INFLUENCE OF PESTICIDES ON SPIDER MITE 

 AND PREDATOP ABUNDANCE IN MASSACHUSETTS 

 APPLE ORCHARDS--1977 RESULTS 



Robert G. Hislop, Charles Acker, and Ronald J. Prokopy 

 Department of Entomology, Fernald Hall 



In the March- April, 1977, issue of Fruit Notes we described 

 the results of our 1976 research aimed at reduced spraying for 

 spider mites in Massachusetts apple orchards. In 1977, we contin- 

 ued our search for natural enemies of mites and discovered that 

 Amblyseius fallacis , our most important mite predator, was even 

 more abundant and widespread than our 1976 survey suggested. Here, 

 we discuss the results of our 1977 field work aimed at enhancing 

 the buildup of this valuable predator in our orchards. 



In June, 1977, we resumed the extensive spider mite (red mite 

 and two-spotted mites) and predator sampling program begun in 1976 

 but concentrated on sampling only apple tree foliage. We sampled 

 4 commercial orchards (A, B, C, and D) , located in 2 separate regions 

 of the state, and 1 abandoned orchard. Two of the commercial 

 orchards employed one type of spray program, the other 2, a differ- 

 ent program. In addition, at the Horticultural Research Center at 

 Belchertown, we applied either Imidan, Guthion, Zolone, or Benlate 

 at biweekly intervals from petalfall to late August to 3 groups of 

 trees, with 3 groups left unsprayed for comparison. All trees in 

 the commercial and Belchertown orchards were sampled at biweekly 

 intervals to determine spider mite and predator populations. The 

 samples were collected, processed, and analyzed in the manner 

 described in the 1977 issue of Fruit Notes . 



Results in 1977 supported the 1976 results in that A. fallacis 

 was common only in certain commercial orchards. In the abandoned 

 orchard its numbers were low but numerous other predator species 

 kept red mites and two-spotted mites at very low levels. 



In commercial orchards A and B, sprayed with combinations of 

 Guthion, Zolone, Imidan, Benlate, Glyodin, and Captan, two-spotted 

 mites reached 10.7 and 14.3 mites per leaf at peak abundance 

 (Table 1) but red mites remained below damaging levels. Popula- 

 tions of A_^ fallacis reached maximum levels of only 0.06 and 0.04 

 mites per leaT'. 



On the other hand, in commercial orchards C and D, sprayed 

 with combinations of Guthion, Captan, and Cyprex, two-spotted 

 mites were virtually absent. In orchard C, red mites remained 

 at very low levels, in contrast to orchard D, where they reached 

 a peak abundance of 36 mites per leaf (Table 1) . A. fallacis was 

 relatively scarce in orchard C in comparison to orchard D, probably 

 due to the low spider mite populations. In orchard D, predacious 

 mites reached very high numbers, (5.4 mites per at peak abundance) 

 but yet were unable to control the red mites. In addition to the 

 large A_^ fallacis populations in orchard D, there were 2 additional 



