Host Preferences of the Green Peach Aphid,
Myzus persicae (Hemiptera: Aphididae)l
BARRY ANNIS!
Yakima Agricultural
RALPH E. BERRY,'
Research Laboratory,
AND
GEORGE TAMAKI
Agric. Res., SEA, USDA, Yakima, Washington
98902
ABSTRACT
Environ.
Entomol.
11; 824-827
(1982)
Gynoparous, oviparous, and apterous green peach aphids, Myzus persicae (Sulzer), preferred radish,
Raphanus sativus L., to the winter host, peach, Prunus persica Batsch, in laboratory tests of settling
behavior. Preference for radish was strongest in the apterae and weakest in the oviparae; however, in
all cases the degree of preference was significant (P = 0.01). Gynoparae discriminated between peach
and a nonhost species, Acer saccharinum L., although few aphids settled on either species during the
test. Although feeding preferences may allow green peach aphid to discriminate between tree species,
these results indicate that such preferences cannot explain the movement of migrants from secondary
to primary hosts. Apterae discriminated readily between various secondary hosts. Marked differences
in preference occurred even between species which have been shown to be highly suitable for reproduction. Rates of settling were higher on preferred hosts than nonpreferred hosts, indicating that the
rate of interplant movement may be significantly greater on nonpreferred hosts.
The green peach aphid (GPA), Myzus persicae (Sulzer),
is a host-alternating species which overwinters in the
egg stage on peach trees, Prunus persica Batsch. In the
Yakima Valley of central Washington, eggs hatch in late
February or early March, and winged migrants begin
leaving the trees in the ftrst half of May (Davis and
Landis 1951, Tamaki 1973). Summer forms populate
vegetable crops and a variety of weed species. Gynoparous migrants return to peach in September (Tamaki
et aI. 1967).
Little is known of the factors which influence aphids
to return to their primary hosts. Kennedy and Booth
(1951) have suggested that aphids respond to nutritional
changes in plants, and leave the primary host as its leaves
mature and become less suitable for growth and reproduction. Aphids return to the primary host in the fall,
when senescence of leaves once again renders the host
suitable for colonization.
Kennedy and Booth (1951, 1954) indicated that for
Aphis fabae Scop., condition of the host plant was the
dominant factor in host alternation. All stages investigated preferred the winter host, spindle, Euonymus sp.,
to a summer host, sugar beet, Beta vulgaris L., in choice
tests. However, Dixon (1971) found life stages of the
bird cherry-oat aphid, Rhopalosiphum padi L., to have
differing preferences. Apterous summer forms preferred
oats in behavioral trials, whereas gynoparae showed a
strong preference for the primary host, bird cherry, Prunus padus L. He concluded that a basic change in the
aphids' feeding preferences resulted in host alternation.
Alate aphids are thought to be highly selective and
primarily responsible for dispersal and host selection
(van Emden et a!. 1969). Kennedy and Booth (1954),
studying A. fabae, found behavioral preferences to be
weakly expressed in the apterae. Their conclusion was
that, as a specialized food exploiter, rather than selector,
the aptera is not particularly demanding of the plant
'Received for publication 27 July 1981. Oreg. Agric. Exp. Stn. Tech. Paper
No. 5934.
2J>resentaddress: Dept. of EnlOmology, University of Idaho. Moscow, lD 83843.
3Depl. of Entomology, Oregon State University, Corvalli" OR 97331.
"flavor." GPA, however, is known to be more prone
to wander between plants than are other aphids (Simpson
et aI. 1945).
We therefore investigated the feeding preferences of
GPA to determine how its responses compared with those
of other species.
First, we compared the preferences of various life
stages to examine the role of feeding preferences in host
alternation. Secondly, we examined the extent to which
apterous GPA could discriminate between various secondary hosts.
Materials and Methods
General
Gynoparous and oviparous GPA were collected from
naturally infested peach trees in early September. Apterae were obtained from continuous greenhouse culture
where they were reared on hoary cress, Cardnria draba
L., a favored secondary host, with a 16-h photoperiod
and a minimum temperature of 24°C.
Leaf discs (2 cm in diameter) were cut from the leaves
of each plant species to be compared. Two leaf discs of
each species were placed alternately around the perimeter of a plastic petri dish on moist filterpaper. Ten
aphids were removed from their feeding sites with an
artist's brush and placed in the center of the dish. The
dish was sealed with masking tape and placed on a laboratory shelf under uniform illumination at room temperature. Each test was replicated 10 times, and each
replicate was rotated 900 relative to the preceeding replicate to compensate for positional effects. A Student's
t test was used to determine if the settling behavior of
the aphids differed significantly from a random distribution.
Comparison of Life Stages
Leaf discs were cut from peach and maple leaves
collected in the field, and from fully expanded leaves
of radish plants grown in field plots. In the first test,
gynoparae, oviparae, and apterae were given a choice
824
August 1982
between radish, Raphanus sativus L., and peach, and in
the second test, gynoparae were given a choice between
peach and a nonhost, silver maple, Acer saccharinum
L. The number of aphids which had settled on each
species was counted 2 and 4 h after the beginning of
each test.
Host Discrimination
Results and Discussion
Comparison of Life Stages
When given a choice between radish and peach, gynoparae, oviparae, and apterae preferred radish, a summer host, to peach. The preference for radish was strongest
in the apterae and weakest in the oviparae, however in
all cases the expressed preference was significant (P =
0.01) (Table 1).
Gynoparae which were given a choice between leaf
discs of peach and silver maple preferred peach, although only 21 % of the aphids in the test settled on
either species within 4 h (Table 2).
These results indicate that feeding preferences alone
cannot account for the phenomenon of host alternation
by GPA. All life stages tested preferred radish to peach,
although the peach leaves were senescent and therefore
presumably nutritionally superior to the mature radish
leaves (Kennedy and Booth 1951). This would suggest
Table I.-Settling behavior of different life stages of
GPA on radish and peach leaf discs in the laboratory
Life stage
Time (h)
Species
Apterae
2
Radish
Peach
96a,b
Radish
Peach
990,b
0
1
Table 2.-Settling behavior of gynoparae of GPA on
peach and silver-maple leaf discs in the laboratory
Time
Species
Peach
Silver-maple
by Apterae
Leaves of commercial mustard (Brassica nigra Kock.
'Florida Broadleaf),
broccoli (Brassica oleracea L.
'Green Sprouting'), potato (Solanum tuberosum L. 'Russet
Burbank'), common mallow (Malva neglecta Wallr.),
redroot pigweed (Amaranthus retroflexus L.), common
lambsquarters (Chenopodium album L.), sweet com (Zea
mays L. 'Morning sun'), and dandelion (Taraxacum officinale Wiggers) were taken from field plots. Radish
('Sparkler'),
hoary cress, hairy nightshade (Solanum
sarachoides Sendt.), and sugarbeet foliage was obtained
from greenhouse grown plants. Fully expanded leaves
of vigorous plants were used in all tests. Apterae were
tested with all combinations of the above secondary hosts.
In early tests, counts were made I, 2, and 24 h after the
beginning of the test. Since an analysis of variance showed
no difference between counts, later tests were terminated
after 2 h and counted at that time.
4
825
ANNIS ET AL.: HOST PREFERENCES OF GREEN PEACH APHID
Gynoparae
Oviparae
52a,b
16
52a•b
30
61a,b
18
5sa,b
28
apercentage of total aphids settled on each species in
10 replicates.
bpercentage of aphids which settled on radish or peach
was significantly different at 1% level (Student's t test).
Type of host
Winter
Nonhost
2h
4h
2oa.b
16a,b
5
4
apercentage of total aphids settled on each species in
10 replicates.
bpercentage of gynoparae which settled on peach or
silver-maple was significantly different after 2 h (P= 0.01)
and 4 h (P = 0.05) (Student's t test).
that "flavor" discrimination is more important than
"nutritional"
discrimination in GPA, but it does not
explain the return of migrants to peach.
Field observations have shown that gynoparous GPA
attempt to colonize a number of tree species and are not
particularly selective in alighting (Hill Ris Lambers 1946,
Kennedy et al. 1959). Kennedy et al. (1959) have reported that only a small fraction of alighting GPA remain on peach, although the rate of departure may be
lower than from other tree species. Although feeding
preferences may allow GPA to discriminate between arboreal species, it is clear from these tests and from field
observations of Kennedy et al. (1959) that peach does
not strongly arrest GPA. Hence, the nature of the stimuli
which influence GPA to return to the primary host is
unclear.
Irrigated agriculture provides aphids with a vastly extended alternate host population throughout the season.
Weeds in all stages of development can be found in
irrigated fields and orchards much of the time. In an
undisturbed ecosystem, the senescent leaves of woody
plants may provide the only desirable food source late
in the season. Yet field observations provide evidence
that host alternation is not just a response to host availability. Kennedy et al. (1959) found that gynoparous
GPA avoided potted Brussels sprout plants placed next
to peach trees. In the fall of 1978, radish plants in field
plots at the Yakima Agricultural Research Laboratory
did not accumulate large numbers of gynoparae as did
peach trees in an adjacent orchard (unpublished data).
In an agricultural setting, GPA populations become
concentrated in small areas each fall as gynoparous migrants accumulate in peach orchards. In an undisturbed
ecosystem, however, the gynoparae would disperse in
all directions through a diverse flora in search of the
relatively rare primary host. The gynopara is as much
an agent of dispersal as its alate viviparous counterpart.
A primary host which strongly arrested movement would
be a hindrance to dispersal, whereas a slight preference
over other tree species would allow a gradual accumulation on the proper host over a wide area.
Our data suggest that habituation to the primary host
could occur among the members of a migrating population. The preference for radish was strongest among
the apterae, which had never been exposed to peach.
Preference was weakest in the oviparae, which had spent
826
ENVIRONMENTAL
their entire lives on peach. The gynoparae, which had
spent some time on both primary and secondary hosts,
were intermediate.
Gregariousness may be an important factor influencing the buildup of GPA on peach. It has been shown
that the rate of settling of both gynoparae and males of
GPA is higher on leaves and twigs which are occupied
by other aphids than on those which are uncolonized
(Tamaki et al. 1970, 1973). As a portion of the migrating population settles on the primary host, their presence could influence the behavior of later arrivals.
Thus, it appears that feeding preferences may allow
migrant GPA to discriminate between tree species, but
the movement of migrants from secondary to primary
hosts cannot be explained in terms of such preferences
alone.
Host Discrimination
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Apterae readily discriminated between secondary hosts.
In general, Cruciferae were highly preferred. In all but
one comparison involving crucifers other than broccoli,
significantly more aphids settled on the cruciferous species than the other species (Table 3). Radish was preferred in all comparisons, whereas dandelion was not
prefered in any test. Surprisingly, however, broccoli was
not preferred over less suitable hosts such as redroot
pigweed and lambsquarters in the behavioral tests. This
may be due to physical factors of broccoli leaves, which
are thick, waxy, and glaucous. One or a combination of
these factors may be repellent to GPA. The basal leaves
of commercial mustard are similar to radish leaves,
whereas leaves arising from the flower stalk are waxy
and glaucous, similar in texture to broccoli leaves. When
given a choice between leaf discs from basal and upper
mustard leaves in a test like those described above, 86%
of the GPA settled on the basal leaves, whereas only
10% settled on upper leaves. Similarly, non waxy varieties of Brussels sprouts are more susceptible to GPA
than waxy varieties (van Emden et al. 1969), and treatment with wetting agents has been found to increase the
susceptibility of some Brassica species to GPA (Heathcote and Ward 1958).
Plant species can be grouped by the degree of preference by GPA. The mean number of aphids settling on
a plant in all comparisons was used as an index of acceptability. The groupings thus obtained roughly follow
taxonomic lines (Table 4).
The restlessness of GP A on less favored hosts was
readily apparent in these tests. If one or both plant species of a test pair were highly preferred, a large proportion of the aphids settled during the test. An average
of 91 % of all aphids settled in tests involving crucifers.
When offered a choice between two nonpreferred species, the settling rate was much lower. In tests involving
only Amaranthaceae,
Chenopodicae,
Graminae, and
Compositae, an average of only 59% of the aphids settled. These results indicate that the tendency of GP.A to
wander from plant to plant is greater on less preferred
hosts. Thus, the restlessness of apterae may contribute
to the buildup of GPA populations on preferred hosts in
Vol. 11, no. 4
ENTOMOLOGY
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ANNIS ET AL.: HOST PREFERENCES
Table 4.-Ranking
of host species based on settling
Host
827
OF GREEN PEACH APHID
behavior
of GPA in the laboratory
Suma
Family
Highly preferred
Radish
Commercial mustard
Hoary cress
Cruciferae
Cruciferae
Cruciferae
862
836
758
78.4
76.0
68.9
Preferred
Potato
Hairy nightshade
Common mallow
Solanaceae
Solanaceae
Malvaceae
563
552
473
51.2
50.2
43.0
Nonpreferred
Redroot pigweed
Common lambsquarters
Broccoli
Sugarbeet
Sweet corn
Dandelion
Amaranthaceae
Chenopodiaceae
Cruciferae
Chenopodiaceae
Graminae
Compositae
297
289
265
259
239
142
27.0
26.3
2'1.1
23.5
21.7
12.9
aTotal aphids on indicated species in all comparisons.
bMean number of aphids which settled on each species in all comparisons.
the field. It may also be a significant factor in the spread
of virus diseases, especially
on less preferred hosts such
as sugarbeet.
Kennedy, J. S., and C. O. Booth. 1951. Host alternation in
Aphis fabae Scop. I. Feeding preferences and fecundity in
relation to age and kind of leaves. Ann. Appl. BioI. 38:
Acknowledgment
1954. Host alternation in Aphis fabae Scop. II. Changes in
the aphids. Ibid. 41: 88-106.
Kennedy, J. S., C. O. Booth, and W. J. S. Kershaw. 1959.
Host finding by aphids in the field. I. Gynoparae of Myzus
persicae (Sulzer). Ibid. 47: 410-423.
Simpson, G. W., W. A. Shands, and O. L. Wyman. 1945.
Weeds and the aphid-Ieafroll problem in potatoes. Maine
Ext. Bull. No. 333. 20 pp.
Tamaki, G. 1973. Spring populations of the green peach aphid
on peach trees and the role of natural enemies in their control. Environ. Entomol. 2: 186-191.
Tamaki, G., B. J. Landis, and R. E. Weeks. 1967. Autumn
populations of green peach aphid on peach trees and the
role of syrphid flies in their control. J. Econ. Entomol. 60:
433-436.
Tamaki, G., B. A. Butt, and B. J. Landis. 1970. Arrest and
aggregation of male Myzus persicae (Sulzer) (Hemiptera:
Aphididae). Ann. Entomol. Soc. Am. 63: 955-960.
Tamaki, G., J. U. McGuire, and J. A. Onsager.
1973.
Spatial distribution of the green peach aphid used in estimating the populations of gynoparae. Res. Pop. Beo!. 15:
We thank Tibor Jermy of the Research
Institute
Plant Protection,
Budapest,
Hungary,
for his critical
view of this manuscript.
for
re-
REFERENCES
CITED
Davis, E. W., and B. J. Landis. 1951. Life history of the
green peach aphid on peach and its relation to the aphid
problem on potatoes in Washington. J. Econ. Entomol. 44:
586-590.
Dixon, A. F. G. 1971. The life cycle and host preferences of
the bird cherry-oat aphid, Rhopalosiphum padi L., and their
bearing on the theories of host alternation in aphids. Ann.
Appl. BioI. 68: 135-147.
van Emden, H. F., V. F. Eastop, R. D. Hughes, and M,
J. Way. 1969. The ecology of Myzus persicae. Annu. Rev.
Entomol. 14: 197-270.
Heathcote,
G. D. and J. Ward. 1958. The preferences of
Myzus persicae (Sulz.) for Brassica, plants sprayed with
wetting agents. Bull. Entomo!. Res. 49: 235-237.
Hill Ris Lambers, D. 1946. The hybemation of Myzus persicae (Sulzer) and some related spec.ies, including a new
one. Bull. Entomol. Res. 37: 197-199.
25-64.
64-75.