26 sites where biological control was predicted to 

 occur, at only one site was this prediction in error 

 and this occurred because T. pyri were 

 inexplicably low in number for much of the 

 growing season. 



How can T. pyri be used to provide cost-free 

 mite control? Achieving biological mite control 

 using T. pyri is minimally a one-step process and 

 may require two steps. First, an environment must 

 be established in the orchard that will allow T. pyri 

 to survive and flourish. This requires that 

 pesticides that are toxic to these beneficial mites 

 not be used. Second, if T. pyri are not already 

 present in the orchard, they must be introduced. 



An environment conducive to T. pyri T. pyri 

 have acquired resistance ro some chemical 

 pesticides used in commercial orchards and are 

 innately tolerant of others. However, some 

 pesticides are quite toxic to T. pyri. If biological 

 mite control is to be achieved using this predator, 

 these toxic materials must be avoided. Because T. 

 pyri are resident in trees year round, and because 

 these predators have a relatively slow growth rate, 

 pesticides toxic to T. pyri cannot be used even 

 intermittently (e.g., every other year) without 

 serious disruption to biological control. A list of 

 pesticides that can be used to control insects and 

 diseases of apple while conserving T. pyri is 

 provided in Table 2. Be advised that estimates of 

 toxicity to T. pyri were obtained using predators 

 from western NY, and there may be differences in 

 susceptibility among predator populations indig- 

 enous to other regions of the Northeast. 



Introducing T. pyri into an orchard There are 

 situations where T. pyri might not be present m an 

 orchard or where they are very scarce. This 

 deficiency can be overcome by moving predators 

 from an orchard where they are known to occur to 

 a recipient site. Because phytoseiid species cannot 

 be identified in the field, it is important that you be 

 sure the source predators are, in fact, T. pyri. The 

 best way of ensuring this is to have someone 

 identify them for you. If this is not possible, you 

 can be reasonably sure the predators are T. pyri if 

 either of the following conditions are met: 1) The 

 predators can be found in the trees either before or 

 just after bloom and the predators are easily found 

 even when ERM are scarce. 2) The predators in the 

 source orchard were themselves introduced as T. 



pyri one or more years ago, and no pesticides 

 harmful to T. pyri have been used since the 

 introduction. 



T. pyri can be moved from a source orchard to 

 a recipient orchard in one of four ways, each of 

 which is described below. It is best to concentrate 

 inoculation material in the recipient orchard 

 rather than spreading it thinly over a site. If the 

 predators are spread thinly, few animals may be 

 introduced into each tree, which may allow for 

 extinction of the populations. Once T. pyri are 

 established in the receiver trees, they can be spread 

 further in subsequent years. While T. pyri do 

 disperse by themselves, assisting this process will 

 hasten biological control throughout the planting. 



The first method of moving T. pyri from one 

 orchard block to another is to place wood pruned 

 from a source orchard in winter or early spring 

 into a recipient orchard. Because T. pyri 

 overwinter as adult females, prunings harbor 

 predators, although numbers in each section of 

 pruning are highly variable. We suggest placing all 

 the prunings from one tree into another tree. It is 

 probably not effective to simply spread the 

 prunings beneath recipient trees. Pruned wood 

 need not be placed in the recipient trees 

 immediately after pruning, but should be placed 

 there before or just when trees begin to produce 

 green tissue the following spring. 



The second method consists of transferring 

 flower clusters from a source orchard to a recipient 

 site. T. pyri move into flower clusters at tight 

 cluster and remain there through bloom, probably 

 to feed on apple pollen. As many as two to three 

 predators can be found in each flower cluster and 

 surrounding leaves. To transfer predators in this 

 manner, at least 20 flower clusters (and associated 

 wood and leaves) should be placed in each 

 recipient tree. The flower clusters are easily 

 attached with paper clips, staples, or twist ties. 

 Flower clusters may be stored for several days in a 

 cooler before being affixed to receiver trees. 



The third method of transferring T. pyri 

 consists of collecting leaves during the summer 

 from trees where T. pyri are abundant, and placing 

 them into recipient trees. Leaves are easily affixed 

 to the target sites using staples. The number of 

 leaves to use depends on the density of T. pyri in 

 the source orchard. As a guide, at least 50 



Fruit Notes, Volume 64 (Number 1), Winter, 1999 



