Effects of Apollo Alone and in 

 Combination with Dormant Oil on 

 European Red Mite Populations in a 

 Commercial Apple Orchard 



Glenn Morin and Roberta Spitko 



New England Fruit Consultants, Montague, MA 01351 



European red mites (ERM) are the most signifi- 

 cant foliar pests in many apple orchards through- 

 out New England. Excessive feeding by ERM popu- 

 lations can severely damage the photosynthetic ca- 

 pability of the tree resulting in a reduction in fruit 

 size and premature fruit drop. 



Effective ERM control is often difficult to 

 achieve. Several predatory mite species have been 

 identified in our region; however, these beneficials 

 rarely build to levels sufficient to impact ERM popu- 

 lations before significant damage occurs. Chemical 

 control is not only costly but is often ineffective. 

 The standard materials used for mite control on 

 apples have been registered for quite some time and 

 various degrees of tolerance are suspected. 



In 1995, AgrEvo received federal registration 

 for use of Apollo on apples. Apollo is the first new 

 acaricide to be registered on apples in recent his- 

 tory and it belongs to a different class of materials 

 with a unique mode of action compared to commonly 

 used miticides. Apollo is primarily an ovicide. It is 

 effective in preventing hatch when mite eggs come 

 in contact with the material but it has little or no 

 effect on adult mites. Apollo is also unique in that 

 the federal label restricts its use to prebloom appli- 

 cations only. 



The backbone of most mite-control programs in 

 New England consists of at least one, if not two, 

 dormant oil applications prior to ERM egg hatch. 

 Subsequent applications of summer miticides are 

 made as needed to suppress ERM populations be- 

 low problem levels. Given the label restriction per- 

 taining to prebloom use, how would Apollo fit into 

 our program? Would it replace one of the oil treat- 

 ments? Would we need to use oil at all if Apollo is 

 such an effective ovicide? Would it be best used in 

 combination with oil? 



The following trial was initiated in the spring 



of 1995 in an attempt to answer these questions. A 

 five-acre block of Mcintosh and Delicious trees in a 

 commercial orchard owned and operated by 

 Fairview Orchards, Ayer, MA. was selected and 

 divided into five plots. This block had a history of 

 high ERM pressure (two or three summer miticides) 

 and visual inspection revealed that a relatively 

 uniform distribution of overwintering eggs was 

 present. Each plot consisted of two rows of Deli- 

 cious trees bordered by a row of Mcintosh trees on 

 each side. Trees were approximately 14 feet tall, 

 planted on a 16 x 22 feet spacing, with a dilute tree 

 row volume of 267 gallons per acre. 



Treatments were applied to adjacent, non-rep- 

 licated plots with an airblast sprayer calibrated for 

 a total output of either 300 gallons per acre (1/4" 

 green) or 150 gallons per acre (tight cluster) while 



Table 1. Materials, dates, and application 

 rates for five treatments in the Apollo trial, 

 1995. 



^Application rate on 4/21 was 2 gal superior 

 oil per 100 gal, delivered at 300 gal per acre. 

 ^Application rate on 5/1 was 1 gal superior 

 oil and/or 1.33 oz Apollo per 100 gal, deliv- 



ered at 150 gal per acre. 



14 



Fruit Notes, Spring, 1996 



