legumes on egg production, adult sUfYival, and o

INFLUENCE OF SELECTED LEGUMES ON EGG PRODUCTION,
ADULT SURVIVAL, AND OVIPOSITIONAL PREFERENCE
OF THE POTATO LEAFHOPPER'·'
A. M. Simmons, B. C. Pass, and K. V. Yeargan'
Department of Entomology, University of Kentucky
Lexington, KY 40546·0091
Abstract: Ovipositional rate, fecundity, and adult longc\'ity differed among female potato
learhoppers. EmpoascCl {obae (Harris), maintained at 27°C and reared on different hosts
("Apollo', 'Buffalo' nnd 'Riley' alfalfa; 'Major' broad bean; 'Kenstar' and 'Kuhn' red clover;
and 'Williams' soybean). A high ovipositional rate (7.6 eggs/femalc/2 d). high fecundity
(136.9 eggs) and long adult survival (X = 36.1 d) were attained by leafhoppers on broad
bean. A low ovipositional rate (0.6 eggs/femate/2 d), low fecundity (2.9 eggs) and shan adult
survival (X = 10.6 d) occurred with leafhoppers on 'Kenstar' red clover. On 'Williams'
soybean. the ovipositional rote and fecundity (2.2 eggslfemale/2 d and 30.5 eggs. respectively)
were low, but adult sUlVival was relatively long (Y = 26.7 d).
The number of eggs deposited per plant was detennined in a free-choice test among the
same seven leguminous plants as above, using potted plants under greenhouse conditions.
The alfalfa hosts were among the most preferred, while broad bean was among the least
preferred for ovi)>osiUon.
Key Words: Potato leafhopper, Empoasca fabae, alfalfa, broad bean, red clover. soybean.
J. Agrie. Enromol. 1(4): 31l·317 (Oerobe, 1984)
The potato Icafhopper, Empoasca [abae (Harris), is an important insect pest of
forage and several other economic crops. It is essential that the biology of the
potato leanloppcr bc understood so that sound management. decisions can be
made. Eggs of the potato leafhopper are deposited inside plant tissues and are not
visible from the outside. Simonet and Pienkowski (1977) described a staining and
clearing technique t.o observe potato leafhopper eggs. Their method, unlike those
available to previous workers, was satisfactory for use with fibrous stems such as
alfalfa. Observations on reproduction by potato leafboppers were reported by
DeLong (1938) and Decker et a!. (1971). Both studies, however, were based on
indirect estimates (i.e., the number of nymphs successfully eclosing). Hence,
neither fecundity nor rate of oviposition could be determined from their work.
Simmons et al. (1984) found that different host plants arfected the rate of
development of the potato leafbopper. Saxena et al. (1974), working with other
species of Empoasca. demonstrated that the host plant affected both egg
production and adult longevity.
The investigation reported herein was undertaken to detennine the ovipositional
rate, fecundity, and adult female survival of the potato leafhopper on selected host
plants, and to test fol' ovipositional preference among these plants by the potato
leafhopper.
1 1:,'trIIJOlU<lI (/loot! (Ham.) t HOM01"Ili:RA; Cic&deUidae). Received for publi~tion 28 (kU)ber 198.1: accepted 4 June
1984.
2 The in\lutiS.tion rel>orted in thill p.per tNo. 63·7-199) 15 in connection with a projecl of lhe Kentucky Arrieultural
Esperimenl Stalion alld i~ published "'ilh approval of the Director_
3 Graduate ""i.tant. ProfelllMlr. lind ProfeUOl'". respeclivel)-. Uni...enit)· of Kenlucky. Lesinl:ton. KY 40546.0091.
311
312
J. Agric. EntomoL, Vol. I, NO.4 (1984)
MATERIALS AND METHODS
The following host plants were used: three alfalfa (Medicago sativa L.) varieties­
'ApoUo,' 'Buffalo,' and 'Riley'; broad bean (Vida. faba L.) variety - 'Major'; two
red clover (Trifolium pratense L.) varieties - IKenstar' and 'Kuhn'; and soybean
(Glycine max (L.) Merr.) variety - 'Williams'.
Egg Production and Adult Longeuity
To obtain a source of newly emerged adult females, potato leafhoppers were
reared from egg to adult on each of the seven host plants at either 24°C or under
greenhouse conditions. Adult female potato leafhoppers were placed in an
environmental chamber within 24 h after emergence and were maintained at 27°C
and a 15:9 (L:D) photoperiod until they died. Each female was caged on the plant
variety on which it developed to adult. Thus, each female lived on 8 single host
from the egg stage until death of the adult Two male potato leafhoppers, collected
from a field of alfalfa, were caged with each female; the cage was then placed in
the environmental chamber.
About 9 cm of plant stem with leaves was inserted into the cage with ca. 5 em
remaining outside. The uncaged portion of the stem was inserted into a vial of
distilled water. Cages used in this experiment were constructed from 11.5 cm diam
plastic petri dishes. A 10 cm diam opening was cut in the center of each lid and
covered with 52 X 52 mesh screening. A 2 em hole was cut in one side to aHow
the host plant to be inserted into and removed from the cage. Cotton was used to
fill the space around the plant stem at the entrance into the cage. During the
period preceding oviposition, all dead males were replaced. Host plants were
replaced every 2 d. The number of eggs deposited during each 2-d interval was
recorded for each female. Sample sizes for the ovipositional rate experiment were
as follows: 20 - 'Apollo' alfalfa, 18 - 'Buffalo' alfalfa, 24 - 'Riley' alfalfa,
15 - broad bean, 16 - 'Kenstar' red clover, 17 - 'Kuhn' red clover, and 10­
'Williams' soybean.
The total number of eggs deposited by each female was recorded every 2 d,
starting on the first. or second day after emergence and continuing until death of
the female. Observations of eggs in stems were made by direct counts, using a
modified version of the lactophenol acid fuchsin technique of Simonet. and
Pienkowski (1977). The modification provided for staining and clearing a large
number of individual plant. samples in a relatively short period of lime and aUowed
use of a smaller volume of staining and clearing solution. Test tubes were used to
boil several samples simultaneously. Test tubes (each containing an individual
plant sample, boiling chips, and the staining and clearing solution) were placed in
a large beaker containing additional staining and clearing solution and boiling
chips. The staining and clearing solution was included in the beaker so that heat
could be conducted to the test tubes via the solution.
Ouipositional Preference
The seven kinds of host plants described above were tested for ovipositional
preference under greenhouse conditions using potted plants. A Plexiglas@ cage
was constructed with the top open and encompassing an area or 0.5 sq. m. The
top was then covered with 52 X 52 mesh screening; t.he sides were 0.6 m high.
313
SIMMONS et. aI.: Influence of legumes on leafhoppers
The bottom and sides were closed except for two 25 em diam sleeve openings in
opposite sides. The sleeve openings were covered with stockinet which permitted
hand entry into the cage. The cage was centered beneath two 40-watt fluorescent
lamps which provided supplemental lighting to maintain a 15:9 (L:D) photo­
period.
A potted plant of each of the seven hosts was placed in the cage in a circular
arrangement with equidistant spacing of plants along the circumference. Eleven
replicates were established, with the arrangement of the plants among the seven
possible locations being randomly chosen for each replicate. Plant height ranged
among the replicates from 9 em to 23 em (usually 12 to 16 em), but differed by no
more than 1.5 cm among plants within a given replicate. In an attempt to have
similar biomass among the plants used for each replicate the following procedures
were used. Three stems of each red clover variety and two stems of each alfalfa
variety were left on the test plants, and the other stems were removed. The
petioles of the alfalfa were removed except for a combined total of the upper
seven on the two stems. Intact soybean plants of growth stage V2 to V3 (Fehr and
Caviness 1977) were used. Si"ty female potato leafhoppers (collected from a field
of 'Buffalo' alfalfa) were placed in the center of the cage, allowed to disperse, and
left for 24 h. The stems then were cut at soil level and the staining and clearing
techniques described earlier were used to determine the number of eggs which
had been oviposited in each of the seven leguminous hosts.
RESULTS AND DISCUSSION
Egg Production
There were significant differences (P < 0.05) in fecundity among potato
leafhoppers whieh were maintained on different host plants (Table 1). Fecundity
was high on broad bean (x ~ 136.9 eggs) and 'Riley' alfalfa (x ~ 87.4 eggs), but
low on soybean (x = 30.5 eggs) and 'Kuhn' and 'Kenstar' red clover (Y = 42.1 and
2.9 eggs, respectively). Highest fecundity for an individual potato leafhopper was
400 eggs, which was attained on broad bean (Table 1). Previously, the highest
fecundity reported for an individual potato leafhopper was 240 eggs on bunch
Table 1. Fecundity and longevity of the potato leafhopper maintained on selected
hosts at 27°C.
X No. eggs
per female
Host plant
Broad bean
Riley (alfalfa)
Apollo (alfalfa)
Buffalo (alfalfa)
Kuhn (red clover)
Soybean
Kenstar (red clover)
n
15
24
20
18
17
10
16
(± S.E.)
136.9 ± 32.0
87.4 ± 22.1
75.7 ± 22.7
73.6 ± 13.5
42.1 ± 11.8
30.5
2.9
±
±
a'
ab
b
b
bc
9.1 be
1.2 c
Maximal
fecundity
400
325
286
200
191
68
18
• Mcnns folla...ed by lhe same letter are not significllnu)" different, according
to
Xd
of adult
female
survival
(± S.E.)
± 5.9 a
± 6.2 ab
± 5.0 ab
± 2.3 ab
± 4.5 ab
± 6.4 ab
± 2.1 b
Maximal
adult
female
survival
36.1
29.7
27.4
23.1
28.1
26.7
10.6
Dunclln's multiple range wst (P
94
98
85
45
74
54
29
>
0.05l.
314
J. Agric. Entomol., VoL 1, No.4 (1984)
bean (DeLong 1938). That estimate, however, was not based on direct counts of
eggs.
Among the plants tested, the potato leafhopper had the highest average
ovipositional rate on broad bean (7.6 eggs/female/2 d) and the lowest average
ovipositional rate on 'Kenstar' red clover (D.B eggs/female/2 d). Among the other
host plants, namely 'Buffalo,' 'Riley' and 'Apollo' alfalfa, 'Kuhn' red clover, and
'Williams' soybean, the average ovipositional fates were 6.8, 5.8, 5.6, 3.0, and 2.2
eggs/female/2 d, respectively.
There were fluctuations in daily egg production, as illustrated with leafhoppers
on 'Kuhn' red clover (Fig. 1). On each type of plant, oviposition began 4 - 6 dafter
emergence. The number of eggs deposited per day then increased until 10· 12 d
of adult age. Following maximal egg production, ovipositional patterns varied
among host plants. On certain hosts, notably broad bean and soybean, a decline in
average ovipositional rate preceded death of a large fraction of the experimental
cohort (Fig. 1 and 2). This is illustrated by the decline in ovipositional rate on
broad bean between about age 30 to 45 d (Fig. 2). After deatb of tbose individuals,
egg production of the remaining population generally increased (Fig. 1 and 2).
Adult Longeuity
Female adult survival was relatively long (x = 36.1 d) on broad bean and
relatively short on 'Kenstar' red clover (x = 10.6 d) (Table 1). In comparison,
DeLong (1938) reported the adult longevity of the potato leafhopper to be
between 30 and 34 d when it was reared on bunch bean, In this study, an
individual female lived 98 d on 'Riley' alfalfa and another lived 94 d on broad
benn. Maximal longevities of individuals on the other five legumes were shorter
(Table 1).
The rate at which the survivorship curve declined (Fig. 1 and 2) varied llmong
host plants. On each variety of alfalfa, survivorship had declined to ca. 50% after 3
wk. The remaining individuals on 'Buffalo' alfalfa died within 3 wk, while some of
those on the two other alfalfa varieties lived much longer. On brond bean, survivor­
ship remained about 50% for about 5 wk. Conversely, on 'Kenstar' red clover less
than 50% of the adult leallioppers were alive only 6 d following emergence,
Survivorship on 'Kuhn' red clover and 'Williams' soybean was comparable to that
observed on alfalfa with 50% of the population surviving after the flfst 3 wk.
Ovipositional Preference
Free-choice tests among the seven legumes showed that the potato leafbopper
exhibited an ovipositional preference (Table 2). Among the three alfalfa varieties,
more eggs were laid in 'Buffalo' than in 'Apollo.' The number of eggs laid in 'Riley'
was not different from either of the other alfalfa varieties. There was no difference
in the number of eggs laid in the two red clover varieties nor between red clover
and soybean. Significantly fewer eggs were laid in broad bean than in any alfalfa
variety. This result was not expected because fecundity and longevity were as high
or higher on broad bean than' other host plants tested in the previously described
(no-choice) experirnGnts on fecundity and longevity. Kieckhefer and Medler (1964)
reported that soybean was less preferred for oviposition than alfalfa (variety not
indicated). However, they reported broad bean to be preferred over alfalfa, a
result contrary to our findings in the open-choice experiment. It is not known why
these results differ.
SIMMONS et. aJ.: Influence of legumes on leafhoppers
315
10
,.
"4nll.,
".d Clo".,
1.0
0 .•
0.'
n
0.1
'0
0 .•
0 .•
0.'
,,
,
.
0.3
0.'
f\ . . /\:/\
to
zo
0.1
30
40
so
eo
10
10
GO
100
Fig. 1. Age-specific oviposition and survivorship of cohorts of mated potato
leafhopper females per 2 d at 27°C.
In summary, potato leafhoppers which lived on broad bean had long adult
survival, high fecundity, and high ovipositional rates. However, broad bean was
one of the least preferred plants for oviposition when leafhoppers had a choice of
plants in which to oviposit. Yet, broad bean is a plant on which the potato
leafhopper is commonly and easily reared in the greenhouse. Among three alfalfa
varieties, the ovipositional rate was highest on 'Buffalo' (a variety commonly grown
in Kentucky), but fecundity and adult longevity were the same as on 'Apollo' and
316
J. Agrie. Entomol., VoL I, No. 4 (1984)
.... ,,
Ape""
...
AUalla
or
0.'
0>
,.
..
..
..
'00
...'.'
.
0.'
~
DO
0.'
0.'
a
~
..
.:
..
TO
'0
..
..
\00
a
;"
(,
.
1Il1l.y
\.0
0.'
0.'
..
.
!
s•
...0.'
.
;
~
0.'
0.'
0.>
O•
.
.
..
I.'
•..
0.'
0.'
0.'
0.'
0.'
0>
Fig. 2. Age-specific oviposition and survivorship of cohorts of mated potato
leafhopper females per 2 d at 27°C.
317
SIMMONS et. 01.: Influence of legumes on leofhoppers
Table 2. Ovipositional preference of the potato leafhopper in free-choice tests
among selected leguminous hosts (n = 60 females per replicate).
Host plant
X No. eggs/replicate
42.5
35.3
29.0
25.0
24.5
19.6
15.7
Buffalo (alfalfa)
Riley (alfalfa)
Apollo (alfalfa)
Kuhn (red clover)
Soybean
Kenstar (red clover)
Broad bean
a'
ab
be
bed
bed
ed
d
• MeliTIS followed by the some leUer lire nul ~ignirkantly differcnl, ftcoording 10 DlInClln'g multiple range les! (P
>
0.05).
'Riley.' 'Kuhn' red clover, a nonpubescent variety not grown comercially in the
United States, was comparable to alfalfa in its influence on egg production and
adult survival of the potato leafhopper. Potato leafllOppers on 'Kenstar' red clover,
a typical pubescent variety grown in the United States, and soybean had relatively
low egg production. Adult survival was short on 'Kenstar' red clover, but relatively
long on soybean.
These results and the findings by Simmons et al. (1984) indicate that
reproduction, survival, and growth of a colonizing population of adult potato
leafhoppers will be influenced by host plants. For example, a population of potato
leafhoppers in an alfalfa field might be expected to increase at a faster rate than
in a crop of 'Kenstar' red clover. Therefore, host plants should be considered in
developing pest management strategies for the potato leafhopper.
ACKNOWLEDGMENTS
The authors thank Dr. R. E. Sigafus for supplying seeds of the alfalfa and red clover
varieties used in this stud)'. and Mr. J. C. Parr for his technical contribution.
REFERENCES CITED
Decker, G. C., C. A. Kouskolekas, and R. J. Dysart. 1971. Some observations on fecundity
and sex ratios of the potato leafhopper. J. Econ. Entomol. 64: 1127-1129.
DeLong, D. M. 1938. Biological studies on the leafhopper Empoasca Jabal! as a bean
pest. U. S. Dept. Agr. Tech. Bull. 618. 60 pp.
Fehr, W. R., and C. E. Caviness. 1977. Stages of soybean development. Iowa Coop. Ext
Ser\'. Spec. Rep. 80. II pp.
Kieckhefer, R. W.• and J. T. MC!dler. 1964. Some environmental factorR innuencing oviposition
by the potato leaOlOppcr, Empoasca {abue. J. Econ. Entomol. 57: 482-484.
Saxena, K. N., J. R. Gandhi, and R. C. Saxena. 1974. Patterns of relationship between
certain leafhoppers and plants. I. Responses to plants. Ent. Exp. & Apl. 17: 303-318.
Simmons, A. M., K. V. Yeargan, and B. C. Pass. 1984. Development of the potato leafhopper
on selected legumes. Trans. Ky. Acad. Sci. 45: 33-35.
Simonet, D. E., and R. L. Picnkowski. 1977. Sampling and distribution of potato leafhopper
eggs in alfalfo stems. Ann. Entomol. Soc. Amer. 70: 933-936.