Second-level IPM in Blocks of 

 Scab-resistant Apple Cultivars 



Daniel R. Cooley, Jennifer Mason, Jian Jun Duan, Xing Ping Hu, 

 Ryan Elliott, and Ronald J. Prokopy 

 Departments of Plant Pathology and Entomology^ 

 University of Massachusetts 



Previously, we have described methods designed 

 to eHminate orchard applications of insecticide and 

 miticide after early June. We have also described 

 our concept of the evolution of integrated pest man- 

 agement (IPM) programs, moving from first level 

 approaches which integrate methods for controlling 

 one class of pests, to a second level which integrates 

 methods for controlling all classes of orchard pests. 

 In 1991, we initiated a second-level IPM program in 

 12 Massachusetts commercial apple orchards com- 

 prised of Mcintosh, Cortland, Empire, and Delicious 

 cultivars. Our strategy used pesticides from April to 

 early June against early-season arthropod pests 

 (particularly mites, plant bug, sawfly, and plum 

 curculio), early-season disease pests (apple scab and 

 blossom-end rot) and early-season weed growth be- 

 neath the tree canopy. After early June, the strategy 

 called for few if any pesticide applications. Instead, 

 cultural, behavioral, and biological control methods 

 replaced pesticides. We felt that this strategy would 

 allow natural enemies of arthropod pests to increase 

 in numbers and provide biological control (especially 

 of foliar-damaging arthropods), slow rates at which 

 pests develop resistance to pesticides, and reduce 

 potential human risks from pesticide residues on 

 fruit at harvest. 



Over the first two years of the program, we saw 

 successes and some problems in all pest areas, but 

 one of the most troublesome areas was disease man- 

 agement. In the second-level blocks, growers used 

 4.6 fungicide dosage equivalents (DEs) during the 

 primary apple scab season. They also used 2.2 

 fungicide DEs to control summer diseases, notably 

 flyspeck and sooty blotch. By comparison, in first- 

 level IPM blocks, growers used 4.8 early-season 

 fungicide DEs and 3.0 summer fungicide DEs. While 

 the second-level blocks showed very modest fungi- 

 cide savings, fungicide use still presented a major 

 impediment in our efforts to reduce pesticide appli- 

 cations, particularly late in the season. 



In addition to reducing risk to humans from 



exposure to pesticide residues, eliminating insecti- 

 cides and miticides late in the season can assist pest 

 control overall, since these materials oflne destroy 

 natural enemies. Fungicides, however, also can 

 have a negative impact on natural biocontrol. 

 Benomyl is the best example, and has been shown to 

 sterilize predaceous phytoseiid mites (Crofl, 1990), 

 and eliminating fungicides from an orchard can 

 stimulate biocontrol (Bower et al., 1993). Further- 

 more, fungi that infect and kill insects and mites in 

 the natural setting may be inhibited by fungicides 

 (e.g.,Loriaetal., 1983; Tedders, 1981). Additionally, 

 there appear to be some pesticide impacts on spiders, 

 which may play a role in mite biocontrol 

 (Wisniewska et al., 1993). Therefore, it is worth 

 examining the effect of fungicide reduction or elimi- 

 nation in the orchard. 



One approach to fungicide reduction is to use 

 scab-resistant apple cultivars (SRCs). Our experi- 

 ences (in the Northeast Apple Sustainable Agricul- 

 ture Research and Education Project and in our own 

 blocks) indicate that SRCs at leastwill allow the 

 elimination of scab fungicides. The degree to which 

 SRCs will allow us to eliminate summer fungicides 

 needs to be determined. However, we sought to test 

 the effects of fungicide elimination in second-level 

 blocks, and in 1993, we added genetic control (host 

 plant resistance) to the tactics of cultural, behav- 

 ioral, and biological apple pest management. Spe- 

 cifically, we emphasized a second-level IPM ap- 

 proach in three commercial orchards having two- 

 acre blocks of SRCs, primarily Liberty and Priscilla. 

 The SRCs were propagated on M.26 rootstock and 

 planted in 1988. 



We also introduced a new technique to tackle 

 another problem: the need to clean red sphere 

 maggot traps frequently. Sticky red spheres have 

 been used in second-level IPM to trap apple maggot 

 fiies at the orchard perimeter. For the first time in 

 any commercial orchard, we used pesticide-treated 

 spheres as a substitute for sticky-coated spheres as 



8 



Fruit Notes, Winter, 1994 



