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pesticides or in the presence of less harmful selective pesticides, 

 the natural enemies may in time lower the pest population to a sub- 

 economi c 1 evel . 



A very real and important part of pest control should be a 

 knowledge of the economic injury level o'r economic threshold of 

 pest populations under a variety of conditions and In different 

 areas. Such a knowledge would help to determine whether or not 

 treatment is necessary and when it becomes necessary. In the ab- 

 sence of this information, growers are often forced to use prophy- 

 lactic treatments as an insurance measure against pest populations. 

 This approach while effective on a short-term basis leaves much to 

 be desired. Insect and mite populations in particular have remark- 

 able adaptability, and in time they usually become resistant to 

 these temporary measures. This necessitates the use of alternate 

 chemicals or some other method of control. Too often growers in- 

 crease the pesticide dosage several fold. We need to have alter- 

 nate methods perfected in advance of the occurrence of this phenom- 

 enon of resistance. The use of natural enemies is one logical al- 

 ternative, and could be used simultaneously with chemical control 

 if the chemicals were highly selective for the pest populations, 

 and/or if the chemicals were applied in a manner that would be in- 

 nocuous to the beneficial insects, that is, as a systemic or at a 

 time when the beneficial insects are not present, or present in 

 only small numbers, or in a resistant state, etc. 



Other methods that could possibly be intergrated are the use 

 of resistant varieties, cultural controls such as pruning and mow- 

 ing techniques, and other modifications of the insect environment 

 that may shift the balance in favor of the natural enemies. 



Integrated control programs require a high level of scientific 

 competence. However, the first steps toward integrated control on 

 apples are being worked out and much work is presently being done 

 in Washington, Pennsylvania, Nova Scotia and other areas. 



Previous work and present outlook . Early workers on apple pests 

 in New England recommended certain cultural controls which later 

 became impractical with the advent W the syntfilitlc organic pesti- 

 cides. Such practices were recbinmenditlons dealing with clean cul- 

 ture to eliminate overwintering sites of apple pests, cultivation 

 under the apple trees to kill plufti curcullo and apple maggot larvae, 

 gathering and disposing of apple drops to eliminate apple maggot 

 and plum curculio larvae from completing their development, and al- 

 lowing pigs or sheep to graze under the trees to eat the Infested 

 apples. Modern pesticides and the high cost of labor have made 

 many of these practices impractical, and hence they have been aban- 

 doned. An integrated control program could make several of them 

 practical again, however, inasmuch as a reduced spray schedule, use 

 of chemicals harml ess to' mammals and beneficial insects and clean 

 cultural practices are essential parts of integrated control pro- 

 grams . 



