showed no signs of leaning and were by far the best 

 anchored. Granted, the lower fruit load on MM.lll trees 

 may have reduced somewhat the tendency to lean, but they 

 also h-^d the largest leaf surface and above-ground por- 

 tions, providing a larger area for wind action and more 

 potential for damage. 



Trees on MM.lll were undesirable in terms of size 

 and yield but were much better anchored than any other 

 rootstock or rootstock-interstock combination. Under 

 certain conditions the better anchorage would make trees 

 on MM.lll much more desirable than other combinations. 



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Prospects for Greater Use of Biological Control Agents 

 Against Pests of Apple in IVIassachusetts 



Roy G. Van Driesche 



Department of Entomology, University of Massachusetts 



A recent publication of the Massachusetts Agricul- 

 tural Experiment Station, Opportunities for Increased Use 

 ofBiological Control in Massachusetts by Van Driesche and 

 Carey (Bulletin 718), has reviewed the status of the use of 

 parasites and predators for insect and mite pest control for 

 all major crops in Massachusetts. This report is available 

 through the Bulletin Distribution Center, Cottage A, at the 

 University of Massachusetts at Amherst for $7.00. For 

 apples, several possibilities exist to expand the degree of 

 pest control provided by predators and parasites. 



Little to no possibility exists for control of the major 

 apple pests (apple maggot fly, plum curculio, and the 

 tarnished plant bug). These species have few exposed life 

 stages suitable for attack by beneficial insects, and because 

 they are direct pests of the fruit, little tolerance exists for 

 their presence in commercial orchards. Certainly a few 

 parasites of these species do exist, but they offer no 

 reasonable hope for commercially acceptable levels of 

 control. The controls applied for these species do, how- 

 ever, play a key role in regard to the biological control of 

 those species for which effective biological control agents 

 do exist - namely aphids, scales, white apple leafhopper, 

 mites, and leafminers. All of these groups can come under 

 effective control by predators or parasites given favorable 

 orchard management. 



The traditional use of continuous insecticide cover 

 sprays from early season through early to mid-August 

 frequently disrupts the control of these secondary pests. 

 The "Second-stage" 1PM program currently being tested 

 at the University of Massachusetts by the tree fruit ento- 

 mologist, Ronald Prokopy, and the IPM coordinator, 

 William Coli, however, has the potential to change this 

 situation. The strategy replaces insecticidal control of 

 apple maggot fly with a control system based on sanitation 

 and intensive trapping. Second-stage IPM may allow 



routine, non-fungicidal sprays to be discontinued after the 

 end of May. The termination of these disruptive sprays is 

 expected to result in more mite predators and leafminer 

 parasites in orchards, and these are expected, based on 

 previous studies, to exert commercial-level control of these 

 pests in most orchards. Preliminary results for one field 

 season did show a substantial increase in predator mites 

 when post-May, non-fungicidal sprays were not applied. 

 We are, therefore, very likely to be at a major turning point 

 in orchard pest control, in which the termination of con- 

 tinuous cover sprays (the rule for at least 40 years) will 

 usher in a mixed chemical/biological control strategy in 

 which mite predators and leafminer parasites will provide 

 control of these pests. 



There are a number of specific actions or studies that 

 need to be undertaken to reach this goal. The most 

 important is, of course, the second-stage IPM project itself, 

 as it is the foundation on which all else rests. This effort 

 currently is underway with primary funding from the 

 Massachusetts Department of Food & Agriculture and the 

 Massachusetts Society for the Promotion of Agriculture. 

 Other specific actions that will be needed include the 

 following. 



Mites . The composition of predacious mite fauna in 

 Massachusetts apple orchards and their response to or- 

 chard pesticides is fairly well understood (Hislop & 

 Prokopy, 1981). The goal of increasing predator numbers 

 in orchards to levels high enough to control spider mites 

 can be reached by 1) earlier termination of cover sprays (as 

 in the second-stage IPM strategy); 2) introducing a strain 

 of the main pTcda\.OT,Amblyseiusfallacis, that has greater 

 resistance to common cover spray insecticides; 3) planting 

 and managing orchard floor vegetation that is most favor- 

 able to predator mite survival and reproduction; and 4) 



