tional second-level blocks. No CM injury was 

 seen in the transitional second-level blocks or 

 their companion first-level blocks. LR injury 

 was sUghtly, but not significantly higher in the 

 transitional second-level blocks than in the first- 

 level blocks. LR injury in transitional second- 

 level blocks was no higher in 1992 than in 1991. 

 No sampled fi-uit in either block were damaged 

 by SJS or LAW (Table 4). 



Foliar Pests and Predators: 

 Full Second-level IPM 



In 1991, we reported season-long average 

 population levels of fohar pests; this year we 

 noted their p>eak populations in an efifort to 

 reflect damage more accurately. Cool and wet 

 summer weather helped to maintain low popu- 

 lations of fohar pests in most cases. 



Mite popxilations remained low in most 

 cases, as were populations ofAmblysieusfallacis 

 predators, which were not seen in full second- 

 level blocks until late August, £md were never 

 present in numbers thought to be sufficient to 

 achieve biocontrol. Yellow mite predator popu- 

 lations were slightly higher in second-level than 

 in first-level blocks throughout the summer, but 

 their abiUty to control any but the lowest mite 

 populations is questionable (Table 5). 



Another predator, Typhlodemus pyri, which 

 is present in orchards in Western New York, was 

 released in two second-level IPM blocks. Sam- 

 pling one month after release revealed high 

 numbers of these mite predators on release 

 trees. We wiU not know until 1993 whether or 

 not they survived the winter and spring and 

 successfully colonized the blocks. 



Both full second-level and nearby first-level 

 blocks were treated with about one dosage 

 equivadent of oil (Table 2). No other miticide was 

 used in full second-level blocks, and only one 

 grower apphed miticide to a first-level block. 



Potato leafhopper peak population levels on 

 terminals were higher in full second-level than 

 in first-level blocks. Potato leafhoppers infested 

 11% of sampled terminals in full second-level 

 blocks and 2% in nearby first-level blocks. Peak 

 potato leafhopper injury to terminals was 15% 

 in second-level and 6% in first-level blocks. 



White apple leafhoppers infested 14% of 

 sampled terminals in second-level blocks and 

 11% in first-level blocks; however, injury to fi-uit 

 averaged only 0.3% in second-level blocks, ver- 

 sus 3.4% in first-level blocks (Table 6). Injury in 

 first-level blocks, however, was confined prima- 

 rily to one orchard. In August, we identified rose 

 leafhoppers in all t)T)es of orchard blocks, but 

 further study is needed to determine their im- 

 portance in Massachusetts orchards. Pesticide 

 was applied against leafhoppers in early June in 

 only one second-level block, which had a signifi- 

 cant late-season infestation in 1991 (Table 2). 



Average peak leafininer population levels 

 were similar in the second-level blocks and first- 

 level blocks (Table 6). All of the six fiill second- 

 level blocks were treated with DimUin™ against 

 leafminers (Table 2). Leafininer population 

 levels throughout the summer confirmed our 

 previous conclusion that apphcation of DimUin 

 against the overwintering generation of 

 leafininer adults, when indicated by trap cap- 

 tures, is the most effective and least invasive 

 technique for their control. Treatment with 

 Dimihn is preferable to use of other materials 

 which are harsher on beneficial insects and 

 mites. Dimilin was not available for vise in first- 

 level blocks, and few growers chose to treat 

 leafminers in those blocks. If registered, Dimilin 

 will be a good option for control of leafminers 

 without serious disruption of beneficials. We 

 chose to apply it before bloom so that it did not 

 affect leafi:x)ller and codling moth populations, 

 which we are trjdng to study in the absence of 

 insecticide use after mid-June. If registered, 

 Dimilin could be used later in the season after 

 first-generation mines have appeared, allowing 

 growers to avoid its use in years in which it may 

 not be needed. 



In other articles, we provide data indicating 

 that predacious spiders are significantly more 

 abundant late in the growing season in second- 

 level blocks than in first-level IPM blocks, and 

 that some of these spiders feed on leafininer 

 larvae inside mines as well as on leafhopper 

 nymphs. 



Green apple aphid (GAA) populations were 

 almost the same in the two types of blocks. At 

 their peak, aphids infested 69% of sampled 



Fruit Notes, Winter, 1993 



29 



