A Sampling Method for Detecting 

 Root-feeding Wooiiy Appie Apliids 



M. W. Brown 



USDAf Agricultural Research Service, Appalachian Fruit Research 



Station, Kearneysville, WV 



The woolly apple aphid generally is consid- 

 ered to be a minor pest of apple world-wide, 

 seldom becoming abundant enough to justify 

 chemical control. This aphid is most often found 

 at pruning scars, other wound sites and at the 

 base of petioles on current year's growth. It also 

 feeds on roots of apple trees where it survives the 

 winter and can remain throughout the year. I 

 have been investigating this root-feeding insect 

 and its effects on apple tree growth and produc- 

 tion. The research literature contains only a few 

 studies of this problem, and those deal with 

 nursery stock. I found that root-feeding woolly 

 apple aphids reduced tree growth in young 

 nonbearing orchards (Brown and Schmitt, 

 1990) and caused a significant economic loss in 

 a seven-year-old 'Delicious' orchard (Brown et 

 al., in preparation). 



The sampling method that I used in my 

 research was to uproot trees and evaluate the 

 root system. This method is efficient for re- 

 search but not for pest management programs, 

 for obvious reasons. To determine if some form 

 of treatment is needed, a sampling method must 

 be quick and easy enough to use with minimum 

 training. The method described in this paper is 

 based on woolly apple aphid biology. During 

 spring, first-instar nymphs migrate up the tree 

 from overwintering populations on roots to re- 

 colonize above-ground portions of the tree (Hoyt 

 and Madsen, 1960). Trapping these migrating 

 woolly apple aphid njnuphs should give an indi- 

 cation of the presence and intensity of root 

 infestation. 



A two-inch-wide strip of masking tape was 

 placed around the trunk of apple trees, one to 

 two feet above the ground but below the lowest 

 scaffold limb. The tape was placed on the 



smoothest section of trunk available. A continu- 

 ous barrier, about 1/8-inch deep and one-inch 

 wide, of Tangle-trap™ was apphed in the center 

 of the masking tape. A portion of the masking 

 tape band was exposed both above and below 

 the Tangle-trap barrier. The trees that were 

 used in this study were planted in 1985 at 308 

 trees per acre. The block contained Frazier 

 (joldspur, Smoothee (jolden Delicious, both on 

 M.7A, and Bisbee Spur Dehcious on M.7 EMLA. 

 The orchard was located at the Appalachian 

 Fruit Research Station in Kearneysville, West 

 Virginia, and was managed using standard 

 commercial practices. 



Trees were banded to coincide with specific 

 tree phenologies from green tip to first cover. 

 Twenty five trees, selected randomly, were 

 banded at each of four sample periods in 1993, 

 as shown in Table 1. One group of 25 trees was 

 banded for the entire green-tip to petal-fall pe- 

 riod. An additional eleven trees with evidence of 

 aphid migration up the tree during bloom were 

 banded at petal fall. At the end of the designated 

 sample periods the bands were removed and 

 field counts of woolly apple aphid nymphs were 

 made. Examination of the tape bands was with 

 the unaided eye, using a hand lens only to verify 

 questionable nymph sightings. On May 25, the 

 trees were uprooted, the number of woolly apple 

 aphid colonies on roots was recorded, and the 

 amount of root galling was evaluated on a scale 

 of to 1. The root gall rating scale incorporated 

 both the proportion of the root system with root 

 galls and the intensity of galling on those roots 

 infested. It can be thought of as the proportion 

 of the root system affected by woolly apple 

 aphids, scored from none (0) to complete infesta- 

 tion (1). 



FruH Notes, Fall, 1993 



