domized complete block design, replicated three times 

 and duplicated for each cultivar. Plots consisted of 

 three adjacent trees, with data taken from the center 

 tree. Trees, on M.7 rootstocks, were spaced 16 ftX 23 ft 

 and were 12 ft tall. 



Four treatments were tested: (Da standard IPM 

 chemical regimen; (2) one-half rate of all chemicals 

 applied in treatment 1, supplemented with Safer's 

 Insecticidal Soap at the recommended rate (two gallons 

 per 100 gallons water) (fungicides were increased to 

 standard rates after July 6); (3) Safer's Insecticidal 

 Soap at the recommended rate, plus standard fungi- 

 cides; and (4) Safer's Insecticidal Soap applied at one- 

 half the recommended rate, plus standard fungicides. 



Treatments were applied to run-off with a Bean 

 hydraulic handgun sprayer at 200 p.s.i., with a delivery 

 rate of 300 to 350 gal/acre. Dormant oil was applied to 

 all plots on April 27. Fungicides (Manzate™ 200DF 

 and Rubigan™ 12.5% EC) were applied on May 3, 12, 

 and 22. Rubigan was applied alone on June 4, and 

 Polyram™ 80% WP was applied on June 27, July 19, 

 and August 7. At petal fall (May 22), Guthion 50W 

 (standard rate: 5/8 lb/ 100 gal) and Safer's Insecticidal 

 Soap were applied in the appropriate plots as described 

 above. Aphid control treatments were applied on June 

 27 (standard: Thiodan™ 50WP at 0.5 lb/100; note that 

 this rate is one-half the recommended rate given in the 

 New England Apple Spray Guide, 1990). Mite control 

 treatments were applied on July 19 and 31 (standard: 

 Omite™ 30WP at 1.5 lb/ 100), and on August 7 and 14 

 (standard: Omite 30WPat2 lb/100). Treatments 3 and 

 4 received only soap, as described above. 



Aphids and predaceous larvae were assessed by 

 determining their presence or absence from 15 termi- 

 nal leaves sampled from the central tree in each plot. 

 ERM were assessed by determining their presence or 

 absence on 15 spur leaves from the central tree in each 

 plot. 



Phytotoxicity to foliage was evaluated by rating 

 leaf yellowing and leaf drop from the central tree in 

 each plotfrom (none) to 4 (severe). Harvest data were 

 collected by examining 100 fruit on the central tree in 

 each plot for any insect, disease, or phytotoxic damage; 

 one-third of the fruit was selected from the inside, 

 outside and top of the canopy. Mcintosh were evaluated 

 on September 6 and Delicious, on October 5. 



Results 



Aphids. Specimens submitted for identification 

 were all identified as Aphis spireacola, a difference 

 from samples in previous years, when Aphis pomi had 

 been the dominant aphid species. 



Proportions of leaves infested with spirea aphid 



were not significantly different among treatments in 

 pre- or post-treatment counts (Figure 1), due at least in 

 part to high variation within treatments. Thiodan 

 applications tended to be more effective in reducing 

 aphid infestations than were Safer's Insecticidal Soap 

 applications. Aphid infestations were not significantly 

 different between cultivars. 



Aphid predators Thiodan applications, even at 

 low rates, reduced aphid predator populations signifi- 

 cantly more than insecticidal soap applications. 

 Syrphid presence was reduced following all treatments 

 (Figure 2). Ten days after treatment, there were sig- 

 nificantly more leaves infested with syrphids in the 

 block treated with the low rate of insecticidal soap than 

 in the other blocks. This result is consistent with other 

 work, which indicates that soap has no residual effect. 

 On June 29, all cecidomyiid larvae were eliminated 

 from all Thiodan-treated trees (Figure 3). 

 Cecidomyiids were reduced in all other treatments as 

 well. However, there were no significant differences 

 among treatments, again, probably due to sampling 

 variation. 



Mites. Delicious trees had significantly more mite- 

 infested leaves than did Mcintosh trees on the first 

 three dates. Within cultivars, mite populations were 

 not significantly different among treatments, except on 

 July 24, when treatment 1 of Mcintosh had the most- 

 mites, treatments 2 and 3 the least, and treatment 4 

 was intermediate (Figure 4). While not statistically sig- 

 nificant, similar results were obtained in the Delicious 

 block; insecticidal soap applications resulted in lower 

 mite densities than applications of Omite alone, and 

 the full rate application of insecticidal soap produced 

 promising results with respect to mite control. How- 

 ever, control of mites in all treatments was inadequate. 

 The length of time between the first two applications 

 (12 days) was too long. The time period between the 

 second split application (7 days) was probably ade- 

 quate, but five inches of rain fell preceding the August 

 17count and few mites survived, eliminating mite con- 

 trol treatment effects. Thus, the most revealing infor- 

 mation on miticide activity was obtained on July 24. 



Phytotoxicity and fruit damage Evidence of leaf 

 phytotoxicity was most severe on Delicious apples re- 

 ceiving a full rate of Safer's Insecticidal Soap (Figure 5). 

 Many leaves on this cultivar turned yellow and 

 dropped following the first soap application. Mcintosh 

 foliage did not exhibit leaf yellowing or drop. At har- 

 vest, direct fruit injury due to fruit damaging insects 

 and disease was within acceptable ranges (Figure 6). 

 No significant difference in insect injury to fruit was 

 found among treatments. Delicious apples receiving 

 Safer's Insecticidal Soap plus standard pesticides had 

 greater scab injury than the low rate of soap alone; this 



22 



Fruit Notes, Spring, 1990 



