre Omite 30W, and 

 August 9 with 3 pts /acre Vydate. 



Trt. Material + rate (product/acre) 



Timing 



1 

 2 

 3 



4 



Savey @ 3 oz 



Agri-mek @ lOoz + oil @ 1 gal 



Agri-mek @ 10 oz + oil @ 1 gal 



Check 



May 9 

 May 23 

 June 17 



Fruit Notes, Volume 62 (Number 1), FaU, 1997 



19 



